Phytophthora andina sp nov., a newly identified heterothallic pathogen of solanaceous hosts in the Andean highlands

A blight disease on fruits and foliage of wild and cultivated Solanum spp. was found to be associated with a new species of Phytophthora. The proposed novel species is named Phytophthora andina Adler & Flier, sp. nov. based on morphological characteristics, pathogenicity assays, mitochondrial DNA haplotyping, AFLP fingerprinting and nuclear and mitochondrial DNA sequence analyses. Isolates of P. andina (n = 48) from the Andean highland tropics of Ecuador were collected from 1995 to 2006. Phytophothora andina is closely related to P. infestans and has semipapillate, ellipsoidal sporangia borne on sympodially branched sporangiophores. It is heterothallic and produces amphigynous antheridia. The species consists of several clonal lineages, including the EC-2 and EC-3 RFLP lineages, which were described previously as P. infestans. Approximately 75% of isolates react as compatibility type A2 when paired with an A1 compatibility type isolate of P. infestans. However, when A2 isolates from the Anarrhichomenum section of Solanum were paired in all combinations, viable oospores were obtained in several crosses, suggesting that there is a unique compatibility interaction in P. andina that is complementary to that described in P. infestans. Nuclear and mitochondrial sequence analysis supported the species designation of P. andina. This newly identified heterothallic pathogen shares a common ancestor with P. infestans and may have arisen from hybridization events with sister taxa in the Andes