Papaya Ringspot Virus Research Articles

Karakterisasi Molekuler Papaya ringspot virus tipe P pada Tanaman Mentimun di Jawa

Moleculer Characterization of Papaya ringspot virus type P on Cucumber in JavaInfection of Papaya ringspot virus (PRSV) on cucumber plants showing mosaic symptom was detected using specific antibody. Further investigation was conducted to determine molecular characters and status of PRSV infecting cucumber in Java. Infection of PRSV was detected from leaf samples collected from the field using dot immunobinding assay (DIBA). Disease frequency caused by PRSV infection reached 81.11%, 95.86%, 91.66%, and 92.3% in East Java, Central Java, Yogyakarta, and West Java, respectively. Characterization of PRSV isolates was conducted by reverse transcription polymerase chain reaction (RT-PCR) using specific primers for PRSV-P and PRSV-W, followed by cloning, and DNA sequencing. DNA fragment of 470 bp was successfully amplified using specific primers for PRSV-P from several samples from Nganjuk, Brebes, Kulon Progo, and Subang; but no amplification was achieved using specific primers for PRSV-W. Nucleotide and amino acid analysis showed high homology among PRSV-P isolates from Nganjuk, Brebes, Kulon Progo, and Subang, i.e. 98.6%-99.7% and 99.3%-100%, respectively. This is an indication of a low genetic variation among PRSV-P from Java. Further phylogenetic analysis indicated that PRSV-P isolate cucumber is in the same cluster with PRSV-P isolate papaya from Bali, Indonesia. This is the first report of PRSV-P infecting cucumber in Indonesia.

Synthesis and antiphytoviral activity of α-aminophosphonates containing 3, 5-diphenyl-2-isoxazoline as potential papaya ringspot virus inhibitors.

α-Aminophosphonates compounds containing 3,5-diphenyl-2-isoxazoline were synthesized and evaluated for their bioactivity. Seventeen of them showed good bioactivity (protection effect > 50%) in vivo against papaya ringspot virus, while two of them (V29 and V45) exhibited excellent antiviral activity (both 77.8%). In the latter case, the antiviral activity was close to that of antiphytovirucides ningnanmycin and dufulin (both 83.3%) at 500mg/L. The preliminary structure-activity relationships indicated that the bioactivity was strongly influenced by the substituents.

Distribution and phylodynamics of papaya ringspot virus on Carica papaya in Cuba

Orchard and garden papaya crops grown in 47 Cuban municipalities were surveyed from 2008 to 2013, revealing the widespread distribution of papaya ringspot virus (PRSV) in Cuba. Phylodynamic analyses performed with the partial coat protein gene of all Cuban PRSV‐P isolates (34 sequences) and 107 sequences of isolates from the American continent and the Caribbean islands showed a most recent common ancestor in 1942 (95% highest posterior density, HPD 95% = 1911–1967). The substitution rate was estimated to be 7.7 × 10−4 substitutions per site per year (HPD 95% = 4.6 × 10−4 to 1.1 × 10−3), which is equivalent to those detected in other RNA viruses. Demographic reconstruction of PRSV showed that viral diversity increased in the 1985–1990 period, which coincides with the implementation of extensive production practices. Moreover in Cuba, viral dispersion occurred from Mexico and other unknown ancestral locations. The spatiotemporal diffusion analysis proposed Mexico as an ancestral area for the origin of diversification in the American continent and suggests new dispersion events between American and Caribbean isolates. The observed widespread distribution, clear geographic grouping of Cuban isolates, virus growth and genetic diversity provide strong evidence of the PRSV dispersion patterns, which has implications for the control strategies of PRSV.

Feeding of Riptortus pedestris on soybean plants, the primary cause of soybean staygreen syndrome in the Huang-Huai-Hai river basin

