RESISTANCE TO INFECTION OF RICE TUNGRO VIRUSES AND VECTOR RESISTANCE IN WILD-SPECIES OF RICE (ORYZA SPP)

Fifteen accessions of 8 species of wild rice (Oryza spp.), which were found to be resistant to rice tungro bacilliform virus (RTBV) infectio n, were reexamined to determine whether resistance was attributed to v ector resistance. Of the 15 accessions, 3 of O. rufipogon (IRGC Acc. n o. 105909, 105908 and 105910) showed low or moderate level of antibios is to the major vector Nephotettix virescens; they were resistant to i nfection of tungro viruses, regardless of vector resistance. Three acc essions of O. officinalis (IRGC Acc. no. 105100, 105365 and 105376) sh owed high levels of antibiosis to N. virescens, but they showed low le vels of antibiosis to N. nigropictus. These O. officinalis accessions were not infected with RTBV in the mass inoculation test and showed no or low percentage of RTBV infection in the forced inoculation test by N. nigropictus. One O. ridleyi accession (IRGC Acc. no. 100821) showe d a moderate level of antibiosis to N. nigropictus and no infection wi th RTBV in the mass inoculation test. These results suggest that resis tance to RTBV infection of these 7 accessions does not depend on vecto r resistance. These wild rice accessions can be useful in developing r ice cultivars with high resistance to tungro.