| Potato tuber moth (Phthorimaea operculella Zeller) is one of the major insect pests of cultivated potato (Solanum tuberosum L. (2n = 4x = 48)) in tropic and sub-tropic regions. Host plant resistance (HPR) is a key tool in an integrated pest management program to control potato tuber moth and has been found among the wild and cultivated Solanum germplasms. Genetic engineering offers the opportunity to introduce the Bacillus thuringiensis (B.t.) toxin gene into potato. In this study, two transgenic potato clones expressing a wild-type cryIA(c) B.t. gene were generated through Agrobacterium-mediated transformation. Gene integration was confirmed by polymerase chain reaction, Southern and northen analyses. One clone (FL 1607-A11) had two copies of the gene while the other clone (FL 1607-A30) had one copy. Detached leaf potato tuber moth bioassays, using first instars, were conducted on the transgenic lines, the untransformed control, and 12 other clones with putative host plant resistance mechanisms. Both transgenic lines, two leptine producing lines (USDA 8380-1 2x and 4x), and a wild species (S. sparsipilum PI 230502) exhibited resistance with 60-68% mortality of potato tuber moth larvae. Seven lines (Roslin Eburu, KWPTM 29 and 24, CIP 85-37.38, Cruza 148, TM-3), including one line with glandular trichomes (NYL 235-4), exhibited moderate resistance with 15-36% mortality. The untransformed control (FL 1607) and two other clones (Santa Catalina and CCC 1386.36) were not resistant (less than 13% mortality). B.t. expression and mortality were higher than previous reports using a similar wild-type gene specific to lepidoptera. Since B.t. can be expressed in any potato line, efforts should be made to introduce the B.t. gene into plants with natural HPR. This material could then be used to develop more durable HPR. |
