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Baseline Susceptibility in Brinjal Shoot and Fruite Borer Populations of North Karnataka

Vijaykumar. N. Ghante

Abstract

Brinjal fruits damaged by the brinjal shoot and fruit borer were collected from ten locations representing North Karnataka during Kharif 2009 and 2010. The adults emerging from the collected damaged fruits were allowed to mate using standardized rearing techniques in the laboratory. Eggs collected from mating cages were allowed to hatch and neonate larvae of these field -collected parents were used in bioassays to determine susceptibility to the Cry1Ac protein. Bioassays involved exposure of neonate larvae to various concentrations of diet incorporated with the Cry1Ac protein that produced 0-100% mortality. A stock solution (250 ìg/ml) of Cry1Ac was made in 0.2% agar solution and dilutions were made in deionized water. MVP II® (Mycogen Corp., USA), which contained 19.7% (by weight) Cry1Ac protein. Neonates exposed to Cry1Ac concentrations were kept in dark at a temperature of 26±1°C and 55 -65% RH. Larval mortality and instar stage of surviving larvae were recorded on 7 th day in dietincorporation assays. Larvae that did not move when disturbed were considered to be dead. The probit analysis (Finney 1971) of mortality data from Cry1Ac bioassays was done using EPA Probit Programme version 1.5. It is observed that the populations have 1-4 fold variability (0.026-0.104 ppm) in their level of susceptibility across the locations. Of the populations studied, Bijapur population recorded highest LC50 value of 0.104 ppm followed by Bellary and Belgaum. Whereas, Koppal recorded the lowest LC50 value of 0.026 ppm. The results were found to be consistent for both the years. The susceptibility to Cry1Ac among ten populations of the fruit and shoot borer observed in this study indicates limited variability

Keyword: Brinjal, Shoot and Fruite

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