Distribution and natural incidence of Onion Yellow Dwarf virus (OYDV) on garlic and its related Allium species in India

A study was done in 2010 and 2011 to determine the presence of Onion Yellow Dwarf virus (OYDV) on garlic and related Allium spp. in India. Garlic leaf samples were collected from 12 garlic growing states of India. Virus identification was based on DAS-ELISA, RT-PCR and qRT-PCR. Out of total 493 samples analyzed, 308 samples from all states were found positive for OYDV in variable proportions. The highest percentage of OYDV positives were recorded from Maharashtra (96%) followed by Gujarat (75%) and Madhya Pradesh (75%). The lowest percentage of OYDV positives were recorded from Rajasthan (25%) followed by Delhi (40%). To know the status of OYDV on commercial cultivars, six leading garlic cultivars were tested. Relative quantification of OYDV concentration in these garlic cultivars was determined through qRT-PCR. No correlation was observed between bulb skin colour and virus concentration. Total 13 accessions of wild and related edible Alliums tested through RT-PCR and qRT-PCR for natural incidence of OYDV, 10 species were found positive for the virus. Three species, viz., A. senescens, A. cepa var. aggregatum (Multiplier onion) and A. fistulosum were found free from OYDV.