Breeding for durable resistance to Cercospora Leaf Spot diseases in groundnuts (Arachis hypogaea L.) in Tanzania.

Abstract

Lack of high yielding groundnut cultivars tolerant to Cercospora leaf spot disease (CLD) and stable across different environments is one of the challenges to groundnut production by smallholder farmers in Tanzania. This makes selection of adaptable high yielding stable varieties under the different agro-ecological zones before release a very important part of the breeding program as this has an impact on the adoption and productivity of the cultivar. The objectives of this study were to evaluate and select genotypes that are tolerant to CLD, high yielding and identify environments that can be used for selection. A total of 24 groundnut genotypes comprising of six double cross population, twelve single cross parents and six checks from the three botanical groups (Valencia, Virginia and Spanish) were evaluated over six environments (viz Tumbi in Tabora region, Mlali, Ilindi and Hombolo in Dodoma region, Njoro in Manyara region and Ikhanoda in Singida region in Tanzania in the 2016/17 cropping season. The experiment was laid out in a 6x4 alpha lattice design replicated twice. Additive main effect and multiplicative interaction (AMMI) model was used in analysis. The study result revealed that, Tumbi (E1) was the most discriminating environment followed by Ilindi (E3), Mlali (E2), Hombolo (E4), Njoro (E5) and Ikhanoda (E6) respectively. The Hombolo (E4), Njoro (E5) and Ikhanoda (E6) environments showed a high correlation, therefore, indirect selection can be applied across the environments. The existence of such unique correlation among test environments has the advantage of reducing the number of sites used for evaluation and thus reducing cost of evaluating the genotypes. Using the first and second interaction principal component axis (IPCA1 and IPCA 2) genotype G2, G5, G11, G7, G3 and G8 was identified as the best performing genotypes however, G7 had relative stability and adaptability across the testing environments. These crosses will be advanced through selfing and selection of CLD tolerant progenies that are yielding high. Key words: AMMI, Cercospora leaf spot disease, Environments, Groundnuts, IPCA1, IPCA2, Stability, Adaptability.