Selective Isolation and Characterization of Phytophthora infestans from Potatoes Using Rye Agar Media in India

Phytophthora infestans is a pathogen that causes late blight, a major disease of potatoes. The isolation of P. infestans from infected potato plants using agar media has been challenging. This study investigated the use of Rye A and Rye B agar media for the isolation of P. infestans from infected potato tubers collected from the Nilgiris district of Tamil Nadu during 2022. The media were evaluated for hyphal growth, sporangial production, oospore formation, and long-term storage of P. infestans. Phenotypic diagnosis based on cultural and morphological characteristics confirmed the identity of P. infestans. The results were confirmed by a molecular identification test using primers specific to P. infestans. Pathogenicity tests were carried out to assess the virulence of the isolates. This study provides a useful protocol for the selective isolation and characterization of P. infestans, the potato late blight pathogen.