Résumé
The
rymv1–3 allele of the eIF(iso)4G-mediated resistance to
Rice yellow mottle virus (RYMV) is found in a few
Oryza glaberrima cultivars. The same resistance-breaking (RB) mutations emerged in the central domain of the VPg after inoculation of isolates of different strains. The RB mutations were fixed, often sequentially, at codons 41 and 52 which paralleled an increase in virus accumulation. RB mutations also emerged after inoculation of an avirulent infectious clone, indicating that they were generated
de novo in resistant plants. Only virus isolates with a threonine at codon 49 of the VPg broke
rymv1–3 resistance, those with a glutamic acid did not. A small subset of these isolates overcame
rymv1–2 resistance, but following a specific pathway. Comparison with the RB process of
rymv1–2, a resistance allele found in a few
Oryza sativa cultivars, showed similarities in the mode of adaptation but revealed converse virulence specificity of the isolates.