Identification of cowpea [Vigna unguiculata (L.) Walp.] germplasm accessions resistant to yellow mosaic disease

Yellow mosaic disease (YMD) of cowpea, predominantly caused by mungbean yellow mosaic India virus (MYMIV) and mungbean yellow mosaic virus (MYMV) is a major constraint to the production of cowpea (Vigna unguiculata L.) in India resulting in significant yield reductions. The present study extensively evaluated 1127 cowpea germplasm accessions from the National Gene Bank of India, New Delhi, at two hotspot locations (Hyderabad and Delhi) for their response to YMD. About 181 accessions showed no symptoms in field screening at both locations and were considered putatively resistant. A set of the best 100 out of 181 was selected for further confirmation of resistance to MYMIV through whitefly-mediated screening along with 40 accessions known to be susceptible to YMD. The results of whitefly-mediated transmission confirmed MYMIV resistance in 20 accessions with a disease score of zero. Further, the YMD-associated Begomovirus was characterized using rolling circle amplification coupled with sequencing of the full DNA-A genome of MYMIV, which shared an identity of 99.02% with the MYMIV isolate infecting cowpea in Pakistan. The 20 cowpea accessions identified as novel resistant sources to MYMIV in the present study could be used for mapping resistance genes and as donors in resistance breeding for yellow mosaic disease.