First report of Groundnut bud necrosis virus infecting wild species of Vigna, based on NP gene sequence characteristics

Symptoms such as chlorotic and necrotic spots on leaves, and necrosis of the stems and petioles, were observed in twelve accessions of wild species/sub-species of Vigna (V. umbellata, V. glabrescens, V. hainiana, V. mungo var. mungo, V. radiata var. radiata and V. radiata var. sublobata) grown at the Indian Institute of Pulses Research, Kanpur, India during August-November 2011. Incidence of symptomatic plants ranged between 7-40%. Based on symptoms appearing on diagnostic host cowpea (Vigna unguiculata cv. Pusa Komal) after mechanical inoculation, RT-PCR and nucleocapsid protein (NP) gene sequence characteristics, Groundnut bud necrosis virus (GBNV) was identified as the causal agent. Analysis of the NP gene from intra-field (within a field) isolates of GBNV revealed 1-4% diversity in nucleotide and 0-4% in amino acids. However, diversity among intra-field isolates and isolates from cultivated Vigna ranged from 2-7% at nucleotide level and 0-6% at amino acids level. This is the first report of GBNV infection in these wild species/sub-species of Vigna, and analysis of intra-field diversity in the NP gene of 12 GBNV isolates is also outlined.