Papaya Ringspot Virus-watermelon Strain Research Articles

Correction to: First report of Papaya ringspot virus-watermelon strain on melon (Cucumis melo L.) in Bali, Indonesia

Correction to: First report of Papaya ringspot virus-watermelon strain on melon (Cucumis melo L.) in Bali, Indonesia

Characterization and Inheritance of Resistance to PRSV-W (Papaya Ringspot Virus-Watermelon Strain) in Squash (Cucurbita pepo L.)

Characterization and Inheritance of Resistance to PRSV-W (Papaya Ringspot Virus-Watermelon Strain) in Squash (Cucurbita pepo L.)

QTL mapping of resistance to Fusarium oxysporum f. sp. niveum race 2 and Papaya ringspot virus in Citrullus amarus.

A Citrullus amarus mapping population segregating for resistance to Fusarium oxysporum f. sp. niveum race 2 and Papaya ringspot virus was used to identify novel QTL, important for the improvement in watermelon disease resistance. Multiple disease screens of the USDA Citrullus spp. germplasm collection have highlighted the value of Citrullus amarus (citron melon or wild watermelon) as a resource for enhancing modern watermelon cultivars (Citrullus lanatus) with resistance to a broad range of fungal, bacterial and viral diseases of watermelon. We have generated a genetic population of C. amarus segregating for resistance to two important watermelon diseases: Fusarium wilt (caused by the fungus Fusarium oxysporum f. sp. niveum; Fon race 2) and Papaya ringspot virus-watermelon strain (PRSV-W). QTL mapping of Fon race 2 resistance identified seven significant QTLs, with the major QTL representing a novel genetic source of resistance and an opportunity for gene pyramiding. A single QTL was associated with resistance to PRSV-W, which adhered to expectations of a prior study indicating a single-gene recessive inheritance in watermelon. The resistance loci identified here provide valuable genetic resources for introgression into cultivated watermelon for the improvement in disease resistance.

The Occurrence of Major Viruses Infecting Zucchini Squash (Cucurbita pepo L.) in Morocco

Zucchini squash, Cucurbita pepo L., is one of the most economically important vegetable crops in Morocco. Virus diseases are a major factor in limiting production of zucchini squash in the country. During the growing seasons 2015, 2016 and 2017, the main areas of field-grown cucurbit production in Morocco (Loukkos, Gharb, Bouznika, Doukkala and Souss) were surveyed for the occurrence and distribution of viruses of zucchini squash. A total of 38 commercial fields were visited and inspected for symptoms of virus diseases and 415 leaf samples were collected from plants showing virus-like symptoms for laboratory analyses. ELISA technique was used to detect the following viruses: Zucchini yellow mosaic virus (ZYMV), Squash mosaic virus (SqMV), Cucumber mosaic virus (CMV), Papaya ringspot virus-watermelon strain (PRSV-W) and Cucurbit aphid-borne yellows virus (CABYV). The obtained results showed that virus diseases were widely distributed in the country with an infection rate of 77.6%, especially in the region of Loukkos where 85% of the tested plants were infected by at least one virus. To the best of our knowledge, this isthe first study on the occurrence and geographical distribution of viruses infecting zucchini squash in Morocco. This study provides valuable information, which could be beneficial and of great interest for the researchers, growers and the plant protection services for planning future strategies to control virus diseases of zucchini squash in Morocco.

Cross protection against the watermelon strain of Papaya ringspot virus through modification of viral RNA silencing suppressor

Papaya ringspot virus watermelon strain (PRSV-W) causes huge economic losses to cucurbits production. Here, we constructed an infectious clone of PRSV-W, pCamPRSV-W, which can induce similar symptoms and accumulate to same levels as wild type virus in plants of Cucurbita pepo, Cucumis melo, Citrullus lanatus and Cucumis sativus. The green fluorescence protein gene gfp was cloned into pCamPRSV-W to produce pCamPRSV-W-GFP, which produced strong green fluorescence in systemic leaves of inoculated Cucurbita pepo, Cucumis melo, Citrullus lanatus and Cucumis sativus plants, indicating that pCamPRSV-W can be used to express foreign genes. Ten mutants of PRSV-W, obtained by site-directed mutagenesis in the RNA silencing suppressor helper-component proteinase encoding region, produced dramatically attenuated symptoms in plants of Cucumis melo. The Cucumis melo plants pre-infected with mutants K125D and G317 K showed effective protection against the challenge inoculation of wild type PRSV-W. The attenuated mutants generated in this study will be helpful for the eco-friendly control of PRSV-W.

