Bio efficacy of UASD bt cotton event no 78 against bollworms complex in comparison with commercially available events in India

Abstract

The investigations were carried out at Agricultural Research Station, Dharwad newline(Hebbali) farm, University of Agricultural Sciences, Dharwad, during Kharif, 2020-21 newlineand 2021-22 on the survival and development of bollworms, field performance and newlineexpression of Cry toxins in UASD Event No. 78 in comparison with commercial Bt newlinecotton events. Seven Bt cotton genotypes of different events and one non Bt cotton were newlineused viz., MON 531 (Suraj Bt), Fusion Bt event (Arjun-21 Bt), UASD-78, MON 15985 newlineevent (Everest Bt and Puli Bt), UASD-78 Bt HxH-25 and UASD-78 Bt HxB-2 and non newlineBt cotton, RAH 100 non Bt. The Cry toxin expression in different parts of the plant was newlinequantified through ELISA at 60, 80, 100, 120 and 140 days after sowing. In general the newlineCry toxin content in the plant was expressed in high concentrations during early stages newlineof crop growth and dwindled down from 90 days onwards. Further, the expression of newlineCry toxin became negligible at 140 DAS. Among the different Bt cotton events the level newlineof toxin was highest in Fusion Bt event (Arjun-21 Bt) followed by UASD Event No. 78. newlineIrrespective of type of endotoxin and Bt events, expression of Cry toxin content was newlinefound higher in leaves followed by bracts, squares, flowers, raw seeds and boll rind. newlineThe per cent mortality of first instar larvae of H. armigera on leaves, squares and tiny newlinebolls of different Bt cotton events revealed that Fusion Bt event (Arjun-21 Bt) recorded newlinehighest mortality rate of 99.33, 97.08 and 93.89 per cent in leaves, squares and bolls, newlinerespectively and was on par with UASD-78 (99.33, 96.67 and 92.22 %) under newlinelaboratory conditions. With respect to efficacy of Cry toxin against P. gossypiella larvae newlineon Bt cotton events, the Fusion Bt event (Arjun-21 Bt) (84.58 %) and UASD-78 newline(82.92%) were recorded highest per cent mortality on flowers of different events and newlinecomparatively least per cent mortality was recorded in MON 531 event (Suraj Bt) newline(62.08 %). In case of mortality of first instar larvae of pink bollworm on bolls Fusion Bt newlineevent (Arjun-21 Bt) record