Enation Leaf Curl Research Articles

Phenotyping of okra germplasm for resistance to okra enation leaf curl disease and field evaluation of insecticides for its management

Okra enation leaf curl virus (OELCuV) adversely affects the potential and productivity of okra crop and in present scenario it is an emerging disease and development of OELCuV-resistant varieties is an economical and environmentally friendly approach to managing the disease. Looking in to this a field screening experiment was conducted. Among the fifty-seven okra varieties and germplasm screened against OELCuV under field conditions during Kharif, 2022, the final disease reaction revealed that 9 varieties/germplasm namely, Prabhani Kranti, GAO 5, GJO 3, Pusasawani, GP-OK-243, GP-OK-262, GPOK-296, GP-OK-373 and GP-OK-391 exhibited highly resistant reaction to OELCuV while, 15 okra germplasm/ varieties exhibited resistant reaction, 13 varieties/germplasm expressed moderately resistant reactions, 11 germplasm/varieties showed moderately susceptible reaction, 5 germplasm/ varieties showed susceptible reaction and 4 varieties/germplasm found to be highly susceptible to OELCuV. The AUDPC and infection rate (r) found to be lower for resistant germplasm/ varieties reaction and higher for susceptible reaction. The field evaluation of insecticides against OELCuV and its vector revealed that two foliar sprays of Tolfenpyrad 15 EC, 0.03 per cent and Diafenthiuron 47 + Bifenthrin 9.4 SC, 0.0705 per cent, at 15 days interval commencing from the appearance of whitefly vector was most effective and economical in managing okra enation leaf curl disease and its vector. The resistant germplasm/varieties selected might be used as OELCuV resistant parent(s) in breeding programs.. KEYWORDS :Field screening, insecticidal management, Okra enation leaf curl virus

Transient expression analysis of promoters of okra enation leaf curl virus in Nicotiana benthamiana, cotton and okra plants.

Viral promoters can be used to drive heterologous gene expression in transgenic plants. As part of our quest to look for new promoters, we have explored, for the first time, the promoters of okra enation leaf curl virus (OELCuV), a begomovirus infecting okra (Abelmoschus esculentus). The Rep and CP promoters of OELCuV fused with the gfp reporter gene, were expressed transiently in the natural host okra and the laboratory host cotton and Nicotiana benthamiana. The expression levels of the promoters were quantified through confocal laser scanning microscopy and GFP assay in N. benthamiana and okra. The results indicated that the Rep promoter was more active than the CP promoter, whose activity was similar to that of CaMV 35S promoter. Additionally, the Rep and CP promoters showed increase of expression, probably due to transactivation, when assayed following inoculation of OELCuV and betasatellite DNAs in cotton plants. A moderate increase in promoter activity in N. benthamiana was also seen, when assayed following the inoculation of the heterologous begomovirus Sri Lankan cassava mosaic virus.

Advances in Okra (Abelmoschus esculentus L.) Breeding: Integrating Genomics for Enhanced Crop Improvement

Okra (Abelmoschus esculentus L.) holds significant importance as a vegetable crop, thriving in tropical and subtropical regions globally, especially in the warmer areas of temperate zones. Traditional breeding approaches tailored for self-pollinated crops have been utilized to enhance the genetic diversity of okra. These methods encompass various techniques such as plant introduction, pure line selection, hybridization combined with selection, mutation breeding, and heterosis breeding. Particularly in countries like India, pedigree selection and heterosis breeding have led to the development of numerous okra varieties and hybrids, significantly impacting local agricultural practices. Contemporary okra breeding focuses on traits crucial for optimal performance, including high yield potential, resistance to prevalent diseases like Yellow Vein Mosaic Virus (YVMV) and Okra Enation Leaf Curl Virus (OELCV), tolerance to sucking pests and borers, ease of harvest, deep green fruit coloration, and desirable plant architecture. Public sector institutions have played a pivotal role in introducing and disseminating improved okra varieties and hybrids, with more than 33 cultivars introduced in recent decades. Some of these varieties have demonstrated substantial improvements in okra production across India. This review offers an overview of the current state of okra breeding, encompassing genetic resources, cytogenetic relationships, breeding goals, varietal development processes, efforts in resistance breeding, biotechnological interventions, and future improvement strategies. By consolidating existing knowledge and highlighting ongoing research initiatives, this article aims to provide guidance and inspiration for further advancements in okra breeding and genomics, ultimately contributing to the sustainability and productivity of this essential vegetable crop.

