Isolation, identification and pathogenicity of Phytophthora species from declining oak stands

Abstract

Summary Within the scope of a research project on the condition of roots of declining oaks (Quercus robur, Quercus petraea), samples of fine roots and surrounding soil, specimens of stripe cankers on the stem base, and samples of stream water were examined for the presence of Phytophthora species using both baiting methods and selective agar media. At 27 sites in Germany (Bavaria, Rheinland‐Pfalz, Schleswig‐Holstein), Switzerland, Hungary, Italy and Slovenia the following species were isolated (mainly from soil): Phytophthora citricola, Phytophthora cactorum, Phytophthora cambivora, Phytophthora gon‐apodyides, Phytophthora undulata, a species with affinity to Phytophthora drechsleri, and two additional species with close affinity to the Phytophthora cactorum group. Moreover, Pythium group P, Pythium anandrum, Pythium chamaehyphon, and many other Pythium species that have not yet been identified could be recovered. In a soil infestation test most isolates induced dieback of long root tips and necrotic lesions in the root cortex and at the root collar of Quercus robur seedlings. All Phytophthora species tested and Pythium group P caused cortical necrosis after stem inoculation of young Quercus robur trees. It could be shown in vitro that Phytophthora gonapodyides and Pythium group P were able to produce a wilting toxin. Nitrogen input and climatic changes are discussed as predisposing factors for root damage observed in the field.

Interactive effects of drought and pathogens in forest trees

“…Several new Phytophtora ssp. have recently been described and suggested to be involved in European oak declines [82,90,[92][93][94][95][96]. Although these species act as primary pathogens, their pathogenicity generally seems to be too low to induce mortality alone, yet Phytophthora spp.…”

Occurrence of Phytophthora multivora and Phytophthora plurivora in the Czech Republic

“…The tissues were cut into segments (approximately 5 × 5 × 5 mm), which were repeatedly washed in sterile water and 95% ethanol, blotted on sterile filter paper or pulp, and plated onto selective PARPNH V8-juice agar medium. The medium consisted of 100 ml V8 juice (Campbell Grocery Products Ltd., Ashford, UK), 15 g agar, 3 g CaCO 3 , 200 mg ampicillin, 10 mg rifampicin, 25 mg pentachloronitrobenzene (PCNB), 50 mg nystatin, 50 mg hymexazol, and 1 l of deionised water (Jung et al 1996). The soil samples were processed via a baiting method.…”

Phytophthora bilorbang sp. nov., a new species associated with the decline of Rubus anglocandicans (European blackberry) in Western Australia

“…Firstly, plugs were prepared as described previously (Butcher et al1984;Rea et al 2010) except that tree lucerne (Cytisus palmensis) was used for the plugs instead of Pinus radiata. Secondly, vermiculite inoculum (vermiculite 1 l, millet seeds 10 g and 600 ml V8 broth) was produced as described previously (Jung et al 1996) The vermiculite inoculum was mixed with pasteurized and washed river sand in a ratio of 40 g/l sand and healthy blackberry plants and attached soil were transferred from the 130 mm pots into 170 mm free-draining pots filled with 1 l of the infested sand (control pots received non-inoculated vermiculite). Each pot also received four colonised or non-colonised (control) tree lucerne plugs.…”