How many begomovirus copies are acquired and inoculated by its vector, whitefly (Bemisia tabaci) during feeding?

Begomoviruses are transmitted by whitefly (Bemisia tabaci Gennadius, Hemiptera: Aleyrodidae) in a persistent-circulative way. Once B. tabaci becomes viruliferous, it remains so throughout its life span. Not much is known about the copies of begomoviruses ingested and/or released by B. tabaci during the process of feeding. The present study reports the absolute quantification of two different begomoviruses viz. tomato leaf curl New Delhi virus (ToLCNDV, bipartite) and chilli leaf curl virus (ChiLCV, monopartite) at different exposure of active acquisition and inoculation feeding using a detached leaf assay. A million copies of both the begomoviruses were acquired by a single B. tabaci with only 5 min of active feeding and virus copy number increased in a logarithmic model with feeding exposure. Whereas, a single B. tabaci could inoculate 8.21E+09 and 4.19E+11 copies of ToLCNDV and ChiLCV, respectively in detached leaves by 5 min of active feeding. Virus copies in inoculated leaves increased with an increase in feeding duration. Comparative dynamics of these two begomoviruses indicated that B. tabaci adult acquired around 14-fold higher copies of ChiLCV than ToLCNDV 24 hrs post feeding. Whereas, the rate of inoculation of ToLCNDV by individual B. tabaci was significantly higher than ChiLCV. The study provides a better understanding of begomovirus acquisition and inoculation dynamics by individual B. tabaci and would facilitate research on virus-vector epidemiology and screening host resistance.

​Molecular Characterization of Viruses Associated with Leaf Curl Symptoms on Capsicum (Bell Pepper) under Protected Cultivations in Dharwad, Karnataka

Background: Leaf curl or yellowing symptoms, typical of those caused by begomovirus infection, are commonly observed in capsicum (bell pepper) plants in polyhouses. Three capsicum samples with leaf curl and yellowing symptoms were collected from polyhouse at Hi-tech Horticulture, University of Agricultural Sciences, Dharwad, Karnataka, India, during 2017-2018. Methods: Total nucleic acid was isolated from symptomatic and non-symptomatic samples by following CTAB (Cetyl trimethyl ammonium bromide) method and PCR amplified using degenerate and coat protein gene primers of chilli and tomato leaf curl virus. The virus was confirmed by gel electrophoresis with 0.8 per cent agarose. Amplified PCR product was eluted and sent to sequencing (Chromous biotech Pvt. Ltd., Bengaluru). Result: The primer pair could amplify only Chilli leaf curl virus at ~500 bp but not Tomato leaf curl virus. Sequence homology of ChiLCV isolate form Dharwad matched with ChiLCV-Papaya-New Delhi (HM14036), ChiLCV-Chilli-Jodhpu (HM007104) and ChiLCV-Chilli-Noida (HM007114) respectively. The present study results showed that Chilli leaf curl virus is associated with the leaf curl and yellowing symptoms on capsicum under protected cultivation in Dharwad, Karnataka, India.