Chlorotic curly stunt: a severe begomovirus disease of bottle gourd in northern India.

Bottle gourd (Lagenaria siceraria) an important vegetable crop in India was observed to be affected by a chlorotic curly stunt disease (CCSD) during 2003-2006 in the vegetable growing areas of Delhi and adjoining state of Haryana. The affected plants are severely stunted and bear very small chlorotic and mildly curled leaves. Incidence of the disease varied from 4.7 to 36%. The disease could be easily transmitted by whitefly, Bemisia tabaci but not by sap. The causal virus was found to be a Begomovirus on the basis of whitefly transmission and sequence identity of putative coat protein (CP) and replication initiator protein (Rep) genes. The virus was transmitted to Cucumis sativus, Luffa acutangula, L. cylndrica, Lycopersicon esculentum, Nicotiana tabacum and Praecitrullus fistulosus but not to Citrullus lunatus, Cucumis melo, Cucurbita moschata and Vigna unguiculata. The N-terminal 60 amino acids of CP of the virus had 100% sequence identity with all the isolates of Tomato leaf curl New Delhi virus (ToLCNDV) and two isolates of Squash leaf curl China virus (SLCCV). The full length amino acid sequence of the CP and Rep genes had 100% similarity with ToLCNDV-Svr and -Luffa isolates. The phylogenetic analysis showed that the virus associated with CCSD of bottle gourd belongs to ToLCNDV cluster of the begomoviruses. This is the first record of emergence of a Begomovirus associated severe disease in bottle gourd in India.