Yield and yield stability of four population types of grain sorghum in a semi-arid area of Kenya

Sorghum [Sorghum bicolor (L.) Moench] is widely grown in semiarid tropics w here local farmers depend on the adaptability of their rainfed crops to unp redictable drought and other stress factors. To investigate the effects of heterozygosity and heterogeneity on the adaptability of grain sorghum, two sets of material, each containing 12 parent lines, six single-cross hybrids , six two-component blends of parent lines, and six two-component hybrid bl ends were grown in eight macro-environments in the semi-arid Makueni Distri ct of Kenya, during 1991 through 1993. Environmental means for grain yield ranged from 584 to 47 g m(-2). In all environments, hybrids outyielded thei r parent lines, with a mean relative hybrid superiority of 54%. Blending ef fects were non-significant. Combined analyses of variance were computed wit h logarithmically transformed data. Entry x environment interaction effects were more important than genetic effects. Lines in pure stand contributed most to the total entry x environment interaction variance. Wide ranges wer e found within all four groups for stability parameters derived from regres sion analysis. On average, hybrids in pure stand had most favorable values. Pattern analysis (classification and ordination techniques) was applied to the environment-standardized matrix of entry means from the individual env ironments. A one-way classification clearly distinguished homozygous from h eterozygous entries. Heterogeneous entries were not consistently grouped to gether. Performance plots for different entry groups showed various pattern s of adaptation and illustrated the superiority of heterozygous entries. Th e biplot from ordination underlined the importance of entry X type-of-droug ht-stress interaction. Principal Components 1 and 2 were highly correlated with entries' mean yield and regression coefficient, respectively. Breeding heterozygous cultivars could contribute to increased grain yields and impr oved yielding stability of sorghum in the target area of Kenya.