Potato proteins, and other plant proteins, as potential transgenic resistance factors to pollen beetles in oilseed rape

Proteinase inhibitors (PIs), lectin and patatin purified from potato tubers were tested in no-choice feeding assays with pollen beetle larvae (Meligethes spp.). The idea was to search for resistance factors possible to introduce into oilseed rape (Brassica napus) by genetic engineering. The larval diet was prepared by soaking oilseed rape anthers in protein solutions of known concentrations. Potato lectin was the most potent in that it was the only of these proteins that reduced both larval survival and growth rate, while cysteine, aspartic and metallo PIs and patatin only reduced larval growth rate. Serine Pis had no significant effect on larval performance. Subsequently, the effect of potato lectin was compared to that of lectins from other food or feed crops, resulting in the following mortality-based ranking of activity: Con A from jackbean > wheat germ lectin > potato lectin > peanut lectin. In choice tests, larvae did not discriminate between Con A- and control-diets. These results suggest that the effect of Con A on larvae is toxic, not deterrent. Adult response was stronger to Con A than to potato lectin in no-choice tests, just as it was in larvae. However, adult survival rate and weight was not affected by Con A but the lectin significantly reduced adult feeding as well as oviposition rates. A resistance factor that suppresses adult feeding on flower buds is important for reduced impact of the pollen beetle on the Brassica oilseed crop.