Screening of new isolates of Bacillus thuringiensis for cry1 genes and testing of toxicity against Dichocrocis punctiferalis (Family: Pyralidae, Order: Lepidoptera)

Abstract

In order to identify the more toxic novel cry gene, the cry1 gene was screened in six indigenous isolates of Bt by PCR with degenerate primers showed amplification in all the Bt isolates. Subsequent screening of cry1 subfamily gene(s) by gene specific primer showed amplification of cry1A gene in the five Bt isolates, three out of the six cry1 positive isolates showed the presence of cry1Aa gene. One of the six Bt isolates showed the presence of cry1Ab gene. Five Bt isolates showed amplification for cry1Ac gene and a variation in size of amplification was observed in one of the Bt isolates Bt, T27. Further, SDS-PAGE analysis of a spore crystal mixture isolated from new isolates of Bt, T27 showed a single band of ~135 kDa indicating presence of cry1Ac gene. The toxicity analysis of Bt strain T27 against Dichocrocis punctiferalis showed 100 per cent mortality on the fifth day after treatment. The varied ~925 bp amplicon of cry1Ac gene of Bt, T27 was amplified and cloned in a T/A vector. Comparison of nucleotide sequence data generated from the cry1Ac (~925 bp) gene showed 99 percent homology and two amino acid variation when comparison with its holotype sequence of Cry1Ac1.

Characterization and Evaluation of Indigenous Bacillus thuringiensis Isolate T352 against Fall Armyworm, Spodoptera frugiperda (J.E. Smith)

“…PCR screening for lepidopteran toxic gene families confirmed the presence of cry1, cry1Ab, cry1Ac, cry2, cry2Aa, cry2Ab and vip3A genes in isolate T352 (Table 2). Various studies on indigenous Bt isolates revealed the cry1, cry1Aa, cry1Ab, cry1Ac, cry2Aa, cry2Ab and cry9 genes contributing the toxicity against major lepidopterous insects [24,[35][36][37][38] and the dominance of cry1 and cry2 gene existing together was usually high [39]. The Bt isolate T352 having cry1 and cry 2 along with vip3A gene and toxic to S. frugiperda was in agreement with previous studies [40].…”

Enhanced Drought Tolerance and Yield in Cry1ac and APX Co-Transformed Transgenic Rice (Oryza Sativa L.)

“…Bt toxins swallowed by insect get stimulated by the midgut proteases in order to develop crystals that disrupts the midgut wall, leading to insect death. The insecticidal activity of the bacterium is dependent on the capability to develop large quantity of delta-endotoxins (Cry proteins) (Manikandan et al 2016).…”