Disruption of the pathogenicity and sex ratio of the beet cyst nematode Heterodera schachtii by host-delivered RNA interference

The beet cyst nematode (BCN) Heterodera schachtii causes serious damage and yield losses in numerous important crops worldwide. This study examines the efficacy of three types of transgenic Arabidopsis RNA interference (RNAi) lines to decrease the biological activity of this devastating nematode. The first RNAi construct (E1E2-RNAi) targets two nematode endoglucanase genes, which are involved in BCN pathogenicity, the second construct (MSP-RNAi) contains a fragment corresponding to the major sperm protein transcript necessary for BCN development and reproduction, and the third construct (E1E2MSP-RNAi) comprises all three target fragments. Transcript expression profiles of the target genes in all biological stages of the nematode were determined for the initial inoculated population and the resulting progeny. Bioassay data under indoor aseptic cultivation indicated that feeding on these RNAi lines did not affect pathogenic activity and reproductive capacity of the initial population, whereas inoculating the progeny into new transgenic plants corresponding with the lines from which they were recovered reduced the nematode penetration and the number of eggs per cyst. In addition, the male/female ratio increased more than the double, and the effects of RNAi continued in the second generation of the nematodes, because the progeny derived from E1E2-RNAi and E1E2MSP-RNAi lines showed an impaired ability to infect wild-type plants