Plant Virology Unit, Division of Plant Pathology, Indian Agricultural Research Institute, New Delhi-110 012, India.
Abstracts of the papers presented at the XVIII National Conference of Indian Virological Society at Post Graduate Institute of Medical Education and Research, Chandigarh, India, December 11–13, 2008.
Onion, garlic and shallot are the major allium crops grown commercially in India. Allium crops are infected by different viruses belonging to diverse taxonomic groups. Five positive sense single stranded RNA viruses belonging to three taxonomic group viz., Onion yellow dwarf virus (OYDV) (Potyvirus), Shallot latent virus (SLV) and Garlic common latent virus (GarCLV) (Carlavirus) and allexiviruses could be detected in these allium crops. These viruses individually or in mixed infection can cause significant yield reduction in onion seed crop, garlic and shallot. OYDV, SLV and GarCLV are aphid (Myzus persicae) borne while allexiviruses are transmitted by eriophyd mites (Aceria tulipae). Since allium species are mostly vegetatively propagated these viruses are passed on from one generation to next by propagating materials such as garlic cloves, shallot and onion bulbs. Initially standard RT-PCR was developed for individual detection of these viruses in different allium crops but individual detection of a virus by RT-PCR is expensive and time consuming. Therefore, multiplex RT-PCR was standardized for detecting these viruses simultaneously in a single reaction and presence or absence of a virus was determined in onion, garlic and shallot. The study indicated the presence of OYDV and Allexivirus in onion, OYDV, SLV, GarCLV and Allexivirus in garlic and SLV and Allexi in shallot. PCR products of individual viruses were either directly sequenced or cloned and sequenced to confirm their identity. Molecular charecterisation and the phylogenetic relationship of these viruses have also been discussed.
