Structural Host Plant Resistance: Influence of Foliar Morphological Traits on Bemisia tabaci Dynamics in Soybean (Glycine max)

The whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), is a devastating polyphagous pest of soybean (Glycine max L. Merrill), causing severe yield losses directly through sap-draining and indirectly by acting as the primary vector for the Yellow Vein Mosaic Virus (YVMV). It has a broad host range of over 700 different plant species with an ability to transmit more than 200 viruses specifically those belonging to the genus Begomovirus, leading to severe economic loss, the environmental hazards and resistance issues associated with chemical insecticides, identifying and utilizing host plant resistance (HPR) is paramount. This study was conducted exclusively during the Kharif 2023 season to investigate the role of foliar morphological traits in conferring structural resistance (antixenosis) against B. tabaci. Twenty diverse soybean genotypes were evaluated under field conditions at the Jawaharlal Nehru Krishi Vishwa Vidyalaya (JNKVV), Jabalpur, Madhya Pradesh,India. Morphological parameters like leaf area, specific leaf weight, leaf succulency, trichome density, trichome width, and trichome length were recorded at 45 days after sowing (DAS). The results demonstrated highly significant genotypic variations in all evaluated Morphological leaf traits, which profoundly influenced B. tabaci. colonization dynamics. Correlation analyses revealed that specific leaf weight (leaf thickness) (r=−0.945) and trichome density (r=−0.886) acted as physical barriers, showing very strong negative correlations with whitefly populations. Conversely, leaf succulence (r=0.919) and leaf area (r=0.817) exhibited highly significant positive correlations, indicating that broader and highly hydrated leaves enhance plant susceptibility by providing a favourable microclimate and easier feeding access. The genotype JS 97-52 emerged as highly resistant, possessing the thickest leaves (0.40 g/cm2), maximum trichome density (434.57 trichomes/cm2), and the longest trichome (562.24 μm), alongside the lowest leaf area (30.50 cm2) and succulency (37.25%) area. On the contrary, the highly susceptible genotype JS-335 exhibited the thinnest leaves (0.17 g/cm2), lowest trichome density (182.64 trichomes/cm2), and the highest leaf succulence (57.26%). These findings conclusively establish that morphological traits are critical determinants of B. tabaci resistance and provide highly reliable phenotypic markers for screening and breeding whitefly-resistant soybean cultivars.