Poria weirii Murr. isolates cultured from various hosts may be divided into two groups on the basis of their ability to parasitize Thuja plicata Donn and to grow on media containing water-soluble T. plicata heartwood extractives. The role of these extractives in determining whether a Poria weirii isolate can parasitize Thuja plicata was examined. Measurement of linear growth along wood micro-sections confirmed that substances inhibitory to one isolate group are hot-water soluble T. plicata heartwood extractives. The tolerance of isolates from T. plicata (Thuja) and Pseudotsuga menziesii (Mirb.) Franco (non-Thuja) to a hot-water extract of Thuja plicata heartwood and its hexane soluble (principally thujaplicins) and insoluble (thujaplicin-free) fractions was studied in detail. Dry weight of mycelium produced in liquid glucose-asparagine medium was measured. Thuja isolates were more tolerant than non-Thuja of the hot-water extract and its fractions; thujaplicins caused the greatest response differences. Thuja isolates showed greater stimulation than non-Thuja at subinhibitory thujaplicin concentrations. Higher thujaplicin concentrations were required to produce fungistatic and -toxic conditions in Thuja isolates than in non-Thuja. There were highly significant differences between isolate groups in response to 7.5 ppm thujaplicin. Tolerance was not related to date of isolation or geographical location. With sufficient inoculum potential, a non-Thuja isolate may overcome T. plicata heartwood toxicity. The resulting infection is usually localized. Unlike Thuja isolates, non-Thuja were unable to increase thujaplicin tolerance during three serial generations on liquid medium containing thujaplicins. Long exposure of non-Thuja isolates to T. plicata heartwood under field conditions did not increase their thujaplicin tolerance. Thuja isolates may be able to adapt the enzyme systems blocked by thujaplicin or to detoxify thujaplicins. These results have significance for control of Poria weirii. Planting Thuja plicata in and around infection centers caused by non-Thuja, isolates could limit their size by reducing the number of root contacts between susceptible species. / Science, Faculty of / Botany, Department of / Graduate

Thesis (M.S.)--Oregon State University, 1993. / Includes mounted photographs. Typescript (photocopy). Includes bibliographical references (leaves 64-86). Also available on the World Wide Web.

Phellinus weirli (Murr.) Gilbertson is an important root rot of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) in western North America. The effect of site and tree species on the growth of P. weirii along roots can be measured by inoculation using naturally infected root material or P. weirii cultured on sterile wood. This thesis reports the development of an inoculation technique using naturally infected root material to infect Douglas-fir and western hemlock (Tsuga heterophylla (Raf.) Sarg.). Intact naturally infected root sections of Douglas-fir used as an inoculum source resulted in P. weirii growing on approximately 87% of roots inoculated. Further inoculations were made using infected root sections split longitudinally with the exposed wood surface placed in contact with the host root. Subsequently an attempt was made to evaluate the influence of xeric, submesic and hygric sites, within the Demonstration area of the UBC Research Forest, Maple Ridge, on inoculation and growth of P. weirii along roots of Douglas-fir and western hemlock. Dry soil conditions experienced during the summer of 1978 reduced the expected number of successful infections of host roots to approximately 20%, 26 weeks after installation. All inoculations of a third series established after heavy rains in the late summer infected the roots of both Douglas-fir and western hemlock, verifying that the technique was successful when conditions were cool and moist. P. weirii inoculum used was collected from two sources, Haney and Surrey. Laboratory studies indicated incompatibility between the two sources when raised on agar media and field results indicated a longer retention of viable P. weirii in inoculum blocks from the Surrey source. / Forestry, Faculty of / Graduate