Rice Genetics IV - IRRI books - International Rice Research Institute

first produced and shown to have virus resistance, little concern was raised over thepossible environmental impact of these plants. However, many discussions have occurredsince then (see Tepfer and Balazs 1997, McLean and Evans 1997) about theuse of such transgenic plants on a larger scale. Some scientists believe that the benefitsof transgenic virus-resistant plants greatly outweigh the minimal risks (Falk andBreuning 1994, Miller et al 1997), whereas others encourage a cautious approach(Gibbs et al 1997). The potential risks posed by plants expressing rice virus genes aresimilar to those expressing other plant virus genes and can be categorized into fourtypes: (1) interaction of transgene proteins with an invading virus, thus causing a newdisease, (2) selection by transgene-mediated resistance for the creation of a new resistance-breakingvirus strain, (3) escape of a transgene into weed species, conferring onthem greater fitness, and (4) recombination between a transgene mRNA and the genomeof an invading virus to create a novel virus and a new disease. Although theserisks are minimal and yet to be demonstrated, each needs to be addressed. Indeed, itmay be necessary to modify some of the PDR approaches in order to ensure completesafety of such transgenic crops and satisfy governments, regulatory authorities, andthe general public. We believe that careful and responsible uses of PDR transgenes inrice will minimize yield losses from viruses and that within a decade transgenic virusresistantrice plants will have a widespread use in integrated disease management.ReferencesBakker W. 1975. Rice yellow mottle virus. Descriptions of Plant Viruses No. 149. Wallingford(UK): Commonwealth Mycological Institute.Baulcombe DC. 1996. Mechanisms of pathogen-derived resistance to viruses in transgenicplants. Plant Cell 8:1833-1844.Beck DL, Guilford PJ, Voot DM, Andersen MT, Forster RLS. 1991. Triple gene block proteinsof white clover mosaic potexvirus are required for transport. Virology 183:695-702.Bonneau C, Brugidou C, Chen L, Beachy RN, Fauquet C. 1998. Expression of the rice yellowmottle virus P1 protein in vitro and in vivo and its involvement in virus spread. Virology244:79-86.Brunt AA, Crabtree K, Dallwitz MJ, Gibbs AJ, Watson L, Zurcher EJ. 1998. Plant virusesonline: descriptions and lists from the VIDE database. URL http://biology.anu.edu.au/Groups/MES/vide/.Carr JP, Zaitlin M. 1991. Resistance in transgenic tobacco plants expressing a nonstructuralgene sequence of tobacco mosaic virus is a consequence of markedly reduced virus replication.Mol. Plant-Microbe Interact. 4:579-585.Collins RF, Gellatly DL, Sehgal OP, Abouhaidar MG. 1998. Self-cleaving circular RNA associatedwith rice yellow mottle virus is the smallest viroid-like RNA. Virology 241:269-275.Cooper B, Lapidot M, Heick JA, Dodds JA, Beachy RN. 1995. A defective movement proteinof TMV in transgenic plants confers resistance to multiple viruses whereas the functionalanalogue increases susceptibility. Virology 206:307-313.Falk BW, Bruening G. 1994. Will transgenic crops generate new viruses and new diseases?Science 263:1395-1396.Engineering for virus resistance in rice 417