The Potential of Rna Interference for the Management of Phytoparasitic Nematodes

Abstract

Abstract. RNA interference (RNAi) is a natural cellular phenomenon in which double stranded RNA (dsRNA) is recognised as foreign by virtue of its conformation and thus sets in motion a chain of events in which the dsRNA and its mRNA homologue are degraded. This leads to silencing of the targeted gene. First described for the microbivorous nematode Caenorhabditis elegans, RNAi has emerged as a powerful tool for investigating gene function in a range of organisms. Practical applications proposed for RNAi include the genetic improvement of crop plants to create novel resistance to plant pathogens. Recent studies have described the successful application of RNAi to plant parasitic nematodes. Key developments in the last year have demonstrated that in planta expression of a double-stranded RNA can target a gene of a feeding plant parasitic nematode, inducing a silencing effect. When the targeted gene has an essential function this leads to a level of nematode resistance, paving the way for the potential use of RNAi technology to control plant parasitic nematodes. 1. INTRODUCTION Plant parasitic nematodes represent one of the major biotic constraints in world agriculture causing global yield losses estimated to be around US$70 billion in 1987 (Sasser & Freckman, 1987). Adjusting for inflation, this figure was revised to US$125 billion in 2003 (Chitwood, 2003). No recent, comprehensive surveys of nematode losses have been carried out and the real figures may be higher than this, as a lack of clear disease symptoms can lead some growers to underestimate yield loss. Yield reductions may also be wrongly attributed to the secondary diseases suffered by crop plants already weakened by nematode attack. Nematodes of the order Tylenchida are responsible for the majority of crop damage. Agronomically important species include both migratory parasites such as Radopholus spp. and Pratylenchus spp. that feed sequentially from plant cells in a destructive manner, and the more specialised sedentary endoparasites. These nematodes each form a unique, biotrophic interaction with the host plant, modifying root cells to establish a permanent feeding site that provides a sustained