An improved method for the detection of Phytophthora cactorum (l. C.) Schroeter in infected plant tissues using SCAR markers

Phytophthora cactorum (Lebert et Cohn) Schroeter is an important plant pathogen that can cause serious damage in agricultural and ornamental crops as well as in a wide range of forest species. The identification of this pathogen, based on morphological and physiological characters, is time consuming, labour-intensive and requires specialised staff to be correctly performed. Recently, PCR-based methods have partially resolved these problems, but the primers used cross react with Phytophthora idaei. To prevent any such reaction the use of a new pair of primers (PC1/PC2) with improved specificity, derived from a specific Random Amplified Polymorphic DNA (RAPD) generated fragment, is proposed. The PC1/PC2 primers, used in a simple PCR protocol, gave a single amplification product of approximately 450 bp; a good degree of specificity, with absence of cross reactions with Phytophthora pseudotsugae and R idaei; sensitivity down to 6 pg of R cactorum DNA extracted from pure mycelium; no reactions with the DNA of the host plants tested (downy oak, pear and walnut trees, potato, strawberry, tomato and pea plants). The detection of R cactorum in infected tissues of pear and walnut trees, potato, strawberry, tomato and pea plants was also confirmed. The specificity, sensitivity and robustness of the PC1/PC2 primers together with the possibility of their use in a rapid, simple and reliable diagnostic method are discussed.