摘要:

Various elements were tested for their effect on the formation of perithecia ofVenturia inaequalis. Apart from nitrogen the elements tested had little effect on the formation of perithecia except at relatively high concentrations. Perithecia did not form in media containing low concentrations of nitrogen and this was influenced by the source of nitrogen and by the cation present in nitrate salts. Perithecial initials developed in higher nitrogen concentrations than perithecia. Nitrogen added 9 weeks after mating of two lines of the fungus prevented the formation of perithecia.Results were difficult to reproduce in a potato-dextrose apple leaf decoction medium but reproducible results were obtained in a synthetic medium.

ISSN:0008-4026    

DOI:10.1139/b61-061

出版商:NRC Research Press    

年代:1961

数据来源: NRC

摘要:

Declines in population of spores ofHelminthosporium sativumin amended soil were due to disappearance that occurred in normal soil and to eradication brought about by the germination–lysis mechanism and by an increase in antagonism. Germination–lysis played a major role in molasses- and vitamin C-amended soils but not in glucose-amended soil, as was evidenced by the density of spore populations in the soils at intervals over a 16-week period.Antagonism which was increased in all three amended soils was responsible to a lesser extent for the eradication of the spores. The data suggest that antagonism was more effective during the early, than during the later, stages in the breakdown of the amendment. A close correlation was noted between spore population and the incidence of seedling infection. Correlation between spore population and disease ratings was much less significant.

ISSN:0008-4026    

DOI:10.1139/b61-062

出版商:NRC Research Press    

年代:1961

数据来源: NRC

摘要:

Nuclear structure and division in the mycelium and basidiospores ofCeratobasidium praticolum(Pellicularia praticola), studied in living and in differently stained preparations, are described and illustrated with photographs. The cells of the mycelium are multinucleate. Nuclear migration occurs from one cell to another through the septal pores. The nuclei consist of a Feulgen-negative nucleolus surrounded by granular Feulgen-positive chromatin. In a nucleus preparing to divide, the nucleolus becomes progressively smaller and finally disappears. The chromatin then elongates, becoming bar-like, and later constricts at the mid-region. New nucleoli appear in the two attached portions of the constricted chromatin. At the end of the division the two portions pull apart to form two sister nuclei. Classic mitotic division as it occurs in higher organisms was not seen. Chromosomal filaments were not discerned in the nuclei of the basidiospores or the mycelium. Chromosomal filaments in reticulate arrangement were observed in the nuclei of the hymenial cells and in the cells of the short, side branches on which the hymenium develops.

ISSN:0008-4026    

DOI:10.1139/b61-063

出版商:NRC Research Press    

年代:1961

数据来源: NRC

摘要:

Chromosome numbers and meiotic behavior were determined in clones ofBromus inermis, Bromus pumpellianus, and theBromus erectuscomplex. Clones ofB. inermiswere octoploid (2n = 56) or near-octoploid, one aneuploid having 2n = 54 chromosomes.B. pumpellianusclones were octoploid, with one bearing a B chromosome.B. erectus-type clones had 56, 59, 65, or 70 chromosomes. Meioses varied widely among plants in extent of irregularity. Meiotic behavior was studied in detail and the sequential interrelationships of irregularities at meiotic stages analyzed. Significant or highly significant positive correlations were obtained for theB. pumpellianusclones between percentages of non-stainable pollen and frequencies of metaphase I univalents, anaphase II laggards, and quartet micronuclei. These relationships were non-significant for theB. inermisandB. erectus-type clones. A significant negative correlation was determined between percentage of non-stainable pollen and percentage of seed set following open pollination, but other relationships between meiotic irregularities or pollen stainability and seed-setting characteristics were non-significant. The wide range in chromosome number and meiotic behavior encountered in material commonly distributed on this continent as "B. erectus” may be due to interspecific hybridization in nurseries in whichBromusintroductions are grown. Interspecific hybridization may be partially responsible also for aneuploidy and meiotic irregularity inB. inermis.

