Plant Breeding

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Breeding bambara groundnut (vigna subterranea (L.) verdc) for enhanced yield and nutritional quality in South Africa = Ukukhiqiza Amantongomane ohlobo lwe-Bambara (Vigna subterranea (L.) Verdc) ukuze uthole Isivuno Esithuthukisiwe kanye Nekhwalithi Yokudla Okunempilo eNingizimu Afrikha.
(2023) Majola, Nomathemba Gloria.; Shimelis, Hussein.; Gerrano, Abe Shegro.
Bambara groundnut (Vigna subterranea (L.) Verdc.; 2n= 2x = 22) is a nutrient-dense grain legume cultivated in sub-Saharan Africa (SSA) and Asia. The current food systems in tropical and subtropical regions depend on the cultivation and use of a few commodity crop species. This causes most indigenous crop species, such as Bambara groundnut, to remain neglected by researchers and underutilised in the value chains. Underutilised crop species have received limited research and development attention from researchers and policymakers, and hence, their economic value, production methods, seed enterprises, product development and commercialisation are not yet fully explored. Due to a lack of systematic genetic improvement, the yield of most underutilised crops is low (<0.85 ton ha-1) and stagnant. Unlocking Bambara groundnut’s economic and value-adding potential as an essential multipurpose food and cash crop will enhance food and nutritional security in developing countries. Research on Bambara groundnut in South Africa is relatively peripheral and there are no known improved varieties of this crop with high yield and nutritional quality. Therefore, specific objectives of this study were: (1) to document the progress made on Bambara groundnut production, utilisation and genetic improvement in SSA to discern the key production constraints, genetic resources and analysis, breeding methods and gains on yield and nutrition to guide breeding; (2) to assess them genotype-by-environment interaction (GEI) effect on grain yield and to select best adapted Bambara groundnut genotypes in South African target production areas for breeding; (3) to determine the compositions of phytochemicals and mineral elements present in Bambara groundnut genetic pool to identify superior and contrasting genotypes to guide product development and breeding; (4) to determine the magnitude of the genetic diversity and population structure of Bambara groundnut collections of South Africa using high throughput single nucleotide polymorphisms (SNP) markers to complement phenotypic and nutrition profile data for genotype selection and breeding; and (5) to determine the combining ability effects and gene action conditioning yield and related traits in Bambara groundnut genotypes to identify the best combiner donor parents and progenies for genetic advancement, cultivar development and release. The first part of the study reviewed progress on Bambara groundnut production, utilisation and genetic improvement in SSA. The study presented key production constraints, genetic resources and analysis, breeding methods and genetic gains on yield and nutritional quality. Modern crop management, production technologies, and value chains are yet to be developed in Africa to achieve economic gains from Bambara groundnut production and marketing. Improved crop management and post-harvest handling technologies, modern varieties with high yield and nutritional quality, value addition and market access are among the key considerations in current and future Bambara groundnut research and development programs. Information presented will guide sustainable production and effective crop breeding to pursue food and nutrition security and improved livelihoods through Bambara groundnut enterprises. In the second chapter of the study, 75 Bambara groundnut genotypes were evaluated across seven selected environments using a 5 x 15 alpha lattice design with three replications. The study revealed significant (p<0.05) differences among genotypes (G), environments (E) and GEI effects on grain yield. A high proportion of the observed variation was due to GEI (36.62%), followed by environment (35.63%) and genotype (24.16%) effects. Grain yield across environments ranged from 1.4 ton ha-1 for ARC Bamb-68 to 0.10 ton ha-1 for ARC Bamb-74. Genotype ARC Bamb-68 (0.96 ton ha-1), ARC Bamb-9 (0.88 ton ha-1) and ARC Bamb-54 (0.84 ton ha-1) attained the highest grain yield across locations, while ARC Bamb-74 exhibited the lowest grain yield of 0.16 ton ha-1. The genotype and genotype-by-environment biplot identified ARC Bamb-17, ARC Bamb-14, ARC Bamb-20, ARC Bamb-18, ARC Bamb-14, and ARC Bamb-26 as the most stable genotypes across locations, while ARC Bamb-18 and ARC Bamb-54 were specifically adapted to Loskop and Brits. The Mafikeng site was ideal for Bambara groundnut evaluation, genotype differentiation, and large-scale seed production. The selected genotypes with high grain yields and stability are valuable genetic resources as breeding parents for Bambara groundnut improvement in South Africa. In the third chapter of the study, 75 genetically diverse Bambara groundnut genotypes were field evaluated across four environments using a 15 x 5 alpha lattice design with three replications during the 2020-2021 cropping season. Genotypes were profiled for fat, phenolic and flavonoids contents at the Agricultural Research Council (ARC) analytical laboratory in South Africa. Further, the genotypes were assessed for the contents of the following minerals: calcium (Ca), iron (Fe), potassium (K), phosphorus (P), zinc (Zn) and nitrogen (N). The nutritional content of the test genotypes varied significantly (P<0.05), which were affected by the genotype and environment interactions. The Ca, Fe, K and Zn content varied from 150.70 to 216.53, 4.30 to 16.77, 771.99 to 1155.89 and 5.50 to 7.17 mg.100 g−1 dry seed sample, respectively. Genotypes, including ARC Bamb-2, ARC Bamb-19, ARC Bamb-73, ARC Bamb-56, ARC Bamb-37, ARC Bamb-3 and ARC Bamb-69 exhibited the highest fat content (>6.00 %). ARC Bamb-40 and ARC Bamb-59 recorded a higher mean Fe content of 16.00 mg.100 g−1. ARC Bamb-2 was the top-performing genotype with high fat content (6%), Ca (211.93 mg.100 g−1), and Zn (7.17 mg.100 g−1 ). Ca, K, and N contents displayed strong correlations (r>0.60, P<0.05). Phosphorus and Zn contents exhibited moderate correlations with Ca. Overall, the study selected genotypes ARC Bamb-73, ARC Bamb-19, ARC Bamb-9 and ARC Bamb-2 with high compositions of essential nutrients for product development or breeding. The selected genetic resources are valuable for trait integration and developing new breeding populations with enhanced nutrient compositions and agronomic and market-preferred traits. In the fourth part of the study, the magnitude of the genetic diversity and population structure of South Africa Bambara groundnut collections was determined using high throughput single nucleotide polymorphisms (SNP) markers. Ninety-three genotypes were genotyped with 2286 SNP markers and phenotyped with some unique complementary morpho-agronomic traits of the crop. The mean genetic diversity value was 0.32, revealing moderate genetic differences among the assessed genotypes. Cluster and structure analyses grouped the tested genotypes into two distinct categories. Further, the analysis of molecular variance partitioned the total genetic variation into among genotypes (90%), within genotypes (8%) and among populations (2%). The results revealed two heterotic groups for hybridisation and selection programs. The following unique genotypes were selected: ARC Bamb-37 (with spreading growth type), ARC Bamb-49 (bunch type), ARC Bamb-61 (semi-bunch) and ARC Bamb-83 (spreading) using the SNP markers and desirable agronomic traits. The study provided new insight on Bambara groundnut genetic profiles of South African collections, which will assist in conservation strategy and management of the crop for effective breeding. The final part of the study assessed combining ability effects and gene action conditioning yield and related traits in Bambara groundnut genotypes to identify the best combiner donor parents and progenies for genetic advancement and breeding. Ten contrasting parents were selected and crossedusing a 10 × 10 half-diallel mating design, and 45 progenies developed. The progenies and their parents were field evaluated using a 5 × 11 alpha lattice design with two replications in two contrasting locations in South Africa. Data was collected on agronomic traits and subjected to statistical analyses to compute genetic parameters. Genotype × location interaction effect was significant (P < 0.05) for the studied agronomic traits. General combining ability (GCA) and specific combining ability (SCA) effects were significant in most assessed agronomic traits, including yield per plant. The GCA × location and SCA × location interaction effects were significant for most traits. A Baker’s ratio of < 1 were recorded for most assessed traits, indicating the preponderance of non-additive gene effects conditioning the traits. The parental lines such as ARC Bamb-25, ARC Bamb-8 and ARC Bamb-55 recorded positive and desirable GCA effects for yield per plant. The progenies ARC25×ARC8, ARC44×ARC9 and ARC6×ARC9 had desirable SCA effects for yield per plant, ARC44×ARC8, ARC44×ARC68, ARC42×ARC8 for higher number of secondary branches per stem, ARC25 ×ARC8 for early maturity, ARC42×ARC55 for higher number of pods per plant and ARC42 ×ARC57 for increased seed width. The new families selected in the current study are useful breeding populations and will be subjected to selection and multilocation evaluation to release the best-performing varieties. Overall, the present study appraised the present production constraints, genetic resources and analysis, breeding methods and genetic gains on yield and nutritional quality to guide future breeding. Moreover, new Bambara groundnut breeding populations were developed with enhanced yield and nutritional compositions for genetic advancement and multilocation selection for variety release and adoption in South Africa. Iqoqa. Amakinati ohlobo lweBambara (i-Vigna subterranea (L.) i-Verdc.; 2n= 2x = 22) ingqukuva yohlamvu olugcwele umsoco olutshalwa phakathi nasezansi ne-Afrikha, e-Afrikha engezansi kwe-Sahara (SSA) kanye nase-Asia. Izinqubo zokudla zamanje ezifundeni ezishisayo kanye nezifudumele zincike ekulimeni kanye nasekusebenziseni izinhlobo ezimbalwa zesivuno esidliwayo. Lokhu kubanga izinhlobo eziningi zesivuno zendabuko, ezifana namakinati ohlobo lweBambara, ukuthi ahlale enganakwa ngabacwaningi futhi angasetshenziswa ngokulindelekile ukudluliseleka kubathengi. Izinhlobo zesivuno esingasetshenziswa ngokulindelekile