Development of specific marker for PCR diagnostic of late blight of potato caused by Phytophthora infestans using RAPD based SCAR methodology

A new marker for rapid and early identification and detection of Phytophthora infestans, the causal agent of late blight of potato and tomato has been developed using PCR. Amplification products obtained from random amplified monomorphic DNA (RAPD) reactions were cloned and sequenced, and two extended primer sets (PITH2-F/PITH2-R) were designed from the resulting data that were used to detect sequenced-characterized DNA markers. A single 1.5 kb DNA amplification product was consistently obtained from primer OPA 12 that was specific for P. infestans but was not produced from other Phytophthora species and fungal pathogen of potato. A 524 bp amplification product was also produced from naturally infected tubers known to be infected with the fungus as verified by microscopic examination. A similar PCR product was obtained from sterile soil samples artificially infested with P. infestans inoculums. This primer is a highly specific to P. infestans only. This PCR based assay enables detection of P. infestans from host tissues, sporangia and Oospores present in the soil in a single day.