Elmer L. Schmidt

Spore germination of and carbohydrate colonization by Morchella esculenta at different soil temperatures

Few detailed data on the life cycle and ecology of morels have been reported from field studies. In this study, spore germination and saprophytic ability of Morchella esculenta in natural soil were investigated as related to progression of soil temperatures during the fruiting season. Ascospores germinated at temperatures as low as 2 C in vitro. However, spores buried in cellophane at morel sites swelled but did not produce germ tubes until the soil temperature exceeded approximately 10 C. Germination is inhibited as the soil continues to warm after fruiting body emergence (i.e., above 15 C). Spores did not remain viable after 1 yr near the soil surface. Sterile rye buried 2 wk in the field was readily colonized by M. esculenta when cased with site soil containing either spores or sclerotia when soil temperatures remained below 10 C. As temperature increased, only other saprophytes were isolated. Frequent observations of germling hyphal growth by a direct path to ungerminated spores suggests that heterocaryon formation could occur at this stage in the life cycle of M. esculenta. Despite the long-standing interest in morels by mycologists and mycophagists, little ecological information, beyond horticultural observation, has been reported from field studies. As stated by Callieux (1969), and recently reiterated by Delmas (1978), the methods for morel cultivation remain undefined and haphazard due to the lack of knowledge of their life cycle and ecology. Owers (1982) report on ascocarp production from initially axenic culture on wheat berries may obviate the need to elucidate their life cycle in nature before they can be commercially cultivated. Nonetheless, the importance of fungi in nutrient cycling under cool soil conditions of spring would justify study of the ecology of this widespread ascomycete. This study explored M. esculenta Fr. (sensu Groves and Hoare) ascospore germination in vitro and in natural soil as related to temperature. Additionally,

Consecutive polymerization and depolymerization of kraft lignin by Trametes cingulata

Abstract In extracellular solutions from white-rot fungal cultures, lignin components typically encounter opposing tendencies to be polymerized and depolymerized. The enzymes most commonly purported to bring about lignin depolymerization—lignin peroxidase, manganese-dependent peroxidase and laccase—can all act as single-electron oxidants. Accordingly they may produce from particular lignin monomer residues, either indirectly or directly, phenoxy radicals that will undergo bimolecular coupling, unless they are otherwise pre-emptively transformed. The present work has sought to elucidate whether discrimination between polymerization and depolymerization is really so precariously established in the progenitorial step of the biodegradative pathway. Some white-rot fungi express no detectable peroxidase activity of any kind and yet degrade lignins very effectively. For the sake of simplicity, one of these, Trametes cingulata, was selected to explore whether there might be some connection between lignin polymerization and depolymerization in vivo. The (Mn-free) culture medium was a multicomponent homogeneous solution containing 0.55 gl−1 softwood kraft lignin, which was adopted as the substrate because of its adequate solubility. As it grew vegetatively, T. cingulata polymerized the dissolved lignin components but then, after cessation of primary growth, the high molecular weight polymerized substrate was completely degraded. No lignin peroxidase or Mn-dependent peroxidase activity was detected in the extracellular culture solution during either metabolic phase, although (laccase-like) oxidase activity towards 2,2′-azinobis(3-ethylbenzthiazoline-6-sulfonate) (ABTS) persisted throughout the entire process. The results suggest that the overall effect of T. cingulata upon the kraft lignin substrate is governed by the consecutive release of distinct polymerizing and depolymerizing enzymes.

Sulfuryl fluoride fumigation of red oak logs eradicates the oak wilt fungus

This work was supported by a grant from the DowElanco Corp. as well as University of Minnesota Agr. Exp. Sta. project 4369. Essential help by James Bean in the fumigation trials as well as statistical evaluations by Peter Scherer (DowElanco) are gratefully acknowledged. Help from consulting foresters Steve Cook and Steve Nelson for tree procurement as well as Kory Cease, Paul Castillo and Tamara Pickens (USDA Forest Service) for technical assistance is also appreciated.Preliminary field trials using red oak logs from trees dying from oak wilt disease were successful in eliminating the oak wilt fungus from sapwood after fumigation with sulfuryl fluoride for 72 h under tarp. These results support earlier laboratory data on the fungitoxicity of sulfuryl fluoride as a potential replacement for methyl bromide treatment of exported red oak veneer logs. However, not all other microorganisms were completely eradicated from oak sapwood at the treatment levels used in this trial.ZusammenfassungErste Versuche zur Bekämpfung des Eichenwelkepilzes an befallenen Roteichenrundholz mit Sulfurylfluorid verliefen erfolgreich. Das Rundholz war 72 Stunden mit Sulfuryl-fluorid begast worden Die Ergebnisse bestätigen frühere Laborbefunde über die fungizide Wirksamkeit von Sulfurylfluorid, das geeignet ist, das gebräuchliche Methylbromid zu ersetzen, womit exportiertes Furmierholz begast wird. Allerdings konnten unter den bisherigen Bedingungen nicht alle anderen Mikroorganismen völlig abgetötet werden.

