Evaluation of yield of promising dual purpose grain- forage sorghum lines (Sorghum bicolor L. Moench) using drought tolerance indices

To evaluate and select the promising lines of dual purpose grain-forage sorghum under drought stress conditions, a field experiment assplit plot arrangements in randomized complete block design with three replications was carried out atresearch field station of Seed and Plant Improvement Research Institute, Karaj, Iran, in 2014 and 2015 growing seasons. Irrigation levels (60 mm, 120 mm and 180 mm of evaporation from class A evaportation pan) were assigned to main plotsand 10 sorghum lines (KDFGS4, KDFGS6, KDFGS9, KDFGS10, KDFGS12, KDFGS13, KDFGS14, KDFGS16, KDFGS20 and KDFGS21) randomized in sub-plots. Combined analysis of variance showed that irrigation effect was significant (P≤0.01) on plant height and grain yield.  However, irrigation effect was significant (P≤0.05) on dry weight, fresh weight, biological yield and 1000 grain weight. The highest fresh and dry weights of forage was obtained in 60 mm (normal) treatment. The results of biplot multivariate analysis and correlation between droughr indices and grain yield under non-stress and stress conditions showed that MP, GMP, and STI were important in predicting performance of sorghum genotypes. These indices can be used for selecting drought tolerant genotypes. Lines No. 8 (KDFGS16), 1 (KDFGS4), 9 (KDFGS20) and 3 (KDFGS9) were high yielding. The highest correlation coefficients between tolerance indices in stress and non-stress conditions was observed for MP, GMP, STI and YI.. Considering the results of biplot analysis and MP, GMP and STI, sorghum genotypes KDFGS20, KDFGS13. KDFGS14, KDFGS21, KDFGS16, KDFGS4 (lines No. 9, 6, 7, 10, 8 and 1, respectively) were identified drought as tolerant.