zithole ukucwaningwa okungenele kanye nokunakekelwa kokuthuthukiswa kubacwaningi kanye nakubaqambi migomo, futhi okuholela ekutheni ubungako bomnotho, izindlela zokukhiqiza, amabhizinisi embewu, ukuthuthukisa umkhiqizo kanye nokuthengiseka akukaphenywa ngokuphelele. Ngengxa yokungabibikho kokuthuthuka kwendabuko elandelelekayo, umphumela wesivuno esingasetshenziswa ngokulindelekile uphansi (<0.85 ton ha-1) futhi awunyakazi. Ukuvula umnotho kanye nokubaluleka okwengezwa amakinati ohlobo lweBambara njengokudla okusemqoka okunezinhloso eziningi kanye nesivuno semali kuzokhulisa ukudla kanye nokulondolozeka komsonco emazweni asathuthuka. Ucwaningo ngamakinati ohlobo lweBambara eNingizimu Afrikha luncane kakhulu futhi azikho izinhlobo ezithuthukile ezaziwayo zalesi sivuno ezinomphumela ophezulu nobunjalo bomsoco. Ngakho-ke, izinhloso ezithile zalolu cwaningo kwaku-: (1) ukushicilela inqubeko eyenziwe yomkhiqizo wamakinati ohlobo lweBambara, ukusetshenziswa kanye nokuthuthukiswa kohlobo eSSA ukwehlukanisa izingqinamba zomkhiqizo ezinqala, umsuka wokuhlobana kanye nokuhlaziya, izindlela zokwandisa kanye nenzuzo ngemiphulela kanye nomsoco ukuklama indlela eya phambili ukwandisa; (2) ukuhlola umphumela wokuxhumana ngokohlobo lwendawo, i-genotype-by-environment interaction (GEI) emiphumelweni yezinhlamvu kanye nokukhatha izinhlobo zamakinati ohlobo lweBambara esivumelana nendawo eNingizimu Afrikha ngokubheka ngqo izindawo zomkhiqizo ukwandisa; (3) ukuhlonza ukuhleleka kwamakhemikhali ezitshalo kanye nezinhlaka zamaminerali ezikhona emthamweni wohlobo lwamakinati ohlobo lweBambara ukukhomba izinhlobo ezidlondlobele futhi eziphikisanayo ukuhlelela ukuthuthuka komkhiqizo kanye nokuwandisa; (4) ukuhlonza ubungako bomehluko wohlobo kanye nohlaka lohlobo lwamaqoqo amakinati ohlobo lweBambara aseNingizimu Afrikha ngokusebenzisa inani elilodwa eliphezulu lezakhi zemisuka eziphindaphindiwe, i-single nucleotide pleomorphisms (SNP) ukusebenzisana kweminingo yokuhlukaniseka okubonakalayo kanye nomsoco ukukhetha uhlobo kanye nokwandisa; kanye (5) nokuhlonza imiphumela yokukwazi ukuhlanganisa kanye nomsebenzi wofuzo oveza umphumela kanye nezinkomba ezihlobene ezinhlotsheni zamakinati ohlobo lweBambara ukukhomba uhlobo olungcono kakhulu lwabazali abangahlanganiswa kanye nenzalo ukuthuthukisa uhlobo lofuzo, ukuthuthukisa kokulima kanye nokukhishwa. Ingxenye yokuqala yocwaningo ibuyekeze inqubeko yokukhiqiza amakinati ohlobo lweBambara, ukusetshenziswa kanye nokuthuthukisa ufuzo e-SSA. Ucwaningo luveze izingqinamba zomkhiqizo ezinqala, umsuka wofuzo kanye nokuhlaziya, izindlela zokwandisa kanye neziphumo zofuzo emiphumeleni kanye nobunjalo bomsoco. Ukwengamela isivuno sesimanje, ubuchwepheshe bokukhiqiza, kanye nokudluliseleka kubathengi kusamele kuthuthukiswe e-Afrikha ukufinyelela emiphumelweni yomnotho emkhiqizweni wamakinati ohlobo lweBambara. Ukwengamela isivuno esithuthukile kanye nobuchwepheshe bokuthwala emva kokuvuna, izinhlobo zesimanje ezinemiphumela ephezulu kanye nezingabunjalo lomsoco, ukwengenza ubungako kanye nokungenekela ezimakethe kungokunye okumele kubukwe ocwaningweni lwamanje nolwesikhathi esizayo lwamakinati ohlobo lweBambara. Ulwazi oluveziwe luzolekelela umkhiqizo ogcinekile kanye nokwandisa isivuno esinomphumela ukuqquqquzela ukudla kanye nokulondolozeka komsoco kanye nokuthuthukisa izimpilo ngamabhizinisi amakinati ohlobo lweBambara. Engxenyeni yesibili yocwaningo, izinhlobo zamakinati ohlobo lweBambara ezingama-75 zahlolwa kuzo zonke izindawo eziyisikhombisa ezikhethiwe kusetshenziswa uhlaka lohlelo oluphezulu lwe-5 x 15 ngokuphindaphindwa kathathu. Ucwaningo luveze umehluko omkhulu (p<0.05) phakathi kwezinhlobo, ama-genotypes (G), izindawo, ama-environments (E) kanye nemiphumela ye-GEI yomphumela wezinhlamvu. Ingxenye ephezulu yomehluko owabonakala kwakungenxa ye-GEI (36.62%), ilandelwe indawo (35.63%) kanye nemiphumela yohlobo (24.16%). Imiphumela yezinhlamvu kuzo zonke izindawo isukela ku-1.4 ton ha-1 we-ARC Bamb-68 kuya ku-0.10 ton ha-1 we-ARC Bamb-74. Uhlobo lwe-ARC Bamb-68 (0.96 ton ha-1), i-ARC Bamb-9 (0.88 ton ha-1) kanye ne-ARC Bamb-54 (0.84 ton ha-1) lwathola umphumela wezinhlamvu omkhulu kuzo zonke izindawo, ngesikhathi i-ARC Bamb-74 iveze umphumela ophansi kakhulu wezinhlamvu we-0.16 ton ha-1. Uhlobo kanye nohlobo ngokwendawo yenhlanganisela yamasampuli amabili lwaveza i-ARC Bamb-17, i-ARC Bamb-14, i-ARC Bamb-20, i-ARC Bamb-18, i-ARC Bamb-14, kanye ne-ARC Bamb-26 njengezinhlobo ezizinzile kakhulu ezindaweni zonke, ngesikhathi i-ARC Bamb-18 kanye ne-ARC Bamb-54 yazinza ngokukhethekile eLoskop kanye naseeBrits. Indawo yaseMafikeng yayikulungele ukuhlola amakinati ohlobo lweBambara, ukuhlukaniseka kohlobo, kanye nokukhiqiza umthamo omkhulu wembewu. Izinhlobo ezikhethekile ezinemiphumela ephezulu yezinhlamvu kanye nokulondolozeka ayimisuka ebalulekile yofuzo njengabazali bokwandisa ukuthuthukisa amakinati ohlobo lweBambara eNingizimu Afrikha. Engxenyeni yesithathi yocwaningo, izinhlobo ezahlukene ngobuhlobo zamakinati ohlobo lweBambara ahlolwa ensimini kuzo zonke izindawo ngokusebenzisa uhlaka lohlelo oluphezulu i-15 x 5 ngokuphindaphindwa ngesikhathi sika-2020-2021 sesikhathi sokuvuna. Izinhlobo zahlukaniswa ngokwamafutha, ubukhona beziyoliso kanye nezakhamzimba ezisamanzi elaborethri yokuhlaziya ye-Agricultural Research Council (ARC) eNingizimu Afrikha. Okunye futhi, izinhlobo zahlolwa ngokuba khona kwalama minerali alandelayo: i-calcium (Ca), i-iron (Fe), i-potassium (K), i-phosphorus (P), i-zinc (Zn) kanye ne-nitrogen (N). Ubukhona bezakhamzimba zezinhlobo ezahlolwa zazehlukile kakhulu (P<0.05), nokwakunomthelela wokuxhumana kohlobo kanye nendawo. Ubukhona be-Ca, i-Fe, i-K kanye ne-Zn kwakuhlukile kusukela ku-150.70 kuya ku-216.53, ku-4.30 kuya ku-16.77, ku-771.99 kuya ku-1155.89 kanye no-5.50 kuya ku-7.17 mg.100 g−1 isampula yembewu eyomile, ngokulandelana kwako. Izinhlobo, okubalwa kuzo i-ARC Bamb-2, i-ARC Bamb-19, i-ARC Bamb-73, i-ARC Bamb-56, i-ARC Bamb-37, i-ARC Bamb-3 kanye ne-ARC Bamb-69 zaveza ubukhona obuphezulu bamafutha (>6.00 %). I-ARC Bamb-40 kanye ne-ARC Bamb-59 yaqopha inani eliphezulu lobukhona be-Fe ka-16.00 mg.100 g−1. I-ARC Bamb-2 yayiwuhlobo oluqukethe ubukhona bamafutha okuphezulu (6%), Ca (211.93 mg.100 g−1), kanye ne-Zn (7.17 mg.100 g−1 ). Ubukhona be-Ca, i-K, kanye ne-N baveza ukuhlobana obuphezulu (r>0.60, P<0.05). Ubukhona be-phosphorus kanye ne-Zn kwaveza ukuhlobana okuphakathi nendawo ne-Ca. Sekukonke, ucwaningo lukhethe izinhlobo ze-ARC Bamb-73, i-ARC Bamb-19, i-ARC Bamb-9 kanye ne-ARC Bamb-2 nezakhiwo eziphezulu zezakhamzimba esisemqoka ukuthuthukisa umkhiqizo noma ukwandisa. Imisuka yofuzo ekhethiweyo ibalulekile ukuhlonza inhlanganisela yenkomba kanye nokuthuthukisa uhlobo olusha lokwandisa nenhlanganisela yezakhamzimba ethuthukile kanye nezinkomba zezenhlabathi kanye nesincanyelwa imakethe. Engxenyeni yesine yocwaningo, umehluko wofuzo omkhulukazi kanye nohlelo lwezinhlobo zamaqoqo amakinati ohlobo lweBambara eNingizimu Afrikha watholakala ngokusebenzisa inani eliphezulu elilodwa lomsuka wezakhi eziningi, (i-single nucleotide polymorphisms (SNP)). Izinhlobo ezingamashumi ayisishiyagalolunye nantathu nezakhi ezingama-2286 ze-SNP kanye nezinkomba ezibonakalayo kanye nezinkomba eziyinhlanganisela yomhlabathi ezihambisanayo zesivuno. Imini yomehluko wofuzo wawu-0.32, ukuveza umehluko wofuzo ophakathi nendawo phakathi kwezinhlobo ezahlolwa. Ukuhlaziya uhlobo kanye nohlelo kwaqoqela ndawonye izinhlobo ezihlolwa ngamaqoqo angefani amabili. Okunye futhi, ukuhlaziya kwenhlayiya encanyana kwahlukanisa isamba somehluko wofuzo phakathi kwezinhlobo ezinga-90%, phakathi kwezinhlobo ezinga-8% futhi phakathi kwezinhlobo ezinga-2%. Imiphumela yaveza amaqoqo amabili ahlotshanisiwe ukuhlanganisa ukungefani kanye nezinhlelo zokukhetha. Izinhlobo ezehlukile ezilandelayo zakhethwa: i-ARC Bamb-37 (nohlobo lokukhula okusabalele), i-ARC Bamb-49 (uhlobo lwesixheke), i-ARC Bamb-61 (uhhafu wesicheke) kanye ne-ARC Bamb-83 (esabalalayo) ngokusebenzisa izakhi ze-SNP kanye nezinkomba ezidingakalayo zokwenhlabathi. Ucwaningo lunikeze umbono omusha ngezinhlobo zofuzo lwamakinati ohlobo lweBambara emaqoqweni aseNingizimu Afrikha, ezizolekelela emaswini okulondoloza kanye nokwengamela isivumo ukwandisa okuyimpumelelo. Ingxenye yokugcina yocwaningo ihlole imiphumela yokukwazi ukuhlanganisa kanye nomsebenzi wofuzo olukhipha umphumela kanye nezinkomba ezihlobene zezinhlobo zamakinati ohlobo lweBambara ukuveza inhlanganisela engcono yabazali abanikezelwe kanye nenzalo ukuthuthukisa ufuzo kanye nokwandisa. Abazali abayishumi abaphikisanayo bakhethwa baphanjaniswa ngokusebenzisa uhlaka lokuzalanisa oluwuhhafu ngokuhambisana ngo-10 x 10, futhi inzalo engama-45 yakhiqizwa. Inzalo kanye nabazali kwahlolwa ensimini ngokusebenzisa uhlaka lohlelo olukhulu ngo-5 x 11 ngokuphindaphinda okubili ezindaweni eziphikisanayo ezimbili eNingizimu Afrikha. Imininingo yaqoqwa ezinkonjeni zokwenhlabathi futhi kwamele zihlaziywe ngezinombolo ukuqopha imikhawuko yofuzo. Umphumela wokuxhumana kohlobo x indawo waba mukhulu ngo-(P < 0.05) ezinkombeni zokwenhlabathi ezacwaningwa. Ukukwazi ukuhlanganisa okwejwayelekile, (i-General combining ability (GCA)) kanye nemiphumela yokukwazi ukuhlanganisa okukhethekile, (i-specific combining ability (SCA)) yaba mikhulu ezinkonjenu eziningi ezahlolwa zokwenhlabathi, okubalwa kuyo umphumela ngesitshalo. I-GCA x indawo kanye ne-SCA x miphumela yokuxhumanisa indawo yaba mikhulu ezinkonjeni eziningi. Isilinganiso sika-Baker sika- < 1 saqoshwa ezinkonjeni eziningi ezahlolwa. Imigudu yabazali efana ne-ARC Bamb-25, i-ARC Bamb-8 kanye ne-ARC Bamb-55 yaqopha imiphumela emihle futhi edingakalayo ye-GCA yemiphumela ngesitshalo. Inzalo eyi-ARC25×ARC8, i-ARC44×ARC9 kanye ne-ARC6×ARC9 yaba nemithelela edingakalayo ye-SCA yemiphumela ngesitshalo, i-ARC44×ARC8, i-ARC44×ARC68, i-ARC42×ARC8 yenombolo enkulu yamagatsha aphakathi nendawo ngesiqu, i-ARC25 ×ARC8 yokushesha sithele, i-ARC42×ARC55 yenombolo enkulu exhaphozini ngesitshalo kanye ne-ARC42 ×ARC57 yokwenyuka kobubanzi bembewu. Imindeni emisha eyakhethwa kulolu cwaningo anomsebenzi wokwandisa amaqoqo futhi kumele ikhethwe futhi ihlolelwe izindawo eziningi ukukhipha izinhlobo ezenza kahle kakhulu. Ukugoqa, lolu cwaningo luhlole izingqinamba zomkhiqizo, imisuka yohlobo kanye nokuhlaziya, izindlela zokwandisa kanye nemiphumela yokuhlobana emiphumelweni kanye nobunjalo bomsoco ukuhlahla indlela eya phambili. Okunye futhi, izinhlobo zokwandisa amakinati eBambara ezintsha ziqanjiwe kanye nemiphumela ethuthukisiwe kanye nenhlanganisela yezakhamzimba ukuthuthukisa uhlobo kanye nokukhetha izindawo eziningi ukukhipha okwahlukehlukene kanye nokusetshensiswa eNingizimu Afrikha.
