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Peach Rusty Spot Is Caused by the Apple Powdery Mildew Fungus, Podosphaera leucotricha

June 2011 , Volume 95 , Number  6
Pages  719 - 724

Tünde Jankovics, Plant Protection Institute of the Hungarian Academy of Sciences (PPI HAS), H-1525 Budapest, Hungary; Nenad Dolovac, Institute for Plant Protection and Environment, Department of Plant Pathology, 11000 Belgrade, Serbia; Aleksandra Bulajić and Branka Krstić, Institute of Plant Protection, Department of Phytopathology, University of Belgrade–Faculty of Agriculture, 11080 Belgrade, Serbia; Thierry Pascal, INRA, Unité de Génétique et d'Amélioration des Fruits et Légumes, UR1052, BP 94, F-84143 Montfavet, France; Marc Bardin and Philippe C. Nicot, INRA, Unité de Pathologie Végétale, UR0407, Domaine St. Maurice, BP 94, F-84140 Montfavet, France; and Levente Kiss, PPI HAS, Budapest, Hungary

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Accepted for publication 13 February 2011.

Peach rusty spot, an economically important disease of peach (Prunus persica var. persica), appears as necrotic spots on fruit. The etiology of the disease is still not well understood, although it has long been suspected that the causal agent is the apple powdery mildew pathogen, Podosphaera leucotricha. This work confirmed this hypothesis based on cross-inoculation experiments and analysis of rDNA internal transcribed spacer sequences polymerase chain reaction amplified from rusty spot and peach powdery mildew lesions. Cross-inoculations of apple and peach leaves with P. leucotricha and P. pannosa, the causal agent of peach powdery mildew, showed that (i) young peach fruit, up to 5 cm in diameter, developed symptoms typical of rusty spot following inoculation with P. leucotricha; (ii) leaves of ‘Jonagold’ apple seedlings developed powdery mildew infections when inoculated by touching young rusty spot lesions to their surfaces; (iii) P. leucotricha sporulated on young peach fruit up to 5 cm in diameter; and (iv) peach leaves and young shoots were not susceptible to P. leucotricha, whereas P. pannosa infected all the green parts of peach. A field experiment revealed that there was only a 2- to 3-week period of time during early peach fruit development when the epidermis was susceptible to P. leucotricha. An outcome of this study is that now a clear distinction can be made between the symptoms caused by P. pannosa and P. leucotricha on peach.

© 2011 The American Phytopathological Society