Search Results (6)

Squash leaf curl China virus (SLCCNV) belongs to the species Begomovirus cucurbitachinaense in the genus Begomovirus and can infect some Cucurbitaceae crops except for watermelon (Citrullus lanatus). In this study, watermelon plants showing symptoms typical to begomovirus infection in field were observed in Zhejiang Province of China, and SLCCNV presence was identified through PCR and next-generation sequencing (NGS). The pairwise sequence identity of the DNA-A genome shows that SLCCNV watermelon isolate belongs to the SLCCNV/CN strain and shares 96% nucleotide identity with the previously sequenced SLCCNV/CN. An infectious clone of SLCCNV watermelon isolate was constructed using the tandem repeat fragment method. Through agrobacterium-mediated inoculation, the clone could induce systemic infection with typical symptoms in watermelon, melon (Cucumis melo), squash (Cucurbita pepo), pumpkin (Cucurbita maxima), wax gourd (Benicasa hispida), cucumber (Cucumis sativus), and N. benthamiana. It was further demonstrated that the progeny virions derived from the cloned watermelon isolate could be transmitted by whitefly rather than the sap. To the best of our knowledge, this is the first report of a natural infection of SLCCNV on watermelon in China, and the first complete report on the molecular characteristics and pathogenicity of watermelon-infecting SLCCNV in the world. Full article

The incidence and severity of begomovirus diseases have been increasing around the world recently, and the ridge gourd [Luffa acutangula (Roxb.) L.] is the latest example of a crop that has become highly susceptible to the outbreak of the tomato leaf curl New Delhi virus (ToLCNDV, genus Begomovirus) in India. Accurate diagnosis of causal agents is important in designing disease management strategies. In this study the coat protein (CP) gene from a ToLCNDV-Rg ridge gourd isolate was used to produce polyclonal antibodies (ToLCNDV-Rg-CP-PAb) in a rabbit. The antibodies successfully detected a 30.5 kDa ToLCNDV-Rg-CP in extracts of symptomatic ridge gourd leaf samples by several assays, such as Western Blotting (WB), Dot Immuno Binding Assay (DIBA), Direct Antigen Coating Enzyme Linked Immuno Sorbent Assay (DAC-ELISA), Immuno Capture Polymerase Chain Reaction (IC-PCR), and Immuno Capture Loop-Mediated Isothermal Amplification (IC-LAMP) assays. However, none of the negative samples tested positive in either of the detection methods. Among all the methods tested, the immunocapture assay, IC-LAMP, was the most sensitive in detecting ToLCNDV-Rg. Furthermore, antibodies generated in this study also detected other commonly occurring begomoviruses in South India, such as tomato leaf curl Palampur virus and squash leaf curl China virus in cucurbits. Together, ToLCNDV-Rg-CP-PAb can be used for detecting at least three species of begomoviruses infecting cucurbits. The obtained antibodies will contribute to monitoring disease outbreaks in multiple crops. Full article

Cucurbits are important economic crops worldwide. However, the cucurbit leaf curl disease (CuLCD), caused by whitefly-transmitted begomoviruses constrains their production. In Southeast Asia, three major begomoviruses, Tomato leaf curl New Delhi virus (ToLCNDV), Squash leaf curl China virus (SLCCNV) and Squash leaf curl Philippines virus (SLCuPV) are associated with CuLCD. SLCuPV and SLCCNV were identified in Luzon, the Philippines. Here, the genetic diversity and geographic distribution of CuLCD-associated begomoviruses in the Philippines were studied based on 103 begomovirus detected out of 249 cucurbit samples collected from 60 locations throughout the country in 2018 and 2019. The presence of SLCCNV and SLCuPV throughout the Philippines were confirmed by begomovirus PCR detection and viral DNA sequence analysis. SLCuPV was determined as a predominant CuLCD-associated begomovirus and grouped into two strains. Interestingly, SLCCNV was detected in pumpkin and bottle gourd without associated viral DNA-B and mixed-infected with SLCuPV. Furthermore, the pathogenicity of selected isolates of SLCCNV and SLCuPV was confirmed. The results provide virus genetic diversity associated with CuLCD for further disease management, especially in developing the disease-resistant cultivars in the Philippines as well as Southeast Asia. Full article

