N605ab, a specific molecular marker for Phytophthora infestans, distinguishes three genotypes in Japan

Random amplified polymorphic DNA (RAPD) analysis using the OPG-06 primer generated specific patterns for Japanese genotypes US-1, JP-1, and a new A1 (JP-2, JP-3, and JP-4) of Phytophthora infestans. N605, a specific RAPD fragment, was cloned and sequenced. PCR primers BD1/BD2 were constructed based on the N605 sequence and were used to clarify the genotypes. PCR products using the BD1/BD2 primers (N605ab marker) easily distinguished the new A1 from US-1 and JP-1. This technique provides a simple and effective method for rapid genotype discrimination that can be used in ecological experiments and forecasts for the occurrence of late blight.