Genetic Diversity and Pathogenicity Characterization of Tomato-Infecting Begomoviruses in Taiwan.

The tomato yellow leaf curl disease (TYLCD) caused by whitefly (Bemisia tabaci)-transmitted begomoviruses (Geminiviridae) has constrained tomato production in Taiwan since 1981. Lisianthus enation leaf curl virus (LELCV), tomato leaf curl Taiwan virus (ToLCTV), and tomato yellow leaf curl Thailand virus (TYLCTHV) were the major viruses associated with TYLCD. In 2019 to 2020, we investigated TYLCD throughout Taiwan, with a 10 to 100% incidence on tomato fields. Begomovirus sequences were detected in 321 out of 506 collected samples by PCR with primers PAL1v1978B and PAR1c715H. In 2015 to 2016, 59 out of 99 samples collected in Hualien-Taitung areas were also found to have begomovirus sequences. Based on the analysis of 68 viral genomic sequences, six begomoviruses were identified, including LELCV, ToLCTV, TYLCTHV, tomato leaf curl Hsinchu virus, and two new begomoviruses, tentatively named tomato leaf curl Chiayi virus (ToLCCYV) and tomato leaf curl Nantou virus (ToLCNTV). Various isolates of LELCV and TYLCTHV were grouped into four and two strains, respectively. Recombinants were detected in LELCV-A, -C, and -D, ToLCCYV, ToLCNTV, and TYLCTHV-F. Based on virus-specific detection, the majority of TYLCD-associated viruses were mixed-infected by TYLCTHV-B with TYLCTHV-F, LELCV-A, -B, or -D, and/or ToLCTV. Meanwhile, viral DNA-B was mostly associated with TYLCTHV, and all identified DNA-Bs were highly homologous with previous TYLCTHV DNA-B. The pathogenicity of selected begomoviruses was confirmed through agroinfection and whitefly transmission. All tomato plants carrying Ty-1/3 and Ty-2 resistant genes were infected by all LELCV strains and ToLCCYV, although they appeared symptomless, suggesting these viruses could be managed through the use of the resistance pyramid.

Relative toxicity of some newer insecticide molecules against vector and sucking pest complex of okra

Sucking pest like leaf hoppers or jassid (Amrasca biguttula biguttula (Ishida)) and vectors i.e., whitefly (Bemisia tabaci (Gennadius)) are regarded as one of the major biotic stresses in okra cultivation in India. Apart from direct sucking the plant sap and thereby devitalizing the crop through their specially adapted mouthparts, many of them also act as vectors for important plant diseases like okra yellow vein mosaic and okra enation leaf curl disease. To control these sucking pests and vectors, several newer insecticide molecules were tested under open field conditions during Kharif seasons of 2021 and 2022. Based up on the two years of pooled data, among the tested insecticides, Tolfenpyrad 15% EC @ 2 ml/L was the best molecule in reducing leaf hopper population in okra (5.40 per leaf) with 63.49% reduction over control (PROC). The next best molecule was flupyradifurone 17.09% SL (5.70 jassids per leaf with 61.46 PROC). In the case of whitefly, flupyradifurone 17.09% SL was the most promising during both years with percent population reductions of 69.90 over control. The next best molecule in the list was tolfenpyrad 15% EC with 67.08 PROC. Interestingly, Imidacloprid-treated plots had the highest leaf hopper (10.39 per leaf) and whitefly (9.55 per leaf) population among all treatments indicating its low activity against these sucking pests of okra. The highest healthy green fruit yields (152 q/ha) were obtained from the plots treated with tolfenpyrad 15% EC with a maximum cost-benefit ratio of 1:2.19 followed by dinotefuran 20% SG (1:2.16) and acetamiprid 20% SP (1:2.15).

