Indian Journal of Virology

Four whitefly-transmitted geminiviruses (WTGs), belonging to the genus Begomovirus, cause leaf curl disease of tomato (TomLCD) in India. These viruses have a wide host range. To identify the natural nontomato hosts and distribution of these viruses, samples from eight weed and ornamental plant species, showing symptoms typical of those induced by WTGs were collected from areas around tomato fields in Delhi, Haryana, Punjab and Rajasthan. The samples collected from Delhi were tested by (a) transmission by whitefly (Bemisia tabaci) to tomato, (b) nucleic acid spot hybridization to detect viral genomic components, and (c) polymerase chain reaction to detect the viruses known to cause TomLCD in India. Whereas, the samples collected from Haryana, Punjab and Rajasthan were tested only by PCR. In all the eight plant species tested from Delhi, DNA A and DNA β were detected, but DNA B was detected only in Solanum nigrum by NASH with probes of DNA A, DNA B and DNA β of Tomato leaf curl New Delhi virus (ToLCNDV). By PCR, using primers designed from the conserved coat protein (CP) and intergenic (IR) regions of DNA A of the four WTGs causing TomLCD in India, amplification was obtained from six of the eight plant species tested from Delhi. The WTGs from these six plant species were also transmitted to tomato cv. Pusa Ruby by whitefly; the infected tomato plants developed leaf curl symptoms with minor variations. Although WTGs were transmitted from six plant species collected from Delhi, the WTGs known to cause TomLCD in India were detected only in two plant species by PCR with virus species specific primers; ToLCNDV was detected in S. nigrum and Tomato leaf curl Gujarat virus (ToLCGV) was detected in Datura metel. ToLCNDV and ToLCGV were also detected by PCR in samples of S. nigrum collected from Punjab, and wild sunflower from Rajasthan, respectively. This is the first report of molecular detection of tomato infecting begomoviruses in D. metel, Eclipta alba, Tagetes erecta, Phyllanthus niruri, S. nigrum and wild sunflower, and first report of Begomovirus infection in Tabernaemontana divaricata. ToLCNDV has been detected for the first time in S. nigrum and cluster bean, and ToLCGV in D. metel and wild sunflower. The other two WTGs - Tomato leaf curl Bangalore virus (ToLCBV) and Tomato leaf curl Karnataka virus - causing TomLCD in southern India were not detected in any of the plant species tested in this study indicating that these two viruses do not occur commonly in Delhi, Haryana, Punjab and Rajasthan. These findings indicate D. metel, S. nigrum and wild sunflower may play an important role in the perpetuation of ToLCNDV and ToLCGV in north-western India. The present study also shows occurrence of so far uncharacterized WTGs in weeds and ornamental plants, which may be causing TomLCD in north-western India.