Efficacy of inoculum type of Pisolithus tinctorius on mycorrhizae formation in Pinus pinaster and Pseudotsuga menziesii

Abstract

Three types of Pisolithus tinctorius inoculum: a) vegetative inoculum produced in peat-vermiculture substrate, b) mycelium entrapped in alginate gel, and c) spores, have been tested to determine their effectiveness to form ectomycorrhizas on container-grown Pinus pinaster and Pseudotsuga menziesii seedlings. Vegetative inoculum, applied at 1:8 (inoculum: substrate, v:v) rate, produced a high root infection level (82 p. 100 of short roots) on 80 p. 100 of P. pinaster inoculated seedlings. The same inoculum was ineffective on P. menziesii. Mycelium entrapped in alginate gel resulted an ineffective inoculum for the development of P. tinctorius ectomycorrhizas on both tree species. Spore inoculations produced a high number of ectomycorrhizal P. pinaster seedlings (96-100 p. 100), but the level of root infection obtained (65 p. 100) was lower than the root colonization achieved when the vegetative inocolum of the strain A-93 was used. Spore application was the only inoculation technique successful in the formation of P. tinctorius ectomycorrhizas on containerized P. menziesii seedlings. Nevertheless, the percentage of ectomycorrhizal seedlings (< 40 p. 100) and the level of root infection (5-12 p. 100) were too low to expect a positive effect on survival and growth of outplanting seedlings.