Genetic characterization of citron watermelon (citrullus lanatus var. citroides [L.H. Bailey] mansf. ex greb.) and development of experimental hybrids = Isimo sofuzo sekhabe i-citron (Citrullus lanatus var. citroides [L.H. Bailey] Mansf. ex Greb.) kanye nokuthuthukiswa kwenhlanganisela yokuhlola
(2023) Ngwepe, Mantlo Richard.; Shimelis, Hussein.; Mashilo, Jacob.
Citron watermelon (Citrullus lanatus var. citroides [L.H. Bailey] Mansf. ex Greb.) is indigenous to sub-Saharan Africa (SSA) with multiple uses, including human food and animal feed. Its succulent leaves are used as leafy vegetables, while the ripened yellow and orange-fleshed fruits are used to prepare various traditional dishes, and the seeds are roasted and consumed as snack. It is an emerging potential rootstock for producing grafted sweet watermelon (Citrulus lanatus var. lanatus) to improve fruit yield and biotic and abiotic stress tolerance. It is also a source of novel genes for breeding in sweet watermelon to improve fruit yield, quality and disease resistance. Citron watermelon in SSA is mainly cultivated using unimproved landrace varieties. Landraces exhibit marked phenotypic variation for fruit shape, size, skin colour patterns, and seed coat colours. Phenotypic and genetic variation among South African citron watermelon landraces is yet to be systematically assessed for diverse use and cultivar design. The overall goal of this study was to initiate a pre-breeding program for citron watermelon through identification and selection of unique and complementary genotypes for production, value-adding and breeding. The specific objectives of this study were: i. To determine the extent of genetic diversity among South African citron watermelon landrace accessions using selected simple sequence repeat (SSR) markers to identify genetically divergent accessions for trait integration and variety development; ii. To assess the phenotypic diversity of citron watermelon landrace accessions of South Africa and to select desirable genotypes with suitable agronomic and horticultural traits for direct production, breeding and conservation; iii. To estimate variance components, heritability and genetic advance of phenotypic traits in citron watermelon to guide the selection of superior genotypes for direct production and breeding; iv. To determine the combining ability and hybrid performance of citron watermelon genotypes for agronomic traits for breeding. In the first study, 48 citron watermelon landrace collections widely grown in the Limpopo Province of South Africa were genotyped using 11 selected SSR markers. The SSR markers amplified a total of 24 alleles, with a mean expected heterozygosity value of 0.38, indicating moderate genetic diversity among the studied accessions. Analysis of molecular variance attributed 8%, 75%, and 17% of the molecular variation between populations, among accessions and within accessions, respectively. Three distinctive genetic groups were identified based on cluster analysis. The following distantly related genotypes are recommended as breeding parents namely: WWM03, WWM04, WWM15, WWM16, WWM18, WWM22, WWM23, WWM24, WWM25, WWM26, WWM28, WWM33, WWM34, WWM35, WWM38, WWM39, WWM41, WWM66, WWM76, WWM78, WWM81, WWM84, WWM86 and WWM89 (selections from Cluster I), WWM14, WWM37, WWM42, WWM44, WWM46, WWM50, WWM65, WWM79, WWM85 and WWM87 (Cluster II), and WWM38, WWM47 and WWM48 (Cluster III). These are useful parental lines for pre-breeding to develop and release new varieties with multiple uses. In the second study, 36 selected citron watermelon landrace accessions were evaluated under field conditions across two environments using a 6 × 6 lattice design with three replicates. Data on key qualitative and quantitative traits were collected and subjected to non-parametric and parametric statistical analyses. The accessions showed wide phenotypic variation and unique traits for genetic improvement. Positive and significant correlations (p < 0.001) were recorded between total fruit yield per plant with plant height (r = 0.64), number of harvestable fruits (r = 0.70), number of marketable fruits (r = 0.73) and marketable fruit yield (r = 0.96). Seed yield per plant positively and significantly (p < 0.001) correlated with number of male flowers (r =0.68), plant height (r = 0.61) and total fruit yield (r = 0.79). Principal component analysis identified nine components which accounted for 86.38% of total variation amongst accessions for assessed phenotypic traits. The study recommended citron watermelon accessions such as WWM14, WWM16, WWM39, WWM41, WWM67 and WWM79 for use as leafy vegetables owing to their profuse branching ability and longer vine production. Whereas accessions including WWM03, WWM17, WWM35, WWM40, WWM50, WWM67, WWM79 and WWM85 are selected with larger fruit size. Accessions WWM05 and WWM09 are sour-flesh types which are suitable genetic stocks for breeding sweet-and-sour and sweet dessert watermelons. Orange-fleshed accessions such as WWM03, WWM04, WWM46, WWM64, WWM66 and WWM67 are recommended for fresh consumption, cooking, processing or variety design. Accessions WWM02, WWM03, WWM08, WWM14, WWM16, WWM23, WWM38, WWM40, WWM41 and WWM67 have red and white seed coat colour which are superior selections to prepare roasted citron watermelon seed snack. In the third study, variance components, heritability and genetic gains of phenotypic traits were estimated involving 36 accessions of citron watermelon grown under field conditions across two test environments using a 6 × 6 lattice design with three replicates. High broad-sense heritability and genetic advance as percent of the mean were recorded for fruit length at 83.86 and 4730.45%, seed length (77.73 and 1731.27%), hundred seed weight (73.73 and 4027.36%), fruit diameter (70.44 and 2949.64%) and fruit weight (70.39 and 8490.05%), respectively. Step-wise regression analysis revealed marketable fruit yield and total number of fruits per plant explaining 89% (R2 = 0.89) of total variation for total fruit yield per plant, whereas number of seed per fruit and hundred seed weight explained 92 (R2 = 0.92) of total variation for seed yield per fruit. Citron watermelon landrace accessions WWM03, WWM14, WWM16, WWM39, WWM65, WWM67 and WWM79 with high total fruit yield and seed yield per fruit were selected for production or breeding programme. In the fourth study, five selected parental genotypes were crossed in a 5 × 5 half-diallel mating design to develop 10 hybrids. The 15 families (five parents and 10 F1 hybrids) were evaluated across two environments using a randomized complete block design (RCBD) with three replications. General combining ability (GCA) and specific combining ability (SCA) effects were significant (p < 0.001) for most traits. Environment × GCA was non-significant, whereas Environment × SCA effects were significant (p < 0.001) for most traits. The ratios of GCA/SCA variances were less than unity for most traits, indicating non-additive gene action of the traits. Broad-sense heritability varied from low to moderate, implying variable selection response of the assessed traits among the F1 hybrids. The parental genotypes WWM16 with positive GCA effects for fruit and seed yield and WWM66, with positive GCA effects for the number of seeds per fruit and seed yield, were identified for hybrid breeding. The following F1 hybrids, namely: WWM04 × WWM16, WWM03 × WWM66 and WWM16 × WWM50 with positive SCA effects on total fruit yield per plant and marketable fruit yield per plant, and WWM04 × WWM50, WWM03 × WWM16 and WWM03 × WWM66 with positive SCA effects for number of seeds per fruit and total seed yield were identified. The study identified novel and best-performing F1 hybrids of citron watermelon for economic traits and are recommended for multi-environmental evaluations, variety registration and commercialization. Overall, the study revealed genetic and phenotypic variation in citron watermelon to select and recommend suitable genotypes for production and for breeding new generation varieties based on market needs and consumer preferences. The study recommends accessions such as WWM14, WWM16, WWM39, WWM64, WWM67, WWM76 and WWM79 with high fruit yield, and WWM03, WWM04, WWM14, WWM15, WWM16, WWM24, WWM28, WWM37, WWM46, WWM66 and WWM68 exhibiting high fruit and seed yield for breeding or direct production. The parents WWM04, WWM03 and WWM16 were identified as good combiners for fruit or seed yield and related-component traits for future breeding. The F1 hybrids derived from these parents, including WWM04 × WWM16, WWM03 × WWM16, WWM03 × WWM66, WWM16 × WWM50, and WWM04 × WWM50 were best performing for economic traits and new breeding population development. Iqoqa. Ikhabe le-citron (i-Citrullus lanatus var. citroides [L.H. Bailey] Mansf. ex Greb.) lingelendabuko e-Afrikha eseMazansi, (i-sub-Saharan Africa (SSA)) elinemisebenzi eminingi, okubalwa kuyo ukudla kwabantu kanye nokudla kwezilwane. Amahlamvu alo amnandi asetshenziswa njengemifino emaqabunga, bese kuthi izithelo esezivuthiwe eziphuzi kanye neziwukudla ezisawolintshi zisetshenziswa ukwenza ukudla kwendabuko okwahlukene, bese imbewu iyosiwa bese idliwa njengokudla okulula. Yisiqu sempande esafufusa ukukhiqiza ikhabe elingxube (i-Citrulus lanatus