Study finds P. ramorum evolution

A Univ. of Calif. Berkeley study found Phytophthora ramorum is evolving in Calif. forests, with unique genotypes appearing in newly infested areas. Samples from the wild were compared with 15 P. ramorum isolates collected from nurseries in 12 states. Matteo Garbelotto identified 35 unique strains of the pathogen. He discovered how those strains were related to each other and that all strains were originally derived from 3 basal strains. The study also found strains from areas of recent forest infestations are more genetically distant from current nursery strains, suggesting that regulations controlling the spread of the pathogen from nurseries to the wild are working. However, moving plant material within the quarantine area allows different strains of the pathogen to freely move within the 14-county quarantine area, he said.