Organic nitrogen use by salal ericoid mycorrhizal fungi from northern Vancouver Island and impacts on growth in vitro of Gaultheria shallon

Salal (Gaultheria shallon) recovers quickly from rhizomes after clear-cut t imber harvesting and dominates clearcuts of Tsuga heterophylla and Thuja pl icata forests. Thus it contributes to considerable problems in regeneration of these sites in coastal British Columbia, Canada. Based on what is known about other ericaceous plants, we speculated that mycorrhizal fungi of sal al play a vital role in the growth and dominance of salal by providing acce ss to organic nitrogen. In this study, the ability of four species of fungi isolated from salal to use different forms of organic nitrogen was tested in pure culture and in association with salal. The organic forms of nitroge n applied were glutamine tan amino acid), glutathione (a peptide), and bovi ne serum albumin (BSA, a protein). The fungi tested were Oidiodendron maius , Acremonium strictum. and two nonsporulating fungi. Inoculated plants alwa ys grew better than noninoculated plants regardless of nitrogen source. Glu tamine was used as readily as ammonium nitrogen by all four fungi and the m ycorrhizal plants of salal colonized by those fungi. There was considerable variation between fungus species or the plants inoculated with those fungi in using glutathione and BSA. Salal inoculated with O. maius grew better o n glutathione than BSA, while A, strictum and unknown 1 produced significan tly greater yields of salal on BSA. Colonization rates of salal by all four fungi was higher on glutathione or BSA than on ammonium or glutamine.