Nursery, cold storage, and field studies on western conifers inoculated with spores of Pisolithus tinctorius

Graduation date: 1983Inoculations of white fir, Shasta red fir, Douglas fir and\ud ponderosa pine with Pisolithus tinctorius spores when outplanted\ud failed to produce P. tinctorius mycorrhizae at the end of the first\ud growing season. In the third year a few P. tinctorius mycorrhizae\ud were formed on white fir. Inoculations reduced seedling survival in\ud some cases. High rate of spore application may have desiccated roots\ud of the true firs; levels of spore application need careful attention.\ud Soil scarification and ripping significantly promoted growth of white\ud fir seedlings compared to scarification alone.\ud White fir, Shasta red fir, Douglas fir and ponderosa pine\ud seedlings were inoculated in a bareroot nursery with spores of P.\ud tinctorius. The spores were applied at three rates with vs. without\ud cold-wet pretreatment of 7 vs. 21 days. Pretreatment did not affect\ud their efficiency as inoculum. Inoculated ponderosa pine seedlings\ud grew significantly more than noninoculated. Growth of inoculated\ud Douglas fir, Shasta red, and white fir seedlings did not differ\ud significantly from that of noninccuiated. Inoculations in the\ud greenhouse with a wider range of spore application rates revealed that\ud a higher concentration of spores was needed to induce an increase in\ud growth and mycorrhiza formation for Douglas fir than for ponderosa\ud pine. The effective application rates were much higher than those\ud used in nursery inoculations.\ud Survival and growth of white fir, Douglas fir and ponderosa pine\ud seedlings and survival of mycorrhizal fungi on their roots were\ud assessed after cold storage with or without 5 ppm ethylene in\ud combination with four root treatments: (1) washed, (2) dipped in Truban solution, (3) dipped in Benlata solution, and (4) no treatment.\ud Ethylene treatment resulted in increased survival, apical bud burst,\ud and new root production when roots were untreated. Root washing and\ud fungicide treatments, however decreased vigor of seedlings, especially\ud that of white fir. ?. tinctorius, which formed mycorrhizae with 10-20\ud percent of the short roots of the seedlings, did not survive cold\ud storage. Thelephora sp. and an ectendomycorrhizal fungus both\ud survived cold storage and rapidly colonized roots newly formed on\ud seedlings planted after cold storage