Evaluation of drought tolerance indices and their correlations in sugar beet lines

Current study aimed at determining the most reliable drought tolerant criteria for identification of sugar beet genotypes. A split plot design based on randomized complete block design with three replications was applied at Motahari Research Station, Karaj, Iran in 2012. Two irrigation treatments including normal irrigation after 80-90 mm and irrigation after 270 mm evaporation (stress condition) from class A evaporation pan were allocated to main plots and 36 sugar beet genotypes to sub-plots. Stress susceptibility index (SSI), harmonic mean (Harm), tolerance (TOL), mean productivity (MP), yield stability (YSI), drought response (DRI), stress tolerance (STI), geometric mean productivity (GMP), yield index (YI), drought resistance (DI), modified stress tolerance (MSTI), stress non-stress production (SNPI), abiotic tolerance index (ATI), stress susceptibility percentage (SSPI), relative decrease in yield (RDY) indices were estimated. According to the abovementioned criteria, genotypes 3, 35, 32, 5, 34, 13, 26, and 36 with high yield under both normal and stress conditions were ranked in group A. Comparison of the 16 indices showed that GMP, Harm, MSTI (based on K2STI), SNPI, STI, YI and YS indices could identify the group A genotypes accurately. However, the results of correlation coefficient between drought tolerance indices and raw sugar yield under normal and stress conditions showed the indices SSPI, ATI, MP, TOL, GMP, STI, RDY, Harm, YI, SNPI and DI as superior criteria.