FULL RESEARCH PAPER Differentiation of two powdery mildews of sunflower (Helianthus annuus) by a PCR-mediated method based on ITS sequences Ruey-Shyang Chen & Chishih Chu & Chi-Wei Cheng & Wen-Yu Chen & Jwu-Guh Tsay Received: 26 January 2007 / Accepted: 4 October 2007 / Published online: 23 October 2007 # KNPV 2007 Abstract Powdery mildew can be found in most sunflower fields during the winter season in Taiwan and causes severe yellowing on the blade, petiole, stem, and calyx, as well as serious defoliation. Two types of powdery mildew fungi isolated from sun- flower leaves showed variable status for fibrosin bodies. But only the cleistothecium of Podosphaera xanthii, one of the pathogens causing this disease, was observed on samples from Chungpu County at the beginning of 2005. With a species-specific primer pair, PN23/PN34, no specific PCR product was amplified from the pathogen’ s genomic DNA. Based upon the ITS sequence of rDNA, three PCR primer sets (S1/S2, G1/G2, and L1/L2) specific to P . xanthii, Golovinomyces cichoracearum and Leveillula taur- ica, respectively, were designed to detect and differ- entiate pathogens causing powdery mildews on sunflower. Only the primer pairs S1/S2 and G1/G2 could amplify PCR products, with product sizes of 454 and 391 bp, respectively. Four samples of fungal DNA were subjected to a multiplex PCR amplification with primer pairs S1/S2 and G1/G2; P . xanthii and G. cichoracearum were successfully detected. These results suggest that the multiplex PCR method is a rapid, simple, and effective technique to detect and differentiate powdery mildews, for example P . xanthii and G. cichoracearum, found on sunflower. With morphologic characteristics, ITS sequence analysis and pathogenicity testing, P . xanthii and G. cichor- acearum, the first case, are two powdery mildews on sunflower in Taiwan. Keywords Multiplex PCR . Polymerase chain reaction . Powdery mildew . Sunflower Introduction Sunflower (Helianthus annuus) is a native plant of North America (Heiser 1954) and has recently been used for oil production. Since 1969, sunflowers have been introduced from Canada, South Africa, and the USA by the Tainan District Agricultural Improvement Station (TDAIS) of Taiwan for its oil production programme. Due to disease problems such as pow- dery mildew, Sclerotinia basal stalk rot, and Botrytis head rot, cultivating sunflowers for economical oil Eur J Plant Pathol (2008) 121:1–8 DOI 10.1007/s10658-007-9234-5 R.-S. Chen : W.-Y. Chen Graduate Institute of Biotechnology, National Chiayi University, Chiayi 600-04, Taiwan C. Chu : J.-G. Tsay (*) Department of Microbiology and Immunology, National Chiayi University, Chiayi 600-04, Taiwan e-mail: jgtsay@mail.ncyu.edu.tw C.-W. Cheng Graduate Institute of Agricultural Biotechnology, National Chiayi University, Chiayi 600-04, Taiwan