Rice Genetics IV - IRRI books - International Rice Research Institute

Engineering for virusresistance in riceN.M. Upadhyaya, Z. Li, M-B. Wang, S. Chen, Z-X. Gong, and P.M. WaterhousePlant viruses together with their insect vectors cause considerable losses inrice production. Several viruses attack rice plants. Resistance sources arelimited or the available resistance genes are either difficult to transfer intocultivated rice or are under threat of being overcome by evolving viral strains.Pathogen-derived resistance (PDR), the expression of pathogen-derivedtransgenes in plants to interrupt the virus infection cycle, has been employedas an alternative strategy. This approach has given resistance in rice againstrice stripe virus (RSV), rice tungro spherical virus (RTSV), rice tungro bacilliformvirus (RTBV), rice ragged stunt virus (RRSV), rice hoja blanca virus (RHBV),and rice yellow mottle virus (RYMV). PDR for viruses was originally achievedusing gene constructs designed to express wild-type or dysfunctional viralproteins. In many cases, however, these PDR genes appear to be operatingat the RNA level associated with posttranscriptional gene silencing. Our latestresearch shows that viral immunity can be efficiently obtained using constructsthat produce dsRNA. This approach has great promise for producingvirus resistance in rice. Our experiences and those of other research groupsin engineering virus resistance are also discussed.Among the 23 different viruses known to infect rice, 15 cause significant yield losses(Brunt et al 1998) with most of them vectored either by the leafhopper or planthopper(see Waterhouse and Upadhyaya 1998). Viruses causing yield losses are the rice tungrovirus (RTV) complex, rice tungro spherical virus (RTSV) and rice tungro bacilliformvirus (RTBV), in India and Southeast Asia, rice stripe virus (RSV) in China and Japan,and rice ragged stunt virus (RRSV), rice grassy stunt virus (RGSV), rice galldwarf virus (RGDV), rice transitory yellowing virus (RTYV), rice dwarf virus (RDV),and rice black-streaked dwarf virus (RBSDV) throughout Asia. The important riceinfectingvirus on the American continent is rice hoja blanca virus (RHBV) and inAfrica it is rice yellow mottle virus (RYMV), which is transmitted by beetles (Bakker1975). The impact of these viruses on rice production has been assessed on nationaland international scales. For example, RTV, RRSV, and RGSV in Southeast Asia causeEngineering for virus resistance in rice 405