Characterization of sorghum [Sorghum bicolor (l.) Moench] parental lines and prediction of their hybrid performance under simulated water and population density stress.
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Date
2006
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Abstract
Sorghum breeders have not made much yield improvement in new sorghum varieties in
Kenya since Serena in was released in the late 1960s. KARI Mtama-1 which was released
in 1993 has no yield advantage over Serena. A yield plateau for sorghum in Kenya is
apparent. A new breeding approach was adopted to break that yield barrier. Development
of hybrid sorghum was proposed and is expected to break the yield barrier and also
deliver cultivars that meet farmers' main requirements. The objectives of the study were to
(1) identify farmers' requirements in sorghum cultivars, constraints to sorghum production
and why improved cultivars from research are not being adopted, (2) characterize male
and female parents and establish if genetic distance could identify superior parent
populations for hybrid production (3) estimate genetic variance components and
determine the possibility of using GCA and SCA estimates in choosing parents for use in
hybrid production, (4) test hybrids and open pollinated variety (OPV) parental lines for
stress tolerance and identify tolerant hybrids for further testing and, (5) compare single
cross hybrids and OPV varieties in yield performance. Participatory rural appraisal in
Kitengei and Nzambani areas of Kambu showed that sorghum was especially important in
semi-arid parts of Kenya. Food, trade, feed, nursing food and thatching were the most
important uses of sorghum. High grain and stover yield, large grain size, early maturity,
drought tolerance, pest and disease resistance, coloured grain and intermediate plant
height were the major requirements of farmers. Fifty-three pollinators and forty-one male
sterile parents were introduced from four sources and screened together with 27 pollen
parents from Kenya. Parents and hybrids were tested in 4 environments: high and low
plant density, in high and low moisture regimes laid out in a triple square lattice design in
Kenya, with parents having two additional tests in South Africa. Males, females, sexes and
parental sources differed significantly in head weight. There were sex x country and sex x
environment interactions for head weight. Genetically distant parents' populations had
higher chances of superior heterosis. Parents showed significant additive genetic variance
in head weight. The regression of non-additive to additive genetic variance was roughly
one and significant. Three female and five male parents were suitable for production of
hybrids adapted to multiple environments. Hybrids and OPV lines significantly varied in
head weight. Hybrids were superior to OPV lines in most agronomic traits. Economic
superiority of the hybrids was sufficient to cover cost of hybrid production and distribution
in Kenya. Hybrids and OPV lines varied significantly for plant density stress. Hybrids were
less sensitive to stress and more productive than OPV lines under population density
stress. KARI varieties were sensitive to plant density stress. In general low sensitivity to
stress was beneficial and hybrids had superior yield to inbred varieties.
Description
Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.
Keywords
Sorghum--Breeding--Kenya., Sorghum--Breeding--Africa., Sorghum--Kenya--Genetics., Sorghum--Varieties--Kenya., Sorghum--Yields--Kenya., Selection (Plant breeding)--Kenya., Sorghum--Spacing--Kenya., Sorghum--Effect of water levels on--Kenya., Sorghum--Effect of stress on--Kenya., Theses--Plant breeding.