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Evidence of the presence of two serotypes of rice yellow mottle sobemovirus in Côte d'Ivoire

N'Guessan P., Pinel A., Caruana M.L., Frutos R., Sy A., Ghesquière A., Fargette D.. 2000. European Journal of Plant Pathology, 106 : p. 167-178.

Serological variability of isolates of rice yellow mottle virus (RYMV) collected in Côte d'lvoire was assessed by immunological tests with polyclonal and monoclonal antibodies (MAbs). Two serotypes (named S1 and S2) were distinguished. The S1 isolates had common epitopes which were absent in S2 isolates, whereas they lacked epitopes shared by S2 isolates. There was no evidence of S1 and S2 mixtures, although S1 and S2 isolates were sometimes found in nearby sites. Serotype S2 was more prevalent in Côte d'lvoire than S1, and was in a large majority in the centre and the south of the country. By contrast, S 1 occurred more widely in the north. S1 isolates were also found in neighbouring countries at the north of Côte d'lvoire. In tests with monoclonal antibodies, three additional serotypes were found, one in West-Africa and two in East-Africa. Using the primers developed against an S2 isolate from Côte d'Ivoire, all S2 but not the S1 isolates were transcribed and amplified by RT-PCR, and another set of primers was developed to amplify S1 isolates. S1 and S2 have different biological properties, and competition between isolates of the two strains was apparent resulting in S2 dominance over S1. This was assessed using S1 and S2 strain specific MAbs, and it occurred whatever the pattern of inoculation or the rice variety tested. Differences in pathogenicity and virus titre did not account for strain competition, as there was no relation between symptom severity, virus content and serotype of the isolates in Oryza sativa indica cultivars. (Résumé d'auteur)

Mots-clés : sobemovirus marbrure jaune riz; sérotype; variation génétique; distribution des populations; côte d'ivoire

Thématique : Maladies des plantes

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