Toxicity to Eldana saccharina of a recombinant Gluconacetobacter diazotrophicus strain carrying a truncated Bacillus thuringiensis cry1Ac gene

The stalk borer Eldana saccharina Walker (Lepidoptera: Pyralidae) is a serious pest of sugarcane in Africa. Because E. saccharina larvae feed inside the stem of sugarcane, expression of insecticidal Bacillus thuringiensis Cry proteins in sugarcane endophytes, such as Gluconacetobacter diazotrophicus, would enable the Cry proteins to be produced in the feeding zones of burrowing larvae. To evaluate the potential of using a Cry-expressing G. diazotrophicus strain for the control of E. saccharina, a truncated B. thuringiensis cry1Ac gene was cloned into a G. diazotrophicus strain and the toxicity of the recombinant strain to E. saccharina larvae was evaluated. Bioassays showed that the recombinant G. diazotrophicus strain carrying the cloned cry1Ac gene caused significantly higher E. saccharina mortality and larval growth inhibition than the non-recombinant G. diazotrophicus strain. This study sets a foundation for E. saccharina control strategies that are based on the expression of truncated cry1Ac genes in G. diazotrophicus.