Characterization of indigenous Bacillus thuringiensis isolate RM11 toxic to the diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae)

Abstract

Background Bacillus thuringiensis (Bt) Berliner is an omnipresent soil bacterium used as world’s leading biopesticide to combat agriculturally important insect pests. This study was aimed at protein and gene profiling of an indigenous Bt isolate RM11, which was toxic to the larvae of diamondback moth, Plutella xylostella (L.) in laboratory bioassays. Results Indigenous Bt isolate RM11 was characterized along with the standard checks B. thuringiensis subsp. kurstaki (Btk) HD1 and 78/11, based on colony characters, protein profile and PCR screening. All three Bt colonies were fried egg type, white in color with flat elevation and undulated margin. PCR screening revealed the presence of cry1Ac and vip3A genes, which encode lepidopteran toxic proteins in RM11. SDS-PAGE results showed the presence of a prominent protein band of cry1Ac, vip3A with molecular weights 135 kDa, 88 kDa and other bands at 70, 50, 32 and 10 kDa. In leaf disk bioassay with spore crystal mixture, RM11 exhibited toxicity with LC50 of 4.51 µg/ml as against 0.07 µg/ml in positive standard HD1, based on mortality at 72 h after treatment. At LC50 of 4.51 µg/ml, solubilized and insolubilized protein of RM11 was found to produce 56 and 70% mortality. Conclusions The present study revealed that RM11 could be a viable alternative for consideration in developing a native Bt formulation and for inclusion in the integrated management of P. xylostella with other native isolates producing different toxins. Furthermore, these findings imply that RM11 could be a source of new cry toxin, which can be confirmed through whole-genome sequencing analysis.

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

“…Manikandan et al [26] observed the occurrence of bipyramidal and cuboidal shapes of inclusions in Bt isolate T30 whereas isolate T48 contains only bipyramidal shaped inclusions. While, Navya et al [32] observed that Bt isolate RM11 effective against Plutella xylostella was found to possess three different shapes of crystals such as bipyramidal, spherical and cuboidal. These results suggested that the Bt isolates toxic to lepidopteran insects were found to have bipyramidal and cuboidal shape of crystal inclusions.…”

“…Maheesha et al[31] recorded LC 50 value of 2.04 µg/ml in an indigenous Bt isolate against S. frugiperda. Similarly, Bt isolate RM11 expressed the toxicity on Plutella xylostella with 4.51 µg/ml[32]. Lone et al[41] reported two isolates, JK12 and JK17 with LC 50 value of 184.62 and 275.39 µg/ml against Helicoverpa armigera.…”

Bacteria-Premised Nanobiopesticides for the Management of Phytopathogens and Pests

“…Bacteria are unicellular prokaryotes with distinctive physiological, morphological, and evolutionary attributes. , They could be used to combat pests and phytopathogens. Bacteria used as BCAs or BBCAs belong to four major categories, , namely, crystalliferous spore formers, ,− obligate pathogens, , potential pathogens, , and facultative pathogens. − BBCAs are a widely utilized microbial biological control (MBCA) that works in various ways for the eradication of pests. The two significant prerequisites to achieving efficacy are interaction and ingestion by the potential pests.…”