Olpidium bornovanus-Mediated Germination of Ascospores of Monosporascus cannonballus: A Host-Specific Rhizosphere Interaction

Monosporascus cannonballus, a host-specific root-infecting ascomycete, is the causal agent of a destructive disease of melon (Cucumis melo L.) known as vine decline. Ascospores germinate only in the rhizosphere of melon plants growing in field soil. However, no germination occurs in the rhizosphere of melon plants if the field soil is heated to temperatures >50°C prior to infestation with ascospores. This observation suggested that germination is mediated by one or more heat-sensitive members of the soil microflora. Although bacteria or actinomycetes were heretofore suspected as the germination-inducing microbes, our data demonstrate that Olpidium bornovanus, an obligate, host-specific, root-infecting zoosporic fungus, is responsible. In four experiments conducted in autoclaved field soil amended with various population densities of culturally produced ascospores, significant ascospore germination was recorded only in the rhizosphere of cantaloupe seedlings colonized by O. bornovanus.

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Microbe-Mediated Germination of Ascospores of Monosporascus cannonballus

Phytopathology ◽

10.1094/phyto.2000.90.3.243 ◽

2000 ◽

Vol 90 (3) ◽

pp. 243-247 ◽

Cited By ~ 24

Author(s):

M. E. Stanghellini ◽

D. H. Kim ◽

M. Waugh

Keyword(s):

Root Exudates ◽

Soil Microflora ◽

Gram Negative Bacteria ◽

Field Soil ◽

Gram Positive ◽

Gram Negative ◽

Monosporascus Cannonballus ◽

Ascospore Germination

Ascospores of Monosporascus cannonballus germinated readily in the rhizosphere of cantaloupe plants growing in field soil. However, little or no germination occurred in the rhizosphere of melon plants growing in field soil that was autoclaved prior to infestation with ascospores. The latter data suggested that root exudates alone do not stimulate ascospore germination and that the soil microflora may be involved in the induction of ascospore germination. Amending field soil with streptomycin (which inhibits gram-negative microorganisms) did not suppress ascospore germination in the rhizosphere of cantaloupe plants. However, amending the soil with penicillin (which inhibits gram-positive microorganisms) did suppress ascospore germination. Pentachloronitrobenzene (PCNB), which inhibits the gram-positive actinomycetes but does not inhibit gram-positive or gram-negative bacteria, also suppressed ascospore germination. These results suggest that actinomycetes, either directly or indirectly, are involved in the induction of ascospore germination in field soil in the presence of exudates from cantaloupe roots. Optimum germination occurred at temperatures ranging from 25 to 35°C, and data indicate that a high percentage (≥72%) of the ascospore population within 500 μm of a root are capable of germination and subsequent penetration of cantaloupe roots.

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Reaction of Melon (Cucumis melo L.) Cultivars to Monosporascus cannonballus (Pollack & Uecker) and their Effect on Total Phenol, Total Protein and Peroxidase Activities

Journal of Phytopathology ◽

10.1111/jph.12069 ◽

2012 ◽

Vol 161 (5) ◽

pp. 363-368 ◽

Cited By ~ 2

Author(s):

Mohammad Salari ◽

Naser Panjehkeh ◽

Zahra Nasirpoor ◽

Javad Abkhoo

Keyword(s):

Total Protein ◽

Cucumis Melo ◽

Total Phenol ◽

Monosporascus Cannonballus ◽

Cucumis Melo L

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First Report of Monosporascus cannonballus on Melons in Saudi Arabia

Plant Disease ◽

10.1094/pdis.1997.81.10.1215b ◽

1997 ◽

Vol 81 (10) ◽

pp. 1215-1215 ◽

Cited By ~ 11

Author(s):

R. S. Karlatti ◽

F. M. Abdeen ◽

M. S. Al-Fehaid

Keyword(s):

Saudi Arabia ◽

Early Stage ◽

Late Summer ◽

Peat Moss ◽

Oat Hulls ◽

Monosporascus Cannonballus ◽

Fruit Maturity ◽

Root Necrosis ◽

Vine Decline ◽

Cucumis Melo L

In the late summer of 1996, a root rot and vine decline was noticed on greenhouse grown melons (Cucumis melo L.) at the National Agriculture and Water Research Center, Riyadh, Saudi Arabia. Melons were grown on sandy clay soil and peat moss was spot applied as organic manure. The pH of the soil was 7.8. Disease symptoms first appeared at early stage of fruit maturity of the crop. Diseased vines exhibited stunting, yellowing, and, at a late stage, complete collapse of the leaf canopy. The roots showed discoloration, discrete lesions on all root systems, and loss of secondary and tertiary feeder roots. Numerous perithecia were observed on the secondary and tertiary roots only. Each ascus contained one large spherical ascospore. The fungus was isolated on potato dextrose agar and identified as a Monosporascus sp. (2). A pure culture was confirmed as Monosporascus cannonballus Pollack & Uecker. IMI (373485(01)) by IMI, Surrey, U.K. Pathogenicity was confirmed in a temperature-controlled growth chamber on the melon cv. Red Queen(F1). A medium that consisted of 3 liters of sand, 275 g of dried ground oat hulls, and 450 ml of distilled sterile water (1) was inoculated and incubated for 40 days. The colonized medium (100 ml) was mixed with a pasturized potting mix (sand/peat moss; 1:1) in 17-cm-diameter plastic pots. Five seeds were planted in each pot and, 15 days after germination, seedlings were thinned to one per pot. Noninfested pots were inoculated with sterile sand/oat hull medium. The pots were placed in chambers maintained at 30/20°C, day/night. At various intervals, the onset and severity of symptom expression were recorded. The isolate caused stunting and root necrosis. The fungus was reisolated from symptomatic plants. This report extends the known range of M. cannonballus to include Saudi Arabia. Other reports of this fungus are from India, Israel, Japan, Libya, Mexico, Spain, Taiwan, Tunisia, and the U.S. References: (1) J. C. Mertely et al. Plant Dis. 77:667, 1993. (2) F. G. Pollack and F. A. Uecker. Mycologia 66:346, 1974.

