Molecular epidemiology of cassava mosaic disease in Madagascar

Harimalala M., Chiroleu F, Giraud-Carriera, Hoareau M., Zinga I., Randriamampianina J.A, VelombolaS., Ranomenjanahary S., Andrianjaka A., Reynaud B, Lefeuvre P., Lett J-M.2014. Molecular epidemiology of cassava mosaic disease in Madagascar. Early view.Plant Pathology, Doi: 10.1111/ppa.12277

Abstract

Cassava is the staple food for hundreds of millions of people in Africa but its cultivation is seriously constrained bycassava mosaic disease (CMD) in Madagascar, and in Africa in general. This study identified the cassava mosaic geminiviruses(CMGs) involved in CMD in Madagascar and their associated epidemiological characteristics from countrywidesurveys. Molecular characterization of CMGs in Madagascar revealed an unprecedented diversity andco-occurrence of six viruses: African cassava mosaic virus (ACMV), East African cassava mosaic Cameroon virus(EACMCV), East African cassava mosaic Kenya virus (EACMKV), East African cassava mosaic virus (EACMV), SouthAfrican cassava mosaic virus (SACMV) and the recently described Cassava mosaic Madagascar virus (CMMGV). Distinctgeographical distributions were observed for the six viruses. While ACMV was more prevalent in the central highlands,EACMV and EACMKV were prevalent in lowlands and coastal regions. Both EACMCV and SACMV occurredin almost all the localities visited. PCR diagnosis revealed that mixed infection (up to four co-infected viruses) occurredin 21% of the samples and were associated with higher symptom severity scores. Pairwise comparisons of virus associationsshowed that EACMCV was found in mixed infections more often than expected while ACMV and SACMV weremostly found in single infections. A greater abundance of whiteflies was observed in lowland and coastal areas. Nevertheless,infected cuttings remain the primary source of CMD propagation (95%) in Madagascar.

Publiée : 23/01/2015