Phytophthora quercina sp. nov., causing root rot of European oaks

• Published in: Mycological research 1999-07, Vol.103 (7), p.785-798
• Main Authors: JUNG, T., COOKE, D. E. L., BLASCHKE, H., DUNCAN, J. M., OßWALD, W.
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; chemotaxonomy; descriptions; Europe; Fundamental and applied biological sciences. Psychology; fungal anatomy; Fungal plant pathogens; Fungi; identification; morphotaxonomy; new species; pathogenicity; physiology; Phytopathology. Animal pests. Plant and forest protection; Phytophthora; Phytophthora quercina; Plant cytology, morphology, systematics, chorology and evolution; plant pathogenic fungi; Quercus; Quercus robur; random amplified polymorphic DNA technique; rhizosphere; root rot; Systematics. Morphology. Development cycle. Physiology; Thallophyta
• ISSN: 0953-7562; 1469-8102
• DOI: 10.1017/S0953756298007734

In a 3 year study of oak decline in Central and Southern Europe, a papillate homothallic Phytophthora species was isolated consistently, with other Phytophthora spp., from necrotic fine roots by direct plating on to selective agar medium and from rhizosphere soil samples by baiting with leaves of Quercus robur. The morphology, physiology, RAPD banding patterns and pathogenicity against apple fruits of this Phytophthora sp. are described and compared with those of other papillate Phytophthora species from Waterhouse's Group I, namely P. cactorum, P. clandestina, P. idaei, P. iranica, P. pseudotsugae and P. tentaculata, and semi-papillate Group III P. citricola. The papillate Phytophthora isolates from oak differed from all other Group I species by their uniform, dome-shaped and cottonwool-like colony growth pattern on V8 juice agar and malt extract agar, the frequent occurrence of sympodially branched primary hyphae, a high proportion of elongated, ellipsoid or ovoid oogonia, the absence of amphigynous antheridia and RAPD banding patterns. Additionally, there was no other species in Group I with as much variation in size and shape of the sporangia or large proportion of sporangia with a curved apex, hyphal projections, lateral displacement of the papilla and lateral attachment to the sporangiophore. In pathogenicity tests with infested soil, the isolates proved to be more pathogenic to Q. robur than any other Phytophthora sp. recovered from declining oaks in Central Europe. Based on their unique combination of cultural, sporangial and gametangial morphology, pathogenicity and close association with Quercus but not other trees, the papillate Phytophthora isolates from oak are described as Phytophthora quercina sp. nov.