DoesPythium anandrumcontribute to the dieback of sessile oak (Quercus petraea) in Turkey?

Abstract

Summary During investigations into the causes of oak decline in six Regional Forestry Directories of the Black Sea Region of Turkey, Phytophthoraspp. were obtained from one region and Pythium spp. were collected from three regions. The most frequently isolated Pythium species,Pythium anandrum, when inoculated on stem bases, caused longer cankers than two isolates of both Phytophthora plurivora and 2 of theP. quercina. This is the first report of Pythium anandrum causing disease on sessile oak. P. anandrum may contribute oak decline inTurkey. 1 Introduction Oak dieback and decline are serious problems in many regions of the world, including Turkey. The disease may be relatedto global climate change, combined with the impacts of pests and pathogens. Various Phytophthora spp. are frequently citedas causal agents of oak decline (Balci and Halmschlager (2003).When examining the occurrence of Phytophthora spp. in the rhizosphere of healthy and declining oak trees in Turkey,Balci and Halmschlager (2003) isolated 7 Phytophthora spp., with P. quercina Jung the most common. Other speciesincluded P. cinnamomi Rands, P. citricola Sawada, P. cryptogea Pethybr. and Laff, P. gonapodyides (Petersen) Buisman, Phy-tophthora sp. 1 and Phytophthora sp. 2. In this same work, sporangia of a variety of Pythium spp. were frequently observedon oak leaflets used as bait, and P. anandrum Drechsler was recovered from over 70% of sites. Despite frequent associa-tion of various Pythium spp. with oaks, Balci and Halmschlager (2003) did not test the pathogenicity of these isolates onplants.There is little information on the pathogenicity of Pythium anandrum on tree species, except the single report ofWardlaw and Palzer (1985) who showed that P. anandrum caused stem rot in nursery grown Eucalyptus spp. inTasmania.During ongoing work on Phytophthora diseases in forests of the Black Sea Region of Turkey, several Pythium specieswere recovered from oak roots and rhizosphere soils. This short communication describes the pathogenicity of P. anandrumon 3-year-old oak saplings, compared with the effects of Phytophthora plurivora and P. quercina.