var. lanatus) ukuthuthukisa umkhiqizo wesithelo kanye nokubekezelela ingcindezi yokuphilayo nokungaphili. Kuyimbangela yofuzo olusha ukukhiqiza ikhabe elinoshukela ukukhulisa ekhabeni elinoshukela ukuthuthukisa umkhiqizo wesithelo, izingabunjalo kanye nokulwa nezifo. Ikhabe le-citron e-SSA litshalwa kakhulu kusetshenziswa izinhlobo ezahlukene zohlobo olusangulube engathuthukile. Uhlobo olusangulube olwehlukile ukumisa isithelo, ubungako, umbala wesikhumba kanye nemibala eyemboze imbewu. Uhlobo lokufanisa nofuzo phakathi kwekhabe lwe-citron lwaseNingizimu Afrikha nezingulube kusamele luhlolwe ngendlela ukuveza umsebenzi owehlukile nohlaka lokutshala. Inhloso enkulu yalolu cwaningo kwakungukuqala uhlelo lokuqalela ukwandisa ikhabe le-citron ngokuveza kanye nokukhetha uhlobo lokulekelela olwehlukie ukukhiqiza, ukwengeza ukubaluleka kanye nokwandisa. Izinhloso ezikhethekile zalolu cwaningo kwakuyilezi: i. Ukuthola ukuthi luhamba luze lufike kuphi uhlobo lomehluko phakathi kwekhabe laseNingizimu Afrikha olusangulube olungenisiwe kusetshenziswa ukulandelana okulula okukhethekile kokuphinda izinkomba, (ama-simple sequence repeat (SSR)) ukuveza ukungena okwehlukile kofuzo ukuveza ukuhlanganisa kanye nokuthuthuka okwehlukile; ii. Ukuhlola umehluko wohlobo lwekhabe le-citron olusangulube olungenisiwe lwaseNiningizimu Afrikha kanye nokukhetha ufuzo oludingekayo kanye nezinkomba zomhlabathi olimekayo kanye notshalekayo ukuqondisa umkhiqizo, ukwandisa kanye nokugcineka; iii. Ukuhlawumbisela umehluko wezinhlaka, ifa kanye nokuqhubeka kofuzo lwezinkomba zohlobo ekhabeni lwe-citron ukuhlola ukukhetha kohlobo lofuzo olukhulu ukuqondisa umkhiqizo kanye nokwandisa; iv. Ukuthola ukukwazi okuhlanganisayo kanye nokusebenza okuyinhlanganisela yohlobo lwekhabe lwe-citron ukulimekela ukwandisa. Ocwaningweni lokuqala, amaqoqa amakhabe ekhabe le-citron olusangulube olutshalwa esiFundazweni saseLimpopo saseNingizimu Afrikha afaniswa kusetshenziswa izinkomba eziyi-11 ezikhethiwe ze-SSR. Izinkomba se-SSR zakhulisa isamba sokuzo olungama-24, ngemini elindelekile ebalwe ngenani lika-0.38, okukhomba umehluko wobuhlobo ophakathi nendawo phakathi kwezingenelelo ezacwaningwa. Ukuhlaziya komehluko wezinhlayiya kwaveza u-8%, u-75%, kanye no-17% womehluko wezinhlayiya phakathi kwamaqoqo, phakathi kwezingenelelo kanye nangaphakathi kwezingenelelo, ngokulandelana kwakho. Amaqoqo ohlobo olwehlukile amathathu avezwa ngokuhlaziya ngendlela yokubeka ngamaqoqo. Izinhlobo ezihlobene ngokuqgagqana ziyaphakanyiswa njengabazali bokwandisa ababizwa: i-WWM03, i-WWM04, i-WWM15, i-WWM16, i-WWM18, i-WWM22, i-WWM23, i-WWM24, i-WWM25, i-WWM26, i-WWM28, i-WWM33, i-WWM34, i-WWM35, i-WWM38, i-WWM39, i-WWM41, i-WWM66, i-WWM76, i-WWM78, i-WWM81,i-WWM84, i-WWM86 kanye ne-WWM89 (ukukhetha eQoqweni I), i-WWM14, i-WWM37, i-WWM42, i-WWM44, i-WWM46, i-WWM50, i-WWM65, i-WWM79, i-WWM85 kanye ne- WWM87 (IQoqo II), kanye ne-WWM38, i-WWM47 kanye ne-WWM48 (IQoqo III). Laba olayini bokuzala abanomsebenzi wokulungiselela ukwandisa ukuthuthukisa kanye nokukhulula izinhlobo ezintsha kanye nemisebenzi eminingi. Ocwaningweni lwesibili, ikhabe le-citron elikhethiwe elingama-36 olusangulube lokungenisiwe lwahlolwa ngaphansi kwezimo zensimi ezimweni ezimbili ezingefani kusetshenziswa uhlobo lohlaka u-6 × 6 nezifaniso ezintathu. Imininingo yezinkomba ezisemqoka zekhwalithethivu kanye nezinombolo yaqoqwa bese yahlotshaniswa nokuhlaziya okunemikhawulo kanye nokungenamkhawulo. Okwangeniswa kwaveza umehluko wohlobo omkhulu kanye nezinkomba ezahlukile zokuthuthukisa ufuzo. Ukuhlobana okuhle futhi okubalulekile (p < 0.001) kwaqoshwa phakathi kwesithelo esikhiqiziwe ngokwesitshalo esinobude baso obu-(r = 0.64), inombolo yezithelo ezinokuvuneka (r = 0.70), inombolo yezithelo ezidayisekayo (r = 0.73) kanye nomkhiqizo wesitho esidayisekayo (r = 0.96). Umkhiqizo wembewu ngokwesitshalo kwahlobana kahle futhi kakhulu (p < 0.001) nenombolo yezimbali zesilisa (r = 0.68), ubude bezitshalo (r = 0.61) kanye nenani lomkhiqizo wesithelo (r = 0.79). Ukuhlaziya kwengxenye enkulu kuveze izinhlaka eziyisishiyagalombili kwachaza u-86.38% yomehluko ohlangene phakathi kokungenisiwe kwahlola izinkomba zezinhlobo ezinofuzo. Ucwaningo luphakamisa ukuthi ikhabe le-citron olufana ne-WWM14, i-WWM16, i-WWM39, i-WWM41, i-WWM67 kanye ne-WWM79 elisetshenziswa njengemifino engamaqabunga liyimbangela yokukwazi ukusabalala okwedlulele kanye nomkhiqizo wesivuno omude. Kanti okungenisiwe okufana ne-WWM03, i-WWM17, i-WWM35, i-WWM40, i-WWM50, i-WWM67, i-WWM79 kanye ne-WWM85 kukhethwa njengesithelo esikhulu ngobungako. Okungenisiwe kwe-WWM05 kanye ne-WWM09 kuyizinhlobo zokudliwayo okumuncu okuwufuzo olulungele ukugcinelwa ukwandiswa kwamakhabe anoshukela nesimuncwana kanye nesidlo sokuphetha. Okungenisiwe okudliwayo okusawolintshi okufana ne-WWM03, WWM04, i-WWM46, i-WWM64, i-WWM66 kanye ne-WWM67 kuphakanyiswa ukudliwa kusekusha, ukuphaka, ukukhiqizwa, noma uhlaka lohlobo. Okungenisiwe kwe-WWM02, i-WWM03, i-WWM08, i-WWM14, i-WWM16, i-WWM23, i-WWM38, i-WWM40, i-WWM41 kanye ne-WWM67 kunembewu ebomvu kanye nemhlophe yemibala yokwembozile okukhetheke kakhulu ukulungisela imbewu eyosiwe yekhabe le-citron lokudla okulula. Ocwaningweni lwesithathu, izinhlaka zoshintsho, ukufuza, imivuzo yofuzo yezinkomba zezinhlobo kwahlawumbiselwa kubalwa okungenisiwe okungama-36 kwekhabe le-citron elitshalwa ngaphansi kwezimo zensimu ngapha nangapha kwezizinda zokulinga ezimbili kusetshenziswa uhlaka lohlelo luka-6 × 6 nezimpinda ezintathu. Ukufuza okusabalele ngokubanzi kanye nokusabalala kohlobo njengephesenti lemini kwaqoshelwa ubude besithelo ku-83.86 kanye no-4730.45%, ubude bembewu (77.73 no-1731.27%), isisindo sembewu esiyikhulu (73.73 no- 4027.36%), ubude bephakathi lesithelo (70.44 no-2949.64%) kanye nesisindo sesithelo (70.39 no-8490.05%), ngokulandelana. Ukuhlaziya ukuphendukela emumva ngokwesigaba ngesigaba kwaveza imiphumela yesithelo edayisekayo kanye nenani lenombolo yezithelo ngesitshalo kuchaza ama-89% (R2 = 0.89) womehluko ophelele wesiphumo sesithelo ngesitshalo, kanti inombolo yembewu ngesitshalo kanye nesisindo sembewu eyikhulu kwachazwa ngo-92% (R2 = 0.92) wenani lomehluko wesiphumo sembewu ngesitshalo. Okungenisiwe kwekhabe le-citron elisangulube i-WWM03, i-WWM14, i-WWM16, i-WWM39, i-WWM65, i-WWM67 ne- WWM79 nenani eliphezulu leziphumo zesithelo kanye nesiphumo sembewu ngesitshalo kwakhethelwa umkhiqizo noma uhlelo lokwandisa. Ocwaningweni lwesine, izinhlobo ezifuzene zokuzalana ezinhlanu zakhethwa ngapha nangapha kuhhafu ka-5 × 5 wohlaka lokuhlanganisa uqondanisa ukuthuthukisa inhlanganisela eyi-10. Imindeni eyi-15 (abazali abahlanu kanye nenhlanganisela ka-10 F1) kwahlolwa ngapha nangapha ezimweni ezimbili kusetshenziswa uhlaka lweqoqo oluphelele olukhethwe ngokungenhloso, (i-randomized complete block design (RCBD)) nokuphindaphinda okuthathu. Ukukwazi kokuhlanganisa okwejwayelekile, (i-General combining ability (GCA)) kanye nemiphumela yokukwazi kokuhlanganisa okuthile, (i-specific combining ability (SCA)) kwakubalulekile (p < 0.001) ezinkombeni eziningi. I-Environment × GCA yayingabalulekile, kanti imiphumela ye-Environment × SCA yayibalulekile (p < 0.001) ezinkombeni eziningi. Ubudlelwane bomehluko we-GCA/SCA babubuncane ngaphansi ngokukodwa ezinkombeni eziningi, okukhomba ukusebenza kofuzo olungengezeleli lwezinkomba. Ufuzo olubanzi ngokusabalele lwehluka kusukela phansi kuya phakathi nendawo, okusho impendulo yokukhetha ivarebuli ezinkombeni ezihloliwe phakathi kwenhlanganisela ye-F1. Uhlobo lofuzo lokuzala i-WWM16 nemiphumela emihle ye-GCA yesithelo kanye nesiphumo sembewu kanye ne-WWM66, nemiphumela emihle ye-GCA enombolweni yembewu ngesithelo kanye nesiphumo sembewu, kwatholakala ukwandisa okuyinhlanganisela. Inhlanganisela elandelayo ye-F1, nokuyi-: WWM04 × WWM16, i-WWM03 × WWM66 kanye ne-WWM16 × WWM50 nemiphumela emihle ye-SCA enanini lesiphumo sesithelo ngesitshalo kanye nesiphumo sesithelo esithengisekayo, kanye ne-WWM04 × WWM50, i-WWM03 × WWM16 kanye ne-WWM03 × WWM66 nemiphumela emihle ye-SCA enombolweni yembewu ngesitshalo kanye nenani lesiphumo lembewu kwatholakala. Ucwaningo lwaveza izinhlanganisela ezintsha futhi ezisebenza kangcono kakhulu ze-F1 zekhabe le-citron ezinkombeni zomnotho kanti ziyanconywa ukuhlolelwa imvelo okuningana, ukubhalisa umehluko kanye nokuthengisa. Sekukonke, ucwaningo luveze ukuthi umehluko wofuzo kanye nowohlobo lofuzo ekhabeni le-citron ukukhetha kanye nokuphakamisa uhlobo lofuzo olulungele imkhiqizo kanye nokwandisa izinhlobo zenzalo entsha kuncike ezidinweni zemakethe kanye nasekukhetheni kwabathengi. Ucwaningo luphakamisa okungeniswayo okufana ne-WWM14, i-WWM16, i-WWM39, i-WWM64, i-WWM67, i-WWM76 kanye ne-WWM79 nesiphumo esiphezulu sesithelo, kanye ne-WWM03, i-WWM04, i-WWM14, i-WWM15, i-WWM16, i-WWM24, i-WWM28, i-WWM37, i-WWM46, i-WWM66 kanye ne-WWM68 kuveza isithelo esiphezulu kanye nesiphumo sembewu ukwandisa umkhiqizo oqondile. Abazali i-WWM04, i-WWM03 kanye ne-WWM16 batholakala njengezihlanganiso zesithelo noma zesiphumo sembewu kanye nezinkomba zezinhlaka ezihlobene ukwandisa kwesikhathi esizayo. Izinhlanganisela ze-F1 ezatholakala kulaba bazali, okubalwa kubo i-WWM04 × WWM16, i-WWM03 × WWM16, i-WWM03 × WWM66, i-WWM16 × WWM50, kanye ne- WWM04 × WWM50 kwakusebenzela kakhulu izinkomba zomnotho kanye nokuthuthukisa inani lokwandisa.
