FULL RESEARCH PAPER Assessment of real-time PCR as a method for determining the presence of Verticillium dahliae in different Solanaceae cultivars Carmen Gayoso Æ Oscar Martı ´nez de Ila ´rduya Æ Federico Pomar Æ Fuencisla Merino de Ca ´ceres Received: 2 May 2006 / Accepted: 5 April 2007 / Published online: 3 May 2007 Ó KNPV 2007 Abstract Real-time PCR was used to detect and quantify Verticillium dahliae and to assess the susceptibility of four Capsicum annuum cultivars (Luesia, Padro ´n, SCM331 and PI201234) and the Capsicum chinense cv. C118 to this pathogen. The symptoms which developed after infection included stunting and yellowing, and were more acute in the cv. SCM331, which also suffered defoliation in later stages of the disease and in C118, which suffered severe stunting. Quantification of the pathogen DNA in roots 23 and 34 days post-inoculation (dpi) revealed that there were significantly higher amounts of Verticillium dahliae DNA in C118 than in the other cultivars, followed by SCM331, Padro ´n and PI201234. The lowest amounts of fungal DNA in roots were found in Luesia. In hypocotyls, the highest amounts of fungal DNA were found in SCM331, while Luesia, Padro ´n and PI201234 had much lower amounts, and C118 had intermediate levels. When a compatible versus an incompatible system was stud- ied, using the near-isogenic tomato lines LA3030 (susceptible) and LA3038 (resistant to V. dahliae), we were able to detect fungal DNA in both lines. As expected, the fungus/plant DNA ratio was lower in LA3038 than in LA3030 and it decreased with time in LA3038. The amount of Verticillium dahliae DNA in the roots of LA3030 remained constant between days 23 and 34 post-inoculation, but increased 10- fold in collars. Finally, when real-time PCR was applied as a diagnostic method to samples from pepper plants, soil and water collected from farms in northwest Spain, we were able to detect V. dahliae DNA in these samples even when symptoms of the disease were not evident. Keywords Capsicum annuum  Capsicum chinense  Lycopersicon esculentum  Real-time quantitative PCR Introduction Verticillium wilt, caused by the soil-borne fungus Verticillium dahliae, is a disease, which limits the production of a broad range of economically impor- tant crops (Pegg 1974). Among its hosts are pepper, aubergine, tomato, sunflower, potato and olive tree (Heale 1988). The first symptom of the disease is leaf chlorosis which can progress to necrosis. Other visible symptoms include stunting, epinasty, wilting, leaf abscission and, eventually, browning of the vascular system. In general, wilting is the result of a restricted water movement that is also mediated by C. Gayoso  F. Merino de Ca ´ceres (&) Departamento de Biologı ´a Animal, Biologı ´a Vegetal y Ecologı ´a, Universidad de La Corun ˜a, 15071 La Coruna, Spain e-mail: fuenme@udc.es O. M. de Ila ´rduya  F. Pomar Centro de Investigaciones Agrarias de Mabegondo, Xunta de Galicia, 15318 La Coruna, Spain 123 Eur J Plant Pathol (2007) 118:199–209 DOI 10.1007/s10658-007-9134-8