摘要:

Morphological studies of theCarex strictacomplex confirm hypotheses based on chromosome numbers that there are three distinct species in eastern North America,Carex stricta,C.emoryi, andC.haydenii, but they do not indicate the existence of any distinct infraspecific taxa. These species are compared phenetically with all other North American species of sectionPhacocystis. Results indicate that the three species examined here do not form a closely related subgroup within the section as suggested by previous authors. Distribution maps, descriptions, and synonomy are provided for these species, and a complete key to the species of sectionPhacocystisin eastern North America is given.

ISSN:0008-4026    

DOI:10.1139/b89-001

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

The zone of antagonism, known as the "black line," that occurred between the confronting margins of diploid isolates of differentArmillaria melleacomplex species was enhanced by incubation inL-β-3,4-dihydroxyphenylalanine (L-DOPA). Intraspecific crosses and crosses of genetically identical isolates did not produce a black line after similar treatment withL-DOPA.

ISSN:0008-4026    

DOI:10.1139/b89-002

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

When the effect of nonsterile soil on vesicular–arbuscular mycorrhizal fungus spore germination was examined, significantly fewerGlomus etunicatum(22 vs. 63 and 64%) orGlomus mosseae(23 vs. 80 and 79%) spores germinated in nonsterile soil than in autoclaved or pasteurized soil, respectively. In some cases, addition of nonsterile soil sievings to autoclaved or pasteurized soil also reduced germination, as compared with germination in unamended pasteurized or autoclaved soil. Germination was reduced by as much as 45% in autoclaved or pasteurized soil if spores were surface sterilized. However, surface sterilization ofG.etunicatumspores did not affect dry weight of inoculated big bluestem plants, but mycorrhizal root colonization was reduced when spore-associated microbes were removed from spores by surface sterilization. The detrimental effect of soil microbes on spore germination and mycorrhizal growth response may reflect microbial competition for nutrients since germination ofG.etunicatumandG.mosseaewas reduced when pasteurized soil was amended with 15, 30, or 60 ppm phosphorus and 60 ppm phosphorus, respectively. An optimum range of available phosphorus may exist, above or below which germination is suppressed.

ISSN:0008-4026    

DOI:10.1139/b89-003

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

The floral phenology, compatibility system, and pollinator fauna ofOpuntia imbricata(Haw.) DC. in southern Colorado were studied. The plants bloom for approximately 4 weeks in June and July.Opuntia imbricatasets numerous seeds when it is open-pollinated or experimentally cross-pollinated; it is self-incompatible and not apomictic. The most effective pollinators were found to be medium to large bees of the generaDiadasiaandLithurge; beetles are ubiquitous on flowers ofO.imbricata, but probably do not effect pollination because they rarely move from flower to flower and usually restrict their activities to the stamens and base of the inside of the flowers.

ISSN:0008-4026    

DOI:10.1139/b89-004

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

The ability of ectomycorrhizal fungal isolates to tolerate imposed water stress in pure culture was examined in 55 isolates of 18 species. Water potential treatments, adjusted with polyethylene glycol, were applied to Petri dish units. These units allowed colony diameter measurements of fungi grown on liquid media. Delayed growth initiation and inhibition of growth rate occurred with increasing water stress. For 87% of the isolates, growth rate was inhibited by the initial water potential treatment applied, leaving only seven isolates where growth increased with initial water potential treatments. No growth was evident under the imposed stress treatments for isolates ofLaccaria bicolor,Laccaria laccata, andLactarius controversus; growth occurred only in the control. Drought tolerant species, demonstrated by an ability to grow at a water potential of −3 MPa, includedBoletus edulis,Cenococcum geophilum,Rhizopogon vinicolor, and five out of eightSuillusspecies. Species intolerant of −1 MPa includedHebeloma crustuliniforme,Laccaria bicolor,Laccaria laccata, andSuillus caerulescens. Fungal drought tolerance was poorly correlated with estimates of annual precipitation for collection locations. Estimates of drought tolerance seems to depend more on fungal classification than on annual precipitation at the site of collection. Reisolation ofLaccaria bicolorincreased growth rate and water stress tolerance when compared with the same fungus prior to reisolation.