Staygreen syndrome or Zhengqing in soybean has recently become a major issue for Chinese growers in the Huang-Huai-Hai river basin. Although previous studies revealed that staygreen can be induced when pods/seeds are damaged, it is unknown whether virus infection or insect infestation causes staygreen. To determine whether viral infection causes staygreen, a survey of soybean staygreen incidence in the Huang-Huai-Hai river basin was conducted in 2016 and 2017. Diseased samples were collected and analyzed using DAS-ELISA for Soybean mosaic virus, Watermelon mosaic virus, Bean pod mottle virus, Cucumber mosaic virus, and Bean common mosaic virus. The survey showed that the severity of soybean staygreen syndrome was most prevalent in Beijing, Henan, Shaanxi, and some parts of Shandong provinces, with yield losses from 0 to nearly 100%, but only a small fraction of samples were positive for the tested viruses. A field cage experiment and an insecticide treatment field trial were conducted to determine the contribution of the bean bug, Riptortus pedestris, to staygreen incidence. The field cage experiment showed that R. pedestris treatment resulted in shorter plants, more empty pods, increased numbers of abnormal seeds, and decreased yields. The field experiment showed that there were fewer R. pedestris and less soybean staygreen incidence in fields treated with insecticide than in untreated control fields. Together, these results suggest that R. pedestris infestation rather than virus infection induces staygreen syndrome and that growers in this region can mitigate staygreen syndrome via bean bug control.

Research status of the development of genetically modified papaya (Carica papaya L.) and its biosafety assessment

Papaya (Carica papaya L.) is one of the crops widely planted in tropical and subtropical areas. The papaya fruit has low calories and are plentiful in vitamins A and C and in minerals. A major problem in papaya production is a plant disease caused by the papaya ringspot virus (PRSV). The first PRSV-resistant GM papaya expressing a PRSV coat protein gene was developed by USA scientists in 1992. The first commercial GM papaya cultivars derived from the event was approved by the US government in 1997. Development of transgenic papayas has been focused on vaccine production and limited agricultural traits, including insect and pathogen resistance, long shelf life, and aluminum and herbicide tolerance. Approximately 17 countries, including the USA and China, produced transgenic papayas and/or commercialized them, which provoked studies on biosafety assessment and development of GM-detection technologies. For the biosafety assessment of potential effects on human health, effects of long-term feeding to model animals have been studied in terms of toxicity and allergenicity. Studies on environmental safety assessment include influence on soil-microbial biodiversity and transfer to soil bacteria of GM selection markers. Many countries, such as Korea, the European Union, and Japan, that have strict regulations for GM crops have serious concerns about unintended introduction of GM cultivars and food commodities using unauthorized GM crops. Transgene- and/or GM event-specific molecular markers and technologies for genomics-based detection of unauthorized GM papaya have been developed and have resulted in the robust detection of GM papayas.

First report of cucurbit aphid-borne yellows virus from Morocco

Zucchini (Cucurbita pepo), which belongs to the family Cucurbitaceae, is a summer squash widely cultivated in Morocco. Viral infections are destructive to cucurbits, often rendering the fruit produced unmarketable. In April 2017, during a field survey for zucchini viruses in Gharb region (western Morocco), a total of 10 leaf samples of variety ‘Bajaty’ were collected from plants showing virus-like symptoms and were processed for laboratory analyses. Commercial available ELISA kits were used to test for the presence of zucchini yellow mosaic virus (ZYMV), squash mosaic virus (SqMV), cucumber mosaic virus (CMV), papaya ringspot virus (PRSV) and cucurbit aphid-borne yellows virus (CABYV). Results showed that all the tested samples were positive to ZYMV, three were positive to SqMV and two were positive to CABYV. To confirm the presence of CABYV, total RNA extracts were obtained from all the 10 samples using RNeasy Plant Mini Kit (Qiagen, Germany) and tested by reverse transcription (RT)-PCR with two sets of primers: CE9 (5′-GAATACGGTCGCGGCTAGAAATC-3′) and CE10 (5′-CTATTTCGGGTTCTGGACCTGGC-3′) that amplify the complete (600 bp) coat protein (CP) gene (Juarez et al. in Plant Dis 88:907, 2004) and CABYVUp (5’-GTCCGAAACCGCCTGACGC- 3′) and CABYVDo (5′- TCGAGGTTCGAGCAAGCTG - 3′) that amplify a partial fragment (294 bp) within the RNA-dependent RNA polymerase (RdRp) gene (Lotos et al. in J Vir Methods 198:1–11, 2014). Amplicons of the expected sizes using both sets of primers were obtained from the two samples positive for CABYV by ELISA, thus confirming the presence of CABYV. PCR products of the CP gene from one positive sample were purified and sequenced in both directions. Obtained sequence (MH414922) showed the highest nucleotide identity (99%) with the isolate Rak-1 (HM771271) from the Czech Republic. Even though CABYV appears to be widespread throughout the Mediterranean Basin (Lecoq et al. in Plant Pathol 41:749–761, 1992; Abou-Jawdah et al. in Plant Dis 81:1331, 1997, Crop Prot 19:217–224, 2000; Juarez et al. in Plant Dis 88:907, 2004; Hattab et al. in Plant Dis 89:776, 2005; Tamassoli and Meneghini in Plant Pathol 56:720, 2007; Yardimci and Ozgonen in Australas Plant Dis Notes 2:59, 2007; Omar and Bagdady in Phytoparasitica 40:177–184, 2012), to our knowledge, it has not previously been described in Morocco. CABYV is transmitted in a persistent manner by severalaphid species; therefore, effective control of aphid vectors is of utmost importance for CABYV management in zucchini as well as in other cucurbit crops.

