Molecular Characterization of a Large Diversity of Bambara Groundnut Potyviruses (Vigna subterranea (L.) Verdc.) in Burkina Faso

Potyviruses are major constraints to grain legume production by causing significant yield losses. Potyviruses infecting Bambara groundnut (Vigna subterranea) were investigated in Burkina Faso. Leaf samples collected from three agroclimatic zones were subjected to RT-PCR and sequence analyses. Of a total of 135 samples, 36 (26.67%) were detected positive in RT-PCR tests using potyvirus universal primers. Analysis of full coat protein (cp) sequences from 24 isolates revealed the occurrence of three groups of Bambara groundnut-infecting potyviruses. Virus isolates in group 1 shared 94.5% - 100% nucleotide (nt) identity with CABMV whereas those in group 2 and group 3 were distantly related Bean common necrosis virus (BCMNV) and Passiflora virus Ugandan which were their respective closest potyviruses. Group 2 shared 77.1% nt and 78.8% - 79.9% aa identity with BCMNV and group 3 shared 77.3% - 78.3% nt and 80.7% - 81.5% aa identity with Passiflora virus Ugandan. All three groups were confirmed by phylogenetic analyses. Taking into account potyvirus demarcation criteria, group 1 isolates belonged to CABMV species. Group 2 and group 3 were assigned to a potentially new potyviruses species and designated Bambara groundnut potyvirus 1 (BGPV1) and Bambara groundnut potyvirus 2 (BGPV2).