Inheritance of Resistance to Papaya Ringspot Virus-Watermelon Strain in Watermelon

Sources of resistance to the watermelon strain of papaya ringspot virus-watermelon strain (PRSV-W) have been identified within the watermelon (Citrullus lanatus) germplasm collection. Inheritance of the resistance to PRSV-W was studied in three Citrullus amarus (formerly C. lanatus var. citroides) PI accessions: PI 244017, PI 244019, and PI 485583. Three susceptible parent lines, ‘Allsweet’, ‘Calhoun Gray’, and ‘New Hampshire Midget’, were crossed with resistant PI accessions to develop F1, F2, and BC1 progenies in six families. A single recessive gene was found to control the resistance to PRSV-W in all three resistant PI accessions. Allelism tests indicated that the three PI accessions carry the same resistance allele to PRSV-W. The gene symbol ‘prv’ is proposed for PRSV-W resistance in PI 244017, PI 244019, and PI 485583 in watermelon.

Resistance to Papaya ringspot virus-Watermelon Strain (PRSV-W) in the Desert Watermelon Citrullus colocynthis

The bitter desert watermelon, Citrullus colocynthis (L.) Schrad is a wild species valuable for biotic and abiotic stress resistance that could be exploited for improving watermelon cultivars [Citrullus lanatus (Thunberg) Matsum & Nakai var. lanatus]. The objective of this study was to survey and identify C. colocynthis accessions displaying resistance to the Papaya ringspot virus-watermelon strain (PRSV-W). Thirty-one accessions of C. colocynthis, collected in Africa, the Middle East, southwest Asia, and India were evaluated for PRSV-W resistance. Of these 31 accessions, 4 U.S. Plant Introduction (PI) accessions, including 525080 (collected in Qena, Egypt) and PI 537277, PI 652554, and Griffin 14201 (collected at the northern Indian desert of Rajasthan and the neighboring region of Punjab, Pakistan) showed high resistance to PRSV-W. Plants of these four resistant PIs were self-pollinated to produce S1 and S2 seeds that continued to maintain the high levels of PRSV resistance. Since there is a wide genetic distance between watermelon cultivars and C. colocynthis, we performed crosses and backcrosses with watermelon cultivars, including ‘Charleston Gray’ and ‘Sugar Baby’ to produce viable seed that would be useful in the development of genetic populations and in introducing the resistance into watermelon cultivars.

Inheritance of resistance to papaya ringspot virus-watermelon strain (PRSV-W) in 'Whitaker' summer squash line

Abstract The objective of this work was to study the genetic control of the PRSV-W (Papaya Ringspot Virus - Watermelon Strain) resistance in Cucurbita pepo 'Whitaker' line. Plants of parental lines Whitaker (resistant) and Caserta (susceptible), and of the generations F1, F2, BC11 and BC12 were evaluated for their reactions to PRSV-W. Caserta plants showed severe mosaic symptoms, while Whitaker grew vigorously and remained almost totally symptom-free. Most of the F1, F2 and backcross plants also presented severe mosaic symptoms. Data were used to test a hypothesis of monogenic inheritance under different presumed degrees of dominance, and genetic models were tested using maximum likelihood tests of genetic control. Broad-sense heritability was of 0.57 for the first evaluation. Resistance to PRSV-W in C. pepo 'Whitaker' is due to a major gene effect summed to polygenic effects.

Development and Field Evaluation of Multiple Virus-Resistant Bottle Gourd (Lagenaria siceraria).

