Abstract
A study was carried out in the experimental area of Ayub Agricultural Research Institute Faisalabad during (2012) to determine the role of morphological and biochemical parameters of Bt cotton genotypes influencing resistance against thrips Thrips tabaci (Lind). Six advance lines and one Bt cotton approved variety IR-NIBGE-5, SITARA 10-M, SITARA 11-M, PB-38, SITARA-009, IR-NIBGE-4 and BT-121 respectively were planted in Randomized Complete Block Design with 3 replications. Varieties differ significantly in response to thrips population on per leaf basis. SITARA 10-M showed maximum population of thrips (5.01/leaf) and did show significant difference with all other genotypes. Various morphological and biochemical traits also differ significantly among seven genotypes of cotton. Gossypol glands on Leaf lamina and phosphorus contents of leaves showed negative and highly significant correlation -0.447 and -0.490 respectively with the thrips population while hair density on veins and lamina and hair length on lamina showed positive and significant correlation 0.806, 0.574 and 0.45 respectively with the thrips population. All others parameters showed non-significant correlation with the thrips population. The R-2 values, computed together for multiple regression analysis for thrips population indicated that hair density on vein was the most important factor which contributed maximum i.e. 58.2% in pest population fluctuation of the pest. Gossypol gland on lamina was the second important factor showing impact of 20%, Hair density on lamina and hair length on lamina showed 6.90% and 0.30% impact in per unit change in pest population. Phosphorus contents showed 24% impact in per unit change in the pest density. Principle component analysis of morphological and chemical factors revealed that gossypol gland on lamina showed contrasting behavior having maximum variance value 95.159%. Hair density on vein also showed contrasting behavior with variance values of 3.741%. Hair density on lamina, hair length of lamina and Phosphorus content was not an important factor due to minimum variance value of 0.804%, 0.234% and 0.064%. Morphological and biochemical take part in resistance against pest which can be used as important tool in integrated pest management model.