Robert L. Gilbertson

Wood-Rotting Fungi of North America

The biology of wood-rotting fungi is reviewed. Discussions are presented in taxonomy, species diversity, North American distribution, developmental response to environmental factors, edibility and toxicity, medical uses, relationships of fungi with insects and birds, the role of fungi as mycorrhiza, pathological relationships with trees, role in wood decay, and ecology. Threats to the continuing existence of these fungi as a result of increased utilization of wood as fuel are also discussed. (ACR)

Degradation of pentachlorophenol by fixed films of white rot fungi in rotating tube bioreactors

A rotating tube bioreactor (RTB) was developed to examine chemical degradation by fungal biofilms under controlled laboratory conditions. Each RTB consists of a sealed tube containing mycelia growing on a piece of steel mesh on the inside wall of the tube. Tubes are mounted horizontally in a tube rotator and slowly rotated to expose the fungal biofilm to a wetting-aeration cycle typical of fixed film reactors such as trickling filters and rotating biological contactors. The extent of pentachlorophenol (PCP) dehalogenation by three different species of fungal biofilms was evaluated by measuring concentrations of PCP (using HPLC) and the total concentrations of organic and inorganic halides (using a TOX analyzer). The three species of fungi removed PCP from solution at similar rates, but they differed in ability to completely dehalogenate PCP. Nitrogen-deficient growth media only slightly increased the extent of PCP mineralization. All species of fungi (grown on nitrogen-sufficient media) removed PCP to 99% removal) within 1 d. Within 8 d, the greatest percent of dehalogenation, measured by the appearance of chloride ion in solution, was achieved by Trametes versicolor (62%), followed by Phanerochaete chrysosporium (38%) and Inonotus dryophilus (21%). These removals based on chloride ion concentrations are comparable to claims by others of complete mineralization for recoveries of 10–50% of 14CO2 from 14C-labeled PCP in static flask cultures.

Adsorption and removal of pentachlorophenol by white rot fungi in batch culture

The adsorption and removal of pentachlorophenol (PCP) by 12 species of white rot fungi is a function of species and culture conditions. In general, PCP adsorption to mycelia was very low, ranging from 0.01 to 0.05 g PCP g mycelium−1 (dry wt basis) at 40 mg PCP l−1, with no apparent corellation between species. after long pre-incubation periods (8–20 d), all species of fungi reduced PCP by > 50% within 12 days of PCP addition. Several species of fungi, including Phanerochaete chrysosporium, Trametes versicolor, and all four Ganoderma sp. removed > 50% of the PCP within 24 h, although the largest overall reduction of PCP (96%) was achieved by Inonotus rickii. PCP removal in 250 ml flasks by shallow (10 ml) cultures was greater than removal by deep (50 ml) cultures indicating that the ratio of surface area to volume of liquid media is an important factor in the extent of PCP removal by white rot fungi.

The efficacy of Guayule resin as a pesticide

Abstract Researchers from the United States are evaluating the nonrubber-producing extract (resin) of the guayule bush (Parthenium argentatum Gray) as a potential wood protectant against marine and terrestrial wood-destroying organisms in Panama. Wood treated with guayule resin was not attacked, or only lightly attacked, by limnorians (crustacean borers) after 45 months in Limon Bay. After 19 months in the Bay of Panama, treated wood was undamaged by teredinids but heavily damaged by pholads; both are molluscan borers. Treated wood was not attacked by termites of the genus Coptotermes during 33 months of exposure in the Panamanian rain forest. Termites of the genus Heterotermes had not attacked wood treated with guayule resin after 45 months in the Panamanian rain forest. A 20-week laboratory evaluation of guayule resin for efficacy against brown-rot (Gleophyllum trabeum, Antrodia carbonica, Formitopsis cajanderi, Lentinus ponderosa) and white-rot (Dichomitus squalens, Trametes versicolor, Ganodermas sp) fungi was performed. Statistical analysis revealed a significant inhibition of decay of the treated wood by these organisms. A 12-week laboratory evaluation of guayule resin for efficacy against soft-rot fungi was also conducted. None of the treated wood was damaged by soft-rot fungi.

BASIDIOSPORES, PILOCYSTIDIA, AND OTHER BASIDIOCARP CHARACTERS IN SEVERAL SPECIES OF THE GANODERMA LUCIDUM COMPLEX'

Morphology of basidiospores and pilocystidia of specimens of Ganoderma colossum, G. zonatum, G. oregonense, and G. meredithae was compared. Structure of basidiospores was similar in all species, but basidiospores of some species differed in length, width, spore index, and shape and distribution of inter-wall pillars. Basidiospores of G. zonatum were cylindrical, while those of the other species were ovate with truncated apex. Basidiospores of Ganoderma colossum had angular inter-wall pillars while those of the remaining species were cylindrical. Pilocystidia were clavate and unbranched for most species, but those of G. zonatum were highly branched or lobed. Pilocystidia of G. colossum were thinwalled, negative to weakly amyloid. Those of G. zonatum were thick-walled, negative to weakly amyloid, while those of the remaining species studied were thick-walled and strongly amyloid. Host relationships are reviewed and known geographical distributions are indicated for each of the species studied.