In an effort to develop bottle gourd (Lagenaria siceraria) as a widely adapted rootstock for watermelon grafting, we sought to identify lines with broad resistance to several cucurbit viruses that are economically important in the United States. Preliminary analysis under greenhouse conditions indicated that the currently available commercial watermelon rootstocks were either highly susceptible or somewhat tolerant to one or more viruses. However, in greenhouse screening, several breeding lines of bottle gourd displayed broad-spectrum resistance to four viruses tested, including Zucchini yellow mosaic virus, Watermelon mosaic virus (WMV), Papaya ringspot virus watermelon strain (PRSV-W), and Squash vein yellowing virus. Resistance to PRSV-W and WMV was confirmed through field trials in two consecutive years at two different locations in South Carolina. Two breeding lines (USVL#1-8 and USVL#5-5) with broad-spectrum virus resistance could be useful materials for watermelon rootstock development.

Distribution of Viruses Infecting Cucurbit Crops and Isolation of Potential New Virus-Like Sequences from Weeds in Oklahoma.

Field surveys were conducted from 2008 to 2010 to detect and determine the incidence of viruses in the major cucurbit-growing areas of Oklahoma. In total, 1,049 symptomatic leaf samples (890 from cucurbits, 109 from weed species, and 50 from crop plants [agricultural crops]) were collected from 90 fields in four counties (Atoka, Blaine, Jefferson, and Tulsa) of Oklahoma. Samples were tested against seven viruses, including Cucumber mosaic virus (CMV), Cucumber green mottle mosaic virus (CGMMV), Melon necrotic spot virus (MNSV), Papaya ringspot virus-watermelon strain (PRSV-W, formerly known as Watermelon mosaic virus-1), Squash mosaic virus (SqMV), Watermelon mosaic virus-2 (WMV-2), and Zucchini yellow mosaic virus (ZYMV), using dot-immunobinding assay (DIBA). Results showed the highest incidence for PRSV (51%), followed by WMV-2 (14%) and ZYMV (10%) among the collected samples. SqMV, MNSV, and CMV were detected in 3.8, 3.3, and 1.1% of the samples, respectively. None of the samples collected during surveys reacted positively against the antiserum of CGMMV. Mixed virus infections were common involving two (5.18%) or three (4.61%) viruses in various combinations. New weed host species were found to be infected with PRSV when confirmed by both DIBA and reverse-transcription polymerase chain reaction (RT-PCR). Some weed species contained possible new viruses when analyzed by random RT-PCR, followed by cloning, sequencing, and BLAST analysis with sequences in GenBank.

Using Protector Plants to Reduce the Incidence of Papaya Ringspot Virus-Watermelon Strain in Zucchini

The use of plant diversification (e.g., mixed cropping, cover crops, border plants, intercrops, etc. ) to protect a primary crop from insect transmitted viral diseases is often referred to as barrier cropping. Specific plants used to mitigate virus incidence in a cash crop are frequently called protector plants. The potential use of protector plants to reduce the density of aphid vectors and incidence of aphid-borne nonpersistent virus in zucchini, Cucurbita pepo L. was evaluated during 2003, 2005, and 2006 on Oahu, HI. Cover crops, buckwheat Fagopyrum esculentum Moench and white clover Trifolium repens L., or sunn hemp, Crotolaria juncea L. and an intercropped vegetable, okra Abelmonchus esculentus (L.), were evaluated for their potential use as protector plants. Results of the field experiments showed that densities of alatae aphids in water pan traps did not differ significantly among treatment habitats during three field experiments. However, the percentage of zucchini plants showing virus symptoms was significantly lower in diculture than monoculture habitat during all 3 yr. Results from field and laboratory experiments support the hypothesis that protector plants reduced the incidence of Papaya ringspot virus-watermelon strain by acting as virus sinks and that the three cover crops were more effective in reducing Papaya ringspot virus-watermelon spread than okra.