ISSN:0008-4026    

DOI:10.1139/b89-005

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Treubiomyces pulcherrimusresemblesChaetothyrium, type of the family Chaetothyriaceae, in the following characters: a pale superficial mycelium appressed to the cuticle of living plants; a globoid ascoma developing beneath a mycelial shield, with which the ascoma is fused in the apical region; a centrum composed of a basal fascicle of aparaphysate asci; a palisade of short periphysoids projecting downward from the roof of the locule to the tips of the asci; and a schizogenous, periphysate ostiole. The asci have a conspicuous refractive ring in the thickened wall at the apex. Ascospores are discharged forcibly, but dehiscence of the presumed bitunicate asci could not be demonstrated. Mycelial cultures were obtained from ascospores discharged onto agar plates. No conidia were found in culture or field material.

ISSN:0008-4026    

DOI:10.1139/b89-006

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Justifications for recognizingH.brachyantherumNevski andH.californicumCovas as separate species are provided from multivariate morphometric analyses and from lodicule and epiblast characters. Although the range of variation of the latter species is included in the range of the former for most morphometric characters, the two are distinct when all of the characters are in multivariate space. Furthermore,H.brachyantherumis allotetraploid (2n = 4X = 28) andH.californicumis diploid (2n = 2X = 14) as previously reported. Identification to species can be done with a high degree of accuracy by means of the linear classification function coefficients, which after cross validation using the bootstrap method, has been found to be reliable, by the lodicules and epiblasts, or more conclusively by the chromosome number.

ISSN:0008-4026    

DOI:10.1139/b89-007

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Volatiles released from sweet potato storage root tissue infected by different sweet potato storage root pathogens stimulated eruptive germination of sclerotia ofSclerotium rolfsiibut did not influence the direction of hyphal growth on agarose. Volatiles from healthy sweet potato storage root tissue did not affect percent hyphal or eruptive germination of sclerotia ofS.rolfsiibut stimulated directional growth of hyphae toward the healthy tissue. In laboratory experiments, the frequency of infection of sweet potato stem segments byS.rolfsiion the surface of natural soil was increased when sclerotia were incubated in the presence of decaying sweet potato storage root tissue. Incidence of sclerotial blight lesions on sprouts in plant beds was increased in the presence of roots infected byFusarium solaniorErwinia chrysanthemi. Volatiles from decaying sweet potato mother roots may predispose sweet potatoes to sclerotial blight.

ISSN:0008-4026    

DOI:10.1139/b89-008

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

A comparison of the histological responses of species within thePhaseolus–Vignaplant complex to single isolates of the bean and cowpea rust fungi revealed that no particular response was restricted to any plant taxonomic group, although species differed in the proportion of infection sites at which a particular response was exhibited. Related species did not always show similar frequencies of responses and sometimes there were differences between different genotypes within a nonhost species. In host and nonhost species, preinoculation heat treatment commonly inhibited prehaustorial defenses and delayed the death of the invaded cell. Growing fungal colonies subsequently developed in many species, even those considered nonhosts, particularly if they exhibited a high frequency of prehaustorial defenses in untreated leaves. It is argued that a lack of heat-induced colony formation is a sign of parasite-specific resistance, which most likely evolved only in originally susceptible plants. Consequently, the data suggest that the bean rust fungus has had a long association with American species of the complex and that extant nonhost species may have evolved from susceptible ancestors. In contrast, the cowpea rust fungus appears to have had little evolutionary contact with these American species and may not be as closely related to the bean rust fungus as originally thought.

ISSN:0008-4026    

DOI:10.1139/b89-009

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

In maize, the DNA content and [3H]thymidine incorporation in embryonic cells and the nuclease activity in the fraction extracted from embryonic cells were determined in a heterotic F1hybrid (Oh545 × W22) and its parental inbred lines. DNA content was higher in the F1hybrid than in parental lines; however, [3H]thymidine incorporation was greater in W22 than in the F1hybrid. Herring DNA splitting activity was higher in W22, and the yeast RNA hydrolyzing activity was almost the same in the F1hybrid and W22. Oh545 had the lowest value in each of these parameters. It is suggested that qualitative and quantitative differences in DNA synthesis during the germination period between the F1hybrid and the parental lines are related to the expression of heterotic vigor.

ISSN:0008-4026    

DOI:10.1139/b89-010

出版商:NRC Research Press    

年代:1989

数据来源: NRC