Albino Strains of Ophiostoma Species for Biological Control of Sapstaining Fungi

New Zealand produces large diameter radiata pine (Pinus radiata) in short rotations, making it the dominant species used in its forest products industry. As with other fast growing pine species, radiata pine produces wood that consists primarily of sapwood, and is susceptible to dark discolorations due to sapstaining fungi. As a result, significant losses are incurred by the New Zealand forest products industry due to these discolorations. Sapstain, also called blue stain, is caused by pioneercolonizing fungi, such as Ophiostoma, Ceratocystis, Leptographium or Sphaeropsis species that utilize simple carbohydrates, fatty acids, triglycerides and other components of the sapwood (Blanchette et al. 1992; Farrell et al. 1993; Wang et al. 1995). The dark stain produced by these fungi is due to melanin and melanin-like compounds that are localized within the fungal hyphae (Zink and Fengel 1988; Zimmerman et al. 1993). As the fungus grows in wood cells, pigmented hyphae impart a discoloration to the wood (Zink and Fengel 1988; Blanchette et al. 1992). Sapstain fungi are not thought to compromise strength properties of wood in early stages of colonization, although discoloration decreases the value of wood used for lumber or paper production (Zabel and Morrell 1992; Seifert 1993). Sapstain has traditionally been controlled with antisapstain chemicals; however, toxicity concerns and the environmental effects of many chemicals used have prompted the search for alternative methods of control. Biological control using albino strains of sapstaining fungi is a new method that can be used. Investigations using colorless strains of Ophiostoma species have been successful in controlling sapstain (Blanchette et al. 1992; Farrell et al. 1993; Behrendt et al. 1995a, b; Schmidt and Müller 1996; White-McDougall et al. 1998). By applying a colorless strain of Ophiostoma to freshly cut logs, the fungus can preferentially colonize the sapwood, thereby capturing nutrient resources and inhibiting subsequent colonization by dark staining fungi. The detrimental effects of sapstaining fungi are also important in the Canadian forest products industry. Surveys recently completed in Canada have identified Ophiostoma species as the most prevalent sapstaining organism (Uzunovic et al. 1999). The objectives of this study were to: 1) develop colorless strains from species of Ophiostoma prevalent in New Zealand, 2) evaluate selected strains for their potential to control aggressive sapstaining fungi on wood, 3) obtain strains that are completely free of pigment including pigmentation in and around synnemata, and 4) to test selected albino strains in field log trials for their anti-sapstain effect. B.W. Held et al.: Biological Control of Bluestain 237