Characterisation of Selected Sorghum Genotypes in Zambia for Field Traits and Aluminium Tolerance

Sorghum (Sorghum bicolor L.) is a major crop of the hotter and drier regions of the tropics and subtropics grown by resource poor farmers for their subsistence. It can also be cultivated in marginal lands and areas of high rainfall characterized by low pH soils high in aluminum (Al). The overall objective of this study was to characterize selected sorghum genotypes for Al tolerance. The specific objectives were to determine performance of selected sorghum genotypes grown in Al prone environments, establish the relationship between yield components and overall yield and develop a selection criterion for Al tolerance in sorghum. Twenty sorghum genotypes (previously identified) were evaluated at three sites with high soil Al levels. Significant differences (P=0.05) were observed for seven of the nine parameters that were measured and/or derived. Interactions were significant for plant height and grain yield. The entries were significantly different for all the measured and derived parameters except for plant count, pest score and agronomic score. Significant differences were observed for location on days to 50% flowering, plant height, pest score, sundried head weight and grain yield. Associations between the measured and/or derived parameters and grain yield were significant. The direct path effects were low except for head weight which had a significant contribution of 1.4. Direct contributions on yield by other parameters were less than 0.1. Plant height, pest score and agronomic score had significant indirect effects of 0.7, 0.7 and 0.5 respectively via head weight. Selection of head weight and head harvest index would contribute effectively to high yielding sorghum genotypes in low pH soil with high Al. The superior genotypes recommended for Al tolerance are entries 11, 16, 17 and 20.