Molecular identification and genetic diversity among six Begomovirus isolates affecting cultivation of cucurbitaceous crops in Uttar Pradesh, India

Abstract

Begomoviruses cause a number of serious diseases of cultivated crops and are considered as the major constraint for the cultivation of several crops all over the world. During a survey in the years 2007 and 2008, the typical symptoms of Begomovirus (yellow mosaic and yellow vein) were observed on six cucurbitaceous crops, viz. bitter gourd (Momordica charantia L.), pointed gourd (Trichosanthes dioica), pumpkin (Cucurbita pepo), pumpkin (Cucurbita maxima), sponge gourd (Luffa cylindrica) and ridged gourd (Luffa acutangula) being cultivated in northern India. Begomovirus infection was suspected due to significant infestation of whiteflies (Bemisia tabaci, the known vector of Begomoviruses) on these species. The presence of Begomovirus was detected from the total DNA extracted from six infected leaf samples of these species by polymerase chain reaction using the specific primers of a well-characterised Begomovirus. The ∼800 bp amplicons of these isolates were cloned, sequenced and the data obtained were compared with each other and with sequence database available in GenBank for best sequence identities and phylogenetic relationships. Based on highest 97–99% sequence identities and closest phylogenetic relationships, four representative Begomovirus species were identified as Ageratum enation virus (from T. dioica), Squash leaf curl China virus (from C. maxima), Tomato leaf curl New Delhi virus (from M. charantia, L. cylindrica and L. acutangula) and Tomato leaf curl Palampur virus (from C. pepo). These results suggested the existence of a high genetic diversity among Begomoviruses infecting cucurbitaceous crops.