Evaluation of Drought Tolerance Indices in Yield of Six Cultivars of Virginia Tobacco (Nicotiana tabacum L.)

To evaluate drought tolerance of tobacco cultivars by quantitative indices, a research was conducted using factorial experiment on the basis of completely randomized design, with six cultivars of Virginia tobacco in four replications in the potty conditions during 2005. Cultivars including K326F, C176, C347, C258, C319 and MN944F were compared in two levels of irrigation including irrigation at the level of field capacity (75% available water) and stress condition in the fast growth stage (irrigation at 25% available water). To evaluate drought tolerance of cultivars, some related indices such as mean productivity (MP), tolerance (TOL), stress susceptibility index (SSI), geometric mean productivity (GMP) and stress tolerance index (STI) were used. On the basis of their correlation with yield under stress and non-stress conditions, MP, GMP, STI were selected as the best indices to separate tolerant cultivars. In respect of these indices, among the cultivars of tobacco, K326F with high yield and drought tolerance characteristics was selected. Using biplot method and comparison of best indices measures for each cultivar, C347 was identified as the most sensitive cultivar to drought stress.