Potato tuberworm (Lepidoptera: Gelichiidae) resistance in potato lines with the Bacillus thuringiensis-cry1ac gene and natural resistance factors

The potato tuberworm (Phthorimaea operculella (Zeller)) is one of the most common and destructive insect pests to potato (Solanum tuberosum L.). Previous host plant resistance work has not produced potato material that has appreciable levels of resistance to potato tuberworm. A potential solution to improve cultivated potato resistance to potato tuberworm is through combining resistance mechanisms of glycoalkaloids and glandular trichomes with cry genes. The objectives of this study were: (1) transform three potato lines which differ in natural host plant resistance with a codon-modified Bt-cry1ac gene; (2) verify insertion of Bt-cry1ac, quantify the protein expression, and determine the number of inserted copies of the gene; and (3) conduct laboratory bioassays to test the potato tuberworm response on Bt-cry1ac transgenic lines. Putative transgenic lines of Spunta, ND5873-15 & NY123, were developed using vector construct (pSPUD 15) with the codon-modified Bt-cry1ac gene. Integration of Bt-cry1ac gene in Spunta and ND5873-15 transgenic lines was confirmed by the PCR and Southern blot analysis. Protein expression in the transgenic lines (0--0.58 ng/mg) was confirmed by ELISA. Detached leaf bioassays with neonate larvae of potato tuberworm showed that cry1ac gene was effective in controlling potato tuberworm 1st instar larvae (up to 97 % mortality). Combining natural host plant resistance and engineered resistance with the Bacillus thuringiensis-cry1ac gene in potato plant was effective in conferring increased resistance to potato tuberworm.