Genetic transformation of potato with nptII-gus marker genes enhances foliage consumption by Colorado potato beetle larvae

Little is known about the effect of transgenic plants containing commonly u sed marker genes, such as aph(3')II (nptII encoding neomycinphosphotransfer ase) and uidA (gus encoding beta-glucuronidase) on insect feeding behaviour . We report here, for the first time, that transgenic potato plants contain ing only nptII and gus marker genes enhance foliage consumption by the Colo rado potato beetle (CPB, Leptinotarsa decemlineata S.). Transformation of p otato cultivar Desiree was performed with Agrobacterium tumefaciens. Intern ode explants were inoculated with different strains of bacteria, carrying e ither nptII-gus or nptII alone. A total of 180 transgenic and untransformed control plants were grown in the greenhouse for the analysis of food consu mption by CPB. For each transformed and untransformed line tested, four bio assays were conducted each consisting of 10 second-instar larvae feeding in dependently on a 2 cm diameter leaf disc for 20 h. Our data show up to 50% increase of mean foliage consumption on plants transformed with the nptII-g us construct, indicating that transgenic plants containing these marker gen es can affect the feeding behaviour of the insects. These results were obta ined from the 'primary regenerants' (R-0 lines) as well as from tuber-deriv ed plants (R-1 lines). Further tests with transgenic plants containing the nptII marker gene only, showed no significant difference in feeding when co mpared to untransformed control plants, allowing us to rule out a direct ef fect of this marker gene on foliage consumption by the insect larvae. It is suggested that gus protein is involved in the increase of foliage consumpt ion by CPB.