Vegetative incompatibility between intraspecific dikaryotic pairings of Ganoderma lucidum and G. tsugae

Intraspecific pairings of dikaryons of Ganoderma lucidum and G. tsugae were conducted on 2% malt extract agar (MEA) and on wood blocks of Quercus hypoleucoides and Abies concolor. Intraspecific pairings of dikaryons from different trees formed interaction zones regardless of geographical distribution. Self-crosses of dikaryons were compatible. Antagonistic reactions on MEA after 10 wk were sparsely colonized, clear zones between opposing cultures. Four types of zone lines developed on the wood blocks after 20 wk: (1) discolored zones of undecayed wood on oak blocks; (2) nondiscolored zones of undecayed wood on white fir blocks; (3) hyphal interaction zones in surface mycelium and within wood of both wood types; and (4) noninteraction zone lines in surface mycelium of both wood types. Evidently, characters of the host wood influenced formation of the interaction zones. Antagonistic hyphal interactions on MEA and wood blocks consisted ofhyphae with swellings and abnormal branching where hyphal fusion occurred. Hyphal noninteraction lines appeared randomly on the surface of the wood blocks where densely packed, pigmented cuticular cells were formed. No self-pairings of dikaryons showed interaction zones and hyphae anastomosed freely. Homokaryons from different G. lucidum dikaryons were interfertile. Homogenicity between dikaryotic isolates of both species apparently allows plasmogamy to occur. Vegetative incompatibility delimits individuals of different genotypes in natural populations of G. lucidum and G. tsugae.

Didymium eremophilum: A New Myxomycete from the Sonoran Desert

Didymium eremophilum is a new species of Myxomycetes cultured from dead tissue of Carnegiea gigantea (saguaro) in moist chambers. It is characterized by small stalked sporangia, crystalline peridia...

Distribution and sporulation phenology of myxomycetes in the Sonoran Desert of Arizona

All pith samples from 68 dead saguaro cacti in 3 plots and 11 isolated dead plants in Saguaro National Monument, Arizona, produced at least one species of myxomycete upon incubation at 20 or 30°C. Three species,Badhamia gracilis (Macbr.) Macbr.,Physarum straminipes Lister, andDidymium eremophilum M. Blackwell et Gilbertson, developed at high frequencies on the substrates in moist chamber culture.Perichaena corticalis (Batsch) Rost, andProtophysarum phloiogenum M. Blackwell et Alexopoulos were also present. Although previous literature reports [9] indicated that Myxomycetes grow best at low pH, these species all tolerated substrates of pH 8.7–10.4.Didymium eremophilum andP. phloiogenum had peaks in sporulation within 6 days; other species were slower. There was no difference in time of sporulation ofB. gracilis orD. eremophilum at 20 and 30°C; however, sporulation ofP. straminipes was significantly later at 30°C. Reduced spore germination and slower buildup of critically sized amoebal populations ofP. straminipes at 30°C may be a factor.

Comparative protein studies of several Pythium species using isoelectric focusing

Buffer-soluble mycelial proteins of six species of Pythium were compared by isoelectric focusing. Species studied included P. aphanidermatum (P.a.), P. deliense (P.de.), P. myriotylum (P.m.), P. dissotocum (P.di.), P. violae (P.v.), P. ultimum var. ultimum (P.u.u.) and P.u. var. sporangiferum (P.u.s.). Each species had one or more distinct bands, in addition to many common bands of protein, when focused between pH 4-8. A higher concentration of proteins focused in the acidic region of broad pH range gels. Major protein bands were detected with Coomassie stain. Silver staining increased detection of proteins in low concentration (minor bands) in acidic, neutral, and alkaline regions. Other distinct bands of protein were identified for each species when protein samples were further resolved by focusing in the acidic region (pH 3-6). Several isolates each of P.a., P.u., and P.de., collected from various regions of North America, produced consistent protein banding patterns with minor variations. Although banding patterns of P. aphanidermatum differed slightly when isolates were cultured on different media, protein patterns were still specifically identifiable. No differences in protein bands were observed between P. u.u. and P. u.s. The utility of isoelectric focusing for the differentiation of species of Pythium is discussed.

Cultural and Other Morphological Studies of Sparassis Radicata and Related Species

SUMMARY Sparassis radicata Weir was found to be heterothallic with a bipolar type of mating system. Multiple alleles for incompatibility occur at the locus for heterothallism. Tests were negative for the production of extracellular oxidases on gallic or tannic acid media and with gum guaiac solution. The optimum temperature for growth on 3.0% malt extract agar medium was 23-25 C. Studies of some basidiocarps and cultures labeled Sparassis crispa Wulf. ex Fr. from Europe and Japan show they are conspecific with S. radicata. Specimens and isolates labeled S. crispa from southeastern United States differed from the European and Japanese specimens and from isolates labeled S. crispa. Apparent dikaryotization of single basidiospore isolates of S. radicata from Arizona by dikaryotic isolates labeled S. crispa from Europe and Japan offers additional evidence for the conspecificity of these fungi. Descriptions of basidiocarps and cultural characters are given for S. radicata and for specimens and cultures labeled S. crispa. Sparassis radicata Weir, a basidiomycete currently placed in the family Sparassidaceae (Aphyllophorales), was described by Weir in 1917. Weir studied some aspects of the life history and decay relationships of S. radicata, and found the fungus to be associated with a brown cubical decay of roots of some western conifer species. No other studies have been made on the fungus and most aspects of its biology are unknown. Field studies have revealed that S. radicata is rather common in coniferous forests of southern Arizona. The fungus has been collected on ponderosa pine (Pinns ponderosa Laws.), Douglas fir (Pseudotsuga menziesii (Mirb.) Franco), white fir (Abies concolor (Gord. et Glend.) Lindl.), and southwestern white pine (Pinus strobiformis Engelm.) in Arizona (Gilbertson et al., 1974). These tree species are important in