POTENTIAL OF SELECTED SORGHUM LINES FOR PRODUCTION OF HYBRIDS FOR DRY AGRO-ECOLOGIES OF EAST AFRICA

Abstract

Sorghum (Sorghum bicolor L. Moench) is staple crop to farmers living in dry lands and sub-humid areas of East Africa, but yield is low (<1tha-1) due to lack of hybrids. Hybrid sorghum can significantly increase productivity. Hybrid development requires diverse and adapted parental lines. A study was conducted between 2010 and 2012 using 121 ICRISAT sorghum lines at selected dry lowland (Kiboko and Miwleni) and sub-humid (Ukiriguru) agro-ecologies to determine performance and genetic diversity, develop test hybrids and assess the heritability of yield and its components, and the combining abilities. There were significant (p ≤ 0.05) phenotypic variations among the sorghum lines and hybrids for yield and its related trait. Highest yielder was ICSR93034, (4.0 t/ha) while the check yielded 2.3t/ha. There was significant genotype and genotype-by-environment interaction suggesting importance of evaluating breeding materials under different agroecologies for effective exploitation of plant vigour. IESV91104DL and IESV91131DL are suitable for dry lowlands whereas IESV23019 and KARI MTAMA1 are for sub-humid environments. These lines yielded high, took short period to flower indicative of early maturity; and were short stature suitable for dry lands and sub-humid environments. Some A’s viz A2DN55, ICSV189, ICSA452, ICSA479, ICSA73, ICSA77 and ICSA469 had low and inconsistent restoration, 0 to 20% and should be avoided in hybrid development programs. Plant height was highly heritable (0.96). Awns at maturity expressed highest genotypic coefficient of variation (GCV%) and phenotypic coefficient of variation (PCV%) across locations. Lines IEBS2, ICSB15, BTX623, IESV91104DL, IESV91131DL and KARI-MTAMA1 were top general combiners for yield and days to 50% flowering (DAF). Hybrids ICSA44×IESV91104DL, ICSA15×IESV91104DL, TX623×IESV91104DL and ICSA12×KARI-MTAMA1 yielded high (6.9t/ha), matured early, 60 to 63 DAF, and had good stature (1.1 m to 2.3m) tall. Heterobeltiosis for DAF varied from -5.23 to -14% indicative of early maturity and can escape terminal drought in rain-fed agriculture which is the characteristic of East African cultivation system. Heterotic response for yield and its components resulted from some cross combinations facilitate to develop high yield sorghum hybrids and varieties suitable for the dry lowland and sub-humid environments than the currently grown genotypes in the region. It is confirmed that significant diversity and hybridity potential exist in sorghum collections held at ICRISAT. Identified genotypes in this study could be advanced to National Performance Trials (NPT) for commercial release in Tanzania and Kenya. Future evaluation for drought tolerance should not involve Kiboko and Miwaleni together, one of the two can give enough information.