Inheritance of resistance to systemic symptom expression of Melon necrotic spot virus (MNSV) in Cucumis melo L. `Doublon'

Abstract A new distribution map is given for Melon necrotic spot virus (Tombusviridae: Carmovirus). The hosts include melon (Cucumis melo), cucumber (Cucumis sativus) and watermelon (Citrullus lanatus). Information is given on the geographical distribution in Europe (France, Greece, Crete, Italy, Sardinia, Netherlands, Norway, Spain, Canary islands, mainland Spain, Sweden, UK, England and Wales), Asia (China, Jiangsu, Iran, Israel, Japan, Hokkaido, Honshu, Kyushu, Shikoku, Korea Republic, Syria and Turkey), Africa (Tunisia), North America (Canada, Ontario, Mexico, USA, California) Central America and Caribbean (Guatemala, Honduras and Panama) and South America (Uruguay). The virus is transmitted by the fungal vector Olpidium bornovanus (syn. O. radicale) (Chytridiomycota: Olpidiaceae).

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Molecular Characterization of a Melon necrotic spot virus Strain That Overcomes the Resistance in Melon and Nonhost Plants

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi.2004.17.6.668 ◽

2004 ◽

Vol 17 (6) ◽

pp. 668-675 ◽

Cited By ~ 48

Author(s):

Juan A. Díaz ◽

Cristina Nieto ◽

Enrique Moriones ◽

Verónica Truniger ◽

Miguel A. Aranda

Keyword(s):

Cdna Clone ◽

Recessive Gene ◽

Genomic Region ◽

Open Reading Frames ◽

Necrotic Spot ◽

Spot Virus ◽

Melon Necrotic Spot Virus ◽

Gomphrena Globosa ◽

Resistance Trait ◽

Cucumis Melo L

Resistance of melon (Cucumis melo L.) to Melon necrotic spot virus (MNSV) is inherited as a single recessive gene, denoted nsv. No MNSV isolates described to date (e.g., MNSV-Mα5), except for the MNSV-264 strain described here, are able to overcome the resistance conferred by nsv. Analysis of protoplasts of susceptible (Nsv/-) and resistant (nsv/nsv) melon cultivars inoculated with MNSV-264 or MNSV-Mα5 indicated that the resistance trait conferred by this gene is expressed at the single-cell level. The nucleotide sequence of the MNSV-264 genome has a high nucleotide identity with the sequences of other MNSV isolates, with the exception of its genomic 3′-untranslated region (3′-UTR), where less than 50% of the nucleotides are shared between MNSV-264 and the other two MNSV isolates completely sequenced to date. Uncapped RNAs transcribed from a full-length MNSV-264 cDNA clone were infectious and caused symptoms indistinguishable from those caused by the parental viral RNA. This cDNA clone allowed generation of chimeric mutants between MNSV-264 and MNSV-Mα5 through the exchange of the last 74 nucleotides of their coat protein (CP) open reading frames and the complete 3′-UTRs. Analysis of protoplasts of susceptible and resistant melon cultivars inoculated with chimeric mutants clearly showed that the MNSV avirulence determinant resides in the exchanged region. The carboxy-termini of the CP of both isolates are identical; therefore, the avirulence determinant likely consists of the RNA sequence itself. We also demonstrated that this genomic region contains the determinant for the unique ability of the isolate MNSV-264 to infect noncucurbit hosts (Nicotiana benthamiana and Gomphrena globosa).

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A New Strain of Melon necrotic spot virus that Is Unable to Systemically Infect Cucumis melo

Phytopathology ◽

10.1094/phyto-98-11-1165 ◽

2008 ◽

Vol 98 (11) ◽

pp. 1165-1170 ◽

Cited By ~ 10

Author(s):

Takehiro Ohki ◽

Isamu Sako ◽

Ayami Kanda ◽

Tomofumi Mochizuki ◽

Yohachiro Honda ◽

...

Keyword(s):

Coat Protein ◽

Cucumis Melo ◽

Genomic Structure ◽

Single Cell Level ◽

Necrotic Spot ◽

Cell Level ◽

Spot Virus ◽

Melon Necrotic Spot Virus ◽

Necrotic Spots ◽

Necrotic Symptoms

We report a new strain of Melon necrotic spot virus (MNSV) that is unable to systemically infect Cucumis melo. A spherical virus (W-isolate), about 30 nm in diameter like a carmovirus, was isolated from watermelons with necrotic symptoms. The W-isolate had little serological similarity to MNSV, and it did not cause any symptoms in six melon cultivars susceptible to MNSV; however, the host range of the W-isolate was limited exclusively to cucurbitaceous plants, and transmission by O. bornovanus was confirmed. Its genomic structure was identical to that of MNSV, and its p89 protein and coat protein (CP) showed 81.6 to 83.2% and 74.1 to 75.1% identity to those of MNSV, respectively. Analysis of protoplast showed that the W-isolate replicated in melons at the single-cell level. Furthermore, chimeric clones carrying the CP of MNSV induced necrotic spots in melons. These results suggested that the absence of symptoms in melons was due to a lack of ability of the W-isolate to move from cell to cell. In view of these findings, we propose that the new isolate should be classified as a novel MNSV watermelon strain.

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A Resistance to Systemic Symptom Expression of Melon Necrotic Spot Virus in Melon

Journal of the American Society for Horticultural Science ◽

10.21273/jashs.128.4.0541 ◽

2003 ◽

Vol 128 (4) ◽

pp. 541-547 ◽

Cited By ~ 10

Author(s):

Cristina Mallor ◽

José María Álvarez ◽

Marisol Luis-Arteaga

Keyword(s):

Screening Program ◽

Cell Movement ◽

Recessive Gene ◽

Systemic Symptom ◽

Necrotic Spot ◽

Spot Virus ◽

Melon Necrotic Spot Virus ◽

Systemic Development ◽

Systemic Symptoms ◽

Viral Distribution

Melon necrotic spot virus (MNSV) has been found affecting melon (Cucumis melo L.) crops. At present the only known resistance in melon is controlled by a single recessive gene, nsv. The presence of nsv in a melon genotype has been correlated with the lack of necrotic lesions on the mechanically inoculated cotyledons. Thus, in a screening program for MNSV resistance, melon genotypes that developed necrotic lesions in the inoculated cotyledons were discarded. However, in this paper we show that some melon accessions mechanically inoculated with MNSV do develop local necrotic lesions, therefore showing the absence of the gene nsv, but fail to develop the systemic symptoms typical of diseased plants under the screening conditions. In some of these accessions the influence of the temperature on the development of systemic symptoms was studied. The results showed that, depending on the accession, temperatures under 25 or 20 °C enhanced the systemic development of the disease. One of the tested varieties, `Doublon', did not develop systemic symptom at any of the tested temperatures (15, 17.5, 20, 22.5, 25, 27.5, and 30 °C). In this variety, the lack of systemic symptoms was correlated to the lack of virus infection of these tissues based upon ELISA results. MNSV was not detected in the uninoculated parts of the plant, and seems to remain confined to the local lesions produced on the cotyledons following the mechanical inoculation. Restriction of viral multiplication and/or cell-to-cell movement could explain the pattern of viral distribution in this variety. This reaction was observed in the `Doublon' plants mechanically inoculated with each of five isolates of MNSV tested, including an isolate that overcomes the nsv gene resistance.

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