Resistance to the whitefly bemisia tabaci (Gennadius) in cotton genotypes

This study on the whitefly Bemisia tabaci (Gennadius) on cotton (Gossypium spp.) evaluates the resistant mechanisms viz., antixenosis, antibiosis and tolerance under free-choice and no-choice conditions. Results reveal that the whiteflies select the host only after initial probing. The genotypes LRA-5166 and DSC-1501 were the least preferred for oviposition under free-choice condition and reduced the nymphal survival (47.50 and 52.50 days), net reproductive rate (R₀) (5.45 and 6.31/ female/ lifetime) and intrinsic rate of increase (r_m) (0.061 and 0.063) under no-choice condition, respectively. Thus, these genotypes exhibited antixenosis and antibiosis. The genotype CCH-4474 demonstrated tolerance with less reduction in the plant height (20.77%), number of internodes (15.27%) and chlorophyll content (13.44%). The high level of resistance in the genotypes LRA-5166 and DSC-1501 could be exploited for developing resistant cotton cultivar.