Notes on powdery mildews (Erysiphales) in Thailand I. Podosphaera sect. Sphaerotheca

Podosphaera sect. Sphaerotheca is a group of powdery mildews mainly infecting herbaceous plants. In tropical countries such as Thailand, asexual morph of Podosphaera is more commonly found than sexual morph. Therefore, studies on diversity and molecular phylogenetics of powdery mildews in Thailand are important. In this study, three species, Po. xanthii, Po. aphanis var. aphanis and Po. pannosa, were determined based on morphological and molecular phylogenetic analyses using ITS sequence. Nine plant species are new world host records of powdery mildews, viz. Cyanthillium cinereum and Spilanthes iabadicensis (Asteraceae), Justicia comata (Acanthaceae), Millingtonia hortensis (Bignoniaceae), Pouzolzia zeylanica (Urticaceae), Hydrocleys nymphoides (Alismataceae), Raphistemma pulchellum, Gymnema inodorum (Apocynaceae) and Leucas decemdentata (Lamiaceae). In addition, 22 new records of Podosphaera were found in Thailand. Phylogenetic affinity of Podosphaera species found in Thailand and related species from other regions is also provided.