Genotype x environment interaction for yield and reaction to leaf spot infections in groundnut in semiarid West Africa. Genotype x interaction and leaf spot resistance in groundnut

Capitalizing on the yield potential in available groundnut germplasm, and high stability of kernel yield are important requirements for groundnut producers in semiarid environments. Forty-seven groundnut genotypes were evaluated from 2003 to 2005 at 4 locations representative of the Guinea and Sudan savanna ecologies in Ghana. The objectives were to assess genotypic differences in reaction to early and late leaf spot infections under natural field conditions, assess the extent of genotype x environment (G x E) interaction for kernel yield, and determine the relationship between yield potential and yield stability. Genotypes differed significantly in their reaction to leaf spot infections indicated by the area under disease progress curve (AUDPC). Genotypic AUDPC was negatively correlated with maturity period (P < 0.01), with kernel yield (P < 0.05) at each of the 3 locations in the Guinea savanna ecology but not in the Sudan savanna ecology and with each of four stability parameters (P < 0.05). High or low yielding genotypes were grouped based on Dunnett's test at P < 0.10. High yielding groups had significantly low AUDPC, high biomass, high partitioning of dry matter for kernel growth, and were later in maturity compared to low yielding genotypes. Significant G x E interaction effect for kernel yield was dominated mainly by the lack of correlation among environments variance (76-78%) relative to the heterogeneity of genotypic variance component (22-24%). Stability of yield assessed through the among-environment variance, Wricke's ecovalence, and Finlay-Wilkinson regression coefficient revealed that genotypes in the higher yielding group were relatively unstable compared to the low yielding group. Indicated by the Kataoka's index of yield reliability, however, relatively unstable genotypes in the high yielding group are expected to be more productive even under assumptions of high risk aversion (P = 0.75-0.95) compared to the more stable, low yielding genotypes. The findings indicate that deploying these recently developed germplasm in semiarid regions in West Africa provides a better match to farmers' risk-averse strategies compared with the use of existing earlier maturing cultivars.