Engineering host resistance against parasitic weeds with RNA interference

Host genetic resistance is a key component of integrated pest management. The present authors and others are investigating the use of RNA interference (RNAi) as a genetic tool for engineering host resistance against parasitic weeds. The general approach is to transform a host plant with a plasmid encoding a double stranded hairpin RNA (hpRNA) targeted against one or more vital parasite genes. When the hpRNAs are specifically designed against parasite gene sequences, the hpRNA should have no phenotypic effect on the host. They will, however, have a dramatic effect on the parasites that have taken up the parasite-specific RNAi from the host via the haustorium. The current status of using RNAi technology for controlling parasitic weeds is reviewed. A key component to success with RNAi technology is identifying the best parasite genes to silence. Some of the criteria for RNAi targets are discussed, the existing status of parasitic plant sequence databases is described and internet access points to the parasite genome data are highlighted. Sequence information obtained from different parasite species can be used to clone the homologous gene from a particular pest or can be directly transformed into crop plants.