Twenty-nine new host records of powdery mildew fungi (Erysiphaceae) in Taiwan with an updated checklist.

Background: Powdery mildews (Erysiphaceae, Ascomycota) belong to the most important plant pathogenic fungi that cause stress to forest and fruit trees and lead to a considerable loss of economic crops worldwide as well as in Taiwan. The checklist of Erysiphaceae in Taiwan is an important basis to control these pathogens. However, it has been published 25 years ago without any updating, while taxonomic concepts of genera and species changed and many new fungus and host records have been published. We update the checklist of Erysiphaceae by applying new taxonomical concepts and we add several new host records worldwide or for Taiwan based on own, recent collections.

Results: The updated checklist of powdery mildew in Taiwan is presented including data on 13 species of Erysiphaceae on 28 species of host plants. Doubtful records are marked as such and proposed for further investigation. For agricultural application, information on the usage of host plants was added to the checklist. Besides, over twenty specimens of Erysiphaceae on common plants in Taiwan recently collected by the authors were identified based on ITS sequences and anamorphic morphology. Among the collections, twelve represented new host records worldwide, while seventeen were new host records for Taiwan. Six species of Erysiphaceae were found in Taiwan for the first time.

Conclusions: The checklist of Erysiphaceae in Taiwan is an important basis for taxonomic and biogeographical studies as well as for quarantine sanctions referring to powdery mildews. Our results reveal that the host spectra of these pathogens are still incompletely known worldwide. Moreover, the list includes some doubtful old records that might be synonyms or wrong identifications. Morphological characteristics and ITS sequences are usually useful for the identification of Erysiphaceae. Several species in certain genera, however, cannot be distinguished since the variation in sequence data of those closely related species is quite low. New collections and re-investigation of old specimens are imperative to clarify some doubtful records.