TRANSGENIC POTATO PLANTS WITH ENHANCED RESISTANCE TO THE TOMATO MOTH,LACANOBIA-OLERACEA - GROWTH ROOM TRIALS

Insecticidal effects of three plant-derived genes, those encoding snow drop lectin (GNA), bean (Phaseolus vulgaris) chitinase (BCH) and wheat a-amylase (WAI), were investigated and compared with effects of the c owpea trypsin inhibitor gene (CpTI). Transgenic potato plants containi ng each of the three genes singly, and in pairwise combinations were p roduced. All the introduced genes were driven by the CaMV 35S promoter ; expression was readily detectable at the RNA level in transformants, but not detectable accumulation of WAI could be detected in transgeni c potatoes containing its encoding gene. GNA and BCH were accumulated at levels up to 2.0% of total soluble protein; both proteins were expr essed in a functional form, and GNA was shown to undergo 'correct' N-t erminal processing. Accumulation levels of individual proteins were hi gher in plants containing a single foreign gene than in plants contain ing two foreign genes. Resistance of the transgenic plants to insect a ttack was assayed by exposing the plants to larvae of the tomato moth, Lacanobia oleracea. All the plants tested which were expressing GNA s howed an enhanced level of resistance. Leaf damage was reduced by more than 50% compared to controls; total insect biomass per plant was red uced by 45-65%, but larval survival was only slightly reduced (20%). T hese results support the hypothesis that GNA has a significant antifee dant effect on insects. Expression of BCH had no protective effect aga inst this insect. Expression of CpTI in transgenic potatoes had simila r effects to expression of GNA on total insect biomass and survival, b ut did not afford protection against insect damage to the plant.