Plant Virus Laboratory and Biotechnology Unit, Division of Crop Protection, Central Research Institute for Jute and Allied Fibres, Barrackpore, Kolkata-700120, India.
Bast fibre crops like jute (Corchorus olitorius and C. capsularis), mesta (Hibiscus cannabinus and H. sabdariffa) and Sunn hemp (Crotalaria juncea) are the economically important cash crop in eastern India and within last four years, rapid increase in the incidence of four viral diseases viz. mesta yellow vein mosaic, mesta leaf curl, jute mosaic, and Sunn hemp leaf curl were noticed in eastern and northern India and imparted heavy yield losses. Whitefly transmission and expected amplification with different Begomovirus specific and satellite DNA beta primers, in different combination, in these samples confirm the presence begomoviruses. In course of further characterization, a ∼2.7 kb DNA A homologue and ∼1.3 kb beta DNA from mesta samples showing yellow vein mosaic symptom was amplified, cloned and sequenced (EF428256, DQ298137). DNA A of the present isolate found to share less than 89% sequence identity with any known Begomovirus and evolved as a new recombinant molecule arisen from recombination between different begomoviruses and their strains reported from north India, south India and China. Results thus indicated the possible appearance of a new species of Begomovirus and a tentative name Mesta yellow vein mosaic virus (MeYVMV) is proposed. The satellite DNA beta associated with this disease showed its similarity with different DNA beta reported to be associated with cotton leaf curl disease and appears as a distinct one in phylogenetic analysis. Analysis on coat protein (EF614152-57) and DNA beta sequences (EF614158-62) of six isolates obtained from north and east India during the present study indicated the existence of two distinct Begomovirus complexes with the disease in north and east India. Analysis on coat protein gene (EF620561-63) and DNA beta (EF620564-66)from mesta leaf curl samples indicated that in east India the disease is associated with a strain of MeYVMV, while in north India a distinct begomovirus related to Malvastrum yellow vein virus is associated with the disease. A 1.2 kb DNA A fragment was obtained from jute yellow mosaic sample using a universal Begomovirus specific primers, cloned and sequenced (EU047706). Analysis on this DNAA fragment interestingly revealed the existence of a new world Begomovirus related to Corchorus golden mosaic virus from Vietnam. A 1.2 kb amplicon of DNA A and 1.3 kb DNA beta amplicon were obtained from the sunn hemp samples showing leaf curl symptom.