First Report of Capsicum chlorosis orthotospovirus Infecting Zucchini (Cucurbita pepo) in China.

Capsicum chlorosis orthotospovirus (CaCV), mostly transmitted by Frankliniella occidentalis (Thripidae, Frankliniella), a tentative species in the genus Orthotospovirus, family Tospoviridae, was first identified in tomato in Australia in 2002 (McMichael et al. 2002). To date, CaCV has been reported to infect peanut (Chen et al. 2007) and tomato (Huang et al. 2010; Yin et al. 2016) in China. During a survey of zucchini (Cucurbita pepo L.) viral diseases in October 2015, about 30% of fruits had chlorosis and rugged symptoms in Shouguang City, Shandong Province, China. The symptomatic fruits of zucchini were collected and tested for virus identification using high-throughput small RNA sequencing. Small unique RNA reads (17 to 28 nt) were assembled into contigs using Velvet 1.0.5 software. BLASTn searches of the resultant contigs in the National Center for Biotechnology Information databases identified about 40 contigs matching four viruses (watermelon mosaic virus, capsicum chlorosis orthotospovirus, watermelon silver mottle virus, and peanut bud necrosis virus) with 86 to 100, 100, 96, and 83% sequence identity, respectively. Among them, one contig nucleotide sequence (50 bp) had 100% identity with the corresponding regions of CaCV M segment genome (KX078566). To confirm this, reverse transcription polymerase chain reaction was conducted with a primer pair CaCV-F (5′-ACTTTCCATCAACCTCTGT-3′) and CaCV-R (5′-GTTATGGCCATATTTCCCT-3′) in eight symptomatic zucchini samples. An expected 812-bp fragment, partial sequence of GN/GC gene on the M RNA, was amplified in one-half of symptomatic zucchini samples and not in a healthy sample. The fragment was purified and sequenced, and the sequence was deposited in GenBank (accession no. MG244190). The nucleotide identity of the amplified fragment was 99% with CaCV-Hainan isolate from Arachnis labrosa (KX078566) and Qld-3432 isolate from pepper in Australia (KM589494), 98% with isolate from Taiwan (KC953854), and 97% with isolate from India (KX499515). The presence of CaCV in the eight symptomatic zucchini samples was verified by using ELISA with CaCV-specific polyclonal antibody (DSMZ, Germany). The infection of pepper (Krishnareddy et al. 2008), tomato (Premachandra et al. 2005), groundnut (Vijayalakshmi et al. 2016), and waxflower (Melzer et al. 2014) with CaCV was previously reported from Australia, Thailand, India, and the United States. No natural infection of zucchini or other cucurbit crops by CaCV has been reported. To our knowledge, this is the first report of CaCV infection of zucchini in China. This study suggests that CaCV may be more widely distributed in China than previously thought.