Pre-breeding of okra (abelmoschus esculentus [L.] moench) for drought tolerance.
(2023) Mkhabela, Sonto Silindile.; Shimelis, Hussein.; Gerrano, Abe Shengro.
Okra (Abelmoschus esculentus [L.] Moench; 2n = 2x = 130) is an important vegetable and oil crop. It is extensively grown in tropical and subtropical regions with limited and erratic rainfall conditions. A lack of improved cultivars with drought tolerance hinders the production of okra in sub-Saharan Africa (SSA). Considerable phenotypic and genotypic variation present in okra genetic resources from SSA useful for cultivar design with enhanced fresh pod and oil yields and drought tolerance. However, the genetic diversity in SSA’s okra germplasm collection is yet to be explored for breeding targeting economic and horticultural traits. There has been limited progress in the breeding of okra for drought tolerance. Therefore, the specific objectives of this study were i) to determine the response of selected okra genotypes to drought stress using fresh fruit yield and yield-related traits to identify and select candidate genotypes for drought tolerance breeding, ii) to determine genetic diversity present among okra accessions using simple sequence repeats (SSR) and complementary phenotypic markers and to select genetically divergent and superior parental accessions for pre-breeding, iii) to assess the levels of drought tolerance in preliminarily selected okra accessions based on leaf gas exchange and chlorophyll fluorescence to determine best-performing genotypes for drought-tolerance breeding and iv) to determine the combining ability and heterosis of selected okra accessions for yield and yield-related traits to identify superior parents and progenies for breeding. The first part of the study involved 26 okra genotypes that were evaluated in glasshouse and field environments under drought-stressed (DS) and non-stressed (NS) conditions using a 13 × 2 alpha lattice design with two replications. The findings revealed significant (P < 0.05) genotype x testing environment x water condition interaction effects for most traits, allowing for the selection of okra genotypes suited for drier conditions. Yield per plant (YPP) positively and significantly correlated with fresh pod length (FPL) (r = 0.66; P ≤ 0.001), dry pod weight (DPW) (r = 0.80; P ≤ 0.001) and number of pods per plant (NPP) (r = 0.58; P ≤ 0.001) under DS condition in the field environment. The study identified genotypes with high yield and other desirable phenotypic attributes, which are useful genetic resources for future crosses and the selection of promising progenies based on combining abilities analyses and heritability under water-limited environments. In the second study, 26 preliminarily selected okra accessions were assessed using nine highly polymorphic SSR markers and phenotyped under DS and NS environmental conditions using a 13 × 2 alpha lattice design with two replications. The SSR markers revealed a mean heterozygosity value of 0.54, indicating moderate genetic diversity among the tested okra accessions. Cluster analysis based on phenotypic and SSR markers differentiated the accessions into three distinct genetic groups. Pod yield per plant (PYPP) was positively and significantly correlated with fresh pod length (FPL) (r = 0.81), above-ground biomass (ABG) (r = 0.69), and harvest index (HI) (r = 0.67) under DS conditions, and FPL (r = 0.83) and AGB (r = 0.60) under NS conditions. Genetically complementary accessions such as LS04, LS05, LS06, LS07, LS08, LS10, LS11, LS15, LS18, LS23, LS24, and LS26 were identified for their high yield potential and related yield-improving traits under DS conditions. The identified accessions were recommended as parents for hybridization and selection programs to improve the yield potential of okra under drought-stressed environments. In the third part of the study, 26 genetically diverse okra accessions were screened for physiological traits response under NS and DS conditions in a controlled glasshouse environment using a 13 × 2 alpha lattice design and three replications in two growing seasons. Statistical analyses revealed a significant genotype × water condition interaction effect for transpiration rate (T), net CO2 assimilation (A), intrinsic water use efficiency (WUEi), instantaneous water use efficiency (WUEins), minimum fluorescence (Fo′), maximum fluorescence (Fm′), maximum quantum efficiency of photosystem II photochemistry (Fv′/Fm′), the effective quantum efficiency of PSII photochemistry (ɸPSII), photochemical quenching (qP), nonphotochemical quenching (qN) and relative measure of electron transport to oxygen molecules (ETR/A). The results suggested variable drought tolerance of the studied okra accessions for selection. Seven principal components (PCs) contributing to 82% of the total variation for assessed physiological traits were identified under DS conditions. Leaf gas exchange parameters, T, A and WUEi, and chlorophyll fluorescence parameters such as the ɸPSII, Fv′/Fm′, qP, qN, ETR and ETR/A had high loading scores and correlated with WUEi, the ɸPSII, qP and ETR under DS conditions. The study identified drought-tolerant accessions, namely LS05, LS06, LS07 and LS08 based on high A, T, Fm′, Fv′/Fm′ and ETR, and LS10, LS11, LS18 and LS23 based on high AES, Ci, Ci/Ca, WUEi, WUEins, ɸPSII and AES. The selected genotypes are high yielding (≥5 g pods/plant) under drought stress conditions. The data presented will complement phenotypic data and guide breeding for water-limited agroecologies. Eight selected okra genotypes were crossed in the fourth part of the study to generate new genetic combinations and breeding populations. The parents were selected based on their high yield potential and tolerance to drought stress. The genotypes were sourced from the Agricultural Research Council-Vegetable, Industrial and Medicinal Plants (ARC-VIMP), South Africa, assembled from diverse regions of origin. The selected eight parents were crossed using an 8 × 8 half diallel mating design during the 2021 cropping season. The parents were planted under field conditions at the ARC-VIMP research station during the 2021/2022 growing season. Subsequently, 28 new generations were developed. The crosses and eight parents were field evaluated using a 12 × 3 lattice design with three replications. The genotypes were evaluated under NS and DS conditions at two locations, namely the ARC – Loskop and ARC – Brits sites. Significant (P<0.01) effects of genotype, environment, and genotype × environment interaction was recorded for fresh pod yield and component traits. General combining ability (GCA) and specific combining ability (SCA) effects were significant (P<0.05) for most traits, indicating the role of additive and non-additive gene action underlying the inheritance of the assessed traits. The GCA × environment and SCA × environment interaction effects were significant for days to flowering (DTF), number of leaves per plant (NOL), fresh pod length (FPL), number of fresh pods per plant (NFPP) and pod yield per plant (PYP). Parental genotypes LS09, LS10 and L24 showed positive GCA effects for PYP under DS conditions and were selected to be valuable germplasm for variety design to widen genetic variability for drought tolerance and yield-related traits. Crosses LS01 × LS17, LS01 × LS18, LS09 × LS10, LS09 × LS18, LS09 × LS24, LS15 × LS18, LS15 × LS21, LS15 × LS24 and LS17 × LS21 expressed positive SCA effects for PYP under DS condition and are recommended for genetic advancement, production, and commercialization in water-scarce environments of South Africa. Overall, the study discerned considerable genetic diversity among the evaluated okra genotypes. Further, the study selected parental lines and new families with good product profiles, drought tolerance and combining ability for genetic advancement and variety design for water-limited environments in South Africa and similar agroecologies. Iqoqa. I-Okra (i-Abelmoschus esculentus [L.] iMoench; 2n = 2x = 130) iyimifino noma uhlaza olubalulekile nesitshalo esinamafutha. Itshalwa kakhulu ezindaweni ezishisayo nezinezimo zemvula ezilinganiselwe neziguquguqukayo. Ukuntuleka kwezitshalo ezakhiwe ezikwazi ukubekezelela isomiso kuphazamisa ukukhiqizwa kwe-okra emazweni asemazansi ne-Afrika, iSub-Saharan Africa (SSA). Ukwehluka okukhulu kokubhekwayo kanye nokubumbeka kofuzo lwe-okra okuvela e-SSA kuwusizo ekwakhiweni kwezitshalo ezinesivuno esithuthukisiwe sembewu namafutha kanye nokubekezelela isomiso. Nokho, ukwehluka kwezakhi zofuzo ekuqoqweni kwembewu ye-okra e-SSA kusadinga ukubhekisiswa kubhekwe ukuqhunyiswa kwakho nomthelela kwezomnotho nokubumbeka kwakho. Kube