Infectivity and genetic recombination of yellow mosaic viruses associated with blackgram (Vigna mungo L. Hepper) in South India

The pulse crops widely cultivated in South India for their protein rich grains are negatively affected by whitefly-transmitted begomoviruses (genus Begomovirus, family Geminiviridae) causing yellow mosaic disease (YMD). Here, YMD-inducing begomoviruses were characterized from cultivation areas in Tamil Nadu, South India, with complete sequences of seven DNA-A and eight DNA-B components determined. The pairwise nucleotide sequence comparisons for complete DNA-A showed that both mungbean yellow mosaic virus (MYMV) and mungbean yellow mosaic India virus (MYMIV) were present. The comparisons of nucleotide sequences of YMD begomoviral isolates revealed the presence of five groups of DNA-B components, which showed only 81–88% identity in the common region with their cognate DNA-A. The recombination analysis revealed significant events in the the non-coding and coding regions in DNA-B components, which were predicted amongst the MYMV isolates and between MYMV and MYMIV sequences. The partial tandem repeat constructs of MYMV and MYMIV DNA-A and DNA-B isolates (GenBank Accession Nos. KC911721, KC911724, AF142440 and AF126406) were infectious in blackgram (Vigna mungo), which showed typical YMD symptoms. Also the blackgram genotypes showed different levels of susceptibility and tolerance under experimental inoculation with MYMV and MYMIV. From the results, it is inferred that MYMV and MYMIV have occurred in mixed infection in blackgram.