Prevalence and molecular diversity of the main viruses infecting cucurbit and solanaceous crops in Azerbaijan

Two surveys were conducted in September 2014 and July 2015 in important vegetable-growing areas in Azerbaijan. Cucurbit and solanaceous plants exhibiting symptoms of mosaic, yellowing, leaf curl or necrosis were collected and tested serologically and molecularly for the presence of the major viruses infecting these crops. For cucurbits, the most common viruses in both sampling sets were aphid-transmitted ones, including potyviruses (watermelon mosaic virus, WMV, zucchini yellow mosaic virus, ZYMV), cucumoviruses (cucumber mosaic virus, CMV) and poleroviruses (cucurbit aphid-borne yellows virus, CABYV). Eggplant mottled dwarf (EMDV) was also detected for the first time in Azerbaijan on cucumber at a low prevalence. In solanaceous crops, CMV was the most common virus detected, followed by potato virus Y (PVY). Tomato spotted wilt virus (TSWV), alfalfa mosaic virus (AMV) and tobamoviruses (tomato mosaic virus (TMV), pepper mild mottle virus (PMMoV)) were also detected in 2015. The begomovirus tomato yellow leaf curl virus (TYLCV) was present on tomato only in the Absheron area, where it had a high prevalence and induced important losses. TYLCV-like symptoms on tomato in other areas of Azerbaijan were due to phytoplasma diseases.

First Report of Moroccan Watermelon Mosaic Virus in Zucchini in Iran.

Cucurbits are among the most important vegetable crops in Iran, growing both in open fields and in greenhouses. They are ranked first in economic value, second in yield, and third in acreage and are susceptible to a number of viruses (Bananej and Vahdat 2008). Whitefly-transmitted viruses, namely, cucurbit chlorotic yellows virus (CCYV) and cucumber yellows stunting disorder virus (CYSDV), and the aphid-borne watermelon mosaic virus (WMV), zucchini yellow mosaic virus (ZYMV), papaya ringspot virus (PRSV), and cucurbit aphid-borne yellows virus (CABYV), have all previously been reported from Iran (Bananej and Vahdat 2008; Bananej et al. 2013). During November 2017, 12 samples were collected from cucumber (Cucumis sativus) and 14 from zucchini (Cucurbita pepo) plants grown in open fields that showed virus-like symptoms such as leaf mosaic, mottling, deformation, and yellowing symptoms in Kerman province in the south of Iran. The majority of both plant species were heavily infested by Bemisia tabaci, whereas no aphid colonies were observed. Leaf samples collected from symptomatic plants were subjected to total RNA extraction (Chatzinasiou et al. 2010). Reverse transcription PCR assays used for the detection of CCYV, CYSDV, and CABYV (Orfanidou et al. 2014) showed that all samples were infected with CABYV (26/26), whereas three cucumber samples were infected with CCYV and four with CYSDV. Moreover, double antibody sandwich ELISA was used for detection of WMV, ZYMV, PRSV, and Moroccan watermelon mosaic virus (MWMV) using polyclonal antisera kindly provided by H. Lecoq (INRA, France). None of the samples (0/26) was found to be infected with WMV, ZYMV, or PRSV; however, 9 out of 14 zucchini samples were positive for MWMV infection, whereas none of the 12 cucumber plants were positive for MWMV infection. For further confirmation, the specific primers MoDetF/MoDetR (5′-AARGAYGTTGATGTTGGRAC-3′, 5′-CCATARTCAYTCTTGACYCCATC-3′) were used to amplify a 211-bp product of the capsid protein gene of MWMV. These results confirmed the presence of the virus in the nine zucchini plants. Two isolates were further characterized by sequencing the amplicon, and the BLASTn analysis of the obtained sequences (accession nos. LT985986 and LT985987) showed 100% nucleotide identity with MWMV isolates from Tunisia and Greece (accession nos. EF579955 and LN810061). To our knowledge, this is the first report of MWMV infecting zucchini in Iran. After the detection of the virus in several countries of the Mediterranean region, this report further extends the information on its geographical distribution in the Middle East. The high sequence similarity of the Iranian MWMV isolate with those from the other Mediterranean countries, but not sub-Saharan Africa, indicates their recent rapid spread in the Mediterranean region (Yakoubi et al. 2008). Further surveys should concentrate on the spread, incidence, and epidemiology of this virus in Iran.

