GENETIC VARIABILITY OF ETHIOPIAN SORGHUM [SORGHUM BICOLOR (L.) MOENCH] GENOTYPES FOR WATER USE EFFICIENCY, DROUGHT TOLERANCE AND GRAIN YIELD

Abstract

Sorghum is one of the most important cereal crops grown in the world for human consumption, animal feed and bio-energy. Biotic and abiotic stress are the most dominant constraints for the production and productivity of the crop. The study was conducted with the objectives of estimating water use efficiency, drought tolerance and grain yield of sorghum genotypes under stress condition. The trials were conducted using 64 sorghum genotypes using alpha lattice design with two replications at Werer and Melkassa. The plant height, panicle length, flag leaf length, stand count at harvest, thousand seed weight, water use, days to flowering, days to maturity and grain yield data were recorded. The data were subjected to analysis of variance using generalized linear model and means were separated using Duncan Multiple Range Test. Analysis of variance for yield revealed significant difference between replications and genotypes under non-stress condition while there was non-significant variation between blocks. Similarly, there was significant and very highly significant difference among genotypes, respectively under stress condition while variation between blocks was non-significant. There were significant differences among the traits measured. Grain yield showed positive and significant phenotypic and genotypic correlations with days to 50% flowering (rg=0.22,rp=0.40), days to maturity (rg=0.24, rp=0.34), stem fresh biomass (rg=0.31,rp=0.48), stem dry biomass(rg=0.34,rp=0.33), head fresh weight (rg=0.71,rp=0.90), dry head weight (rg=0.42,rp=1.07), and thousand seed weight(rg=0.69,rp=0.1.18). Thousand seed weight (TSW) also showed positive and significant phenotypic and genotypic correlation with days to 50% flowering (rg=0.23, rp=0.33), days to maturity (rg=0.15, rp=0.49), stem fresh biomass (rg=0.19, rp=0.46), head fresh weight (rg=0.34, rp=0.81), dry head weight (rg=0.19, rp=1.28). The first four principal components (PCs), with eigenvalues greater than 1, explained about 81.4% of the total variation among genotypes for all traits. Highest heritability estimates were found in Plant height and Days to maturity, while medium and low heritability was obtained for the other traits. Values of genetic advance shown very high value for panicle length, days to flowering, panicle exertion, plant height, days to maturity and grain yield which is greater than 20%, moderate GAM value occurred in water use efficiency. Thousand seed weight and low GAM (> 10%) revealed in stem biomass and stem dry biomass. Greater magnitude of broad sense heritability coupled with higher genetic advance in traits studied provided the evidence that these were under the control of additive genetic effects indicating that selection in the genotypes should lead to a fast improvement of the traits. Water use efficiency has shown a highly significant positive genotypic correlation to stand count at harvest, days to maturity, stem biomass, stem dry biomass, head fresh biomass, head dry weight, and grain yield. Phenotypic correlation also found that a highly significant positive correlation to stand count at harvest, flag leaf width, stem biomass, head fresh weight, head dry weight, thousand seed weight and grain yield for the stress regime. xii Generally, genotypes Acc20842, Acc216739, ETSC300302, and Acc28546 recorded a high SSI and TOL index values which are considered as less drought tolerant. In addition genotypes Acc8218, Acc220268, Acc28549, Acc235791, Acc220249, Acc234115, and Acc28551 showed no or negligible yield reduction upon stress treatment that may be due to their drought tolerance feature.