MYCORRHIZA FORMATION AND GROWTH OF EUCALYPTUS-GLOBULUS SEEDLINGS INOCULATED WITH SPORES OF VARIOUS ECTOMYCORRHIZAL FUNGI

As many eucalypts in commercial plantations are poorly ectomycorrhizal there is a need to develop inoculation programs for forest nurseries. The use of fungal spores as inoculum is a viable proposition for low technology nurseries currently producing eucalypts for outplanting in developing countries. Forty-three collections of ectomycorrhizal fungi from southwestern Australia and two from China, representing 18 gener a, were tested for their effectiveness as spore inoculum on Eucalyptus globulus Labill. seedlings. Seven-day-old seedlings were inoculated w ith 25 mg air-dry spores in a water suspension. Ectomycorrhizal develo pment was assessed in soil cores 65 and 110 days after inoculation. By day 65, about 50% of the treatments had formed ectomycorrhizas. By da y 110, inoculated seedlings were generally ectomycorrhizal, but in man y cases the percentage of roots colonized was low (<10%). Species of L accaria, Hydnangium, Descolea, Descomyces, Scleroderma and Pisolithus formed more ectomycorrhizas than the other fungi. Species of Russula, Boletus, Lactarius and Hysterangium did not form ectomycorrhizas. The dry weights of inoculated seedlings ranged from 90% to 225% of the uni noculated seedlings by day 110. Although plants with extensively colon ized roots generally had increased seedling growth, the overall mycorr hizal colonization levels were poorly correlated to seedling growth. S pecies of Laccaria, Descolea, Scleroderma and Pisolithus are proposed as potential candidate fungi for nursery inoculation programs for euca lypts.