Inheritance of resistance to rice yellow mottle virus
Ahereza, Cissy Clare
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Rice is one of the most important food crops in Africa, where rice and the economic activities related to its production, processing, distribution, and consumption are widely considered a key for economic development, food security, and poverty reduction. In Uganda, rice production is constrained by biotic and abiotic factors; among the biotic factors is Rice Yellow Mottle Virus (RYMV) which causes yield loss of approximately 100% for highly susceptible varieties. The Uganda rice breeding programme has introduced new rice varieties and lines to broaden its existing germplasm base and increase rice yield through different strategies including improvement of genetic resistance to RYMV. Different crosses have been generated from these new rice varieties with the local susceptible Supa local variety, however their reaction to RYMV has not been determined. Therefore the main objective of this study was to improve rice yields in Uganda through breeding RYMV resistant varieties and the specific objectives were to assess the level of resistance to RYMV in F2 populations of rice developed from crosses with variety Supa and to assess the yield potential of F2 segregating populations developed from Supa. The study was carried out at National Crops Resources Research Institute (NacRRI). The study was comprised of F2 progeny from four crosses of lowland rice varieties SL x ARC 1, SL x Gigante, SL x ARC 3, and ARS 11 x SL populations generated using North Carolina II mating design. F2 seed were planted in the field with parent checks in 11 rows and 9 columns per cross. Parental checks were planted after every third row of F2 offsprings. The experiment was set up in Alpha lattice design. RYMV symptoms were recorded on plants using a scale of 1-9. Disease scoring was done weekly for 6 weeks. The data collected on disease and yield parameters were summarized in Microsoft excel sheet and subjected to Analysis of Variance (ANOVA) using GenStat statistical package 14th edition. Significant differences between treatment means were separated using Fisher’s Least Significant Difference (LSD) test at 5% confidence level. Results from the study showed that RYMV disease severity score throughout the crop growth period was significant (P ≤ 0.001). Cross SL x ARS 11 showed relative resistance compared to others. Therefore, the resistant lines should further be evaluated and consistent ones in terms of resistance to RYMV can be introduced to the rice breeding program. This will ensure both high yields of rice and the preferable aroma of Supa rice.