Natural occurrence of papaya ringspot virus in Clitoria ternatea in India

Natural occurrence of papaya ringspot virus in Clitoria ternatea in India

First report of Cucurbit aphid‐borne yellow virus infecting bitter gourd (Momordica charantia) and spiny gourd (Momordica dioica) in Sri Lanka

The rapid spread of a virus-like disease with severe leaf yellowing symptoms from bitter gourd and spiny gourd fields in Sri Lanka was observed in 2016-2017. Correct identification based on symptoms is difficult due to mixed infections of cucurbit viruses. Therefore, twenty bitter gourd samples and nine spiny gourd samples were selected from five geographically distinct areas in Sri Lanka (Agnukolapelessa, Balangoda, Kirindiwela, Mulathiuv and Thiththapaththara). The plants showed yellowing and thickening of basal leaves, necrosis of older leaves, reduction of plant growth and interveinal chlorosis (Fig. 1). The samples were tested for infection with Cucurbit chlorotic yellows virus, Cucurbit yellow stunting disorder virus and Zucchini yellow mosaic virus by RT-PCR but all results were negative. Additionally, the symptomatic plants were tested by TAS-ELISA using a monoclonal antibody for Cucurbit aphid-borne yellow virus (CABYV) (Agdia Inc., USA). The test was positive for CABYV in five bitter gourd and two spiny gourd samples. In order to confirm the serological results, total RNA was extracted from four of the samples which had tested positive using ELISA, using the size-fractionated silica extraction method (Boom et al., 2). Virus-specific primers CABYV- CP-5' (5'-CGCGTGGTTGTGGTCAACCC-3') and CABYV-CP-3' (5'- CCYGCAACCGAGGAAGATCC-3') (Bananej & Vahdat, 1) were used to amplify the coat protein gene of CABYV. An amplicon of approximately 500 bp was obtained from each of the four ELISA-positive samples and none from the symptomless samples. One RT-PCR product from spiny gourd and one from bitter gourd (GenBank Accession No. MH802612) were sequenced. The sequences were identical and a BLAST search showed 99% identity with a CABYV isolate from South Korea (LC413786). Additionally, an infected bitter gourd sample was analysed by electron microscopy. The presence of spherical particles, 25 nm in diameter, was observed in a partially purified preparation (Rowhani & Stace-Smith, 1979; Waterhouse & Murant, 5). CABYV has been reported to generally be present in mixed infection with other viruses, including the viruses tested for in this study and Beet pseudo-ellow virus, Cucumber vein yellowing virus and Watermelon mosaic virus. The significance of mixed infections in disease associated with CABYV in Sri Lanka is unclear and requires further investigation (Kassem et al., 3). To the best of our knowledge this is the first report CABYV on bitter gourd in Sri Lanka and the first report of its occurrence on spiny gourd in the world.

Viral Diseases of Crops in Nepal

Viral diseases are the important diseases next to the fungal and bacterial in Nepal. The increase in incidence and severity of viral diseases and emergence of new viral diseases causes the significant yield losses of different crops in Nepal. But the research and studies on plant viral diseases are limited. Most of the studies were focused in viral diseases of rice (Rice tungro virus and Rice dwarf virus), tomato (Yellow leaf curl virus) and potato (PVX and PVY). Maize leaf fleck virus and mosaic caused by Maize mosaic virus were recorded as minor disease of maize. Citrus Tristeza Virus is an important virus of citrus fruit in Nepal while Papaya ringspot potyvirus, Ageratum yellow vein virus (AYVV), Tomato leaf curlJava betasatellite and Sida yellow vein Chinaalphasatellite were recorded from the papaya fruit. The Cucumber mosaic virus (CMV) and Zucchini yellow mosaic potyvirus (ZYMV) are the viral diseases of cucurbitaceous crop reported in Nepal. Mungbean yellow mosaic India virus (MYMIV) found to infect the many crops Limabean, Kidney bean, blackgram and Mungbean. Bean common mosaic necrosis virus in sweet bean, Pea leaf distortion virus (PLDV), Cowpea aphid‐borne mosaic potyvirus (CABMV), Peanut bud necrosis virus (PBNV) in groundnut, Cucumber mosaic virus (CMV). Chili veinal mottle potyvirus (CVMV) and Tomatoyellow leaf curl gemini virus (TYLCV) were only reported and no any further works have been carried out. The 3 virus diseases Soyabean mosaic (SMV), Soybean yellow mosaic virus and Bud blight tobacco ring spot virus (TRSV) were found in soybean.Int. J. Appl. Sci. Biotechnol. Vol 6(2): 75-80

Resistance of Cucurbita maxima ‘Exposição’ to zucchini lethal chlorosis virus is likely associated with restriction to the systemic movement of the virus

