Detection and quantification of the air inoculum of Caliciopsis pinea in a plantation of Pinus radiata in Italy

Caliciopsis pinea has been historically described as a secondary pathogen of pines. However, it has recently been associated with severe damages on Pinus radiata in Italy. Our study focused on the description of the seasonal spore dispersal of C. pinea and its relation to meteorological conditions (temperature, leaf wetness, relative humidity and precipitations). For this experiment one infected P. radiata plantation was sampled in Tuscany (Italy). A rotating arm spore trap together with a weather station were installed to sample the aerospora for 24 h every week from May to November 2016. Exposed tapes from spore traps were directly analyzed after DNA extraction by qPCR using specific primers and TaqMan MGB probe. The study shows an irregular occurrence of the inoculum of C. pinea throughout the whole sampling period with peak levels in mid-June and early August. The statistical analysis of the DNA and climatic data clearly show the strong influence of precipitation on the spore production of this pathogen. Furthermore, the very low detection limit of the qPCR experiment shows the efficacy and suitability of rotating arm spore traps for early detection of this pathogen.