Interaction of acid exudates in chickpea with biological activity or cry toxins from Bacillus thuritgiensis berliner against Helicoverpa armigera (hubner)

V Surekha Devi, 'Interaction of acid exudates in chickpea with biological activity or cry toxins from Bacillus thuritgiensis berliner against Helicoverpa armigera (hubner)', 2012

The H armigera egg and larval numbers before and after sprays of B. rhuringiensis(Bt) formulation ~iole~w'e re low on the chickpea genotypes ICC 506 and ICCV 10 acrossBI concentrations as compared to those on L 550 and C 235 during vegetative and floweringstages. Leaf feeding and pod damage were lowest on ICC 506, followed by ICCV 10 acrossBt concentrations as compared to that on L 550 and C 235. During the 2005-06 post-rainyseason and first planting during the 2006-07 post-rainy season, highest grain yield wasrecorded in case of ICCV 10. In the second planting, the genotypes ICCV I0 and ICC 506recorded the highest total grain yield. There were no significant d~fferences between thegenotypes and Bt concentrations for grain yield.Significantly lower leaf damage was recorded on ICC 506 across Br concentrations indetached leaf assay under laboratory conditions. Larval survival and larval weights werelower in ICC 506, ICCV 10. and C 235 across Br concentrations as compared to that of L550. Survival and development of H. armigera on ICC 506, ICCV 10, and C 235 sprayedwith different concentrations of Bt differed significantly with that of the unsprayed plants ofthese genotypes. At higher concentrations of Br (0.1.0.2. and 0.5%), there was no survival ofthe armigera larvae. At lower concentrations of Br (0.05%), the larval survival and larvaland pupal weights were lower on the sprayed (0.05%) plants than those on the unsprayedplants of different chickpea genotypes. Larval and pupal periods were prolonged on plantssprayed with Bt. There was a significant reduction in fecundity of H armigera reared onchickpea plants sprayed with Br.At the vegetative and flowering stages, ICC 506 had the highest amounts of oxalicacid on dry weight and leaf area basis. At the podding stage, ICCV 10 had the highest amountof oxalic acid on dry weight basis. On dry weight basis, ICCV 10 had the highest amount ofmalic acid at the vegetative, flowering, and podding stages. On leaf area basis, ICCV 10 hadthe highest amount of malic acid at the vegetative stage, whereas C 235 had the highestamount of malic acid at the flowering and pcdding stages. Fumaric and citric acids wererecorded at the podding stage only. The genotype C 235 had the highest amounts of fumaricand citric acids. There was no citric acid in ICC 506.The survival and development ofH armigera larvae reared on artificial diet withleaflpod powder of different chickpea genotypes and Br were significantly lower as comparedto that on the standard artificial diet, and the diets without Br. Larval survival, larval andpupal weight, and pupation and adult emergence were lower on the resistant genotypes thanon the susceptible ones, and the standard artificial diet. Oxalic and malic acids in the artificialdiet increased the biological activity of Br toxins on the H armigera, and resulted in reducedlarval weight, prolonged development, and reduced longevity and fecundity.The food, midgut, and faecal matter samples of larvae fed on diet with differentamounts of organic acids and BI indicated the conversion of protoxin to toxin, and binding tothe brush border membrane vesicles (BBMV) of midaut. Due to the conversion of p rot ox in totoxin and binding to the BBMV, the amount of Bl toxin in the midgut samples w& greater ascomaared to that in the food sam~lesT. here were no significant differences in the amounts ofBt p;otein present in the midgutsamples of the larvae-fed on diet with different amounts ofoxalic and malic acids and BI toxin, indicating that the organic acids did not influence theconversion of protoxin to toxin. The amounts of protein in the BBMV preparations rangedfrom 0.131 to 0.326 mg c&". The amount of protein estimated from the BBMV of larvae fedon diets with Bt was higher as compared to the amounts in the BBMV of the larvae fed ondiet without Bt, indicating the binding of the BI protein to the BBMV, which resulted inincreased protein content in the BBMV.The insecticidal activity of BI endotoxins depends on the amounts of food ingested bythe target insects. The organic acids (oxalic and malic acids) also act as antifeedents, andtherefore, may reduce the effect of B1 as less amounts of food will be consumed by the larvae.However, the amounts of oxalic and malic acids impregnated in to the diet did not effect the