Growth of containerized jack pine seedlings inoculated with different ectomycorrhizal fungi under a controlled fertilization schedule

Containerized jack pine (Pinusbanksiana Lamb.) seedlings were grown in a peat moss - vermiculite substrate and inoculated at sowing with pure cultures of three ectomycorrhizal fungi. After 18 weeks of growth in the greenhouse, seedlings inoculated with Laccariabicolor had 97% of their short roots mycorrhizal, while those inoculated with Hebelomacylindrosporum had 36% of their rootlets mycorrhizal. No mycorrhizae were obtained with Rhizopogon sp. After both 12 and 18 weeks of growth with the fertilization schedule used, seedlings colonized with L. bicolor and H. cylindrosporum were significantly smaller than those inoculated with Rhizopogon sp. or control seedlings. After 18 weeks of growth, the available nitrogen (N) content of the substrate was considerably greater with L. bicolor inoculated seedlings than with control seedlings, whereas the available phosphorus (P) content of the substrate was the same for these two treatments. Also, after 18 weeks, seedlings mycorrhizal with L. bicolour had a. greater concentration (%) of N and P in their tissues than control seedlings; however, they contained fewer milligrams of N and P than control seedlings. From our results on substrate fertility of mycorrhizal seedlings, we state that it is possible to induce mycorrhiza formation of jack pine seedlings with L. bicolor when substrate fertility in available N and P is less than or equal to 39 and 60 ppm, respectively, and that it is possible to maintain L. bicolor mycorrhizae when N and P fertility is less than or equal to 24 and 28 ppm, respectively. From analysis of tissue nutrient content in mycorrhizal seedlings, it appears that the appropriate N and P concentrations to maintain mycorrhiza formation of jack pine seedlings with L. bicolor are less than or equal to 1.6 and 0.2%, respectively.