Deciphering Host Plant Resistance in Upland Cotton (G. hirsutum) against Amrasca biguttula biguttula (Ishida) pest in North Indian Zone

Background Cotton leafhopper or jassid has become a major pest of cotton and inflicts substantial yield losses. Developing insect-resistant cultivars is a key economic strategy for mitigating this damage. Host plant resistance (HPR) through morpho-physiological and biochemical traits reveals a crucial role in plant defence against sucking pests. In this study, 127 Gossypium hirsutum accessions were evaluated during Kharif 2021 and 2022 for various morpho-physiological and biochemical traits/parameters to determine their impact on leafhopper population. Results Leafhopper population showed significant positive correlations with jassid injury grade (r = 0.77), total sugars (r = 0.62), stomatal conductance (r = 0.45), transpiration rate (r = 0.33) and leaf water content (r = 0.24). Conversely, significant negative correlations were observed with gossypol content (r=-0.77), trichome density (r=-0.68), phenol content (r=-0.67), tannin content (r=-0.66), seed cotton yield (r=-0.39), trichome length (r=-0.26) and photosynthetic rate (r=-0.23). Regression analysis indicated that morpho-physiological and biochemical traits collectively explained 75.88% impact on leafhopper population, with trichome density alone had 45.33% impact. On the basis of two-year field evaluations for jassid injury grade studies, four genotypes viz ., H 1652, HS 45, H 1655 and DL1 were found to be resistant. Three genotypes (B 61-2128, HS 1652, SHAHD 50) significantly out yielded the tolerant check RS 2013 (100.37 g/plant), producing seed cotton yield of 118.65, 115.03 and 111.97 g/plant, respectively. Traits such as leaf trichome density, trichome length, and the contents of sugar, phenol, tannin, and gossypol showed both high heritability and high genetic advance, suggesting the predominance of additive gene action and implying that these traits can be effectively improved through direct selection. Conclusions The present investigation identified the major role of leaf trichome density and phenol content on leafhopper population in cotton. Four genotypes viz. , H 1652, HS 45, H 1655 and DL1 were identified as resistant against leafhopper and these can be effectively exploited in future breeding programmes against leafhopper resistance. Three genotypes viz. , B 61-2128, HS 1652 and SHAHD 50 (moderately resistant/resistant against leafhopper) showed significantly higher seed cotton yield (118.65, 115.03 and 111.97 g/plant, respectively) than the tolerant check RS 2013 (100.37 g/plant). These can be utilized for the simultaneous improvement of yield and leafhopper resistance.