Effect of drought stress on yield and its components in four cotton genotypes in Darab region.

To evaluate the effect of drought stress on yield and its components in cotton and introduce the suitable cotton genotype for Darab region, four genotypes of cotton (Gossypium hirsutum) were studied in a filed experiment using split plot arrangement in a randomized complete blocks design (RCBD) with three replications. Main factor, included four levels of irrigation (70, 100, 130 and 160 mm cumulative evaporation from class A pan) and four genotypes consisting of Siokra, 818-312, B-557 and Bakhtegan (control) assigned as sub-plots. Studied traits were plant height, length and numbers of monopodial (L.M.B and N.M.B) and sympodial branches (S.B), boll number, boll weight, yield and earliness. Also leaf area and water use efficiency were studied. Analysis of variance showed that the effect of irrigation interval on plant height, L.M.B, L.S.B, boll weight, and earliness were highly significant. Drought stress reduced boll weight, however, Bakhtegan cultivar had the biggest and heaviest bolls. The 70 and 100 mm irrigated treatments were in one group and 130 and 160 mm treatments grouped togather.Therefore, there was high significant difference between them. The genotype 818-312 had the highest yield of 3322 Kg/ha in 100 mm (I2) irrigation treatment. Water used in this treatment was 9646 m3/ha in 13 times and irrigation intervals were approximately every 10 days.