Ophiostomatoid fungi vectored by bark beetles and colonizing trees of Pinus sylvestris in Sumy region (Ukraine)

Abstract

• K. Davydenko[1], D. Baturkin[2] Intensive mortality of Pinus sylvestris trees has recently been observed in the Sumy region in eastern Ukraine. There are two pine bark beetle species (Ips acuminatus and Ips sexdentatus), which spread resulted in considerable forest damage in Ukraine. The study of ophiostomatoid fungi vectored by bark beetles is very important to assess total harm of these insects. Therefore, the aim of our research was i) to identify ophiostomatoid fungi associated with weakened and dying Scots pine trees infested by bark beetles in the Sumy region; ii) to test the pathogenicity of these ophiostomatoid fungi to evaluate their potential threat to Scots pine. The fungi were isolated from bark beetle galleries and identified based on morphological properties and DNA sequences. In total, eight ophiostomatoid fungi (Graphium sp., Grosmannia sp.1, Ophiostoma bicolor, O. ips, O. canum, O. piceae, O. minus, Ophiostoma sp.1) were isolated from Scots pine trees infested by bark beetles. Scots pine seedlings were inoculated with eight fungi and sterile medium (control) to evaluate their pathogenicity. The inoculated seedlings were examined finally in 6 month after inoculation. Inoculation with O. minus produced significantly largest lesions and only this fungus caused mortality of pine seedlings. In total, all eight fungal species inoculated caused resin exudation and staining the bark around inoculations in Scots pine seedlings and five fungi caused different rate of seedlings decline. The size of stained sapwood was also greater following O. minus inoculations than other fungi or the control. All ophiostomatoid fungi caused significantly longer necrotic lesions and more occlusions in the sapwood than the controls. Therefore, based on the ability of various ophiostomatoid fungi to weaken and kill pine seedlings and stain sapwood, O. minus was the most dangerous species for Scots pine trees, followed by Graphium sp. and Ophiostoma sp.1. The occurrence of ophiostmatoid fungi in the sapwood of Scots pine is consistent with the concept of their primary role in the colonization of the fresh sapwood of trees in the succession of microorganisms during wood decay.

Keywords

• ophiostomatoid fungi; scots pine; bark beetles; pathogenicity; forest health.