Temporal patterns of airborne Phytophthora spp. in a woody plant nursery area detected using real-time PCR

In this study, spore trap monitoring was applied to provide a proof of concept for the use of qPCR to detect Phytophthora in aerial samples and provide valuable information for epidemiological studies in nurseries. Two qPCR TaqMan assays were developed to detect pathogen DNA: the first used a generic probe to detect Phytophthora spp., and the second was based on a specific probe for detecting P. ramorum and P. lateralis. All samples tested positive for the genus Phytophthora, although P. ramorum and P. lateralis were not detected. In late spring and in autumn, two main peaks of Phytophthora sporulation were observed. Peaks were preceded by rainfall, high relative humidity, and mild temperature. From mid-May to the end of August, Phytophthora DNA detected in the air increased with relative humidity, while it decreased with increasing mean temperature. There was also a positive correlation between Phytophthora DNA detected and rainfall in the same period. No significant correlations between Phytophthora DNA and temperature or rainfall were found from the end of August to December. Our results are in agreement with those obtained with classical diagnostic methods based on microscopy, but the approach used here enabled rapid detection and relative quantification of the target organisms, thus assisting in the implementation of disease management strategies.