Monitoring physiological races of<Emphasis Type="Italic">Podosphaera xanthii</Emphasis> (syn.<Emphasis Type="Italic">Sphaerotheca fuliginea</Emphasis>), the causal agent of powdery mildew in cucurbits: Factors affecting race identification and the importance for research and commerce |
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| Authors: | Email author" target="_blank">R?CohenEmail author Y?Burger N?Katzir |
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| Institution: | (1) Dept. of Plant Pathology, ARO, Newe Ya’ar Research Center, 30095 Ramat Yishay, Israel;(2) Dept. of Vegetable Crops, ARO, Newe Ya’ar Research Center, 30095 Ramat Yishay, Israel |
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| Abstract: | Identification of the physiological races ofPodosphaera xanthii (syn.Sphaerotheca fuliginea), the causal agent of powdery mildew in cucurbits, is based upon the differing responses of various melon cultigens to the
pathogen. Eight races of the pathogen have been identified to date in the USA, Africa, Europe and around the Mediterranean
Sea, and four new races were reported from greenhouse melons in the major growing area of Japan. Plant responses to powdery
mildew may be affected by environmental factors such as light intensity, temperature and humidity, as well as by age and nutritional
status of the plants. The same factors affect the accuracy and reliability of race identification. In an attempt to overcome
those obstacles, the genetic diversity ofP. xanthii was studied using molecular markers. Unfortunately, no correlation was found between DNA polymorphism and the race of the
pathogen as identified by biological tests. The usefulness of race identification as a guide for the grower in selecting appropriate
cultivars is limited because changes or shifts in the pathogen population are common. Such changes may be found among growing
seasons, geographic regions and hosts, and also within a single greenhouse during a single season. On the other hand, race
identification is important for basic research and is especially important for the commercial seed industry, which requires
accuracy in declaring the type and level of resistance to powdery mildew in its products.
http://www.phytoparasitica.org posting March 2, 2004. Contribution from the Agricultural Research Organization. No. 501/04. |
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| Keywords: | Podosphaera xanthii Sphaerotheca fuliginea cucurbits Cucumis melo molecular markers race identification powdery mildew |
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