Non-target effects of proteinase inhibitors expressed in potato as an anti-nematode defence

The survival and rate of growth of nymphs of Myzus persicae and Macrosiphum euphorbiae were adversely affected by ingestion of cystatins in artificial diet assays. Prolonged exposure to cystatins in diets produced a reduction in the rate of development, survival time and fecundity of M. persicae adu lts. However, when aphids were caged on transgenic potato expressing chicke n egg white cystatin (CEWc) there was no adverse effect on aphid fitness. S imilarly, there were no significant differences in field populations of aph ids between control and CEWc-expressing potato grown under field conditions , although the levels of expression were sufficient to provide control of p otato cyst nematodes. The results highlight that tissue-specific levels of expression are important in determining the effects of cystatins on differe nt invertebrates and it is suggested that aphids feeding on transgenic plan ts may provide a route via which various natural enemies are exposed to cys tatins.