Zucchini lethal chlorosis virus (ZLCV), genus Orthotospovirus, so far was only reported in Brasil. The main natural hosts of ZLCV are in the cucurbit family. Pumpkin (Cucurbita maxima) cultivar Exposicao was previously reported as highly resistant to ZLCV infection. The objectives of this work were to better characterize the resistance of the Exposicao cultivar to ZLCV and to evaluate the interference of potyviruses (papaya ringspot virus type W, PRSV-W, and zucchini yellow mosaic virus, ZYMV) in the ZLCV resistance of this cultivar. C. maxima ‘Exposicao’ and zucchini (C. pepo) ‘Caserta’ (susceptible control) plants were mechanically inoculated with ZLCV in the cotyledons. Resistance to infection and systemic virus movement were evaluated at 7 and 20 days later. Virus detection was performed using PTA-ELISA and RT-PCR in the cotyledons and upper leaves. The interference of the potyviruses in ZLCV resistance was evaluated in greenhouse and field assays. ZLCV was detected in the inoculated cotyledons of both cultivars, but it did not move systemically in C. maxima ‘Exposicao’. The potyviruses PRSV-W and ZYMV did not interfere in the response of C. maxima ‘Exposicao’ to infection with ZLCV. The resistance of ‘Exposicao’ to ZLCV can be explored in future cucurbitaceae breeding programs.

Progress in introgression ofPapaya ringspot virusresistance fromVasconcellea pubescenstoCarica papaya

An attempt to develop Carica papaya L. resistant to Papaya ringspot virus type P (PRSV-P) has been established via an intergeneric cross using Vasconcellea pubescens as the resistance donor. V. pubescens has consistently been reported to be resistant to PRSV-P, unlike the resistance in other species (d’Eeckenbrugge et al., 2014). The immunity to PRSV-P is also controlled by a single dominant gene (Dillon et al., 2006), which should be easy to transfer across crops. Because of the genetic distance between the two genera and genetic incompatibility, Vasconcellea parviflora was introduced as a bridging species to transfer the PRSV-P resistance gene(s) to papaya (C. papaya). Backcrossing has been achieved to BC4 in order to maximize the V. parviflora genetic background to improve fertility. The PRSV-P resistance genotype of the BC4 was determined with previously published sequences linked to the prsv-1 locus (Dillon et al., 2006). One of the heterozygous lines, BC4#113, was selected to use as a resistance donor to cross with C. papaya line 2.001. Embryos were rescued, initiated and multiplied in vitro. The cross was successfully micropropagated and produced 18 F1 lines [C. papaya × (V. parviflora backcrossed to V. parviflora × V. pubescens)]. These F1s were genotyped at the prsv-1 locus as previously mentioned. They were subsequently acclimatized and planted in a field in north Queensland. True hybridity was revealed through morphological characterization, including pink flowers, which is a dominant trait from V. parviflora. The hybrid F1s carrying the PRSV-P locus were then successfully backcrossed to C. papaya to generate BC1 generations. They were also sib-crossed with the F1 to generate F1:F2 generations. These lines will be planted in a quarantine laboratory at Griffith University, Nathan, for evaluation of virus resistance. Fertile plants that carry the virus-resistance alleles will be used as parental lines in future breeding strategies.

First Complete Genome Sequence of a Distinct Papaya Ringspot Virus Isolate from the Northeastern Region of India.

ABSTRACTThis is the first report of a Papaya ringspot virus (PRSV) isolate from the northeastern region of India. The nucleotide sequence identity of PRSV-Meghalaya was in the range of 72.6 to 82.5% with other Indian PRSV isolates, and the highest identity of 84.4% was with a French isolate. Population genetic analysis indicated positive selection.

