PJB-2017-682
EVALUATION OF CRY1AC EXPRESSION IN COMMERCIAL BT COTTON (GOSSYPIUM HIRSUTUM L.) FOR THE MANAGEMENT OF HELICOVERPA ARMIGERA IN PAKISTAN.
Jam Nazeer Ahmad
Abstract
Cotton plant has always faced major threats from chewing and sucking insect pests. Among the chewing, Helicoverpa armigera is the most dangerous insect pest of cotton and it has ability to resist the toxin produced by transgenic cotton (Bt Cotton). The present study was conducted on 11 locally bred Bt cotton genotypes to check the expression of Cry1Ac and their efficacy against H. armigera. All the genotypes were grown in same conditions and leaf samples from upper, middle and lower canopy were taken at the age of 60 DAS to check the expression of Cry1Ac endotoxin protein. The quantitative ELISA and Polymerase Chain Reaction (PCR) were performed to study the Cry1Ac expression level. The insect bioassays against 2nd instar larvae of H. armigera were used to determine the lethality of Cry1Ac endotoxin under controlled conditions. Data on protein expression and larval mortality before and after bioassays showed highly variable expression of Cry1Ac within and between the genotypes. Intra-plant variation in the expression of Cry1Ac was also significant. Maximum expression of Cry1Acprotein was observed in upper canopy leaves of Bt cotton plants followed by middle canopy leaves and lower canopy leaves. Larval mortality was maximum on the upper leaves and the lower leaves were found with minimum larval mortality. The value of LC50 (0.74 µg/g) was estimated through probit analysis and it was concluded that the genotypes having the expression of transgene equal or more than the value of LC50 are best to grow in field conditions for the 50% control of H. armigera. Our results of Cry1Ac expression through ELISA was also confirmed by the expression of Cry1Ac gene through PCR in all Bt genotypes. The study would be highly significant for farmers and cotton breeders to develop new Bt cotton varieties for sustainable insect pest management.
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