Potato Tuberworm (Lepidoptera: Gelichiidae) Resistance in Potato Lines with the Bacillus thuringiensis cry1Ac Gene and Natural Resistance

Abstract

The potato tuberworm [ Phthorimaea operculella (Zeller)] is one of the most destructive insect pests to potato ( Solanum tuberosum L.) in tropical and subtropical regions, and it has recently become established in the Pacific Northwest of the United States. Combining natural resistance mechanisms with Bacillus thuringiensis ( Bt ) cry genes could be a potential solution to improve potato resistance to tuberworm. We have expressed Bt cry1Ac in two potato lines: Spunta, a susceptible potato line, and ND5873-15, a moderately resistant line with high foliar glycoalkaloids derived from Solanum chacoense . Putative transgenic lines of Spunta and ND5873-15 were developed using a vector construct pSPUD15 with the codon-modified Bt cry1Ac driven by the 35S CaMV promoter. Integration of Bt cry1Ac in Spunta and ND5873-15 transgenic lines was determined by PCR and Southern analysis. Protein expression in the transgenic lines (0–580 ng·g −1 ) was determined by ELISA. Plants expressing Bt cry1Ac were effective in controlling potato tuberworm first-instar larvae in the detached-leaf bioassays (up to 97% mortality) and in tuber bioassays (up to 99% mortality). Based on the assays conducted, the Bt cry1Ac Spunta lines were similar to the Bt cry1Ac ND5873-15 lines for potato tuberworm mortality. Constitutively expressed Bt cry1Ac would be a useful gene to use for host plant resistance to potato tuberworm.