Resistance to Rice yellow mottle virus and performance of selected improved rice genotypes in central Uganda

Rice yellow mottle virus causes yield losses of 10-100%, depending on disease epidemiology, cultivar grown and cropping system. Resistant rice varieties with farmer and consumer-preferred traits are, however, not available in Uganda. This study was conducted to identify new sources of resistance to RYMV. One hundred twelve (112) genotypes were evaluated twice under screen house conditions using virus isolates from three "hot-spots" in Uganda namely, Iganga, Lira and Namulonge. Relative area under disease progress stairs, plant height reduction, delay in days to flowering, reduction in chlorophyll content and reduction in grain weight were positively correlated (>= 0.47) and exhibited high heritability (>= 0.71). Eleven resistant and six highly resistant genotypes were identified. These genotypes were further evaluated for performance in field trials for two seasons in central Uganda. Analysis of variance revealed high diversity among genotypes for disease reaction, agronomic traits and yield. Genotypes IRL 53 (GP 54) and Namche 2 performed best in most traits evaluated, with high selection indices (22.74 and 21.92, respectively). Genotypes IRL 2 (GP 54) and IRL 4 (69 GP 54) were the most yielding. These four rice genotypes should be screened further for resistance to narrow leaf brown spot, brown spot and bacterial leaf streak. Multi-locational evaluation should also be done to identify the most promising genotypes for development of improved varieties with fanner-preferred traits.