Oomycete compositon in Proteaceae orchards and natural stands on three continents

Abstract The Proteaceae is an important southern hemisphere family with many species known to be susceptible to Phytopthora cinnamomi, both in the natural environment and in cut-flower orchards. Very little in known about the prelevence of P. cinnamomi and other oomycetes across these landscapes. To address this lack of knowledge we a used double ITS1 and RSP10 gene metabarcoding approach and traditional isolation protocols to investigate oomycetes in orchards and natural stands of Proteaceae across four countries on different continents. Results revealed a consistent oomycetes richness within native and planted Proteaceae. Species richness and community composition were significantly influenced by the country of collection, while they did not show any variation between orchards and natural vegetation. RSP10 barcoding detected, the largest number of species and, provided a greater statistical confidence than ITS1 when considering oomycete species composition. Metabarcoding also showed that orchards had a higher abundance of P cinnamomi compared to native stands, but this outcome was not confirmed using isolation protocols.. These results and those of other recent studies show that metabarcoding provides an effective tool to describe the ecological dynamics of soil oomycetes in different ecosystems.