Characterization of tomato leaf curl New Delhi virus causing mosaic disease of sponge gourd (Luffa cylindrica L.) and its seed transmissible nature

Abstract

Sponge gourd is a common vegetable crop cultivated and consumed extensively in northern India. Mosaic disease caused by virus infection becomes a major constraint for its cultivation by farmers with inadequate resources. Samples of sponge gourd showing severe mosaic with reduced leaf size, malformed vines, severe curling and puckering of leaves with a disease incidence ranging between 65-100% in Varanasi region were collected and analysed. Samples were tested positive for the presence of begomovirus through PCR analysis. Rolling circle amplification (RCA) product of representative samples subjected to restriction analysis yielded ~2.7kb presumed bands of virus was cloned, sequenced and analyzed. Sequence analysis revealed the presence of bipartite begomovirus, Tomato leaf curl New Delhi virus (ToLCNDV). It constitutes two distinct DNA-A molecules having 88.9% identity among themselves and one DNA-B molecule sharing identity of 96% with earlier reported ToLCNDV isolates from India. Besides, the association of tomato leaf curl New Delhi alphasatellite (ToLCNDA) and tobacco leaf curl Patna betasatellite (TbLCPB) were also detected. Additionally, seed-borne nature of ToLCNDV was ascertained through PCR assay in different parts of the fruit viz., pericarp, mesocarp and immature seed. Further presence of virus in matured seed and seedlings obtained through grow-out test were confirmed through serological assay. To our knowledge, this is the first documentation for the seed transmissible nature of ToLCNDV causing mosaic disease on sponge gourd.