Efficacy of genetically transformed Metarhizium anisopliae against Spodoptera litura and Aphis craccivora

Abstract

To increase the insecticidal potency of the entomopathogen, Metarhizium anisopliae (Metsch.) Sorok, the fungus was genetically modified with scorpion neuro β-toxin LqqIT1a and two different insect specific heterologous toxic proteins viz., Cry1a and GNA. LqqIT1 is an anti-insect neurotoxin derived from yellow scorpion, Leiurus quinquestriatus quinquestriatus (Ehren.). The present study reports the bio-efficacy of genetically modified fungus, M. anisopliae, in which scorpion neurotoxin gene ‘LqqIT1′ is stacked in its genome, for improved efficacy against the tobacco caterpillar, Spodoptera litura (Fab.) and Aphis craccivora (Koch). All the transformed clones of M. anisopliae were found potent against S. litura and A. craccivora under laboratory conditions. The virulent clones viz., Ma-2(2), Ma-2(7) and MaGKS-14 caused 40 to 90 per cent mortality at fourth day of treatment. Compared to untransformed parent strain, Ma-C, the median lethal time of transformed clones Ma-2(2), Ma-2(7) and MaGKS-14 got reduced by 2, 3 and 3-folds, respectively. No significant differences were noted with respect to percent mortality of transformed clone, MaGKS-13 in comparison to untransformed strain Ma-C. The results indicated that the incorporation of LqqIT1 toxin gene enhanced the potency of strain Ma-C, against immature stages of S. litura and A. craccivora by shortening the median lethal time without affecting conidial development. Therefore, LqqIT1 scorpion toxin gene showed the potential to improve efficacy of M. anisopliae against lepidopteran and hemipteran insects.