Effects of two fumigants and a fungicide formulation on the development of kiln brown stain in radiata pine lumber

Two fumigants (methyl bromide and sulphuryl fluoride) were used to treat freshly sawn radiata pine (Pinus radiata D. Don) lumber and log sections to evaluate their influence on development of kiln brown stain. Both treatments reduced severity of stain when compared with controls. The sulphuryl fluoride treatment was notably better than methyl bromide at the highest fumigant dosage, but levels of overall stain were still considered unacceptable with only 20–30% of lumber having either no or slight stain beneath the surface. Sulphuryl fluoride showed superior penetration into sapwood compared to methyl bromide as determined by a colour assay of parenchyma cell viability. A fungicide formulation which was successful in preventing brown stain in kiln dried eastern white pine was ineffective against kiln brown stain in radiata pine. The results of the present study indicates that the mechanism for kiln brown stain in radiata pine differs from that in eastern white pine.ZusammenfassungFrische Schnittholz- und Rundholzproben der Monterey-Kiefer (Pinus radiata D. Don) wurden mit zwei verschiedenen Gasen (Methylbromid, Sulfurylbromid) behandelt, um deren Einfluß auf die Entwicklung von Braunverfärbung zu untersuchen. Beide Gasbehandlungen veringerten, im Vergleich zu unbehandelten Proben, die Verfärbungsintensität. Bei der höhsten Konzentration ergab die Behandlung mit Sulfurylchlorid deutlich bessere Ergebnisse als mit Methylbromid, jedoch waren nur 20–30% der Schnittware entweder unverfärbt, oder leicht verfärbt, und somit gesehen war der gesamte Verfärbungsanteil nicht akzeptabel Im Verhältnis zu Methylbromid wies das Sulfurylflorid ein ausgezeichnetes Eindringvermögen ins Splintholz auf, wie mit einem Farbtest nachgewiesen werden konnte. Ein Pilzschutzmittel, welches die Baunverfärbungen in der technischen Trocknung von Weymouthskiefer vollständig verhindert hatte, war nicht erfolgreich gegen die Braunverfärbung in der Monterey-Kiefer. Die Ergebnisse dieser Untersuchung wiesen darauf hin, daß für die Braunverfärbung der Monterey-Kiefer ein anderer Verfärbungsmechanismus besteht, als für die Weymouthskiefer.

AN ATTEMPT TO QUANTIFY RELATIVE MYCELIAL DEVELOPMENT OF PHANEROCHAETE CHRYSOSPORIUM USING THE FLUORESCEIN DIACETATE SPECTROPHOTOMETRIC ASSAY

The spectrophotometric fluorescein diace- tate assay was used to quantify viable mycelial growth of Phanerochaete chrysosporium on Pinus banksiana wood chips. Tests were conducted on inoculated nonsterile and sterile chips with noninoculated nonsterile and sterile chips as control. Additionally, some chips were compressed to make nutrients more readily accessible by mechanically rupturing the wood parenchyma cells. Comparisons were made of chips heavily colonized with P. chrysosporium against chips with only scattered mold mycelium to test the effectiveness of the fluo? rescein diacetate assay for this particular species. It was found that P. chrysosporium did not produce sig? nificant hydrolysis of fluorescein diacetate as com? pared to other resident microflora.

INFLUENCE OF POLYOXIN D ON BASIDIOSPORE GERMINATION OF TWO WOOD DECAY FUNGI

The increasing awareness of the potential value of pesticides with narrow and specific target activities has led to investigation of chemicals such as plant lectins (1) and inhibitors of chitin synthesis as anti-fungal agents (2-6). In fact, many fungicides currently used in agriculture (e.g., triazines, sulfenimides) are specific chitin synthetase inhibitors (7). Though fungi differ greatly in their sensitivity to such agents, it has been shown that one group of such compounds, the polyoxins, can produce abnormal hyphal morphology, retard or stop growth, and reduce wood decay by basidiomycete fungi (4-6). As spores of decay fungi are known to be more sensitive to certain wood preservatives than is established mycelium (8, 10), this study sought to determine the effect of such a chitin synthesis inhibitor-Polyoxin D-on spore germination and early hyphal development of a brown rot and a white rot fungus in vitro. Polyoxin D is a competitive, substrateanalogue type of chitin synthetase inhibitor (2). The drawbacks to use of such a compound as a wood preservative (i.e., cost, possible leaching or degradation) might be reduced should it be effective in preventing decay initiation by spore germination at very low concentrations. Basidiospores from 3 week-old cultures of Gloeophyllum trabeum (Pers.: Fr.) Murr. [MN 51 isolate] and Poria tenuis (Schw.) Cooke [ATCC 36207] were collected from covers on inverted cultures which had been changed 24 hours earlier. These fungi (brown and white rot, respectively) sporulate well on 2% malt extract (Difco) agar when grown in deep glass dishes (8). Spore suspensions were made in 0.5% malt extract in sterile distilled, deionized water and adjusted to a density of approximately 1 x 106/ml. Equal volumes of spore suspension and water solution of Polyoxin D (from a Streptomyces speciesBehring Diagnostics, La Jolla, California) were micropipetted (70 ,l each) into a well slide. A cover slip was placed over the well to retard evaporation during incubation, and the slides were placed in Petri plate incubation chambers containing filter paper wetted with sterile water and 10% glycerol. Plates (2 replicates per concentration) were incubated at 25 C on the lab bench in diffuse light. Final polyoxin concentrations in the wells ranged from 1 ppb (0.001 ,ug/ ml) to 400 ppm (jig/ml). Aliquots from stirred well slide solutions were removed at 24 hours to