Abstract

MORENO-RICO, Onésimo et al. Phytopathological diagnosis of major diseases in various species of oak and its distribution on the Sierra Fria, Aguascalientes, México. Polibotánica [online]. 2010, n.29, pp.165-189. ISSN 1405-2768.

Oak trees (Quercus spp.) are a very important resource for mankind. For several years oak mortality has been observed on the Sierra Fría, Aguascalientes, Mexico. The objectives of this study were: 1) to know those agents causing oak mortality on the Sierra Fría, 2) to establish the distribution of affected areas on this sierra, 3) to determine oak species affected in the area of study and 4) to indicate their importance as a plant pathogens. Twenty-eight locations on the Sierra Fría were sampled by means of transects. Each transect comprised a visual inspection of 20 trees to observe symptoms and signs on affected trees. In addition, 100 trees were inspected at each location in order to detect ascomata and basidiomata of plant pathogens. The identification of plant pathogens was based upon the presence of symptoms and signs (ascomata, basidiomata) on the trees. Cankers were the most important observed symptom, being present in 92% of study locations and on 15 to 75% of trees. On living and mature oak trees, the plant pathogens causing the cankers were: Phellinus robustus, P. gilvus and P. everhartii. Ganoderma lucidum was found on both young and adult trees. Biscogniauxia atropunctata and Hypoxylon thouarsianum, opportunistic fungi of low pathogenic capacity, were also identified, affecting weak trees stressed by abiotic factors (drought, frost) and other plant pathogens. The most abundant oak species, and the one most affected, was Q. potosina. Hypoxylon thouarsianum was the most widespread fungus, being present in 12 out of the 28 study locations, followed by B. atropunctata, which was found in eight locations.

Keywords : Quercus spp.; oak mortality; Phellinus robustus; Phellinus gilvus; Phellinus heverhartii; Biscogniauxia atropunctata; Hypoxylon thouarsianum; Ganoderma lucidum.

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