Genetic enhancement of okra [Abelmoschus esculentus (L.) Moench] germplasm through wide hybridization.

The introgression of genetic material from one species to another through wide hybridization and repeated back-crossing, plays an important role in genetic modification and enriching the cultivated gene-pool with novel genetic variations. Okra (Abelmoschus esculentus [(L.) Moench)] is a popular vegetable crop with high dietary fibre and protein, rich in essential amino acids, lysine and tryptophan. The wild Abelmoschus genepool has many desirable traits like ornamental value, short internodal length, more number of productive branches, extended bearing, perennation tendency, reduced fruit length (more consumer preferred trait), high mucilage content (medicinal value), abiotic stress tolerances such as drought, high temperature and biotic stress resistances such as okra Yellow Vein Mosaic Virus (YVMV) and Enation Leaf Curl Virus (ELCV) diseases. The repeated use of elite breeding lines led to narrowing of the genetic base of the okra crop, one of the major factors attributed to breakdown of resistance/ tolerance to biotic stresses. YVMV and ELCV are the two major diseases, causing significant yield loss in okra. Hence, wide hybridization was attempted to transfer tolerance genes from wild species to the cultivated genepool to widen the genetic base. The screening of germplasm of wild Abelmoschus species at hotspots led to the identification of tolerant species (Abelmoschus pungens var. mizoramensis, A. enbeepeegeearensis, A. caillei, A. tetraphyllus and A. angulosus var. grandiflorus), which were further used in a wide-hybridization programme to generate interspecific hybrids with the cultivated okra. Presence of pre- and post-zygotic barriers to interspecific geneflow, differences in ploidy levels and genotype specific variations in chromosome numbers led to varying degrees of sterility in F1 plants of interspecific crosses. This was overcome by doubling the chromosome number of interspecific hybrids by applying Colchicine at the seedling stage. The 113 cross derivatives generated comprising amphidiploids in the F1 generation (30), F3 (14), one each in F2 and F4 generations, back cross generation in BC1F2 (03), BC1F3 (25), and BC2F3 (02), crosses between amphidiploids (27), multi-cross combinations (07) and inter-specific cross (between A. sagittifolius × A. moschatus subsp. moschatus) selfed derivatives at F8 generation (03) were characterized in the present study. Besides they were advanced through selfing and backcrossing. The amphidiploids were found to possess many desirable genes with a considerable magnitude of linkage drag. Majority of the wide cross derivatives had an intermediate fruit morphology and dominance of wild characters viz., hispid fruits, stem, leaves, tough fruit fibre, vigorous perennial growth habit and prolonged flowering and fruiting. The fruit morphology of three BC progenies exhibited a high morphological resemblance to the cultivated okra, confirming successful transfer of useful genes to the cultivated okra genepool. The detailed morphological characteristics of the various combinations of Abelmoschus amphidiploids and the genetic enhancement of the genepool achieved in this process is reported here.

First report of okra enation leaf curl virus and the associated alphasatellite infecting basil in Iran

First report of okra enation leaf curl virus and the associated alphasatellite infecting basil in Iran

Sentinel plot surveillance of cotton leaf curl disease in Pakistan- a case study at the cultivated cotton-wild host plant interface

