Factors affecting transfer and spread of Phellinusweirii mycelium in roots of second-growth Douglas-fir

Abstract

Effects of site, root diameter, soil depth of interroot contact, length of root surface in contact, type of contact, and relative position of roots were investigated on the frequency of transfer of Phellinusweirii (Murr.) Gilbertson mycelium between roots and its spread along roots of second-growth Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco). Successful transfer of P. weirii as ectotrophic or endotrophic mycelium occurred in 32 and 3%, respectively, of total number of interroot contacts. Unsuccessful transfers occurred in 4 and 62%, respectively, with the balance of contacts having undetermined transfers, owing to extension of mycelium to the root collar of both roots in contact. A Pseudotsuga–Polystichum site had a higher frequency of unsuccessful transfer than two Pseudotsuga–Gaultheria sites. Average root diameter was greater and average depth was less in contacts with successful transfers than in those with unsuccessful transfers. Type or length of contact or relative position of roots had no significant effects on transfers. There was a highly significant inverse relationship between root diameter and length of endotrophic mycelial spread as measured by decay column. The regression of endotrophic on ectotrophic mycelial spread along roots was highly significant for both proximal and distal spread. In most roots, ectotrophic mycelium had spread distally to the tip and proximally to the stump, whereas endotrophic mycelium had not.