The relationship between morphological characteristics of cotton (Gossypium spp.) genotypes and whitefly (Bemisia tabaci Genn.) population in the Gorgan region

Tolerant cultivars are the important components of integrated pest management. In this study, 20 different cotton genotypes were evaluated during 2 years using RCBD in Gorgan in order to compare genotypes for frequency of whitefly (Bemisia tabaci Genn.) eggs, nymphs and adult population, and also to determine the relationship between effective morphological characteristics of cotton and pest accumulation. Results showed significant differences among genotypes for majority of morphological characteristics and B.tabaci population. Deformed Leaf, Red Leaf Okra, Broad Red Leaf, Siokra and Frigo Bracteeles genotypes had the least nymph's density, but Termez, Alyaf Rangi and Pak showed the highest density of nymphs. Regarding adult whitefly population, Deformed Leaf genotype had the least pest density, and also Siokra, Red Leaf Okra, Super Okra and Broad Red Leaf genotypes had the low pollution, but Termez, Alyaf Rangi, Pak and Smooth Leaf had the highest density of adult whiteflies. Results suggested that leaf shape and area could be supposed as two most important factors affecting pest population density, as the more reducing leaf area and more deep evolve its dents, the less pest population density. In addition, the low pest population on red leaf genotypes suggested non-preference or escape mechanism. There was positive correlation between density and height of pubescences and whitefly population density, as the more and higher pubescences, the more pest population. In addition, there was positive correlation between leaf area, plant height and sympodia number with whitefly population density, but there was negative correlation between the traits of leaf color, flower color and shape of the flower bracts with density of this pest. Overall, results showed that the characteristics of okra leaf shape, low leaf area, red plants, low density of pubescences and high density of glands could be effective in reducing the whitefly population density.