Resistance to thrips (Thrips tabaci) in Bt cotton genotypes in Punjab, Pakistan, based on population dynamics and plant morpho-chemical properties
2013
Saleem, M.W. (University of Agriculture, Faisalabad (Pakistan). Dept. of Agricultural Entomology) | Ahmed, S. (University of Agriculture, Faisalabad (Pakistan). Dept. of Agricultural Entomology) | Wakil, W. (University of Agriculture, Faisalabad (Pakistan). Dept. of Agricultural Entomology) | Sahi, S.T. (University of Agriculture, Faisalabad (Pakistan). Dept. of Plant Pathology)
The present study was conducted to evaluate twenty Bt-cotton genotypes for their resistance to thrips, Thrips tabaci (Lind.) under field conditions in Faisalabad, Pakistan. Thrips population seedling and leaf was recorded from each genotype in 2008 and from these data, six genotypes were selected for final screening trial in 2009. Thrips density per leaf was correlated with abiotic factors, morphological and chemical characteristics to establish basis of resistance mechanism. Results showed that AA-802 and VH-259 with 3.40 and 4.45 thrips per leaf were resistant and susceptible genotypes, respectively and two had significant difference between each other (p less than 0.05). Weather factors were non-significantly correlated with leaf thrips populations except relative humidity, which was positively and significantly correlated (r=0.451; p = 0.014). Hair density on leaf midrib (r=0.850) and vein (r=0.762) were positively whereas gossypol gland on leaf lamina (r-0.462) were positively correlated with per leaf thrips population. Moisture contents, total minerals, protein, lipids, reducing sugar, calcium, magnesium, and zinc were significantly correlated with thrips population. These findings are discussed in comparison with basis of resistance on non-Bt-cotton varieties reported earlier, in the study area.
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