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Resistance to Melon necrotic spot virus in Cucumis melo L. ‘Doublon’ artificially inoculated by the fungus vector Olpidium bornovanus

Crop Protection ◽

10.1016/j.cropro.2005.07.007 ◽

2006 ◽

Vol 25 (5) ◽

pp. 426-431 ◽

Cited By ~ 6

Author(s):

Cristina Mallor ◽

Marisol Luis-Arteaga ◽

José María Álvarez ◽

Celia Montaner ◽

Elena Floris

Keyword(s):

Cucumis Melo ◽

Necrotic Spot ◽

Spot Virus ◽

Melon Necrotic Spot Virus ◽

Olpidium Bornovanus ◽

Cucumis Melo L

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Cucumis melo L. New Breeding Lines Tolerant to Melon Vine Decline

HortScience ◽

10.21273/hortsci.44.7.2022 ◽

2009 ◽

Vol 44 (7) ◽

pp. 2022-2024 ◽

Cited By ~ 2

Author(s):

Ana Fita ◽

Cristina Esteras ◽

Belén Picó ◽

Fernando Nuez

Keyword(s):

Cucumis Melo ◽

Breeding Lines ◽

Vine Decline ◽

Cucumis Melo L

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Differential Fruit Load in Melon (Cucumis melo L.) Affects Shoot and Root Growth, and Vine Decline Symptoms

HortScience ◽

10.21273/hortsci.32.3.526b ◽

1997 ◽

Vol 32 (3) ◽

pp. 526B-526 ◽

Cited By ~ 2

Author(s):

David W. Wolff ◽

Daniel I. Leskovar ◽

Mark C. Black ◽

Marvin E. Miller

Keyword(s):

Root Rot ◽

Cucumis Melo ◽

Growth Parameters ◽

Symptom Expression ◽

Germplasm Screening ◽

Fruit Maturity ◽

Vine Decline ◽

Cucumis Melo L ◽

Root Size ◽

Fruit Load

The effect of zero, one, and two fruits per vine on plant growth and reaction to Monosporascus root rot/vine decline were investigated. In the first study, four cultivars with differing levels of tolerance were evaluated (`Primo', `Deltex', `Caravelle', `Magnum 45'). Vine decline ratings were taken weekly during the harvest period for 4 weeks. Treatments with no fruit showed delayed and less-severe vine decline symptoms. Temperature also effected vine decline symptom expression. In a Fall test, with lower temperatures during fruit maturity, symptoms were delayed in all treatments and often absent in treatments with no fruit load. Vine decline symptom expression is greatly effected by physiological (fruit load) and temperature stress. A subsequent study was conducted to more precisely quantify the effect of various fruit loads on shoot/root partitioning and vine decline symptoms. In addition to growth parameters root disease ratings were taken. `Caravelle', the most-susceptible genotype, was grown under differing fruit loads as mentioned above in Weslaco and Uvalde, Texas. As fruit load increased, root size decreased. Increased vine decline symptoms were observed under higher fruit loads. The implications on germplasm screening and breeding for resistance will be discussed.

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Differential Reaction of Melon (Cucumis melo L.) Germplasm to Monosproascus Vine Decline

HortScience ◽

10.21273/hortsci.30.4.827f ◽

1995 ◽

Vol 30 (4) ◽

pp. 827F-827

Author(s):

David W. Wolff

Keyword(s):

Physiological Stress ◽

Natural Infection ◽

Disease Symptoms ◽

Monosporascus Cannonballus ◽

Differential Reaction ◽

Vine Decline ◽

Moderate Resistance ◽

Cucumis Melo L ◽

Resistant Genotypes ◽

Symptom Rating

We conducted a field screen of 130 melon cultigens to identify potential sources of host-plant resistance to Monosporascus cannonballus. Seed were sown in Speedling trays with inoculated or non-inoculated media. Plants were transplanted into a field known to be highly infested with Monosporascus cannonballus. Noninoculated plots were planted in rows that were fumigated with Telone II. Cultigens were arranged in a randomized complete block with three replications in each treatment (fumigated, nonfumigated). A disease symptom rating (1 = complete death to 5 = no symptoms) was taken at 78 and 90 days post-transplanting. Disease symptoms were most severe and occurred earliest in the inoculated, nonfumigated plots. Natural infection by Monosporascus occurred in the fumigated plots as over 95% of root samples collected contained perithecia. At the second rating date, 108 of the 130 cultigens tested were classified as moderately to highly susceptible (rating < 2.5). The four most resistant genotypes had a second rating equal or close to 4.0 (`Galia', `Deltex', `Rocky Sweet', and `Charlynne'). A group of 14 genotypes showed moderate resistance with a second rating of 3.0. Included in this group were `Morning Ice', `Doublon', `Israeli', `MR-1', `Santa Clause', and `Primo'. The physiological stress of a concentrated fruit set increases severity of vine decline symptoms.

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