A sentinel plot case study was carried out to identify and map the distribution of begomovirus-betasatellite complexes in sentinel plots and commercial cotton fields over a four-year period using molecular and high-throughput DNA ‘discovery’ sequencing approaches. Samples were collected from 15 study sites in the two major cotton-producing areas of Pakistan. Whitefly- and leafhopper-transmitted geminiviruses were detected in previously unreported host plant species and locations. The most prevalent begomovirus was cotton leaf curl Kokhran virus-Burewala (CLCuKoV-Bu). Unexpectedly, a recently recognized recombinant, cotton leaf curl Multan virus-Rajasthan (CLCuMuV-Ra) was prevalent in five of 15 sites. cotton leaf curl Alabad virus (CLCuAlV) and cotton leaf curl Kokhran virus-Kokhran, ‘core’ members of CLCuD-begomoviruses that co-occurred with CLCuMuV in the ‘Multan’ epidemic were detected in one of 15 sentinel plots. Also identified were chickpea chlorotic dwarf virus and ‘non-core’ CLCuD-begomoviruses, okra enation leaf curl virus, squash leaf curl virus, and tomato leaf curl New Delhi virus. Cotton leaf curl Multan betasatellite (CLCuMuB) was the most prevalent CLCuD-betasatellite, and less commonly, two ‘non-core’ betasatellites. Recombination analysis revealed previously uncharacterized recombinants among helper virus-betasatellite complexes consisting of CLCuKoV, CLCuMuV, CLCuAlV and CLCuMuB. Population analyses provided early evidence for CLCuMuV-Ra expansion and displacement of CLCuKoV-Bu in India and Pakistan from 2012-2017. Identification of ‘core’ and non-core CLCuD-species/strains in cotton and other potential reservoirs, and presence of the now predominant CLCuMuV-Ra strain are indicative of ongoing diversification. Investigating the phylodynamics of geminivirus emergence in cotton-vegetable cropping systems offers an opportunity to understand the driving forces underlying disease outbreaks and reconcile viral evolution with epidemiological relationships that also capture pathogen population shifts.

Molecular Identification and Characterization of a Begomovirus Associated with Okra Enation Leaf Curl Disease in Mali

Molecular Identification and Characterization of a Begomovirus Associated with Okra Enation Leaf Curl Disease in Mali

Unraveling different begomoviruses, DNA satellites and cryptic species of Bemisia tabaci and their endosymbionts in vegetable ecosystem.

Bemisia tabaci species complex contains more than 46 cryptic species. It has emerged as an important pest causing significant yield loss in many cultivated crops. This pest is also a vector for more than 100 species of begomoviruses, that are a major threat for the cultivation of many crops in different regions of the world. The relation between cryptic species of the B. tabaci species complex and associated begomoviruses that infect different crops remains unclear. In the present study, four cryptic species (Asia I, China 3, Asia II 5 and Asia II-1) of B. tabaci and four associated endosymbionts (Arsenophonus, Cardinium, Rickettsia and Wolbachia) were identified in different vegetable crops. The vector-based PCR detection revealed five different begomoviruses such as okra enation leaf curl virus (OELCuV), tomato leaf curl Palampur virus (ToLCPalV), squash leaf curl China virus (SLCCNV), chilli leaf curl virus (ChiLCuV), and tomato leaf curl New Delhi virus (ToLCNDV). Of these begomoviruses, the maximum infection rate was observed (9.1%) for OELCuV, followed by 7.3% for ToLCNDV. The infection rate of the other three viruses (SLCCNV, ChiLCuV, ToLCPalV) ranged from 0.9 to 2.7% in cryptic species of B. tabaci. Further, each cryptic species was infected with multiple virus species and the virus infection rate of Asia I, Asia II-5, China 3 and Asia II-1 was 21.2%, 15.1%, 15.1% and 0.6% respectively. Similarly, in case of betasatellites the highest infection rate was 12% for ToLCBDB, followed by 6% for OLCuB and PaLCB. With regard to alphasatellites, the highest infection rate was 18.2% for AEV and 3% for CLCuMuA. This study demonstrates the distribution of cryptic species of whitefly and their endosymbionts, and associated begomoviruses and DNA satellites in vegetable ecosystem. We believe that the information generated here is useful for evolving an effective pest management strategies for vegetable production.

