Old foe, new host: epidemiology, genetic diversity and pathogenic characterization of maize streak virus in rice fields from Burkina Faso.

Abstract

Rice is of critical significance regarding food security worldwide including in Africa. Only two viruses impacting rice production in Africa have been deeply investigated for decades: the rice yellow mottle virus (Solemoviridae) and the rice stripe necrosis virus (Benyviridae). Using viral metagenomics, we aimed at exploring the diversity of viruses circulating in Burkina Faso rice fields. We performed an epidemiological survey in this country between 2016 and 2019 involving 57 small farmers rice fields under two production systems (rainfed lowlands and irrigated areas). More than 2700 rice samples were collected without a priori (not based on symptom observation) following a regular scheme. In addition, wild and cultivated (maize and sugarcane) Poaceae growing nearby rice fields were also collected. Unexpectedly, metagenomics detected maize streak virus (MSV, Geminiviridae) in analyzed rice samples. Further molecular analyses using RCA-PCR showed that MSV is widely distributed and highly prevalent in both rainfed lowlands and irrigated rice areas. MSV-A and MSV-G strains were identified. MSV-G, exclusively identified so far in wild grasses, was the most prevalent strain while MSV-A, known to cause severe symptoms in maize, was sporadically identified. No genetic differentiation was detected between MSV isolates either infecting wild or cultivated plant species. Using infectious clones in experimental conditions, we confirmed the pathogenicity of both MSV strains on rice. Thus, in addition to contribute to the epidemiological surveillance of rice production in Africa, our results illuminate new epidemiological and pathogenic aspects of one of the most studied plant viruses with significant economic consequences in Africa. FundingFrench National Research Agency > program (ANR-10-LABX-001-01), Agropolis Fondation (ANR-16-IDEX-006), French National Research Agency "young researchers" program (ANR-20-CE35-0008-01), CGIAR Research Program on Rice Agri-food Systems (RICE), Cooperation and cultural action department of the French Embassy (SCAC) in Burkina Faso.