Cucurbits are important crops in the world. However, leaf curl disease constrains their production. Here, begomovirus diversity and pathogenicity associated with the disease in Malaysia were studied based on 49 begomovirus-detected out of 69 symptomatic plants from seven cucurbit crops in 15 locations during 2016 and 2017. The presence of Squash leaf curl China virus (SLCCNV) and Tomato leaf curl New Delhi virus (ToLCNDV) were confirmed by virus detection by polymerase chain reaction, viral DNA sequence analysis and specific detection of the viral components. ToLCNDV Malaysian isolates were further distinguished into strains A, B, C and D. Virus co-infection was detected in bitter gourd, bottle gourd and squash. Among them, eight bitter gourd samples were detected without SLCCNV DNA-A. However, one bottle gourd and five squash samples were without ToLCNDV DNA-B. Pseudorecombination of ToLCNDV DNA-A and SLCCNV DNA-B was detected in two bitter gourd samples. The pathogenic viruses and pseudorecombinants were confirmed by agroinoculation. The viral DNA-B influencing on symptomology and host range was also confirmed. The results strengthen the epidemic of cucurbit-infecting begomovirus in Malaysia as well as Southeast Asia. Especially, the natural pseudorecombinant of begomovirus that extends host range and causes severe symptom implies a threat to crops. Full article

The Bemisia tabaci species complex consists of at least 44 cryptic species, which are potential vectors of approximately 320 begomovirus species, most of which are significant plant viruses. However, the relationship of begomovirus transmission through vectors at the cryptic species level is uncertain. In our previous study, three cryptic species (Asia I, Asia II 1, and Asia II 5) of B. tabaci were identified from 76 B. tabaci samples collected across 23 districts in Nepal. Using the same individuals we identified seven different begomovirus species (Squash leaf curl China virus [SLCCNV], Tomato leaf curl New Delhi virus [ToLCNDV], Okra enation leaf curl virus [OELCuV], Synedrella leaf curl virus [SyLCV], Tomato leaf curl Kerala virus [ToLCKeV], Ageratum enation virus [AEV], and Tomato leaf curl Karnataka virus [ToLCKV]) by PCR using universal begomovirus primers. The begomoviruses were detected in 55.26% of whitefly samples, and SLCCNV was the most prevalent species (27.63%). Among the three cryptic species of B. tabaci, the virus detection rate was highest in Asia I (60%), followed by Asia II 1 (58.82%) and Asia II 5 (53.06%). Most viruses were detected in all three species, but AEV and ToLCKV were found only in Asia I and Asia II 1, respectively. Geographic analysis showed that SLCCNV was distributed in the whole country, which is similar to the distribution of the Asia II 5 species, but OELCuV and SyLCV were detected only in the middle region of Nepal. Our results provide important information on the begomovirus profile in Nepal which can be beneficial for plant virus risk assessment and develop the management strategies to reduce the damage of whitefly transmitted viruses. Full article

The Squash Leaf Curl China Virus (SLCCNV) and Tomato Leaf Curl New Delhi Virus (ToLCNDV) are species of Begomovirus (whitefly-vectored Geminiviridae) and cause serious damage to the cucurbit crops of the genus Cucurbita in the areas of South and Southeast Asia, across Asia, the Middle East and the Mediterranean, respectively. Cucurbita moschata’s inbred line AVPU1426, developed at the World Vegetable Center (WorldVeg) from a Bangladeshi landrace through pedigree selection, was observed to be resistant to both begomoviruses in field tests conducted at the WorldVeg Research and Training Station, Kasetsart University, Kamphaeng Saen, Thailand, which is a hotspot for these viruses. When AVPU1426 was tested for reaction to inoculation by viruliferous whiteflies with Squash Leaf Curl Philippines Virus (Taiwan strain) (SLCPV-TW) in the screen net-house at WorldVeg headquarters in Taiwan, it showed good resistance, though SLCPV-TW DNA-A could be detected in all inoculated plants, indicating that it did not show immunity to this virus. The objective of this study was to validate the resistance to SLCCNV and ToLCNDV in AVPU1426 by using whitefly-mediated inoculations to determine the mode of inheritance of the resistance. The results showed that AVPU1426 was resistant to SLCCNV and ToLCNDV. Upon crossing AVPU1426 with a susceptible check variety, Waltham Butternut, the resistance to both begomoviruses was observed to be conferred by a single recessive gene. This open-pollinated pumpkin line AVPU1426 bears flat round, mottled green immature fruits with yellow flesh in mature fruit. The fruit yield of AVPU1426 (20.74 t/ha⁻¹) was comparable to ‘Rajah’ (18.61 t/ha⁻¹), a recently released commercial F1 hybrid of East-West Seed (EWS). The fruit of AVPU1426 were estimated to have a good average β-carotene content (1.57 mg/100 g fresh weight). This line is a good source to breed pumpkins resistant to the three begomoviruses. Full article