Identification of begomoviruses associated with the insect vector Bemisia tabaci and various host plants on Java Island, Indonesia.

Begomoviruses are economically important plant viruses and are transmitted by Bemisia tabaci which is a complex of various cryptic species. However, it is uncertain whether most begomoviruses that infect host plants are transmitted by B. tabaci at a similar rate. We compared the begomovirus profiles that were detected in a total of 37 whitefly populations and 52 host plants on Java Island, Indonesia. Seven begomovirus species were detected in B. tabaci at different rates: pepper yellow leaf curl Indonesia virus (PepYLCIV, 56.8%), tomato yellow leaf curl Kanchanaburi virus (TYLCKaV, 46.0%), tomato leaf curl New Delhi virus (ToLCNDV, 21.6%), squash leaf curl China virus (SLCCNV, 21.6%), ageratum yellow vein China virus (AYVCNV, 2.7%), mungbean yellow mosaic India virus (MYMIV, 2.7%), and okra enation leaf curl virus (OELCuV, 2.7%). The begomoviruses were detected at different rates in three cryptic species of B. tabaci. In addition, six begomovirus species were detected in the various host plants at different rates: PepYLCIV (67.3%), TYLCKaV (53.9%), ToLCNDV (13.5%), MYMIV (11.5%), AYVCNV (3.9%), and Tomato yellow leaf curl Thailand virus (TYLCTHV) (1.9%). By comparing the virus presence between whiteflies and plants, five begomoviruses (AYVCNV, MYMIV, PepYLCIV, ToLCNDV, and TYLCKaV) were detected in both samples, but their sequence similarity was highly variable depending on the begomovirus themselves; TYLCKaV was highest (99.4%-100%) than any other viruses. Our study suggests B. tabaci acquire begomoviruses at different rates from plants. This study provides important information on the potential variation in the begomovirus transmission mechanism.

Lisianthus enation leaf curl virus, a begomovirus new to Japan, is more virulent than the prevalent tomato yellow leaf curl virus in Ty-gene-mediated resistant tomato cultivars

Lisianthus enation leaf curl virus, a begomovirus new to Japan, is more virulent than the prevalent tomato yellow leaf curl virus in Ty-gene-mediated resistant tomato cultivars

Standardization of artificial screening technique for okra enation leaf curl disease resistance in wild okra (Abelmoschus moschatus ssp. Moschatus) germplasm

Okra enation leaf curl disease (OELCuD) is a recently emerged whitefly insect vector transmissible viral disease of okra which adversely affects the quality and quantity of okra fruits. Okra enation leaf curl virus (OELCuV) is a main disease causative agent. Two year (kharif 2018 and 2019) field experiments were conducted at research farm of ICAR-National Bureau of Plant Genetic Resources, Pusa, New Delhi for field screening of 10 wild okra (Abelmoschus moschatus ssp. moschatus) accessions, viz. EC360586, EC360794, EC360830, EC360900, EC359730, EC359836, EC359870, EC360351, EC361111 and EC361171. Out of 10 accessions, 4 accessions, viz. EC360794, EC360586, EC360830 and EC361171 showed resistance (R) reaction in both the seasons. Whitefly population was also monitored in both the rainy (kharif) season, since, OELCuD is transmitted by whitefly insect vector. Majority (>77%) of okra genotypes were moderately preferred by the whiteflies. To further validate the resistance reaction in these 4 field resistant accessions, artificial screening experiment was conducted using viruliferous whitefly vector and VRO 6 as susceptible check. Prominent okra enation leaf curl symptom appeared after a minimum incubation period of 15 days under controlled conditions. Betasatellite (DNA-β) molecule of OELCuV was amplified (1.3 kb) using PCR for virus detection and these 4 accessions were found free from virus. These 4 promising accessions would serve as resistance source in breeding programmes to develop varieties resistant to OELCuV.

