摘要:

Restriction fragment length polymorphisms in ribosomal DNA were used to assess the degree of variation among 71Cenococcum geophilumisolates of both geographically distinct and similar origins. Southern hybridizations using clonedC.geophilumribosomal DNA indicated extensive variation among isolates, greater than has been previously reported to occur within a fungal species. Most of the polymorphisms were located within the region from the intergenic spacer through internal transcribed spacer 1. Restriction-site and length polymorphisms also occurred within the 5.8S through 26S genic region. Sixteen size categories of length mutations, six restriction-site additions, and four restriction-site deletions were observed compared with a reference isolate.HindIII-digested DNAs displayed fewer polymorphisms in the mitochondrial 24S ribosomal RNA gene (and flanking regions) than in nuclear ribosomal DNA.UPGMAcluster analysis of shared nuclear ribosomal DNA patterns indicated 32 unique phenotypes and groupedC.geophilumisolates into a broad range of clusters ranging from 100 to 44% similarity. The amount of ribosomal DNA variation demonstrated in this study indicates thatC.geophilumis either an extremely heterogenous species or a fungal complex representing a broader taxonomic rank than presently considered.Key words:Cenococcum geophilum, ribosomal DNA, restriction polymorphisms.

ISSN:0008-4026    

DOI:10.1139/b91-294

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Effects of nitrate-N and ammonium-N fertilization on foliar nitrogen concentrations, carbon dioxide assimilation, leaf conductance, transpiration, intercellular carbon dioxide, xylem pressure potentials, specific leaf mass, and growth were measured on naturally established juvenile and small adultJuniperus occidentalisgrowing in central Oregon where ammonium-N was the dominant form of soil nitrogen throughout the summer. Fertilization with both forms of nitrogen increased foliar nitrogen concentrations in juveniles and small adults in May; concentrations in small adult foliage from the nitrate-N treatment were still higher than controls in September. Both forms of nitrogen reduced carbon dioxide assimilation and potential photosynthetic nitrogen-use efficiency. The negative relationship between nitrogen addition and carbon dioxide assimilation was more apparent in juveniles than in small adults; negative effects were more pronounced in the ammonium-N treatment than in the nitrate-N treatment. Leaf conductance and transpiration were also reduced, but reductions of water loss were greater than were negative effects of fertilization on carbon gain; thus water-use efficiency of juvenile and small adults increased in May and July. The depression in gas exchange processes was detectable for a longer period during the summer in juveniles than in small adultJ.occidentalis. Branchlet elongation of juvenile and small adultJ.occidentaliswas increased with nitrate-N and ammonium-N addition, but variability reduced significance levels.Juniperus occidentalisappears to be adapted to utilize low, ambient levels of soil nitrate at the research site and did not preferentially utilize ammonium.Key words: gas exchange, water relations, foliar nitrogen, growth.

ISSN:0008-4026    

DOI:10.1139/b91-295

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The influence of amino acids on spore germination ofAlternaria eassiaewas investigated to develop a basis for improvement of mycoherbicide formulations. At a 1% concentration, the majority of amino acids exhibited little or no effect on spore germination in vitro. However, aspartic and glutamic acids stimulated germination, and serine, tryptophan, cysteine, and phenylalanine inhibited spore germination. Cysteine was the strongest inhibitor of germination and was active in the presence of potato dextrose broth, which is normally stimulatory. One percent cysteine reduced germination 96% after 4 h. Derivitization of the mercaptan or amino group but not the carboxylic acid group diminished the ability to inhibit spore germination. Cysteine also inhibited spore germination ofAlternaria crassaandAlternaria macrospora. Application of cysteine reduced development of Alternaria leaf spot on cotton plants inoculated withA.macrospora. The results demonstrate diverse effects of amino acids on spore behavior and suggest cysteine or similar compounds may be useful in preventing diseases caused byAlternariaspecies.Key words: amino acids, biological control, cysteine, germination, potato dextrose broth, Alternaria leaf spot.

ISSN:0008-4026    

DOI:10.1139/b91-296

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The genusTrichodermaPers.:Fr. is defined to include anamorphs ofHypocrea, previously placed inGliocladiumandVerticillium, having elongate phialides and irregularly branched conidiophores. A sectional classification is proposed forTrichodermarecognizing the following five sections: sectionTrichoderma, sectionLongibrachiatumBissett, sectionSaturnisporumDoi et al., sectionPachybasium(Sacc.) stat.nov., and sectionHypocreanumsect.nov.Trichoderma lacteasp.nov. is described, typifying sectionHypocreanum. The species in sectionTrichodermahave narrow and flexuous conidiophores and branches, with branches and phialides uncrowded, frequently paired, and seldom with more than three elements in a whorl. SectionPachybasiumincludes species with highly ramified conidiophores that are often aggregated into compact fascicles or pustules and with relatively short, broad branches bearing inflated phialides in crowded verticils. SectionHypocreanumaccommodatesTrichodermaanamorphs ofHypocreathat have effuse conidiation, sparingly branched conidiophores, and cylindrical to subulate phialides. The placement of existingTrichodermaspecies, species aggregates, and some anamorphs ofHypocreain the five sections is discussed, and a key is provided to differentiate the sections ofTrichoderma.Key words:Trichoderma, sectional classification,Hypocrea,Gliocladium.

