Evaluation of some agronomic traits and estimation of drought resistance indices for seed yield in sunflower inbred lines under with and without water stress

In order to evaluation and screening of drought tolerant sunflower inbred lines, an experiment was conducted in randomized complete block design (RCBD) with six replications at Khoy agriculture and natural resources station during 2014 and 2015. Twenty sunflower lines were evaluated in favored and limited irrigation conditions. Drought stress was imposed by water withholding in R4-R6 stages. The result showed that drought stress reduced plant height and stem diameter, seed weight, head diameter, growth duration and grain yield. Significant differences were observed among lines for these traits. Mean comparison showed that the highest seed yield was belonged to RGK55, BGK375 and BGK1 in non-stressed; and BGK1 and BGK375 in stressed conditions. For evaluation of drought stress tolerance indices such as mean productivity (MP), geometric mean productivity (GMP), stress tolerance index (STI), tolerance index (TOL), stress sensitivity index (SSI), harmonic mean of productivity (HARM), yield stability index (YSI), sensitive drought index (SDI), stress susceptibility percentage index (SSPI), relative drought index (RDI), modified stress tolerance index in optimum irrigation (K1STI), modified stress tolerance index in moderate and severe stress (K2STI) were used. According to these indices and simple correlation, STI, MP, GMP and HARM were the most suitable indices for selection of genotypes under stress and non-stress conditions. Based on the results, BGK1 and BGK375 were determined as the most drought tolerant lines where as RGK23 and RGK26 had the lowest yield and most sensitive to drought stress.