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Author:Yu-Lun Dai, Jin-Hsing Huang, Jyh-Nong Tsai, and Chu-Ping Lin*
Abstract:
Three types of powdery mildew symptoms were observed on tomatoes. Type 1 symptoms displayed typical white-powdery spots with numerous spores on the upper surface of leaves. Type 2 symptoms were irregular yellowish-halo lesions on the upper surface of leaves with a few spores on the lower surface of leaves. Type 3 symptom showed circular to irregular brown lesions with a few spores on the upper surface of leaves. Conidiospores but not ascospores were microscopically observed on leaves with these types of symptoms, and several single-spore from these infected leaves were individually isolated and then cultured on tomato leaf discs for pathogen identification and pathogenicity tests. Based on morphological characteristics and phylogenetic analysis of internal transcribed spacer (ITS), the fungus was identified as Pseudoidium neolycopersici. Pathogenicity tests showed that Type 1 symptoms occurred when the inoculum was sprayed on the upper side of leaves. Type 2 symptoms occurred when the inoculum was applied on lower side of leaves. Type 3 symptoms occurred when the temperature and humidity fluctuated severely. Furthermore, P. neolycopersici caused severe leaf symptoms and produced abundant spores on large fruit tomato cultivars ‘Lu Zuan Shi’, ‘Golden Lucky’, ‘Farmers 301’ and ‘Sensation’, and caused mild symptoms and reduced sporulation on cherry tomato cultivars ‘Beauty’, ‘Jade Girl’, ‘Li Jin’ and ‘Golden Sweet’. P. neolycopersici caused severe symptoms on cv. ‘Jolly’. This study is the first report confirming the pathogenicity of P. neolycopersici on tomato in Taiwan and describing the variable symptoms of the disease.
Key words:Powdery mildew, Identification, Symptoms, Pseudoidium neolycopersici .
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