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First Report of Banana mild mosaic virus Infecting Plantain in Ivory Coast

Plantain (Musa sp., genomic group AAB) is an important crop for millions of the world's poorest people. In Ivory Coast, it is the second most consumed food and an important source of income for farmers. Between 2010 and 2011, a survey for viruses infecting plantain (AAB) was conducted in 10 major plantain-growing regions located in eastern (Abengourou), middle-western (Bouaflé, Daloa, Issia, Oumé, Sinfra, Zuenoula), central (Yamoussoukro), and southern (Aboisso, Gagnoa) Ivory Coast. Leaf samples showing yellow streaks or mild chlorotic streaks were collected and dried on CaCl₂ for storage. A representative sample from each location was selected and tested for the presence of Cucumber mosaic virus (CMV, genus Cucumovirus), Banana streak virus (BSV, genus Badnavirus), Banana mild mosaic virus (BanMMV, family Flexiviridae), and Banana bract mosaic virus (BBrMV, genus Potyvirus). Immunocapture (IC)-PCR was used for the detection of BSV while reverse transcription (RT)-PCR was used for the detection of CMV, BanMMV, and BBrMV. The following primers sets were used: BSV cl1 and BSV cl2 (1), CMV 3′ and CMV 5′ (3), BanMMV BanCP1 and BanCP2 (4), BBrMV Bract N2 and Bract NR (2). BanMMV was detected as mixed infections with BSV in the 10 tested samples, one of which also contained CMV. To confirm the identity of the amplification products from the BanMMV primers, one cDNA fragment was directly sequenced in the forward direction (Macrogen Inc., Seoul, South Korea). BLAST search in GenBank revealed that the partial coat protein (CP) sequence of the Ivorian isolate shared 80 to 88% nucleotides and 81 to 92% deduced amino acid similarities with BanMMV isolates. In contrast, partial CP sequence of the Ivorian isolate had less than 40% deduced amino acid sequence identity with other Flexiviridae CP sequence. The partial CP sequence of the Ivorian BanMMV isolate was deposited in GenBank under Accession No. JX014304. To further confirm the identification, all the samples were tested by plate trapped antigen (PTA)-ELISA with rabbit polyclonal antiserum specific to BanMMV (obtained from B. E. Lockhart, University of Minnesota, U.S.A.) and anti-rabbit IgG (Sigma-Aldrich, Belgium/A3687). The 10 samples reacted positive for BanMMV by ELISA. CMV and BSV have been reported in Ivory Coast, but to our knowledge, this is the first report of BanMMV in the country. The detection of BanMMV in association with BSV or CMV in mixed infection in 10 locations which are important plantain growing areas is a first step in the evaluation of the impact of virus diseases on plantain production in this country.

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