​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.

Effects of Tomato Leaf Curl Virus on Growth and Yield Parameters of Tomato Crop

Iftikhar, Y., M. Mubeen, A. Sajid, M.A. Zeshan, Q. Shakeel, A. Abbas, S. Bashir, M. Kamran and H. Anwaar. 2021. Effects of Tomato Leaf Curl Virus on Growth and Yield Parameters of Tomato Crop. Arab Journal of Plant Protection, 39(1): 79-83. Tomato is an important vegetable crop, belongs to the family Solanaceae and is the second most consumed vegetable following potatoes. The tomato crop is grown all over the world in both summer and winter seasons, and plant viruses are a major threat to tomato production. Among these viruses, tomato leaf curl virus (TLCV) causes considerable yield loss to tomato crop. This virus is transmitted by a whitefly (Bemisia tabaci) vector. In this study, the effect of TLCV infection, on the following tomato growth and yield parameters, was evaluated: plant leaf number and area, plant biomass, plant height, root length, and plant stem diameter and yield. Tomato plants were transplanted in wellprepared plots with 4 replications. The control group was covered with polyethene bag to avoid whitefly infestation. Plants were scored on the 15th and 30th day after inoculation and TLCV disease severity was recorded. Analysis of variance (ANOVA) showed the significant differences between the healthy and infected tomato plants. Moreover, growth and yield parameters were reduced with the increase in disease incidence, disease severity and whitefly infestation. Disease severity was increased with the increase in temperature during the growing season. It can be concluded from this study that TLCV significantly affects growth and yield of the tomato crop. Keywords: Tomato, Tomato leaf curl virus, TLCV, disease incidence, disease severity.

A BRIEF DESCRIPTION OF TOMATO LEAF CURL VIRUS AND ITS MANAGEMENT

The tomato crop is affected by various biotic and abiotic factors. Among the biotic factors, Tomato Leaf Curl Virus (TLCV) is one of the most devastating viruses of tomato. The virus belongs to Begomovirus and family Gemniniviridae. The genome of virus is single-stranded-DNA. It is naturally transmitted through whitefly (Bemisia tabaci). The virus is responsible for causing severe economic losses up to 80% in tomato crop-growing regions and continuously threatening the tomato crops. The increasing severity of TLCV has compelled plant virologists to develop accurate detection and identification of the virus. TLCV is responsible for certain biochemical changes and considerably affecting the plant growth. Tomato Leaf Curl Virus is significantly influenced physiological parameters and metabolic activities of all tomato varieties. The biochemical changes of cellular components are caused due to morphological deviation of infected virus plants, and symptoms expressed by the plants can determine the magnitude of the vegetable losses. It is evident from the previous reports, that nutrients were effective in reducing TLCV from a tomato plant. Moreover, the usage of resistant varieties and controlling of whitefly population and management of TLCV by different nutrients are some of the economical and recommendable ways to manage TLCV. Among the organic management strategies, the compost is also considered best in suppressing disease severity. Moreover, epidemiology plays a vital role in the spread and progress of the disease. Keeping in view the importance of TLCV and its effects on tomato crop, the present review will highlight the etiology, physiology and management of TLCV.

Metagenomic analyses and genetic diversity of Tomato leaf curl virus complex affecting tomato plants in Kenya

Background Tomato production is threatened worldwide by the occurrence of begomoviruses which are associated with tomato leaf curl diseases. There is little information on the molecular properties of tomato begomoviruses in Kenya, hence we investigated the population and genetic diversity of begomoviruses associated with tomato leaf curl in Kenya. Methods In 2018, we obtained tomato leaf samples with virus-like symptoms from farmers’ fields across Kenya and used Illumina sequencing to identify associated begomoviruses. Using the sequences, we determined the genetic diversity of begomoviruses. Additionally, selection pressure and recombinant isolates within the population were evaluated. Results Twelve complete begomovirus genomes were obtained from our samples with an average coverage of 99.9%. The sequences showed 95.7–99.7% identity among each other and 95.9–98.9% similarities with a Tomato leaf curl virus Arusha virus (ToLCArV) isolate from Tanzania. When we analyzed the amino acid sequences, we detected the highest identities in the regions coding for the coat protein gene (98.5–100%) within the isolates, and with the C4 gene of ToLCArV (97.1–100%). Phylogenetic algorithms clustered all Kenyan isolates in the same clades with ToLCArV, thus confirming the isolates to be a variant of the virus. Recombination analyses identified four putative events (P ≤ 0.05) among the isolates. Estimation of selection pressure within the virus population revealed the occurrence of negative or purifying selection in 5 out of the 6 coding regions. Conclusions The begomovirus associated with tomato leaf curl diseases in Kenya is a variant of ToLCArV possibly originating from Tanzania. Recombinant virus strains were detected within the population and there are divergence evolutionary events within the coding regions of the virus in Kenya. This information is useful in the development of appropriate management strategies for the disease.