ORIGINAL PAPER Mycorrhizal status of an ozone-sensitive poplar clone treated with the antiozonant ethylene diurea Marina Katanic ´ • Elena Paoletti • Sas ˇa Orlovic ´ • Tine Grebenc • Hojka Kraigher Received: 2 February 2013 / Revised: 11 October 2013 / Accepted: 15 November 2013 / Published online: 28 November 2013 Ó Springer-Verlag Berlin Heidelberg 2013 Abstract The antiozonant ethylene diurea is proven to prevent growth reductions in forest trees induced by ozone. The community of mycorrhizal fungi could be useful indicator of environmental stress. In this study, response of mycorrhizal fungi and fine roots to a 4-year exposure to ambient ozone and treatment with antiozonant was inves- tigated in ozone-sensitive poplar clone under field condi- tions. The community of ectomycorrhizal fungi and root length colonization with ectomycorrhizal, arbuscular mycorrhizal fungi, and root endophytic fungi was analyzed in antiozonant-treated poplar plants and in poplar plants irrigated with water. In general, plants protected by anti- ozonant showed higher total number of fine roots, number of ectomycorrhizal types, Shannon–Weaver diversity index, and Species richness index compared to the plants treated with water. The ectomycorrhizal community shifted from contact exploration type in the trees irrigated with water to short-distance exploration type in ethylene diurea- treated trees. Ozone protectant may beneficially affect the belowground community of mycorrhizal fungi colonizing roots of ozone-sensitive poplar clone. Keywords Ground-level ozone Á Ectomycorrhizal fungi Á Antiozonant ethylene diurea Á Fine roots Á Root length colonization Á Populus maximoviczii 9 berolinensis Introduction In the atmosphere, ozone (O 3 ) is generated from oxides of nitrogen and volatile organic compounds reacting in the photochemical oxidant cycle during warm sunny weather. It is an oxidant gas present at the ground level in a back- ground concentration range from 20 to 40 ppb (Vingarzan 2004). When its concentration in the air exceeds the normal background concentration, ozone becomes an air pollutant (Manning et al. 2011). Nowadays, ozone is considered as the air pollutant of most concern for forests and other terrestrial ecosystems (Serengil et al. 2011). Its concentrations recorded in rural areas are frequently higher than those in the cities (Gregg et al. 2003). In plants, O 3 causes physiological changes in leaves that affect the carbon source strength and the amount of carbon available for allocation to sink tissues (Andersen 2003). Decreased allocation of belowground carbon, due to an increased ozone concentration, can affect fine roots and root symbionts (Grebenc and Kraigher 2007b), as well as rhizodeposition, litter quality and quantity, and the whole soil wood web (Andersen 2003). This article originates from the IUFRO Conference ‘‘Biological Reactions of Forests to Climate Change and Air Pollution,’’ held in Kaunas/Lithuania during May 18–27, 2012, as organized by IUFRO Research Group 7.01.00 in cooperation with COST Action FP 0903 ‘‘MAFor,’’ North American Air Pollution workshop ENVeurope and ICP monitoring task force (local organizer: Algirdas Augustaitis). Communicated by R. Matyssek. M. Katanic ´(&) Á S. Orlovic ´ Institute of Lowland Forestry and Environment, University of Novi Sad, Antona C ˇ ehova 13, 21000 Novi Sad, Serbia e-mail: marinakatanic44@gmail.com E. Paoletti Institute of Plant Protection, National Council of Research, Via Madonna del Piano 10, 50019 Sesto Fiorentino, Florence, Italy T. Grebenc Á H. Kraigher Slovenian Forestry Institute, Vec ˇna pot 2, 1000 Ljubljana, Slovenia 123 Eur J Forest Res (2014) 133:735–743 DOI 10.1007/s10342-013-0751-9