Identification of sapstain fungi from Scots pine pallets and assessment of their staining ability

Wood-staining fungi, moulds and decay fungi colonize freshly cut wood. Of these, only ophiostomatoid fungi are considered major agents of sapstain on logs and freshly sawn lumber because they can cause permanent staining and discoloration. Sapstain in pine pallets significantly reduces their market value and use in the food industry. The aim of this study was to identify the sapstaining fungi that colonize Scots pine wood used in pallet production. In addition, we evaluated the growth and stain intensity of six isolates of ophiostomatoid fungi on freshly cut Scots pine billets. Fungi were isolated from samples of Scots pine and identified based on morphology and DNA sequence comparisons for three gene regions (ITS, β-tubulin, TEF-1α). A total of 1259 isolates representing 31 fungal species were obtained from the pine samples in Poland during July and September. The isolates represented different ecological and taxonomical groups and belonged to the categories of staining fungi, decay fungi and surface moulds. The most frequently isolated fungi were ophiostomatoid fungi (14 species including an unknown Leptographium sp. and Ophiostoma sp.) and moulds (mainly Trichoderma and Mucor spp.). Of the ophiostomatoid species, Ophiostoma floccosum , O. piceae , O. piliferum and Endoconidiophora pinicola were the predominant species. The results of pine billet inoculation showed that among the six fungal species tested, E. pinicola exhibited the fastest growth in all three directions on the billets. Ophiostoma minus and O. piliferum displayed moderate growth rates in pine billets, while O. floccosum , O. piceae , and Leptographium lundbergii grew very slowly, especially in the tangential and radial directions. The information provided in this paper will help develop more effective control strategies for sapstain prevention in Scots pine.