Evaluation of Ugandan Rice Cultivars for Resistance Against Rice yellow mottle virus

抄録

Rice yellow mottle disease caused by Rice yellow mottle virus (RYMV) is one of the major threats to rice production in Uganda. Host resistance which is considered as the most effective and sustainable control measure is hindered by limited resistant genetic resources. We evaluated the reaction of Ugandan and some foreign rice cultivars against RYMV to select moderately resistant cultivars. To validate the assessment by symptom appearance and ELISA, plants were inoculated at 21 (early inoculation) and 35 (late inoculation) days after sowing (DAS) and evaluated at 28 days post inoculation. A positive relationship between assessment by ELISA value and symptom appearance was observed. Significant differences were observed between the influence of early inoculation and late inoculation. In early inoculations lowland rice cultivars showed higher disease severity than upland cultivars. Early inoculation was suitable for selection of highly resistant cultivars while late inoculation was better in selection of moderately resistant cultivars. Also, wild rice species and some Japanese upland rice cultivars were examined by inoculation at 21 DAS. Overall, using symptom appearance, plant height reduction percentage, ELISA and RT-PCR, 2 foreign rice cultivars and 4 wild rice species were highly resistant and 4 foreign cultivars and 6 Ugandan upland rice cultivars were moderately resistant. All the Ugandan farmer favored cultivars tested in this study were susceptible to RYMV. Cultivars with moderate resistance selected in this study should be introduced alongside the existing sensitive cultivars desired by the farmers.