Screening of wild okra (Abelmoschus esculentus) against yellow vein mosaic and enation leaf curl diseases

Okra yellow vein mosaic (OYVMD) and enation leaf curl diseases (OELCuD) are the most important biotic diseases which cause yield and quality loss in okra (Abelmoschus esculentus (L.) Moench). Therefore, development of viral resistance varieties and lines become important breeding objective worldwide. Wild relatives are the natural source for disease and pest resistance. Hence an experiment was conducted at research farm of ICAR-Indian Agricultural Research Institute, New Delhi during rainy (kharif) season 2020 and for screening of 24 wild genotypes to identify the resistance source for OYVMD and OELCuD diseases of okra. PDI (Percent disease incidence) for OYVMD varied from 3.12–93.72, while PDI for OELCuD ranged from 0.00–83.29. The area under disease progress curve for both the diseases indicated that the rate of disease incidence was in increasing trend with the growth of the crop. Based on the natural epiphytotic screening A. moschatus (IC 141055), A. tetraphyllus (IC 90476-1) and A. caillei (Sikkim) were 3 top most genotypes from different species which showed very less incidence of OYVMD and no incidence of OELCuD. These genotypes were grouped in highly resistant category for both the diseases; other genotypes grouped in this category were A. moschatus (EC 360900), A. tetraphyllus (IC 90515 and IC 470735). These genotypes can be used further for interspecific breeding programme and resistant variety development in okra.

Mixed infection of a new begomovirus, Jatropha leaf curl Guntur virus and recombinant/chimeric jatropha leaf curl Gujarat virus in Jatropha gossypiifolia.

The Jatropha gossypiifolia plant showing the severe leaf curl symptoms grown in the borders of chilli fields in Guntur, Andhra Pradesh, India was collected. The infection of begomovirus was detected using the degenerate primers followed by rolling circle amplification (RCA). The RCA products digested with KpnI and EcoRI showing the unit length of the begomovirus genome were cloned in pUC19 and sequenced to obtain the complete begomoviral genome. The sequence information of DNA-A of the two clones GuWC10 contained 2794 nt (MZ217773) and an incomplete genome GuWC3 with 2337 nt (MZ217772). The BLAST analysis of GuWC3 and GuWC10 sequence showed 85·57% identity with jatropha leaf curl Gujarat virus (JLCGV) and 82·68% identity with croton yellow vein mosaic virus (CroYVMV), respectively. The sequence analysis also showed that the GuWC10 clone had a 177 bp recombinant/chimeric sequence of JLCGV while the other region containing 2611 bp showed 92·63% identity with papaya leaf curl virus (PaLCuV/PK). However, the global alignment of the GuWC10 sequence showed a maximum of 80·60% identity with croton yellow vein virus (CroYVV) (FN645902), CroYVMV (JN817516) and PaLCuV/PK (KY978407). The second clone GuWC3 although shorter in length had recombinant sequences of JLCGV, jatropha leaf curl virus (JLCuV/ND) and okra enation leaf curl virus (OELCuV). The nucleotide sequence identity among the GuWC10 and GuWC3 was 71·9%. The phylogenetic analysis placed both the viral strains in the same clade located between PaLCuV/PK and JLCuV clades. According to the ICTV species demarcation criteria of 91% DNA-A sequence identity, the present isolate was considered as a new species of begomovirus and the name Jatropha leaf curl Guntur virus was proposed. This is the first report of a new begomovirus species infecting J. gossypiifolia and the study also reports a mixed infection of Jatropha leaf curl Guntur virus with a recombinant/chimeric JLCGV in the host J. gossypiifolia. Present study suggests the role of weed Jatropha in harbouring begomoviruses and probable source for viral recombination.

