RICE YELLOW MOTTLE VIRUS IN WEST AFRICA

The incidence and severity of rice yellow mottle virus (RYMV) Sobemovirus group was monitored in various rice-growing areas of West Africa. Its presence or absence was determined by symptomatology and serological tests. RYMV was found in all the rice environments but at different levels of incidence and severity of the disease which appeared to depend on the type of variety planted, the rice environment and vegetation zones. Graminaceous weeds, including some wild rice species, were confirmed as alternative hosts for RYMV. Twenty-five rice cultivars comprising local and locally developed cultivars were resistant to RYMV. Most of these cultivars showed stable resistance to rice blast (Pyricularia oryzae (Cavara). The occurrence of RYMV symptoms on some uninoculated plants indicated the possibility of the virus being transmitted either by the beetle vector or through being carried on the seed.