Antixenosis: mechanism of resistance to whitefly in upland cotton introgression lines

Screen house experiments were conducted under free-choice conditions to determine the antixenosis mechanism of host plant resistance in nineteen cotton test entries against whitefly, Bemisia tabaci (Gennadius). They were assessed for settling behavior and oviposition preference. The study revealed that introgression line D-12-7-4-P-2 was most preferred for whitefly settling and oviposition and categorized as highly susceptible, whereas synthetic polyploid, C1-P-1, C1-P-31, C1-P-20, and C1-P-36 were least preferred for oviposition by whitefly, falling under the resistant category and exhibiting an antixenosis mechanism of resistance. Various biophysical and biochemical parameters were estimated for each treatment and correlated with both settling and oviposition preference. Among biophysical parameters, trichome density, leaf area, and vascular bundle length showed significantly positive correlations, whereas leaf lamina thickness was negatively correlated with settling behavior and ovipositional preference. Sugars were predominantly higher in whitefly susceptible lines, whereas phenols, tannins, and proteins were comparatively higher in resistant genotypes. Among biochemical parameters, total soluble sugars and reducing sugars registered a positive  association, while total soluble proteins, crude proteins, total phenols, and total tannins showed negative correlations with whitefly settling and ovipositional preference. It may thus be concluded that the antixenosis mechanism of resistance is operating in cotton lines and that biophysical and biochemical parameters play a predominant role in imparting resistance against B. tabaci. These identified resistant cotton introgression lines can be used to obtain whitefly-resistant cultivars.