Assessment of yield stability in sorghum

Sorghum (Sorghum bicolor L. (Moench)) is the third major cereal crop in Ethiopia in terms of area and production next to tef (Eragrostis tef) and maize (Zea mays). It is the major crop in drought stressed lowland areas that cover 66% of the total arable land in the country. Yield stability is one of the setbacks facing plant breeders in developing widely adapted varieties with superior yield. The present study was carried out to investigate the effect of genotype by environment (GxE) on the yield stability of sorghum (Sorghum bicolor) using fifteengenotypes in eight environments (Locations x years combination). There were significant differences among the genotypes, the environments and GxE interactions. Thus, the three types of univariate stability models: Type-1 (CVi and S2i), Type-2 (W2i, s2i, and bi) and Type-3 (Sd2i) were compared for ranking of the genotypes. Theparameters of W2i and si2 had perfect positive correlation (r=1.0) and strong positive correlation with bi (r=0.80),but either weak or no correlation with the rest of the parameters. Similarly, CVi and S2i had strong rank correlation(r=0.97) but both had either very weak or no rank correlation with the rest of the parameters tested. The Sd2i had very weak negative correlation with the remaining parameters. Based on the three stability statistics, the different genotypes were classified as stable. To compliment and verify findings of this univariate approach, the GxE which uses a mulivariate approach was used. The multivariate approach (AMMI model) gives a broader inference. Based on the AMMI model, genotypes 2 and 5 were the most stable, although genotypes 1 and 3 had satisfactory levels of yield performance as well as stability. Therefore, these four genotypes with wider adaptationare recommended for sorghum growing dry lowlands of the country.