Combining ability of summer-squash lines with different degrees of parthenocarpy and PRSV-W resistance

The aim was to assess heterosis in a set of 16 summer-squash hybrids, and evaluate the combining capacity of the respective parental lines, which differed as to the degree of parthenocarpy and resistance to PRSV-W (Papaya Ringspot Virus-Watermelon strain). The hybrids were obtained using a partial diallel cross design (4 × 4). The lines of parental group I were 1 = ABX-037G-77-03-05-01-01-bulk, 2 = ABX-037G-77-03-05-03-10-bulk, 3 = ABX-037G-77-03-05-01-04-bulk and 4 = ABX-037G-77-03-05-05-01-bulk, and of group II, 1′ = ABX-037G-77-03-05-04-08-bulk, 2′ = ABX-037G-77-03-05-02-11-bulk, 3′ = Clarice and 4′ = Caserta. The 16 hybrids and eight parental lines were evaluated for PRSV-W resistance, parthenocarpic expression and yield in randomized complete-block designs, with three replications. Parthenocarpy and the resistance to PRSV-W were rated by means of a scale from 1 to 5, where 1 = non-parthenocarpic or high resistance to PRSV-W, and 5 = parthenocarpic or high susceptibility to PRSV-W. Both additive and non-additive gene effects were important in the expression of parthenocarpy and resistance to PRSV-W. Whereas estimates of heterosis in parthenocarpy usually tended towards a higher degree, resistance to PRSV-W was towards higher susceptibility. At least one F1 hybrid was identified with a satisfactory degree of parthenocarpy, resistance to PRSV-W and high fruit-yield.

Dot-Blot Hybridization for Detection of Five Cucurbit Viruses by Digoxigenin-Labelled cDNA Probes

Dot-blot hybridization was applied in this paper to detect five viruses infecting cucurbitaceous crops, Zuccini yellow mosaic virus (ZYMV), Watermelon mosaic virus (WMV), Cucumber mosaic virus (CMV), Papaya ringspot virus-watermelon strain (PRSV-W) and Squash mosaic virus (SqMV), as a good alternative assay in seed health test and epidemiological and transgenic research. Digoxigenin-labelled cDNA probes of the five viruses were synthesized by PCR with the specific primers and applied in dot-blot hybridization to detect five viruses in crude extraction of the infected leaves. And three SqMV probes of different lengths (0.55, 1.6, and 2.7 kb, respectively) were designed to investigate the effect of hybridization. The results showed that the sensitivity for detecting the crude extraction of infected leaves by ZYMV, WMV, CMV, PRSV-W, and SqMV was down to 1:160, 1:160, 1:320, 1:160, and 1:320, respectively. Three SqMV probes of different length showed no differences on the sensitivity and specificity. The digoxigenin-labelled probes prepared by PCR could be used for accurate and rapid identification of 5 viruses infecting cucurbitaceous crops with good stabilities, sensitivities, specificity, and reproducibilities.

Establishment of Economically Important Viruses on Watermelons by Elisa Method in Bulgaria

ABSTRACTThe reaction of widespread watermelon varieties to economically important viral pathogens was studied by ELISA method in Bulgaria. It was established that Crimson Suit, Sugar Baby and Mramorna 17 were susceptible to Zucchini Yellow Mosaic Virus (ZYMV), Papaya Ringspot Virus watermelon strain W - (PRSV-W), Watermelon Mosaic Virus 2(WMV2), Squash Mosaic Virus(SqMV) and Cucumber Mosaic Virus(CMV). ZYMV reached the highest viral concentration in watermelon plants infected by artificial inoculation. PRSV-W reached the highest viral concentration in natural infection of commercial crops from Crimson Suit. This virus was followed by WMV2, SqMV, ZYMV, CMV, or followed by SqMV, ZYMV, CMV, WMV2. For the first time in Bulgaria, it was established, that SqMV was a pathogen for watermelon, because it appeared in high viral concentration in plants. The grown watermelon varieties were not immune or tolerant to CMV, because CMV reached high viral concentration in some plants from these varieties.