nenqubekelaphambili elinganiselwe ekutshalweni kwe-okra ukuze ikwazi ukubekezelela isomiso. Ngakho-ke, izinhloso eziqondile zalolu cwaningo bekuyilezi: i) ukucacisa ngofuzo olukhethiwe lwe-okra ekucindezelweni yisomiso kusetshenziswa isivuno esisha sezithelo kanye nezinto ezihlobene nesivuno ukukhomba nokukhetha uhlobo lofuzo lokukwazi ukubekezelela isomiso, ii) ukunquma ukuhlukahluka kofuzo okukhona phakathi kokukhula kwe-okra kusetshenziswa ukuphindaphinda okulandelanayo okulula, isimple sequence repeats (SSR) kanye nezimpawu ezihambisanayo zohlobo lwesitshalo nokukhetha uhlobo oluhlukile oludalwa ufuzo namandla esitshalo esiwumsuka uma kukhiqizwa izitshalo, iii) ukuhlola amazinga okubekezelela isomiso kwe-okra ekhethwe ngaphambilini okusekelwe ekushintshaneni kwegesi yeqabunga kanye nokwakheka kwamandla esitshalo esuka elangeni kuya ekukhetheni uhlobo lofuzo olusebenza kahle kakhulu ekuzaleni nokubekezelela isomiso, iv) ukuveza amandla kanye nobungxubevange bezitshalo ezikhethiwe ze-okra ukuhlonza lezo ezifanele ukutshalwa ngempumelelo. Ingxenye yokuqala yocwaningo yayihlola izinhlobo zofuzo lwe-okra ezingama-26 ahlolwa endlini eyingilazi nasensimini ngaphansi kwezimo ezihlaselwe isomiso, idrought-stressed (DS) nezingenasomiso, inon-stressed (NS) kusetshenziswa i-13 × 2 alpha lattice design enezimpendulo ezimbili. Imiphumela yembule okubalulekile (P <0.05) imvelo yokuhlola izinhlobo zofuzo -x, imiphumela yokusebenzisana kwesimo samanzi ezindaweni eziningi, okuvumela ukukhethwa kohlobo lofuzo lwe-okra olufanele izimo ezomile. Isivuno ngesitshalo ngasinye, iYield per plant (YPP) (YPP) sihambisana kahle futhi ngokuphawulekayo nobude bembewu entsha, ifresh pod length (FPL) (r = 0.66; P ≤ 0.001), isisindo sembewu eyomile, idry pod weight (DPW) (r = 0.80; P ≤ 0.001) kanye nenani lembewu ngesitshalo ngasinye, inumber of pods per plant (NPP) (r = 0.58; P ≤ 0.001) ngaphansi kwesimo se-DS ensimini. Ucwaningo luhlonze izinhlobo zofuzo ezinesivuno esiphezulu kanye nezinye izinto ezibalulekile, okuyimithombo yofuzo ewusizo yesikhathi esizayo uma kukhethwa izitshalo zangomuso ngokusekelwe ekuhlanganiseni ukuhlaziya amakhono okukwazi ukubekezela ngaphansi kwezimo ezingenawo amanzi anele. Engxenyeni yesibili yocwaningo, ukwenyuka kwe-okra kwesikhashana okungama-26 kwahlolwa kusetshenziswa izinhlobo ezahlukene ze-SSR eziyisishiyagalolunye ngaphansi kwezimo zemvelo ze-DS kanye ne-NS kusetshenziswa i-13 × 2 alpha lattice design enezinhlobo ezimbili ezakhiwe. Omaka be-SSR bembule inani elimaphakathi le-heterozygosity elingu-0.54, okubonisa ukuhlukahluka kofuzo okumaphakathi phakathi kokutholwa kwe-okra okuhloliwe. Ukuhlaziywa okuyinhlanganisela kwezinhlobo ezahlukene kanye ne-SSR kuhlonze izinhlobo ezintathu ezahlukene zofuzo. Isivuno sembewu ngesitshalo ngasinye (PYPP) sasihlotshaniswe kahle futhi ngokwempumelelo nobude bembewu entsha (FPL) (r = 0.81), ngesisindo sangaphezu komhlaba, i-above-ground biomass (ABG) (r = 0.69), kanye nenkomba yokuvuna iharvest index (HI) (r = 0.67) ngaphansi kwezimo ze-DS, kanye ne-FPL (r = 0.83) ne-AGB (r = 0.60) ngaphansi kwezimo ze-NS. Ukukhula okuhambisanayo nokofuzo okufana ne-LS04, i-LS05, i-LS06, i-LS07, i-LS08, i-LS10, i-LS11, i-LS15, i-LS18, i-LS23, i-LS24, kanye ne-LS26 kwahlonzwa ngenxa yamandla akho esivuno esiphezulu nezinto ezihambisanayo zokuthuthukisa isivuno ngaphansi kwezimo ze-DS. Ukukhula okuhlonziwe kuphakanyiswe njengesizinda ezinhlelweni zokuhlanganisa nezokukhetha izitshalo ukuze kuthuthukiswe amandla esivuno se-okra ngaphansi kwezindawo ezinesomiso. Engxenyeni yesithathu yocwaningo, ama-okra angama-26 ahlukahlukene ngokwezakhi zofuzo ahlolelwa ukwakheka kwawo ngaphansi kwezimo ze-NS kanye ne-DS endlini eyingilazi kusetshenziswa i-13 × 2 alpha lattice design kanye nezinhlobo ezintathu zezitshalo ezakhiwe ezinkathini ezimbili zokulima. Ukuhlaziywa kwezibalo kuveze umphumela obalulekile wokusebenzisana kwezinhlobo ezahlukene zofuzo × wesimo sokuhamba kwamanzi ngaphakathi ezitshalweni (T), ukuhlangana kwamanzi, inet CO2 assimilation (A), ukusetshenziswa kwamanzi kwangaphakathi (WUEi), ukusetshenziswa kahle kwamanzi nangokushesha (WUEins), isilinganiso esifanele sefluorescence (Fo′), isilinganiso esiphezulu sefluorescence (Fm′), ukusebenza kahle kokwakha kwamandla ezihlahla akhiqizwa yilanga II (Fv′/Fm′), ukusebenza kahle kokwakheka kwamandla ezihlahla ngokwe-PSII (ɸPSII), iphotochemical quenching (qP), inonphotochemical quenching (qN) kanye nesilinganiso sokuhamba komoya (ETR/A). Imiphumela yaphakamisa ukubekezelela isomiso okuguquguqukayo kokungena kwe-okra okuhloliwe ukuze kukhethwe. Izingxenye eziyinhloko eziyisikhombisa (ama-PC) zanikeza amaphesenti angama-82 engqikithi yokuhlukahluka kwezinto ezihloliwe zobunjalo bezitshalo ngaphansi kwezimo ze-DS. Umkhawulo wokushintshanisa igesi yamaqabunga, i-T, A ne-WUEi, kanye nokwakheka kwamandla emaqabungeni adalwa ilanga okufana ne-ɸPSII, i-Fv′/Fm′, i-qP, i-qN, i-ETR kanye ne-ETR/A kube nezinga eliphezulu lokulayisha futhi lihlotshaniswa ne-WUEi, i-ɸPSII, qP ne-ETR ngaphansi kwezimo ze-DS. Ucwaningo luhlonze izindawo ezikwazi ukumelana nesomiso, okuyi-LS05, i-LS06, i-LS07 ne-LS08 esekelwe ku-A, T, Fm′, Fv′/Fm′ ne-ETR ephezulu, kanye ne-LS10, LS11, LS18 ne-LS23 ngokusekelwe ku-AES, i-Ci, i-Ci /Ca, i-WUEi, i-WUEins, i-ɸPSII kanye ne-AES. Izinhlobo zofuzo ezikhethiwe zathela kakhulu (≥5 g yembewu/isitshalo) ngaphansi kwezimo zengcindezi yesomiso. Izinhlobo zofuzo lwe-okra ezikhethiwe eziyisishiyagalombili zingena engxenyeni yesine yocwaningo ukuze kukhiqizwe inhlanganisela yofuzo olusha kanye nesibalo salezi zitshalo. Izitshalo ezikhethelwe ukukhiqiza ezinye zakhethwa kubhekwa amandla azo okuletha isivuno esiphezulu kanye nokubekezelela ingcindezi yesomiso. Izinhlobo zofuzo zithathwe eMkhandlwini Wocwaningo Lwezolimo-Eziyizitshalo, Izimboni kanye Nezitshalo Zokwelapha i-Agricultural Research Council-Vegetable, Industrial and Medicinal Plants (ARC-VIMP), ezithathwe eNingizimu-Afrika, ezihlanganiswe ezifundeni ezihlukahlukene. Izitshalo ezikhethelwe ukukhiqiza eziyisishiyagalombili zahlolwa kusetshenziswa indlela yokuhlanganisa idiallel eyi-8 × 8 ngesikhathi sonyaka sokutshala sonyaka wezi-2021. Izitshalo ezikhethelwe ukukhiqiza zatshalwa ensimini endaweni yocwaningo lwe-ARC-VIMP ngesikhathi sokutshala ngonyaka wezi-2021/2022. Kamuva, kwasungulwa izizukulwane ezintsha ezingama-28. Izitshalo ezikhethelwe ukukhiqiza eziyisishiyagalombili zahlolwa kusetshenziswa indlela yokuhlola yelattice eyi-12 × 3 enezimpinda ezintathu. Izinhlobo zofuzo zahlolwa ngaphansi kwezimo ze-NS kanye ne-DS ezindaweni ezimbili, okuyizindawo ze-ARC - iLoskop kanye ne-ARC - yaseBrits. Imiphumela ebalulekile (P<0.01) yezinhlobo zofuzo, indawo ezungezile, nezinhlobo zofuzo × ukusebenzisana kwemvelo kwashicilelwa mayelana nokuvunwa kwembewu okusha kanye nezinto eziyingxenye yazo. Ikhono elivamile lokuhlanganisa (i-GCA) kanye nemiphumela ethile yekhono lokuhlanganisa (i-SCA) yayibalulekile (P<0.05) ezintweni eziningi, okubonisa amandla nokungabi namandla kofuzo ukuveza okwakuhlosiwe. Isimo se-GCA × kanye nesimo se-SCA × nokusebenzisana kwakho kwakubalulekile ezinsukwini ezandulela ukuvela kwezimbali (DTF), inani lamaqabunga ngesitshalo ngasinye (NOL), ubude bembewu entsha (FPL), inani lezimbewu ezintsha lesitshalo ngasinye (NFPP) kanye nesivuno sezimbewu ngesitshalo ngasinye konke kwaubalulekile (PYP). Izinhlobo zofuzo zezitshalo ezikhethelwe ukukhiqiza i-LS09, LS10 ne-L24 zibonise imiphumela emihle ye-GCA ye-PYP ngaphansi kwezimo ze-DS futhi zakhethwa ukuba imbewu ebalulekile yokwakheka okuhlukahlukene ukuze kwandiswe ukuhlukahluka kofuzo ukubekezelela isomiso nezinto ezihlobene nesivuno. Amaklumela e-LS01 × LS17, i-LS01 × LS18, i-LS09 × LS10, i-LS09 × LS18, i-LS09 × LS24, i-LS15 × LS18, i-LS15 × LS21, i-LS15 × LS24 LS24 kanye ne-LS17 kwaveza imiphumela emihle ye-SCA ye-PYP ngaphansi kwemibandela ye-DS kanti kuphakanyiswa ukuthi kungaba usizo kwezokukhiqizwa nezokudayiswa kwayo ezindaweni ezinenkinga yamanzi eNingizimu-Afrika. Sekukonke, ucwaningo lwaveza ukuhlukahluka kofuzo okukhulu phakathi kofuzo lwe-okra oluhloliwe. Ngaphezu kwalokho, ucwaningo lukhethe izinhlobo zezitshalo ezizala ezinye neziqhamuka kuzona ezibonakala zinamandla okuletha imikhiqizo emihle ukubekezelela isomiso kanye namandla okuthuthukisa ufuzo kanye nemiklamo ehlukahlukene ukubhekana nezimo zokuntuleka kwamanzi eNingizimu-Afrika kanye nasekutshaleni.
Pre-breeding of sorghum [sorghum bicolor (L.) moench] for drought tolerance in the semi-arid zones of Nigeria=Ukulungisela ukuzalanisa kweSorghum [Sorghum bicolor (L.) Moench] Yokubekezelela Isomiso Ezindaweni Ezomile ZaseNigeria.
(2023) Yahaya, Muhammad Ahmad.; Shimelis, Hussein Ali.
