First report of Phytophthora macrochlamydospora associated with tree decline in Pinus taeda in Brazil

In 2019, 18-year-old Pinus taeda trees with symptoms of chlorosis in the aerial part, shortening of needles and reduced plant growth, ultimately leading to tree decline, were found in plantations in southern Brazil. When collecting roots, a reduction in the volume of fine roots in trees and absence of ectomycorrhiza was observed. An oomycete was isolated from the roots and soil of the rhizosphere, and its pathogenicity was confirmed through Koch's postulates. The morphological characteristics of this oomycete were similar to the Phytophthora macrochlamydospora, which was confirmed by the molecular characterization from three gene regions (ITS-rDNA, COX I and TEF1α). This is the first report of P. macrochlamydospora associated with tree decline in P. taeda in Brazil and worldwide.