Molecular characterization and infectivity of Mungbean Yellow Mosaic India virus associated with yellow mosaic disease of cowpea and mungbean

Grain legumes are an important source of dietary protein across Southeast Asia, but they suffer severe losses due to Yellow mosaic diseases (YMD), caused by members of the genus Begomovirus (family Geminiviridae). Cowpea is an annual tropical grain legume extensively cultivated in sub-Saharan Africa, Southeast Asia and South America. More than 20 viruses are reported in cowpea around the world. Despite its economic importance, little attention has been paid to the viruses infecting cowpea in India. We conducted an elaborate survey and characterization of begomoviruses infecting cowpea in the central and northeast region of India. We report complete sequences of 13 components (6 DNA-A, 6 DNA-B, and 1 complete genome) belonging to four strains of MYMIV, each of CGMV and FbSLCV. Nucleotide sequence comparison analysis showed the cowpea isolates MYMIV DNA-A [KY556679] having highest similarity (98%) with reported soybean isolate of MYMIV segment DNA-A [AY049772] and lowest similarity (77%) with lima bean isolate of horsegram yellow mosaic virus (HYMV) [AM932429] whereas cowpea isolates MYMIV DNA-B [KY556680] showed highest identity (98%) with MYMIV Brebs3 segment [JN368446] and lowest identity (94%) with MYMV LBG623 segment [KF928962]. Our survey revealed maximum incidence of MYMIV infection in cowpea in the central and northeast India. We therefore characterized the MYMIV infection in cowpea as well as its natural host, mungbean through agroinoculation of dimeric infectious clones and confirmed the pathogenicity of MYMIV. This is the first report of cowpea isolate of MYMIV infecting mungbean with YMD symptoms which is experimentally demonstrated through Koch's postulate.