Morphological and molecular identification of phytophthora species isolated from the rhizosphere of declining oak trees in krotoszyn plateau

Abstract

The following paper presents the results on the determination of the diversity of species from the Phytophthora genus occurring in the declining oak stands in Krotoszyn Plateau in Poland. From the 50s of the last century, significant deterioration of oak health was observed in these stands, and Phytophthora species were suggested as one of the factors of the decline. In order to determine the presence of pathogenic organisms from the Phytophthora genus in these stands, 180 rhizosphere soil samples from three forest districts throughout the Krotoszyn Plateau were collected and subjected to the isolation method. Phytophthora species were consistently isolated from all the sampled stands, and 194 isolates from 111 positive samples were obtained. However, 150 (77%) and 44 (23%) isolates originated from the samples taken under the symptomatic and asymptomatic trees, respectively. All the obtained isolates were morphologically classified using the light and scanning electron microscopy and divided into morphological groups. Genomic DNA was isolated from selected isolates representing each group, ITS regions were amplified and sequence analyses were performed. In total, four different Phytophthora species were detected, including P. cactorum, P. plurivora, P. quercina and P. europaea. The most often isolated species were P. cactorum and P. plurivora. This is the first report of P. europaea in oak stands in Poland.