First report of Tomato leaf curl Karnataka virus associated with leaf curl disease of Zinnia elegans in India

Tomato leaf curl Karnataka virus (ToLCKV) is a species of begomovirus which has a circular, ssDNA monopartite genome and is transmitted by the whitefly (Bemisia tabaci). Zinnia elegans is a popular ornamental bedding plant which is grown worldwide for its beautiful flowers. A few begomovirus species have been reported to infect Z. elegans, including Ageratum yellow vein China virus in Vietnam (Li et al., 2013), and Ageratum enation virus and Zinnia leaf curl virus in India (Kumar et al., 2010; Pandey & Tiwari, 2012). In March 2019 symptoms of excessive leaf curling with mild mosaic were observed on Z. elegans plants growing in a nursery in Bhopal, central India (Fig. 1). To investigate the aetiology of the disease total DNA was extracted from leaf samples from two diseased and one asymptomatic Z. elegans plant using a plant genomic DNA purification kit (Promega, USA), following the manufacturer's instructions. A begomovirus was detected from both diseased samples (but not the asymptomatic sample) by PCR using begomovirus-specific primers: CPIT-I/CPIT-T (AM180920/AM180921) (Singh, 2005), PALIv 1978/ PARIc 496 and PALIv 722/ PALIc 1960 (Rojas et al., 1993). The expected amplicons (~800 bp, 1.2 Kb and 1.2 Kb, respectively) were purified using a PCR Clean-up System (Promega, USA) and Sanger sequenced in both directions by Bioinnovations Connecting Technologies to Life (Mumbai, India). The consensus sequence from both samples was identical and the complete viral DNA-A genome of 2761 nucleotides was deposited in GenBank (Accession No. MK965196). Sequence analysis was done by BLASTn and showed that the DNA-A genome had the highest identity (96-97%) with ToLCKV (KX219744, HM007094, LN878123, U38239); Sunflower leaf curl virus (JX678965) and 94–95% with Tomato leaf curl virus (JX524172, KX831454). Phylogenetic analysis using neighbour-joining in MEGA v.7.0 showed a close relationship with isolates of ToLCKV and relationships with other begomoviruses (Fig. 2). The disease was successfully transmitted by B. tabaci from naturally infected Z. elegans to healthy seedlings of Nicotiana tabacum, Solanum lycopersicum and Z. elegans (each 3/3), symptoms being observed 30 days post inoculation. The test plants all tested positive by PCR using the begomovirus-specific primer pairs above. Positive amplicons were sequenced and the nucleotide sequences were identical to each other and the original isolate (MK965196). The present study demonstrates that Z. elegans is a host of ToLCKV. ToLCKV is a serious threat to the production of several economically important crops in India and has been reported at an incidence of >80% on soybean, sunflower and tomato in India (Malathi et al., 2017). Recently, ToLCKV and satellite molecules have been found associated with enation leaf curl disease of another ornamental plant, Pseuderanthemum reticulatum, in India (Ashwathappa et al., 2021). The whitefly transmission study provides additional evidence that ToLCKV causes the observed disease in Z. elegans and it is possible that ornamental plants may act as a reservoir of the virus. To the best of our knowledge, this is the first report of the association of ToLCKV with leaf curl disease of Z. elegans. The authors are thankful to the Vice Chancellor of Barkatullah University, Bhopal, India, for use of the facilities and the UGC, New Delhi, India for financial support under the UGC-BSR Research Start-Up grant.

Copy number variation of two begomovirus acquired and inoculated by different cryptic species of whitefly, Bemisia tabaci in Okra.