Inheritance of Resistance to the Watermelon Strain of Papaya Ringspot Virus in Watermelon

Sources of resistance to the watermelon strain of papaya ringspot virus (PRSV-W) have been identified within the watermelon (Citrullus lanatus) germplasm collection. Inheritance of resistance to papaya ringspot virus-watermelon strain was studied in three C. lanatus var. citroides accessions: PI 244017, PI 244019, and PI 485583. The susceptible parent lines `Allsweet', `Calhoun Gray', and `New Hampshire Midget' were crossed with resistant accessions to develop F1, F2, and BC1 generations for six families. A single recessive gene was found to control resistance to PRSV-W. The gene symbol `prv' is proposed for PRSV-W resistance in watermelon. Additional work is needed to determine whether the genes in PI 244017, PI 244019, and PI 485583 are allelic for resistance to PRSV-W.

Epidemics of aphid-transmitted viruses in melon crops in Spain

A survey of mosaic diseases in fields of open air grown melon was done in three provinces of Spain over 3 years. The incidence of the mosaic-inducing viruses Cucumber mosaic virus (CMV), Watermelon mosaic virus-2 (WMV-2), Papaya ringspot virus watermelon strain (PRSV-W) and Zucchini yellow mosaic virus (ZYMV) was assessed. The only viruses present in the three provinces during the 3 years studied were CMV and WMV-2, but their incidence differed according to year and region. For each epidemic, disease progress curves (DPC) were obtained, all of them well described by the Gompertz model. With the five descriptive variables of the model, a principal component analysis was done and two principal components, representing a severity factor and a time factor were found. Cluster analyses done with these two principal components, grouped the epidemics into 6 clusters that did not correlate with year, virus or province. Correlation analyses between epidemics caused by WMV-2 and CMV and climatic variables were done. Although the temperature in the spring months was the main factor associated with the severity of the epidemics caused by these two viruses, other differential correlations were found. Spatial evolution of CMV and WMV-2 epidemics was also different suggesting different aphid species acting as vectors for the viruses.

Resistance to papaya ringspot virus in summer squash Cucurbita pepo L. introgressed from an interspecific C. pepo × C. moschata cross

Early infections of the papaya ringspotvirus-watermelon strain (PRSV-W) in summersquash Cucurbita pepo may causemarketable yield losses of up to 100%. Because control of the viral disease viamanagement of vector insects is notefficient, incorporation of PRSV-W geneticresistance into C. pepo cultivarswould be highly desirable. Althoughresistant accessions have been described inC. ecuadorensis, C.foetidissima, C. maxima and C.moschata, resistant accessions of C.pepo are rare. This paper reports oninterspecific hybridization between C.pepo and a PRSV-W-resistant C.moschata squash accession, and on theearly steps in introgression of thisresistance into the former species. C. pepo cv. Asmara was crossed with twoPRSV-W resistant C. moschataaccessions. Immature F1 (C.pepo× C.moschata) embryos were excised20 days after pollination, and culturedasseptically in two different culturemedia, each under two different lightregimes. No adult plants could berecovered from immature embryos of thecross C. pepo cv. Asmara × C.moschata cv. Piramoita. From the crossC. pepo cv. Asmara × C.moschata cv. Duda, 4 seedlings wererecovered from 6 embryos incubated in agrowth chamber [25° to 28 °C,16 hours of light with 1500–2000 lux/ 8 hdark period] immediately after excision andinoculation in a culture medium [=Murashige and Skoog (MS) + 0.01 mg/L of IAA(indolacetic acid) + 0.1 mg/L of Kinetin],without an intervening dark period. F1 (C. pepo × C. moschata)plants were fertile, and upon selfingyielded viable F2 seeds. PRSV-Wresistance was assessed in the F2 (C. pepo × C. moschata) population,using C. pepo cv. Asmara and C.moschata cv. Duda, respectively, as thesusceptible and resistant (tolerant)checks. Plants were mechanically inoculatedwith a known PRSV-W isolate. The F2population showed a PRSV-W responseintermediate between those of the parentalaccessions, and estimates of the meandegree of dominance indicates incompletedominance in the direction ofsusceptibility. The mean broad-senseheritability estimate of PRSV-W resistancewas 0.48, a medium to high value,indicating the likelihood of a significantresponse to selection for resistance. Theintrogression of the resistance to PRSV-Wof C. moschata into C. peposeems to be technically viable.

