Morphological and biochemical plant characters in relation to resistance against some sucking insect pests in Bt cotton
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Date
2017
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Punjab Agricultural University, Ludhiana
Abstract
The studies on morphological and biochemical plant characters in relation to resistance against some sucking insect pests in Bt cotton were carried out at Entomological Research Farm, PAU, Ludhiana during 2014 and 2015. Experiment on incidence of sucking insect pests on different cotton cultivars, revealed that leafhopper population was significantly higher on Bt cotton cultivar, RCH 773 (4.70 / 3 leaves), whitefly and thrips on Bioseed 6588 (7.47 and 2.47 /3 leaves, respectively). However, lower population of leafhopper, whitefly and thrips was recorded on the desi cotton cultivar, FDK 124 (1.78, 3.25 and 0.83/ 3 leaves, respectively). Incidence of sucking insect pests was also significantly higher at 130 Kg nitrogen as compared to 100 and 65 Kg nitrogen per acre. The population of leafhopper, whitefly and thrips showed significantly positive correlation with maximum and minimum temperature whereas evening relative humidity and rainfall has significantly positive correlation with leafhopper only. However, leafhopper and whitefly showed significant positive correlation with evaporation. Sunshine hours showed significant negative correlation with thrips but positive with whitefly. In another experiment on effect of various morphological plant characters revealed significant positive correlation with leafhopper population and gossypol gland on midrib. However, leafhopper, thrips and whitefly showed significant positive correlation with leaf lamina thickness and highly significant positive correlation with leaf area. Among the biochemical plant characters revealed that higher amount of total phenol, flavonols, O-dihydroxy phenol, tannins, total sugar and reducing sugars were recorded in cultivars infested with sucking insect pests over uninfested condition. Significantly higher biochemical content were recorded at lower level of nitrogen (65 Kg) followed by 100 and 130 Kg per acre. Leafhopper population had significant positive correlation with reducing sugar whereas whitefly and thrips with total sugar. However, thrips population showed significantly negative correlation with O-dihydroxy phenol. In another experiment on detection of the presence of Cry toxin revealed that highest amount of Cry1Ac and Cry2Ab was detected at 60 days after sowing as compared to 120 days after sowing. Higher expression of Cry toxin was recorded at high level of nitrogen (130 Kg) followed by 100 and 65 Kg. ELISA analysis showed presence of Cry toxin (Cry1Ac and Cry2Ab) in leafhopper nymphs and whitefly adults fed on Bt cotton cultivars and traces in honeydew excreted by whitefly feeding on Bt cotton cultivars.
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