ISSN:0008-4026    

DOI:10.1139/b91-297

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Twenty species assigned toTrichodermasectionPachybasium(Sacc.) Bissett are described and differentiated on the basis of conidiophore and conidium morphology. Included in sectionPachybasiumareT.hamatum,T.polysporum,T.piluliferum,T.harzianum, andT.virensthat were already recognized inTrichoderma;T. flavofuscumcomb.nov. transferred fromGliocladium; the anamorphs ofHypocrea gelatinosa,H.semiorbis, and two unnamedHypocreaspecies; and 10 new species segregated from theT.hamatumspecies aggregate of M. A. Rifai (1969. Mycol. Pap. 116: 1–56). The new speciesTrichoderma crassum,T. croceum,T. fasciculatum,T. fertile,T. longipilis,T. minutisporum,T. oblongisporum,T. pubescens,T. spirale,T. strictipilis,T. strigosum, andT. tomentosumare proposed. Keys are provided to distinguish the 20 known species in sectionPachybasium.Key words:TrichodermasectionPachybasium,Hypocrea, taxonomy.

ISSN:0008-4026    

DOI:10.1139/b91-298

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Trichoderma parceramosumnom.nov. replaces the illegitimate nameTrichoderma atrovirideBissett, a later homonym ofT.atrovirideKarsten. TheTrichodermaanamorph ofHypocrea schweinitzii(Fr.:Fr.) Sacc. is described and differentiated from the four other species in sectionLongibrachiatum.Key words:TrichodermasectionLongibrachiatum, taxonomy.

ISSN:0008-4026    

DOI:10.1139/b91-299

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Restriction-site analysis of chloroplast DNA was carried out on a total of 13 North American species ofHordeum, 7 native and 6 introduced. Sites associated with polymorphic banding patterns were omitted so that only invariant sites within species were used in the analyses. A number of taxa whose species status is in dispute can indeed be supported at species rank, i.e.,H.brachyantherum,H.californicum,H.pusillum,H.intercedens,H.marinum, andH.geniculatum. The maternal progenitor ofH.arizonicumisH.pusillum, and this is further discussed in light of other possibilities. Both phenetic and cladistic analyses indicate a tripartite relationship wherebyH.vulgareis distant from the group ofH.leporinum,H.glaucum, andH.murinumand from a second group comprising the native speciesH.brachyantherum,H.californicum,H.arizonicum,H.jubatum,H.pusillum,H.intercedens, andH.depressum.Hordeum marinumandH.geniculatumoccupy a central position in this relationship. Speculation that the putative ancient form ofHordeumresembled aH.murinum–H.geniculatum-like species is discussed.Key words: chloroplast DNA,Hordeum, phylogenetic relationships.

ISSN:0008-4026    

DOI:10.1139/b91-300

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

A coelomycetous anamorph was obtained in axenic spore cultures ofChaenothecopsis savonica(Mycocaliciaceae, Cali-ciales). This anamorph is described. The anamorph has also been found on specimens collected in the field. A coelomycetous anamorph has not earlier been reported fromChaenothecopsis. The similarity between the anamorph ofC.savonicaandAsterophoma mazaediicola, a lichenicolous coelomycete occurring in the mazaedia ofCaliciumspecies, is striking.Asterophoma mazaediicolawas grown from conidia, and conidiomata developed in culture. It is suggested thatA.mazaediicolais the anamorph of aChaenothecopsisspecies. In some cultures ofC.savonica, aPhialophora-likehyphomycetous synanamorph developed. Key words: Mycocaliciaceae, Chaenothecopsis, Asterophoma, Phialophora, anamorphs, cultures.

ISSN:0008-4026    

DOI:10.1139/b91-301

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

We conducted a population genetic study of the western gall rust fungus (Peridermium harknessii) using isozymes as genetic markers. Electrophoresis of 341 single-gall aeciospore isolates collected from several pine species revealed that western gall rust is comprised of two distinct zymodemes (multilocus electrophoretic types) in the western United States. Within zymodemes, all 15 loci studied were monomorphic (0.95 criterion), although variants were found at low frequencies (≤ 0.03) at 3 loci. Zymodeme I was characterized by single bands, indicating homozygosity at all loci; it consisted of isolates from all pine species and environments studied, including the Pacific Coast and Cascade Ranges and the Sierra Nevada and Rocky Mountains. Zymodeme II, which was absent from coastal forests, was characterized by double or triple bands at 6 of 15 loci. The additional bands were interpreted as products of alternative alleles in heterozygous condition; isozyme phenotypes at the other nine loci were identical to those of zymodeme I. Presumed heterozygotes were fixed within zymodeme II, and homozygotes of alleles unique to this zymodeme were not found. Generally, all isolates sampled from a forest stand were in the same zymodeme, and when isolates from both zymodemes were found in the same location, recombinant genotypes between zymodemes were not observed. Such extreme disequilibrium is inconsistent with sexual reproduction, indicating thatP.harknessiiis asexual.Key words: western gall rust,Pinusspp., genetic variation.

ISSN:0008-4026    

DOI:10.1139/b91-302

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

A sequence of ectomycorrhizal colonization was observed on lateral roots ofAfzelia africanaSm. seedlings. Four ectomycorrhizal types were obtained by a baiting method. Among the four types, two were recognized as occurring first in the ectomycorrhizal colonization sequence and the others occurred later. This sequence of ectomycorrhizal colonization was interpreted as follows: initial ectomycorrhizal types were related to the presence of vegetative propagules in the soil (mycorrhizal root fragments, fragments of mycelial strands, and sclerotia) and to the ability of the hyphae from these propagules to grow and quickly colonizeAfzeliaroot systems. The time required for mycorrhizal colonization from spores, however, would be much longer. The types of mycorrhizal symbionts that were established first did not affect subsequent mycorrhizal colonization. An ultrastructural study suggested that vegetative propagules could function either as structures for long-term survival of the fungus in the soil or as structures for immediate opportunistic root colonization.Key words: ectomycorrhizal colonization, baiting method, fungal propagules, early stage fungi,Afzelia africana.

ISSN:0008-4026    

DOI:10.1139/b91-303

出版商:NRC Research Press    

年代:1991

数据来源: NRC