Immunocapture RT-PCR detection of Bean common mosaic virus and strain blackeye cowpea mosaic in common bean and black gram in India

The strains of Bean common mosaic virus (BCMV) and blackeye cowpea mosaic (BICM), genus Potyvirus, were detected from 25 common bean and 14 black gram seeds among 142 seed samples collected from different legume-growing regions of India. The samples were subjected to a growing-on test, an indicator plant test, an electron microscopic observations, an enzyme linked immunosorbent assay and an immunocapture RT-PCR. The incidence of the two tested viruses in common bean and black gram seed samples was 1–6% and 0.5–3.5%, respectively in growing-on test evaluations. Electron microscopic observations revealed filamentous virion particles from the leaves of plants showing characteristic virus disease symptoms in growing-on and host inoculation tests. The identity of the strains was confirmed by immunocapture RT-PCR, with a final amplification product of approximately 700 bp for BCMV and BCMV–BICM. The complete identity of the two viruses was further confirmed by nucleotide sequencing of the partial coat protein and 3'-UTR regions. The sequences of the four BCMV and BCMV–BICM isolates each consisted of 583–622 and 550–577 nucleotides. The present report confirms the widespread nature of these two serious potyviruses in the two most important legume crops in India.