CHARACTERIZATION OF BEGOMOVIRUS ASSOCIATED WITH LEAF CURL DISEASE OF WATERMELON
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Date
2018-07
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University of Horticultural Sciences, Bagalkot (COLLEGE OF HORTICULTURE, GKVK POST, BENGALURU)
Abstract
Watermelon is one of the important vegetable crops and is affected by several biotic and abiotic factors. Among the different biotic factors, watermelon leaf curl disease (WmLCD) is new emerging threat for the production of watermelon. The affected plants showed chlorotic mottle, reduction of leaf size, crinkled and malformed leaves, downward/ upward leaf curling and stunted growth of the plants. Incidence of the disease varied from 8.70-50.40 per cent. The virus inoculated watermelon seedlings by whitefly, Bemisia tabaci produced typical leaf curling, mottling and stunted plant growth symptoms 12-15 days after inoculation. Host range studies revealed that five plant species were infected with leaf curl disease of watermelon viz., tomato, tobacco, sponge gourd, cucumber and bottle gourd. Begomovirus infection was confirmed by PCR using begomovirus specific primers. Based on PCR analysis with DNA-A and DNA-B specific primers revealed that begomoviruses associated with Gokak isolate, Chamarajanagar isolate, Chikkaballapur isolate and Bengaluru rural isolates were bipartite, where as Raichur and Muddebihal isolates were monopartite. Absence of alphasatellite molecule in all the six isolates, whereas only defective betasatellite was found in Chamarajanagar isolate. Amplified PCR products were cloned and the sequenced. Based on sequence analysis, begomoviruses associated with the watermelon samples were closely related to tomato leaf curl palampur virus (ToLCPalV). Sequence analysis performed using the Species Demarcation Tool (SDT) analysis of DNA-A revealed that all six isolates were showed highest per cent nt identity (91.5-93.3 per cent) with ToLCPalV infecting different crop plants. Similarly, SDT analysis of the DNA-B-like sequence of all four isolates were showed more percent nt identity (80.2-84.5 %) with ToLCPalV infecting different crop plants. Insilico analysis of begomoviruses associated with watermelon revealed that all the Bengaluru isolated proteins are non-polar in nature. Isoelectric point (IEP) of all proteins range from 6.4976 to 10.6169. The improbability of expression in inclusion body (IEI) of the proteins of begomovirus range between 0.517 to 0.935. Negative GRAVY value indicates that the protein is non-polar and positive value indicates that the protein is polar hence all proteins are non-polar in nature. Rep protein has 92.2 per cent residues in favoured region therefore it is a good quality model. This is first report of ToLCPalV association with WmLCD from India.