PCR based identification of the virus causing yellow mosaic disease in wild Vigna accessions

Nine accessions of two wild species of Vigna viz., V. hainiana and V. trilobata, and five accessions of sub-species of Vigna viz., V. mungo var. silvestris and V. radiata var. radiata grown at Indian Institute of Pulses Research, Kanpur, India during 2010 were observed to be affected by yellow mosaic disease. The main symptoms, bright yellow spots on the leaflets, were similar to those noticed in cultivated genotypes of Vigna and appeared to be of viral etiology. The causal virus was identified by PCR using specific primers designed to amplify a segment of DNA A that contained CP gene of four begomoviruses viz., Mungbean yellow mosaic virus (MYMV), Mungbean yellow mosaic India virus (MYMIV), Horsegram yellow mosaic virus (HgYMV) and Dolichos yellow mosaic virus (DoYMV) and a segment of DNA B that contains movement protein gene. All accessions showing yellow mosaic symptoms tested positive with primers specific to segments of DNA A and DNA B of MYMIV. PCR results with primers specific to MYMV, HgYMV and DoYMV were negative. Accessions of Vigna umbellata and Vigna glabrescens were free from yellow mosaic symptoms and gave negative results in PCR with primers specific to all the four viruses. Attempts to detect β DNA also showed negative results. Results showed that the virus causing yellow mosaic in wild species/sub-species of Vigna grown at Kanpur is caused by MYMIV.