Effects of ethylene and fungicide dips during cold storage on root regeneration and survival of western conifers and their mycorrhizal fungi

Survival and growth of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), ponderosa pine (Pinusponderosa Dougl. ex. Laws.), and white fir (Abiesconcolor (Gord. and Glend.) Lindl.) seedlings and survival of mycorrhizal fungi on their roots were assessed after cold storage with or without 5 ppm ethylene in combination with four root treatments: (i) washed, (ii) dipped in Truban solution, (iii) dipped in Benlate solution, and (iv) no treatment. Ethylene treatment resulted in increased survival, apical bud burst, and new root formation in the greenhouse if roots had not been washed or dipped in fungicide. None of the gas storage or root treatments greatly affected seedling field survival. Root washing decreased vigor of the seedlings, especially white fir. None of the root treatments or gas storage conditions affected root fungal populations; bacterial and actinomycete populations appeared to be affected and the response varied according to host species. Pisolithustinctorius (Pers.) Coker and Couch, which formed mycorrhizae with 10-20% of the short roots of the seedlings, did not survive cold storage. Thelephora spp. and an ectendomycorrhizal fungus both survived cold storage and rapidly colonized roots newly formed on seedlings planted after cold storage.