1. Transgenic cowpeas (Vigna unguiculata L. Walp) expressing Bacillus thuringiensis Vip3Ba protein are protected against the Maruca pod borer (Maruca vitrata)
- Author
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Robert M. Harding, Thomas J. V. Higgins, Stephanie Gollasch, Andrew D. Moore, Bosibori Bett, Tom Walsh, William James, and Joel Armstrong
- Subjects
0106 biological sciences ,0301 basic medicine ,biology ,Maruca ,fungi ,food and beverages ,Agrobacterium tumefaciens ,Horticulture ,biology.organism_classification ,01 natural sciences ,Vigna ,Lepidoptera genitalia ,03 medical and health sciences ,Transformation (genetics) ,030104 developmental biology ,Maruca vitrata ,Bacillus thuringiensis ,Botany ,PEST analysis ,010606 plant biology & botany - Abstract
Although cowpea is an important food security crop in Africa, its production is constrained by insect pests such as the legume pod borer (Maruca vitrata) (Lepidoptera). Potential control strategies have focussed on using insecticidal toxins such as the crystal Cry proteins and vegetative insecticidal proteins (Vips) encoded by the cry and vip genes, respectively, of the bacterium Bacillus thuringiensis (Bt). This study sought to identify vip genes encoding toxins active against Maruca Pod Borer (MPB), from Australian Bt isolates. A collection of 224 Bt isolates was screened with gene-specific primers to identify those containing target vip genes namely vip3Aa35, vip3Af1, vip3Ag, vip3Ca2 and vip3Ba1. The coding sequences of the vip3 genes were cloned and over-expressed in Escherichia coli to produce Vip3 protein. The proteins were incorporated into Maruca artificial diets for use in insect bioassays with MPB larvae to screen for toxicity. Of these, Vip3Ba1 protein was found to strongly inhibit larval growth and was selected as the candidate gene for cowpea transformation. A vip3Ba gene reconstructed for plant expression was used in transforming cowpea via Agrobacterium tumefaciens. Transgenic lines expressing Vip3Ba protein were used in insect feeding trials to assess protection against Maruca and were found to be completely protected from this pest. We propose that the vip-cowpea lines could be combined with existing cry-transgenic cowpea to introgress this additional resistance trait and thus avoid or greatly delay the development of resistance in Maruca.
- Published
- 2017