Characterization of Squash leaf curl China virus associated with mosaic and vein clearing disease of pointed gourd (Trichosanthes dioica Roxb.) and its vector whitefly cryptic species

Pointed gourd ( Trichosanthes dioica Roxb.) also known as parwal, is an important nutritive vegetable crop cultivated throught Indian subcontinent. Survey was conducted during 2016 and 17 for assessing the vrial disease incidence and whitefly infestation in pointed gourd at 30 farmer’s fields in Mirzapur and Varanasi districts, Uttar Pradesh State of India. Incidence of pointed gourd plants expressing typical begomovirus symptoms such as mosaic and vein clearing, upword curling, shriveled fruits and dwarfing of entire vines ranged from 15 to 25 per cent. Infestation of huge number of whiteflies ( Bemisia tabaci Genn.) in both healthy and infected pointed gourd plants was observed with average number of 50–100 whiteflies per leaf in vine. All the thirty infected samples (PG1–PG30) collected from different farmers fields of pointed gourd gave positive amplification for begomovirus DNA-A genome specific primers with expected amplicon of 1.2 kb. The partial viral genome (1.2 kb) sequences obatined from 30 samples of pointed gourd are having more than 98% similarity among them and are closely related to previously described bipartite begomovirus, Squash leaf curl China virus (SLCCNV). No amplification was obatined for alpha and betasatellites specific primers in all samples. Complete nucleotide sequence of DNA-A and DNA-B obtained from one representative sample (PG1) of pointed gourd by rolling circle DNA amplification showed maximum nucleotide (nt) identity of 93.2–96.0% and 89.0–98.1%, respectively with Indian strains of SLCCNV. In the current study, begomovirus isolate associated with pointed gourd is identified as SLCCNV. The putative recombination analysis of genome of the SLCCNV-PG1 isolate showed that major part of the viral genome was likely descended from the begomoviruses reported previously, which are known to infect tomato and cucurbits. Further, the whitefly, B. tabaci cryptic species occurred in the begomovirus associated pointed gourd fields was identified as Asia-I group.