INRA avignon-Inra - Epidemiology of bacterial blight of cantaloupe

Study background
Principal results
Ongoing studies
National working group on bacterial blight of cantaloupe

Study background
France produces annually about 300,000 tons of cantaloupe (Cucumis melo var. cantalupensis Naud.) on about 15000 ha situated in the southwest, central west and southeast regions.
In 1993, cantaloupe fields in the Tarn-et-Garonne district of southwestern France were devastated by a bacterial blight that growers considered to be a new disease. That region has been the victim of the most important and re-occurring epidemics, notably in 1995, 1996 and 1997. In 1997, virtually all fields in the Lot and Tarn-et-Garonne districts were attacked and the regional governments officially recognized that the diseased fields had suffered a natural catastrophe. Since 1993, this disease has been observed in all cantaloupe regions of France when favorable conditions for the disease prevail. The rainy, cool spring of 2002 was conducive to the first severe epidemics witnessed in the southeast where some of the early plantings that were fruiting in mid-June were completely lost.

symptôme de bactériose dans les melonnières

symptôme de bactériose sur fruit de melon

Morris C.E., Glaux C., Latour X., Gardan L., Samson R., Pitrat M. 2000. The relationship of host range, physiology and genotype to virulence on cantaloupe in Pseudomonas syringae from cantaloupe blight epidemics in France. Phytopathology 90: 636-646.

Creation of a collection of about 2000 strains of P. syringae from blight epidemics in France since 1995

Creation of an illustrated bulletin to aid visual diagnosis

Elucidation of potential inoculum sources for disease epidemics

- Water retention basins used for irrigating fields harbor concentrations of P. syringae sufficient for inducing epidemics under favorable environmental conditions.

Riffaud C. M.-H., Morris C.E. 2002. Detection of Pseudomonas syringae pv. aptata in irrigation water retention basins by immunofluorescence colony staining. European Journal of Plant Pathology 108: 539-545.

Riffaud C.M-H., Glaux C., Guilbaud C., Dominguez H., Prior P., Morris C.E. 2003. Epidemiological clues for developing methods of control of bacterial blight of cantaloupe caused by Pseudomonas syringae pv. aptata. pp. 3-15 In: Iacobellis N. et al (eds). Pseudomonas syringae Biology and Genetics. Kluwer Plenum, London.

- Soil and seeds apparently do not favor survival of P. syringae in detectable quantities.

Riffaud C.M.-H. 2002. La bactériose du melon: écologie et stratégies de lutte contre Pseudomonas syringae pv. aptata. INRA 'Avignon, Unité de pathologie végétale Montfavet (FRA), Université Claude Bernard – Lyon I (FRA). Thèse (Dr. d'Université) option Ecologie microbienne. 135 p.

- Rain and snow, stream and lake water, wild plants and epilithic biofilms harbor populations of P. syringae

Identification of climate conditions favorable for disease epidemics. An analysis of several years of epidemiological data reveals that the risk of bacterial blight epidemics is important if, over a period of 4 days, i) the mean minimal temperature is less than 12-13 °C, ii) the duration of rain exceeds 7 – 9 h and iii) the cumulative amount of rain is greater than 11 mm. About 95% of bacterial blight epidemics have occurred during these conditions I

Mention P., Lavigne, D., Leix-Henry F., Bouchu S., Morris C.E., Prior P., Pitrat M., Mercy L., Dours O. 2004. Bactériose du melon: acquis et perspectives. PHM-Revue Horticole, n°459:22-26.

Our ongoing studies In collaboration with the national working group we are seeking means for the control of this disease. Copper-based compounds are the only phytosanitary compounds currently registered for use against this disease in France, and they are relatively ineffective.

To investigate the possibility of breeding lines of cantaloupe resistant to this disease we have screened multiple commercial cultivars as well as hundreds of lines of Cucumis melo maintained at Avignon’s Research Unit for Genetic Improvement of Fruit and Vegetables. All commercial cultivars are sensitive to bacterial blight and we have not found any promising resistance in the different genetic lines of cantaloupe tested.

We are currently exploring other biological, chemical and cultural means of control compatible with sustainable production of cantaloupe.

National working group on bacterial blight of cantaloupe
In 1997 a national working group on bacterial blight of cantaloupe was created. Our laboratory was among the founding members of this working group that also consists of representatives of regional experimental stations, extension services, inter-professional organizations, chambers of agriculture, grower's associations and INRA’s plant breeders. The group meets twice a year to plan and evaluate results from field experimentation and laboratory research to characterize the causal agent and its sources of inoculum, to identify the climatic factors favoring disease, and to evaluate different means of control.

Unité de Pathologie Végétale d'Avignon	INRA
Unité de génétique et d'amélioration des fruits et légumes	INRA
Centre technique interprofessionnel des fruits et légumes	CTIFL
Centre d'expérimentation fruits et légumes de Midi-Pyrénées	CEFEL
Service régional de la protection des végétaux	SRPV
Fédération régionale de défense contre les ennemis des cultures	FREDEC
Association interrégionale de recherche et d'expérimentation légumière	AIREL
Association Charentes-Poitou d'expérimentation légumière	ACPEL
Association régionale d'expérimentations légumières en Pays de Loire	ARELPAL
Société civile légumes Centre Loire	SCL
Association provençale de recherche et d'expérimentation légumière	APREL
Centre expérimental horticole de Marsillargues	CEHM

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See also

Epidemiology of bacterial blight of cantaloupe