Evaluating Genotypic Resistance in Transgenic and Conventional Cotton (Gossypium hirsutum L.) Varieties Against Whitefly (Bemisia tabaci) Population Dynamics
Cotton (Gossypium hirsutum L.) serves as a cornerstone of Pakistan’s agricultural economy, yet its productivity is severely threatened by the sap-sucking whitefly (Bemisia tabaci). While chemical control strategies face rising insecticide resistance, host plant resistance offers a sustainable alternative. This study evaluated the population dynamics of whitefly nymphs across ten distinct cotton genotypes comprising five transgenic cultivars (IUB-13, IUB-222, CIM-600, FH-114, FH-901) and five conventional cultivars (NIAB-1048, NIAB-545, MNH-1016, MNH-1020, CIM-496) at Ghazi University, Dera Ghazi Khan. The trial was arranged using a Randomized Complete Block Design (RCBD) with three replications, omitting any chemical plant protection measures. Nymph populations were monitored fortnightly over a six-week period spanning for a cotton season. One-way analysis of variance (ANOVA) revealed significant variations in whitefly infestations among the genotypes across all time points. Early in the season (11 July), genotypic differences were minimal but statistically significant ($F = 1.731, p = 0.040$). However, variations peaked dramatically during the vegetative stage on 22 August ($F = 9.847, p < 0.001$), indicating strong morpho-biochemical differentiation among cultivars. Moderate significance was observed on 12 September ($F = 1.917, p = 0.019$), followed by a highly significant late-season population resurgence on 22 September ($F = 5.488, p < 0.001$). These findings indicate that specific cotton genotypes harbor persistent, growth-stage-dependent defense mechanisms. Integrating these resistant cultivars into national variety evaluation systems provides an eco-friendly foundation for robust integrated pest management (IPM) systems in whitefly-prone regions.