Sorghum [Sorghum bicolor (L.) Moench] is a staple food crop serving millions of people in Africa and Asia's arid and semi-arid agro-ecologies. Sorghum is widely cultivated in Northern Nigeria, serving diverse value chains, including the food and feed sectors and the brewery industry. However, the potential production and productivity of sorghum in Africa, including Northern Nigeria, is constrained by severe drought stress associated with climate change. Furthermore, smallholder farmers in Nigeria still cultivate low-yielding and drought-susceptible unimproved sorghum landraces. Developing drought-tolerant sorghum cultivars adapted to semi-arid regions would enhance yield gains and stability with desirable product profiles according to the needs of the farmers and the marketplace. Therefore, the overall objective of this study was to improve sorghum productivity in Nigeria by developing new generation, locally adapted and drought-tolerant varieties. The specific objectives of this study were to: (1) present the current opportunities and constraints to sorghum production in Nigeria and make recommendations as a guide to new variety design and sustainable production, (2) determine drought tolerance and genotype-byenvironment interaction (GEI) effect on grain yield of a population of African sorghum genotypes to identify high-yielding and drought-adapted genotypes for production and breeding, (3) assess the genetic diversity and deduce the population structure among 200 sorghum accessions to guide the selection of contrasting parents for pre-breeding and breeding of drought-tolerant sorghum cultivars and (4) determine the combining ability, heterosis and gene action conditioning agronomic traits and grain yield among sorghum genotypes to select genetically superior and contrasting parental genotypes and new families for drought tolerance breeding, cultivar release and commercialization. In the first chapter, a participatory rural appraisal (PRA) study was conducted in three selected sorghum growing zones in Northern Nigeria involving 250 farmers. Socio-economic data were collected through surveys and focus group discussions. Results showed that sorghum was cultivated mainly by males (80%) who had grade 6-12 level of education (31.3%), with a productive age of 21-45 years (75.7%) and a household family size of below five members (52.3%). Low-yielding landrace varieties such as Kaura (37.4%) and Fara-fara (29.3%) were the most widely cultivated types across the study zones due to their good grain quality. The major farmers' preferred traits from a sorghum variety were high yield, drought tolerance and Striga resistance. The study recommends integrated sorghum technology development incorporating the described preferences of the farmers for sustainable production and economic gains of the crop. The second chapter examined 225 sorghum genotypes assembled from diverse origins to determine drought tolerance and GEI effects on grain yield. The collections were evaluated under non-stressed (NS), pre-anthesis drought stress (PreADS), and post-anthesis drought stress (PoADS) conditions under field and greenhouse environments. The additive main effect and multiplicative interaction (AMMI) analysis revealed that genotype (G), environment (E), and GEI were significant (p<0.05) and accounted for 38.7, 44.6, and 16.6% of the total explained variation in grain yield, in that order. AMMI 4 was the best-fitting model for genotype selection with better grain yield. Based on AMMI 4 and the Best Linear Unbiased Predictors (BLUPs) analyses, genotypes Yar Lazau and Dangama Wulchichi, with a grain yield of 5.6 t/ha and 6.3 t/ha, were selected as being suitable for non-stressed conditions, respectively. Genotypes ICNSL2014-022-4 and Takumbo with BLUPs of 2.5 t/ha and 2.6 t/ha were best-suited for pre-anthesis drought stress conditions, whereas genotypes Danyar Bana and Gagarau - 4 with BLUPs of 4.2 t/ha and 4.3 t/ha are recommended for post-anthesis drought-prone environments, respectively. The identified sorghum genotypes are valuable genetic resources to develop novel drought tolerance cultivars or for production in dry agro-ecologies of sub-Saharan Africa characterized by pre-and-post anthesis drought stress. In the third chapter, diversity arrays technology (DArT) –derived single nucleotide polymorphism (SNP) markers were used to assess the genetic diversity and discern the population structure of 200 sorghum accessions to select complementary lines for breeding. The markers have moderate discriminatory power, with the polymorphism information content ranging between 0.09 to 0.38. The average gene diversity value (0.32) was high, while the average observed heterozygosity (0.15) was relatively low, a typical value for autogamous crop species like sorghum. The population structure and cluster analyses revealed four main clusters with a high level of genetic diversity among the accessions studied. The variation within populations (41.5%) was significantly higher than that among populations (30.8%) and between samples within a structure (27.7%). The high genetic variation within the population could be attributed to the preservation of sorghum landraces by farmers and differences in the genetic constitution, adaptation and parentage. The study identified distantly related sorghum accessions such as Samsorg 48, Kaura Red Glume (from Cluster 1); Gadam, AS 152 (Cluster 2); CSRO1, ICNSL2014−062 (Cluster 3); and Yalai, Kafi Mori (Cluster 4) useful in developing new gene pools and novel genotypes for the West and Central Africa (WCA) sorghum breeding programs. Based on the phenotypic and genotypic data, 12 contrasting parents were selected for breeding population development with high yield and drought tolerance. In the last chapter, 12 contrasting sorghum parents were selected from a diverse set of 225 genotypes exhibiting variable agronomic traits, including high grain and drought tolerance and farmer-preferred attributes. The 12 parents were crossed using a half-diallel mating design to create 66 F1 progenies. The F1 progenies, the parents, and two check varieties were evaluated under three environments in Nigeria. The results revealed the presence of significant variations amongst test genotypes allowing the selection of suitable parents and hybrids for traits of interest. The contribution of the specific combining ability (SCA) variance to total variance was higher than that of the general combining ability (GCA) for most of the studied traits, indicating that nonadditive gene action was more dominant in conditioning trait inheritance. GCA x environment and SCA x environment interaction effects were significant (p<0.05) for days to anthesis, aboveground biomass and grain yield. Parental genotypes Samsorg 7, Masakwa, and SSV2008091, recorded significant and positive GCA effects for grain yield and are useful germplasm resources for breeding high-yielding cultivars. Crosses AS 152 x SSV2008091, Samsorg 7 x Kurumbasau, AS 152 x ICNSL2014-022-8, and Masakwa x Hindatu exhibited high and positive SCA effects and were the top performers recording above-ground biomass yield of 29.3, 23.4, 27.2 and 16.5 t/ha and grain yield of 6.4, 6.6, 6.6 and 6.5 t/ha, in that order. The crosses exhibited high parent heterosis for grain yield and other agronomic traits, revealing that hybrid breeding is an effective strategy for boosting sorghum production. The newly selected F1 progenies had higher yields than the local checks and are recommended for hybrid or pure line breeding and variety release in Nigeria's drought-prone areas and similar sub-Saharan Africa (SSA) agro-ecologies after continuous selection and multi-environment testing. Overall, the study identified drought stress as the most critical sorghum production constraint in Northern Nigeria. Also, the study highlighted significant genetic diversity among the test genotypes. Best performing genotypes Yar Lazau, ICNSL2014-022-4 and Danyar Bana were selected as suitable for non-stressed, pre-anthesis and post-anthesis drought stress conditions, respectively. The selected genotypes are recommended for production or breeding in droughtprone areas. In addition, the study identified drought-tolerant and early-maturing genotypes (e.g., Samsorg 7, Masakwa, and SSV2008091) with good general combining ability effects for breeding population development and heterosis breeding in the semi-arid region of Northern Nigeria. IQOQA Amabele [Sorghum bicolor (L.) Moench] iyisivuno sokudla okuyinhloko esiphakela izigidi zabantu e-Afrika kanye ne-agro-ecologies eyomile necishe koma yase-Asia. Amabele atshalwa kakhulu eNyakatho yeNigeria, asetshenziselwa uchungechunge lwezinto ezahlukahlukene, kufaka phakathi imikhakha yokudla kanye nomkhakha wokuphiswa kotshwala. Kodwa-ke, ukukhiqizwa okungenzeka kanye nomkhiqizo wamabele e-Afrika, kufaka phakathi iNyakatho yeNigeria, kucindezelwa ukucindezeleka okukhulu kwesomiso okuhambisana nokuguquka kwesimo sezulu. Ngaphezu kwalokho, abalimi abancane eNigeria basalima amabele akhiqiza kancane nesezindaweni ezizwelayo esomisweni. Ukuthuthukisa kokutshalwa kohlobo lwamabele abekezelela isomiso ezifundeni ezomile kungathuthukisa ukuzuza kwesivuno nokuzinza ngamaphrofayili omkhiqizo ofiselekayo ngokwezidingo zabalimi kanye nendawo yemakethe. Izinhloso ngqo zalolu cwaningo zazithi: (1) ukwethula amathuba amanje kanye nezingqinamba zokukhiqiza amabele eNigeria futhi wenze izincomo njengesiqondiso sokuklama izinhlobonhlobo ezintsha kanye nokukhiqizwa okuqhubekayo, (2) ukunquma ukubekezelela isomiso kanye nomphumela wokusebenzisana kwegenotype-by-environment (GEI) ekuvuneni okusanhlamvu kwabantu be-African sorghum genotypes ukuhlonza amagenotypes aphezulu futhi avumelaniswe nesomiso sokukhiqiza nokuzala, (3) ukuhlola ukuhlukahluka kwezakhi zofuzo nokuthola isakhiwo sokusabalala phakathi kokufinyelela kwamabele angama-200 ukuqondisa ukukhethwa kwabazali abahlukile bokuzalanisa kwangaphambili nokuzalanisa amacultivars amabele abekezelela isomiso futhi (4) ukunquma ikhono lokuhlanganisa, iheterosis kanye nesenzo segene esilungisa izici ze-agronomic kanye nesivuno sokusanhlamvu phakathi kwamagenotypes amabele ukukhetha amagenotypes aphakeme ngofuzo futhi ahlukile wabazali kanye nemindeni emisha yokuzalanisa ukubekezelelana kwesomiso, ukukhululwa kwecultivar nokuthengisa. Esahlukweni sokuqala, ucwaningo lwe- participatory rural appraisal (PRA) lwenziwe ezindaweni ezintathu ezikhethiwe zokukhulisa amabele eNyakatho yeNigeria ezibandakanya abalimi abanga-250. Imininingwane yezenhlalo nezomnotho yaqoqwa ngokusebenzisa inhlolovo kanye nezingxoxo zeqembu lokugxila. Imiphumela ikhombise ukuthi amabele alinywa ikakhulukazi ngabesilisa (80%) ababenezinga lemfundo lebanga le-6-12 (31.3%), abaneminyaka ekhiqizayo yeminyaka engama-21-45 (75.7%) kanye nobukhulu bomndeni wasekhaya obungaphansi kwamalungu amahlanu (52.3%). Izinhlobo zomhlaba ezithela kancane ezifana neKaura (37.4%) neFara-fara (29.3%) zaziyizinhlobo ezitshalwa kakhulu kuzo zonke izindawo zokufunda ngenxa yekhwalithi yazo enhle yokusanhlamvu. Izici ezikhethiwe zabalimi abakhulu ezivela ezinhlobonhlobweni zamabele zaziyisivuno esiphezulu, ukubekezelela isomiso nokumelana neStriga. Ucwaningo luncoma ukuthuthukiswa kobuchwepheshe obuhlanganisiwe bamabele okufaka izintandokazi ezichaziwe zabalimi zokukhiqiza okuqhubekayo kanye nokuzuza kwezomnotho kwesivuno. Isahluko sesibili sihlole amagenotypes anga-225 amabele ahlanganiswe kusuka ezimvelaphini ezahlukahlukene ukunquma ukubekezelela isomiso nemiphumela ye-GEI ekuvuneni okusanhlamvu. Amaqoqo ahlolwe ngaphansi kwezimo ezingacindezelekile, ezinon-stressed (NS), ukucindezeleka kwesomiso sangaphambi kwe-anthesis, ipre-anthesis drought stress (PreADS), kanye nepost-anthesis drought stress (PoADS) ngaphansi kwezindawo zensimu kanye negreenhouse. Umphumela oyinhloko wesengezo kanye nokuhlaziywa kokusebenzisana kwemultiplicative (AMMI) kuveze ukuthi igenotype (G), imvelo okuyi-environment (E), ne-GEI yayibalulekile (p<0.05) futhi yaba ngama-38.7, 44.6, ne-16.6% wokuhlukahluka okuphelele okuchaziwe kwesivuno sokusanhlamvu, ngaleyo ndlela. I-AMMI 4 yayiyimodeli efaneleka kakhulu yokukhethwa kwegenotype ngesivuno esingcono sokusanhlamvu. Ngokusekelwe ekuhlaziyweni kwe-AMMI 4 kanye neBest Linear Unbiased Predictors (BLUPs), amagenotypes uYari Lazau noDangama Wulchichi, ngesivuno sokusanhlamvu se-5.6 t / ha ne-6.3 t / ha, bakhethwa