Screening the Watermelon Germplasm Collection for Resistance to Papaya Ringspot Virus Type‐W

Papaya ringspot virus watermelon strain (PRSV-W), formerly watermelon mosaic virus-1, is a major disease of watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai]. The objectives of this study were (i) to screen the USDA watermelon germplasm collection for PRSV-W resistance, (ii) to verify the disease rating for the most resistant and most susceptible accessions, (iii) to determine the number of escapes on the basis of the retest of the germplasm screening test. The experiment was a randomized complete block with five replications and 1275 accessions. 'Charleston Gray' susceptible checks were used to verify that the PRSV-W inoculum was virulent. Enzyme-linked immunosorbent assay (ELISA) was performed after the last rating to determine whether the virus was in the plant tissue. The PI accessions with the highest resistance to PRSV-W that also had resistance to other watermelon viruses (ZYMV, zucchini yellow mosaic virus or WMV, watermelon mosaic virus, formerly watermelon mosaic virus-2) were PI 244018, PI 244019, PI 255137, and PI 482299. The first retest of the most resistant 21 PI accessions showed that there were some escapes that were not resistant to PRSV-W. Of the 21 PI accessions in the retest, seven PI accessions were identified for further testing. Of the 60 resistant PI accessions in the final retest, eight had resistance with a rating of 3.6 or less for the best, average, and maximum ratings: PI 244017 (best over all tests), PI 244019, PI 482342, PI 482318, PI 485583, PI 482379, PI 595203, and PI 244018.

Methods for screening watermelon for resistance to papaya ringspot virus type-W

Papaya ringspot virus-watermelon strain (PRSV-W) affects all agriculturally important species of the Cucurbitaceae, and is of economic interest because of its destructiveness. The objective of this study was to develop a consistent and reliable method to screen watermelon for resistance to PRSV-W. PRSV-W isolates 1637, 1870, 2030, 2038, 2040, 2052, 2169, 2201, 2207, and W-1A were maintained in ‘Gray Zucchini’ squash, and were used in the inoculations. Three experiments were run, a preliminary experiment to determine the important factors involved in disease development, a main experiment to quantify the effects of those factors, and a retest of three cultigens to determine test variability. The experiment was a split-plot treatment arrangement in a randomized complete block design with four replications. Whole plots were growth stage (cotyledon, first true leaf), subplots were pot size (55 or 100 mm), and sub-subplots were the 10 isolates. Plants were rated on a scale of 0–9 for each of three traits: leaf necrosis, mosaic symptoms, and leaf deformation. We found the best method for a screening of the watermelon germplasm collection for resistance to PRSV-W is to grow the seedlings in square, 100 mm diameter pots (or 55 mm diameter pots if uniform germination is expected) and inoculate plants at the first true leaf stage using PRSV-W isolate 2052 and the rub method. Significant differences were obtained (with LSD values of 0.6–1.5) using four replications of five plants per plot, but fewer replicates and plants may be adequate for a large germplasm screening experiment. The method can be used by researchers interested in screening for PRSV-W resistance in watermelon, verifying that resistance, studying its inheritance, and transferring it to elite cultivars.

Occurrence, Distribution, and Relative Incidence of Mosaic Viruses Infecting Field-Grown Melon in Spain.

The main areas for field-grown melon (Cucumis melo) production in Spain were surveyed for the occurrence and relative incidence of cucumber mosaic virus (CMV), papaya ringspot virus-watermelon strain (PRSV-W), watermelon mosaic virus-2 (WMV-2), and zucchini yellow mosaic virus (ZYMV) during the growing seasons of 1995 and 1996. Samples from 1,152 plants showing symptoms of virus infection were collected from commercial melon fields and analyzed by enzyme-linked immunosorbent assay (ELISA). CMV and WMV-2 were the most frequently found viruses, both by the number of locations and by their incidence in each location. In contrast, PRSV-W and ZYMV were detected in fewer sites and at lower incidences. PRSV-W was not found in 1996. In 79% of the samples, only one virus was detected; 15% of the samples were doubly infected. Both the incidence of plants showing symptoms of viral infection and the relative incidence of each of the four viruses varied according to the region, while the main trends of virus distribution were similar for 1995 and 1996.