Interactions Between Rice yellow mottle virus (RYMV) Isolates and Rice Germplasm from Niger

Rice yellow mottle virus (RYMV) is the most damaging virus in Niger’s rice agrosystems. We analysed host plant-RMYV interactions using 175 accession from the rice germplasm collection of Niger and 52 accessions from Mali. Five different virus isolates from Niger (three), Benin (one) and Burkina Faso (one) were used for inoculation. The assessment was based on visual disease symptom scoring, and secondary disease-related traits such as leaf chlorophyll content and plant height. Most rice accessions were susceptible to RMYV but a few African rice accessions displayed a level of resistance to some virus isolates, which was similar to that of the highly resistant TOG5681. Their host plant resistance was characterised by the absence of symptoms, low chlorosis and limited plant height reduction. Examining alleles using primers derived from the RYMV1 resistance gene revealed that one of these accessions has the rymv1-3 allele and other two accessions bear the rymv1-4 allele. We could not identify any known allele in one highly resistant accession, suggesting the presence of another resistance gene. The RYMV isolate BF1 from Burkina Faso was more aggressive than the three isolates from Niger, which were in turn found to be more aggressive than the isolate from Benin.