njengabafanele izimo ezingacindezelekile, ngokulandelana. IGenotypes ICNSL2014-022-4 neTakumbo enama-BLUP we-2.5 t / ha ne-2.6 t / ha yayilungele kakhulu izimo zokucindezeleka kwesomiso sangaphambi kwe-anthesis, kanti amagenotypes Danyar Bana noGagarau - 4 nge-BLUPs ye-4.2 t / ha ne-4.3 t / ha kunconywa ezindaweni ezithambekele esomisweni ngemuva kwe-anthesis, ngokulandelana. Igenotypes yamabele ehlonziwe iyimithombo yofuzo eyigugu ukuthuthukisa amacultivars okubekezelela isomiso senoveli noma ukukhiqizwa kuma-agro-ecologies omile e-Afrika engezansi kweSahara ebonakala ngokucindezeleka kwesomiso sangaphambi kokuthunyelwe kwe-anthesis. Esahlukweni sesithathu, idiversity arrays technology (DArT) – nezimpawu amaderived single nucleotide polymorphism (SNP) kwasetshenziselwa ukuhlola ukuhlukahluka kwezakhi zofuzo nokuqonda isakhiwo senani sokufinyelela kwamabele okungama-200 ukukhetha imigqa ehambisanayo yokuhiqiza. Izimpawu zinamandla okubandlulula ngokulinganisela, ngokuqukethwe kolwazi lwepolymorphism okuphakathi kuka-0.09 kuya ku-0.38. Inani elijwayelekile lokuhlukahluka kwezakhi zofuzo (0.32) laliphezulu, kanti isilinganiso sabona iheterozygosity (0.15) yayiphansi kakhulu, inani elijwayelekile lezinhlobo zezitshalo ze-autogamous njengamabele. Isakhiwo senani kanye nokuhlaziywa kweqoqo kwaveza amaqoqo amane aphambili anezinga eliphezulu lokuhlukahluka kwezakhi zofuzo phakathi kokufinyelela kokufundiwe. Ukuhlukahluka ngaphakathi kwenani (41.5%) kwakuphakeme kakhulu kunalokho phakathi kwenani (30.8%) naphakathi kwamasampula ngaphakathi kwesakhiwo (27.7%). Ukuhlukahluka okuphezulu kwezakhi zofuzo ngaphakathi kwenani kungabangelwa ukulondolozwa komhlaba wamabele ngabalimi kanye nokwehluka komthethosisekelo wofuzo, ukuzivumelanisa nezimo kanye nokuba ngumzali. Ucwaningo luveze ukufinyelela kwamabele okuhlobene kude njengeSamsorg 48, i-Kaura Red Glume (kusuka ku-Cluster 1); Gadam, AS 152 (Cluster 2); CSRO1, ICNSL2014−062 (Cluster 3); noYalai, uKafi Mori (Cluster 4) owusizo ekuthuthukiseni amachibi amasha ezakhi zofuzo kanye namagenotypes amasha ezinhlelo zokuzalanisa amabele zaseNtshonalanga naphakathi ne-Afrika (WCA). Ngokusekelwe emininingweni yephenotypic negenotypic, abazali abayi-12 abaphikisanayo bakhethwa ukuthuthukisa inani lesivuno esiphezulu nesinokubekezelela isomiso. Esahlukweni sokugcina, imithombo eyi-12 eyahlukene yamabele yakhethwa esethini ehlukahlukene yamagenotypes anga-225 abonisa izici eziguquguqukayo ze-agronomic, kufaka phakathi okusanhlamvu okuphezulu nokubekezelela isomiso kanye nezici ezikhethiwe zomlimi. Imithombo eyi-12 yaxutshwa kusetshenziswa umklamo wokukhwelana wesigamu sediallel ukudala inzalo ye-66 F1. Inzalo ye-F1, imthombo, kanye nezinhlobo ezimbili zokuhlola zahlolwa ngaphansi kwezindawo ezintathu eNigeria. Imiphumela yaveza ukuba khona kokuhlukahluka okuphawulekayo phakathi kwamagenotypes okuhlola okuvumela ukukhethwa kwemithombo efanelekayo kanye namahybrid ezici ezithakazelisayo. Umnikelo ispecific combining ability (SCA) ukuhlukahluka kokuhlukahluka okuphelele kwakuphakeme kunalokho kwekhono igeneral combining ability (GCA) iningi lezici ezifundiwe, okubonisa ukuthi isenzo segene esingangeziwe sasibusa kakhulu esimweni sefa lesici. I-GCA x imvelo kanye ne-SCA x imvelo kwakubalulekile (p<0.05) ezinsukwini kuya ku-anthesis, ngaphezu kwebiomass yomhlaba kanye nesivuno sokusanhlamvu. Amagenotypes awumthombo i-Samsorg 7, i-Masakwa, ne-SSV2008091, aqophe imiphumela ebalulekile futhi emihle ye-GCA yesivuno sokusanhlamvu futhi ayimithombo ewusizo yegermplasm yokuzalanisa amacultivars aphezulu. Ukuxutshwa kwe-AS 152 x SSV2008091, i-Samsorg 7 x Kurumbasau, i-AS 152 x ICNSL2014-022-8, ne-Masakwa x Hindatu kubonise imiphumela ephezulu futhi emihle ye-SCA futhi yayingabadlali abaphezulu abaqopha isivuno se-biomass esingaphezulu komhlaba we-29.3, 23.4, 27.2 ne-16.5 t / ha kanye nesivuno sokusanhlamvu se-6.4, 6.6, 6.6 no-6.5 t / ha, ngaleyo ndlela. Ukuxuba kwabonisa iheterosis ephezulu yomthombo wesivuno sokusanhlamvu nezinye izici ze-agronomic, eveza ukuthi ukuzalanisa ihybrid kuyindlela ephumelelayo yokukhulisa ukukhiqizwa kwamabele. Inzalo esanda kukhethwa ye-F1 yayinesivuno esiphezulu kunokuhlolwa kwendawo futhi inconywa ukuzalanisa umugqa wehybrid noma ohlanzekile kanye nokukhishwa kwezinhlobonhlobo ezindaweni zaseNigeria ezithandwa isomiso kanye ne-agro-ecologies efanayo yesub-Saharan Africa (SSA) ngemuva kokukhethwa okuqhubekayo nokuhlolwa kwemvelo eningi. Sekukonke, ucwaningo lwaveza ukucindezeleka kwesomiso njengengcindezi ebucayi kakhulu yokukhiqiza amabele eNyakatho Nigeria. Futhi, ucwaningo lwaqhakambisa ukuhlukahluka okuphawulekayo kwezakhi zofuzo phakathi kwamagenotypes okuhlola. Amagenotypes enza kahle kakhulu uYar Lazau, ICNSL2014-022-4 noDanyar Bana akhethwa njengafanelekile ezimweni zokucindezeleka ezingacindezelekile, zangaphambi kwe-anthesis kanye nezimo zokucindezeleka kwesomiso ngemuva kwe-anthesis, ngokulandelana. Amagenotypes akhethiwe anconywa ukukhiqizwa noma ukuzala ezindaweni ezithambekele esomisweni. Ngaphezu kwalokho, ucwaningo lwaveza amagenotypes abekezelela isomiso futhi avuthwa ekuqaleni (isib., iSamsorg 7, iMasakwa, ne-SSV2008091) ngemiphumela emihle ejwayelekile yokuhlanganisa ikhono lokuthuthukiswa kwenani elizalayo kanye nokuzalanisa iheterosis esifundeni esomile saseNyakatho Nigeria.
Variation for agronomic traits, biomass allocation, and carbon storage in sorghum (sorghum bicolor [L.] moench) genotypes.
(2024) Ngidi, Asande Satisfy.; Hussein , Shimelis.; Figlan, Sandiswa.; Chaplot, Vincent.
Sorghum (Sorghum bicolor [L.] Moench, 2n = 2x = 20) is an ancient grain crop of Africa cultivated worldwide. The productivity of sorghum is low (< 1.5 t/ha) under smallholder farming systems in the region due to severe drought stress, poor soil health, diseases, insect pests, and noxious weeds. Besides its grain production for food, feed, and industrial raw materials, sorghum produces relatively high biomass for the biofuel and bioplastic industry. Sorghum’s high biomass production can transfer atmospheric carbon (C) to the soil throughout its growth stages, thereby enhancing soil fertility and crop productivity through atmospheric C sequestration. There is a need to select sorghum genotypes with optimised agronomic traits, high biomass production and water and nutrient use efficiencies to enhance economic yield and carbon sequestration capacity. Therefore, the overall aim of this study was to screen and select sorghum genotypes with better agronomic traits, biomass allocation, and C storage. The specific objectives of the study were: i. to quantify the extent of variation in biomass allocation and C storage between major crops, including sorghum for crop production, and C sequestration potential through a meta-analysis. ii. to assess agronomic performance, biomass production and carbon accumulation in selected sorghum genotypes for production and breeding. iii. to assess the extent of genetic variability for agronomic and carbon storage traits in selected sorghum genotypes to identify the best candidates for production or breeding. iv. to assess the trend and magnitude of relationships between agronomic and carbon storage traits in sorghum to identify grain yield and carbon storage contributing traits and to guide future sorghum variety development and release. A metanalysis was conducted from 40 global studies that reported on the allocation of plant biomass and C between roots and shoots of sorghum, maize, and wheat cultivars. Key statistics were calculated to determine the variability among the cultivars for total plant biomass (PB), shoot biomass (SB), root biomass (RB), root-to-shoot biomass ratio (RS), total plant carbon content (PCc), shoot carbon content (SCc), root carbon content (RCc), total plant carbon stock (PCs), shoot carbon stock (SCs), root carbon stock (RCs), and root-to-shoot carbon stock ratio (RCs/SCs). Maize exhibited the highest variability for PB (with a coefficient of variation [CV] of 31.2% and a mean of 4.2±1.3 Mg ha-1 yr-1), followed by wheat (CV of 24.2% and mean of 1.5±0.4 Mg ha-1 yr-1) and sorghum (16.8% and 2.0±0.8 Mg ha-1), respectively. A similar trend was observed for PCs, with maize (CV of 40.1% and mean of 1.6±0.7 Mg ha-1) showing the highest total plant C stock variability, followed by wheat (24.4% and 0.2±0.1 Mg ha-1), and sorghum (16.3% and 0.9±0.3 Mg ha-1), respectively. Maize exhibited the highest variability for RS (with a CV of 24.4% and mean of 0.1±0.03), while wheat exhibited the highest variability for RCs/SCs (30.92% and 0.2±0.05). The meta-analysis revealed that maize and sorghum have the highest variability for total plant biomass and plant carbon stocks, while wheat exhibits the highest variability for the below-ground biomass and carbon stocks. In the first experiment, 50 sorghum genotypes were evaluated using a 5 x 10 alpha lattice design with two replications at three locations (Silverton, Ukulinga, and Bethlehem) in South Africa during the 2022/23 growing season. The following agronomic and carbon storage traits were assessed: days to 50% heading (DTH), days to 50% maturity (DTM), plant height (PH), PB, SB, RB, RS, GY, HI, GCc, SCc, RCc, PCs, SCs, RCs, RCs/SCs, and grain carbon stock (GCs). A combined analysis of variance revealed significant (P < 0.05) genotype x location interaction for DTH, DTM, PH, PB, SB, RB, RS, and GY. Genotypes AS115, AS251, and AS134 were the best performing with the highest GY of 5.08 g plant-1, 21.83 g plant-1, and 21.42 g plant-1, respectively. Genotypes AS122 and AS27 ranked first and second, respectively, for all the carbon stock parameters except for RCs, whereas genotype AS108 had the highest RCs of 8.87 g plant-1. The principal component analysis identified GY, DTH, PH, PB, SB, RB, RCs, RCs/SCs, PCs, SCs, and GCs as the most discriminated traits among the test genotypes. The cluster analysis using agronomic and carbon-related parameters delineated the test genotypes into three genetic groups. The selected sorghum genotypes are recommended for further breeding and variety release adapted to various agroecologies in South Africa. Data from field experiments were computed to deduce variance components, heritability, and genetic advance to guide genotype selection. Higher phenotypic coefficient of variation (PCV) were recorded for PH (68.91%), followed by GY (51.8%), RB (50.51%), RS (41.96%), RCs/SCs (44.90%), and GCs (41.90%). In contrast, higher genotypic coefficient of variations (GCV) were recorded for GY (45.92%), followed by RB (39.24%), RCs/SCs (38.45), and RCs (34.62). The high PCV and GCV values suggest the availability of genetic variability among the test genotypes for the assessed traits. High to moderate broad-sense heritability and genetic advance were observed for HI (83.76 and 24.53%), GY (78.59 and 9.98%), PB (74.14 and 13.18%) and PCs (53.63 and 37.57%), respectively, suggesting a marked genetic contribution to the traits. High broad-sense heritability combined with increased genetic advance were computed for PB, RB, GY, HI, RS, GCs, RCs, and RCs/SCs, indicating that genetic effects primarily control these traits. In the third experimental chapter, correlation and path coefficient analyses were computed to discern the trend and magnitude of associations of assembled traits to guide simultaneous selection for enhanced grain yield, its components and carbon storage. Significant (P < 0.05) positive phenotypic and genotypic correlations were observed between GY with HI at r = 0.79 and r = 0.76, DTH (r = 0.31 and r = 0.13), PH (r = 0.27 and r = 0.1), PB (r = 0.02 and r = 0.01), RB (r = 0.06 and r = 0.05), respectively. Further, the path analysis revealed significant positive direct effects of SB (0.61) and RB (0.46) on GY. The RS exerted a positive significant genotypic indirect effect (0.26) on GY through SB. The overall association analyses revealed that PB, SB, RB, RS, RCs, and RCs/SCs significantly influenced GY performance and are the principal traits when selecting sorghum genotypes with high carbon storage capacity. The present study identified the following promising genotypes: AS251, SS27, AS134, AS203, and AS563 for their high biomass production, grain yield, and C sequestration potentials. The identified genotypes could be advanced for cultivar development and further evaluated for net carbon contribution to the soil.

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