The whitefly, B.tabaci is a major pest of agricultural crops which transmits begomovirus in a species-specific manner. Yellow vein mosaic disease (YVMD) and okra leaf curl disease (OLCD) caused by distinct begomovirus are a major limitation to production of okra in India. In this framework the present investigation reports, for the first time, comparative study of begomovirus species viz. yellow vein mosaic virus (YVMV) and okra enation leaf curl virus (OELCuV) ingested and egested by two cryptic species (Asia I and Asia II 5) of B.tabaci at different time interval using detached leaf assay. A gradual increase of both virus copies were observed with increased feeding exposure in Asia I and Asia II 5. Both the genetic groups of whitefly could acquire the viruses within just 5 minutes of active feeding however, a significant amount of variation was noted in virus uptake by the both. At 24 hours of active feeding Asia II 5 acquired more of YVMV whereas, Asia I ingested more OELCuV. Similarly, the genetic group acquiring higher titre of virus egested higher amount during inoculation period. On the whole, it can be presumed that Asia I is a more effective transmitter of OELCuV whereas, Asia II 5 of YVMV further suggesting increased risk of virus pandemics (both YVMV and OELCuV) in regions where Asia I and Asia II 5 is dominant.

Phenotypic screening of cultivated and wild okra germplasm against yellow vein mosaic and enation leaf curl diseases of okra in India

Okra yellow vein mosaic (OYVMD) and enation leaf curl diseases (OELCuD) caused by whitefly (Bemisia tabaci) transmitted begomoviruses are important constraint for improvement and production okra in India. Okra germplasms consists of 178 cultivated/advanced lines (147 Advances okra lines + 31 popular varieties) and 146 accessions from 14 wild species originally collected from different national institutes located at different agro-climatic zones of India were evaluated for their response against OYVMD and OELCuD. The resistance levels both cultivated and wild species were assessed by visual scoring of symptoms in the field under natural conditions for two consecutive years in 2015 and 2016. None of the cultivated genotypes and wild species tested was found to be disease free except Abelmoschus enbeepeegeearnse, however, considerable variation in responses against OYVMD and OELCuD was observed among the genotypes. Of the 178 cultivated/advanced lines screened against OYVMD and OELCuD, seven genotypes showed highly resistant, one resistant, 2 moderately resistant and 146 accessions from 14 wild species, 17 accessions were showed highly resistant reaction, one accession resistant, 5 accessions moderately resistant for OYVMD. Similarly, for OELCuD, fifty-two okra genotypes showed highly resistant, three moderately resistant in cultivated/advanced lines and 125 accessions were found to be highly resistant, two resistant and three moderately resistant in wild accessions. The resistance cultivated/advanced lines could be used directly as varieties to manage OYVMD and OELCuD after adaption to various agro-climatic regions. The resistance in wild accessions could be used in future breeding programmes to develop okra cultivars resistant against both OYVMD and OELCuD.

Okra enation leaf curl virus

This datasheet on Okra enation leaf curl virus covers Identity, Distribution, Hosts/Species Affected, Further Information.

Phylogenetic Analysis of Okra Enation Leaf Curl Virus (OELCV) Transmitted by Bemisia tabaci Using Coat Protein Gene Fragment of OELCV in Tamil Nadu

Okra enation leaf curl virus (OELCV) is a severe emerging disease of okra, Abelmoschus esculentus in India, causes systemic infections and has a very effective mode of transmission by the sweet potato whitefly, Bemisia tabaci; thus, preventing their spread has been made very complicated. It is essential to understand the OELCV isolates to study the disease reactions in plant accessions. The okra OELCV infected young leaves were collected from the Salem (Northwestern Zone) and Madurai (South Zone) of Tamil Nadu and the DNA was extracted and used to amplify the OELCV utilizing specific primers (JKOE34F, JKOE35R) targeting the OELCV coat protein gene and produced a 796 bp band in the polymerase chain reaction (PCR). The homology analysis of nucleotide sequence was carried out using BLAST programme and the results revealed that the Salem region coat protein gene sequence grouped into OELCV clone 6.2, complete genome (MK084768.1) with 99.71% of homology, and Madurai region coat protein gene sequence grouped into OELCV isolate Vijayawada coat protein (AV1) gene complete cds (KT935487.1) with a 99.38% of homology. The amplified OELCV (Salem and Madurai zone) from the study had aligned in the same cluster along with HG938362.1 and KX710156.1. This study had indicated that the OELCV pathogen alike in these zones successfully being transmitted by B. tabaci.