Author(s):
1. Ivan Milenković, Phytophthora Research Centre, Mendel University, Zemědělská 1, 613 00 Brno, Czech Republic, Czech Republic
2. Nenad Keča, University of Belgrade-Faculty of Forestry, , Serbia
3. Dragan Karadžić, University of Belgrade-Faculty of Forestry, , Serbia
4. Zlatan Radulović, Institute of Forestry Belgrade,, Serbia
5. Thomas Jung, Phytophthora Research Centre, Mendel University, Zemědělská 1, 613 00 Brno, Czech Republic, Czech Republic

Abstract:
During the studies of Phytophthora species on maple trees in Serbia, four different species were detected on different maple species, including P. cactorum (Lebert and Cohn) Schröt., P. lacustris Nechwatal et al., P. gonapodyides (Peterson) Buisman and P. plurivora Jung and Burgess. The aims of this study were to test the pathogenicity of isolated Phytophthora species to maple trees. Other Phytophthora species isolated from tree species in Serbia were also included. One-year-old A. pseudoplatanus plants, as the most widespread and the most damaged maple species in Serbia were grown in eight litre plastic containers from seeds of known origin. Substrate was prepared using the sterilized mixture of humus and perlite (3:1 volume ratio). Average size of the plants was 19.2±0.43 cm, with average collar diameter of 5.97±0.09 mm. Plants were inoculated under the bark with 14 isolates of 12 different Phytophthora species, including. P. cactorum (strains from maple (CAC30) and from walnut (CAC51), P. citrophthora (Smith and Smith) Leonian (CIT), P. xcambivora (Petri) Buisman (CAM), P. cryptogea Pethybr. and Laff. (CRY), P. gonapodyides (GON), P. lacustris (LAC), P. plurivora (strains from tissue (PLU34) and soil (PLU29) of maple), P. polonica Belbahri et al. (POL), P. xserendipita Man in ’t Veld et al. (SER), P. sp. Kelmania (KEL), and two yet not described strains of P. sp. 1 and P. sp. 2. All the isolates were transferred onto fresh carrot agar media (CA) and incubated at 22°C in the dark for three days. Bark of the plants was surface sterilized with cotton and 70% ethanol, and pieces of bark were removed using a sterilized 6-mm metal cork borer. Same-sized agar discs were cut from the edges of young colonies, and placed upside down on the exposed wood tissue. The inoculation points were covered by moistened sterile cotton and sealed with parafilm. In total 12 plants per treatment were inoculated. As control group 12 plants were inoculated with sterile agar pieces. All the plants were kept in the laboratory at 22-25°C at natural light and observed weekly for the presence of any symptoms. After 11 weeks most of the plants started to decline in CIT treatment, followed by PLU and GON treatments and the experiment was finished and all necroses were assessed. Phytophthora citrophthora proved to be the most aggressive species causing 3.2 times bigger necroses compared to the control group. Second most aggressive were both strains of P. plurivora causing ca. 2.6 times bigger necroses than the control. In Duncan's Multiple Range test (One-way Anova, STATISTICA 12 (StatSoft Inc., Tulsa, OK, USA) the differences to the control were statistically significant. Interestingly, dieback was observed in the PLU isolate originating from soil, but not in the isolate obtained from the symptomatic tissues. In contrast, lesions caused by CRY, POL and sp. 1 and 2 were not statistically significantly different from the control group, while the rest of treatments formed a medium homogenous group based on Duncan's test. These results demonstrated the ability of different Phytophthora species to cause bark lesions on maple plants, suggesting their involvement in the maple decline. Acknowledgements: We are grateful to the projects: TR 37008, MPNTR, Republic of Serbia; European Union’s Horizon 2020 research and innovation programme under grant agreement – “Pest Organisms Treating Europe-POnTE” Project ID: 635646, and to “Phytophthora Research Centre”- CZ.02.1.01/0.0/0.0/ 15_003/0000453, for material support during these studies.

Key words:
Sycamore maple, Phytophthora spp., pathogenicity, stem inoculation

Thematic field:
Forest protection

Date of abstract submission:
27.06.2017.

Conference:
Šumarska nauka u funkciji održivog razvoja šumarstva
25 godina šumarstva Republike Srpske