Mixed deployment of Bt-expressing eggplant hybrids as a reliable method to manage resistance to Colorado potato beetle

Eggplant cultivations are severely damaged by Colorado potato beetle (CPB) attacks. Two transgenic eggplant hybrids bearing a mutagenized Bacillus thuringiensis Berl. Cry3B gene were tested to assess their resistance to this insect pest. Field trials were performed at two locations for two consecutive years. Transgenic hybrids were deployed as pure stands (100% transgenic plants) and as mixed plot with 20% of non-toxic wild-type plants. Samples were taken bi-weekly to assess insect abundance; at harvest, total yield was recorded. In both locations, CPB infestation was relevant only in 1 of the 2 years. Field observations confirmed that Bt-expressing eggplant hybrids were able to control insect infestation both as pure stands and as the mixed ones. When insect infestation was massive, transgenic hybrids gave a significantly higher yield than untransformed ones, regardless of their deployment method. Mixed deployment of Bt-expressing eggplants may well be considered as a useful means of CPB control, which could possibly help delaying insect adaptation to cry toxin.