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An Investigation of Drought Tolerance Indices in Some Soybean Genotypes under Restricted Irrigation Conditions

In order to study the most effective traits as well as drought tolerance indices and to introduce tolerant soybean genotypes in drought conditions, 49 soybean genotypes were evaluated in a simple lattice design at the SPII research farm in year 1999. Two levels of irrigation with 18 day (drought stress) and 8 day (control) intervals were considered after flowering in the 49 genotypes. In the experiment some traits such as days to the end of flowering, days to maturity, vegetative growth duration, plant height, root length, leaf area mean, number of nodes, branches, and pods, yield per plot , one hundred grain weight, oil, as well as protein percent were evaluated. The results showed that three traits of yield per plot, plant height and number of pods per plant diminished under drought stress conditions. Yield reduction was due to flower abortion under drought stress treatment which had lead to the number of pods and grains being reduced per plant. The calculated correlation coefficients as well as tolerance indices (TOL, SSI, HARM, MP, GMP and STI) showed STI and GMP were the best indices for selection of tolerant genotypes. The biplot display of 39 early maturing genotypes which acquired the most stress as well as comparison of GMP and STI indices in each genotype indicated eight tolerant genotypes namely, Bonus, Kador, Union, Willams, linen S.RF450 * Hobbit, L.17, M.4, Line 29 S.R.F 450 * Hobbit.