SCREENING WILD-SPECIES OF RICE (ORYZA SPP) FOR RESISTANCE TO RICE TUNGRO DISEASE

Tungro is one of the most serious rice diseases in South and Southeast Asia. Production of tungro-resistant cultivars is a major breeding ob jective. Wild species of rice (Oryza spp.) and African cultivated rice , O. glaberrima, were evaluated as possible sources of resistance to r ice tungro disease. Two hundred and ten accessions were tested for res istance to RTBV and RTSV infection. Of these, 52 accessions were not i nfected with RTSV and 15 accessions were not infected with RTBV when i noculated with viruliferous green leafhoppers. Three accessions of O. rufipogon (IRGC Acc. no. 105908, 105909 and 105910), 3 accessions of O . officinalis (IRGC Acc. no. 105100, 105365 and 105376) and 1 accessio n of O. redleyi (IRGC Acc. no. 100821) showed a degree of resistance t o RTBV infection independent of vector resistance. The level of resist ance to rice tungro disease shown in these 7 accessions of 3 wild spec ies was higher than that found in cultivated rice. These wild rice acc essions could be useful in developing rice cultivars with a high resis tance to tungro.