Morphological and molecular characterizations of powdery mildew, Podosphaera xanthii occurring on cucurbits in Changchun Agri- Expo Garden, China

Mycosystema ›› 2011, Vol. 30 ›› Issue (5) : 702-712.

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PDF(753 KB)
Mycosystema ›› 2011, Vol. 30 ›› Issue (5) : 702-712.
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Morphological and molecular characterizations of powdery mildew, Podosphaera xanthii occurring on cucurbits in Changchun Agri- Expo Garden, China

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Abstract

In autumn of 2009, powdery mildew broke out on cucurbits in Changchun Agri-Expon, Jilin Province, China. A large number of chasmothecia of the fungus were found on plants of four genera belonging to Cucurbitaceae (Lagenaria, Cucumis, Trichosanthes and Cucurbita). A survey was conducted to evaluate the resistance of these plants to powdery mildew based on disease incidence, disease severity and disease index. The results indicated that almost all varieties cultivated in CCAEG are susceptible to the fungus. Morphological observation shows that the conidia were produced in chains with well developed fibrosin bodies, and chasmothecia contained a single ascus with 8 ascospores and a wide apical oculus (15.6-28.8μm). The morphological characteristics of anamorphic and teleomorphic stages reveal that this fungus belong to Podosphaera xanthii. The molecular analyses of the nucleotide sequences of the internal transcribed spacer (ITS) rDNA regions including the 5.8S rRNA gene indicate that the fungus was clustered in the clade of P. xanthii recorded from different hosts and the same host from different regions. The teleomorphs of powdery mildew on cucurbits are rarely found. It is the first report of the sexual stage found on Trichosanthes in the world, and on Cucurbita pepo in Jilin Province, China. Moreover, Watermelon Citrullus lanatus without chasmothecia was a new host record of the powdery mildew in Jilin Province. Further research on the host range, epidemiology, resistant cucurbits selection and control is required.

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Morphological and molecular characterizations of powdery mildew, Podosphaera xanthii occurring on cucurbits in Changchun Agri- Expo Garden, China[J]. Mycosystema, 2011, 30(5): 702-712
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