Characterization of Papaya ringspot virus isolates infecting transgenic papaya \u2018Huanong No.1\u2019 in South China

In 2006, the release and cultivation of the genetically modified papaya cultivar ‘Huanong No.1’ successfully controlled the destructive papaya ringspot disease caused by Papaya ringspot virus (PRSV) in South China. However, some transgenic papaya plants from Guangdong and Hainan are found infected by PRSV. In this study, Field investigation was carried out and susceptible transgenic papaya samples were collected during 2012–2016. Twenty representative isolates were artificially inoculated into Cucurbita pepo and commercialised ‘Huanong No.1’ papaya, and results indicated that the plants showed obvious disease symptoms. Phylogenetic analysis of CP genes of 120 PRSV-infected isolates showed that PRSV can be divided into three groups. Isolates from Guangdong and Hainan belong to Group III, which is further divided into two subgroups. The isolates collected in this study have greatly diverged from the previously reported dominant strains Ys, Vb and Sm in South China, indicating that they belong to a new lineage. Further analysis showed a highly genetic differentiation between isolates, and 27.1% of the isolates were identified as recombinants on the basis of CP nucleotide sequences. These results indicate that the genetic variation of PRSV and the formation of the new virus lineage may explain the loss of transgenic papaya resistance in South China.

Evaluation of Weeds as Virus Reservoirs in Watermelon Crops

ABSTRACT: Watermelon is one of the most important vegetable crops in Brazil, which is grouped among the greatest producers worldwide. Viruses stand out among the most damaging disease agents, which can drastically reduce fruit production. In this context, weeds present in the field can also interfere in crop production, acting as reservoirs for viruses. Thus, this study aimed to investigate virus occurrence in weeds at the main watermelon-growing regions in the State of Tocantins. Viruses identification (e.g. potyviruses: Watermelon mosaic virus - WMV; Papaya ring spot virus - type watermelon -PRSV-W; Zucchini yellow mosaic virus- ZYMV; the cucumovirus Cucumber mosaic virus - CMV, and the orthotospovirus Zucchini lethal chlorosis virus - ZLCV) infecting weeds was performed by serology and confirmed by RT-PCR tests. Serological and molecular test results indicate that Amaranthus spinosus, Nicandra physaloides, Physalis angulata and Heliotropium indicum were infected by at least one virus species. The highest infection rate was represented by ZYMV (52.7%), followed by PRSV-W (22.2%); CMV, WMV, and ZLCV that showed the same infection rate (8.3%) each. Plants of P. angulata were infected by all five viruses, singly or in mixed infection, and represented 50% of the total number of infected samples. The highest virus infection rates, 50% and 44.4%, occurred in weeds collected at Lagoa da Confusão and Formoso do Araguaia, respectively. The results on occurrence and distribution of viruses infecting weeds in watermelon commercial plantations in the State of Tocantins provide important information about the role of weeds as virus reservoirs contribute to the knowledge of the epidemiology of these diseases, and enable a proper weed management aiming at reducing the secondary spreading control of viruses by insect vectors.

Behavior of Watermelon Cultivars after Inoculation with Watermelon mosaic virus in Saudi Arabia

Behavior of Watermelon Cultivars after Inoculation with Watermelon mosaic virus in Saudi Arabia

Characterization of a Watermelon mosaic virus Isolate Inducing a Severe Disease in Watermelon in Saudi Arabia

Characterization of a Watermelon mosaic virus Isolate Inducing a Severe Disease in Watermelon in Saudi Arabia

Transmission of the umbra-like Papaya virus Q in Ecuador and its association with meleira-related viruses from Brazil

Papaya virus Q (PpVQ) is an umbra-like virus found in papaya plantings of Ecuador. A most recent study conducted in Brazil has reported the presence of a virus with 70% nucleotide identity to PpVQ. The Brazilian virus was shown to act synergistically with Papaya meleira virus (PMeV) to induce a devastating disorder known as papaya meleira. This finding prompted us to investigate epidemiology aspects of PpVQ, especially its transmission and potential involvement with meleira like symptoms in Ecuador. Three out of ten plants inoculated with ‘viruliferous’ whiteflies (Bemisia tabaci) tested positive for PpVQ; whereas no mechanical or seed transmission was observed. Surveys using a multiplex RT-PCR assay for the simultaneous detection of PpVQ, PMeV and Papaya ringspot virus (PRSV) revealed that PpVQ is found most commonly in co-infections with PRSV, but also in single infections in asymptomatic plants. PMeV, on the other hand, was not detected in any of the tested plants. Interestingly, two virus sequences with homology to PpVQ and PMeV, respectively, were found in leaf samples from babaco (Vasconcellea x heilbornii, syn. Carica pentagona), a sub-tropical relative of papaya native to Ecuador, highlighting the importance of implementing a surveillance scheme for papaya meleira disease in Ecuador as a preventative management and control strategy.