GERMINATION OF BASIDIOSPORES OF MYCORRHIZAL FUNGI IN THE RHIZOSPHERE OF PINUS RADIAT A D. DON

SUMMARY A method was developed to inoculate the surfaces of young roots of Pinus radiata D. Don uniformly with basidiospores of mycorrhizal fungi. Germination of basidiospores in the rhizosphere was 46 to 69 % in different experiments with Rhizopogon luteolus Fr. and Nord and 34 and 31 % with Suillus luteus (L. ex Fr.) S. F. Gray and S. granulatus (L. ex Fr.) 0. Kuntze, respectively. This compared with 0-1 % germination usually obtained for all fungi on synthetic media. Using the method, single spore cultures of R. luteolus were obtained which formed mycorrhizas on P. radiata seedlings. Germination did not respond to roots of Eucalyptus globulus Labill, Medicago truncatula Gaertn., Trifolium subterraneum L. or Lolium perenne L., showing the germination response was specific to P. radiata, although other host tree species may produce a similar response. Specificity in such mycorrhizal associations may operate both at the germination and the infection stages. It is suggested that in vivo the necessity for a host plant to stimulate spore germination is a highly effective method of inoculum conservation in the absence of host plants. The viability of inoculum remained high during storage at freezing temperatures. High spore germination rates were also obtained when the method was used in unsterilized soil.