ISSN:0008-4026    

DOI:10.1139/b61-064

出版商:NRC Research Press    

年代:1961

数据来源: NRC

摘要:

Extracts from primary leaves of Lee wheat were prepared at various days following inoculation with races of leaf rust and tested for ribonuclease (RNase) activity. As early as 24 hours after inoculation there was a marked increase in the specific activity of the enzyme in extracts of rusted host tissues. A further increase in activity was observed during later stages of infection, with the susceptible and resistant reacting tissue differing only in the degree of their response. Extracts from noninoculated control leaves exhibited a constant RNase activity throughout the period of observation. The germination medium and extracts from germinating uredospores contained comparatively little RNase activity. No direct evidence was obtained either for the possible release of the enzyme from particulate cellular fractions of the host tissue as a result of infection or for the removal of an RNase inhibitor in the host tissue responding to infection.

ISSN:0008-4026    

DOI:10.1139/b61-065

出版商:NRC Research Press    

年代:1961

数据来源: NRC

摘要:

Heterocaryons involving nutritionally deficient mutant strains ofGibberella fujikuroiand mutant strains of this species and of four formae ofFusarium oxysporumwere obtained. It was not possible to get heterocaryons ofG. fujikuroiandF. oxysporumf.pisiuntil the latter mutant strain was adapted to grow on minimal medium. Spores from heterocaryons had either the genotype of only one component strain or of either component strain, depending on the heterocaryon. It was possible to alter nuclear ratios by growing certain heterocaryons on minimal medium supplemented with the compound(s) required by one or the other component strain. Sectors from certain heterocaryons grown on potato dextrose agar were homocaryotic for the nutritional requirement(s) of one component strain. Heterocaryosis as a taxonomic tool and the difficulties involved in demonstrating the parasexual cycle in the genusFusariumare discussed.

ISSN:0008-4026    

DOI:10.1139/b61-066

出版商:NRC Research Press    

年代:1961

数据来源: NRC

摘要:

Fifty isolates ofAscochyta imperfectafrom alfalfa seed grown in Ontario, Manitoba, Saskatchewan, Alberta, and British Columbia produced varying degrees of infection on excised leaves ofMedicago falcata, Medicago sativa(three strains),Melilotus alba, Melilotus officinalis, Trifolium pratense, Lotus corniculatus, Pisum sativum, andVicia faba. Ftests from analyses of variance of disease ratings showed that the differences in susceptibility between hosts and between strains ofMedicagowere highly significant. Among the 10 hosts and within the strains ofMedicago, the interaction isolates × hosts was highly significant. Thus, specificity among the isolates was clearly demonstrated. This is interpreted to mean that parasitic strains existed among the 50 isolates.A. imperfectawas isolated from 50 to 70% of the seed samples from each province. The heaviest infestation was on seed from Manitoba, where the weather at harvest time was wet and where the crop overwintered in the field.

ISSN:0008-4026    

DOI:10.1139/b61-067

出版商:NRC Research Press    

年代:1961

数据来源: NRC

摘要:

Comparative studies have shown that branch infections are almost twice as frequent in aspen (Populus tremuloidesMichx.) in mesic sites as in trees of similar ages in dry sites. This has been attributed to: (1) the proneness to infection of young dead branches, and (2) the greater mortality of young branches in mesic sites. No difference was found between the two sites with respect to the pattern of air temperature and relative humidity. The moisture content of dead branches was influenced to a minor extent by site, but only after considerable rain had fallen did branch moisture reach a level favorable for infection by fungi. Although several species of imperfect fungi and bacteria infected aspen branches from 4 years following mortality, wood-destroying fungi, namelyCorticium polygoniumPers. andPolyporus adustus(Willd.) Fr., did not appear until 7 and 8 years after the death of branches. After 19 years, decay ofFomes igniarius(L. ex Fr.) Kickx. occurred in branches only as lateral extensions of heartwood infection. The feasibility of artificial pruning to reduce the risk of heart rot infection in young aspen stands is discussed.

ISSN:0008-4026    

DOI:10.1139/b61-068

出版商:NRC Research Press    

年代:1961

数据来源: NRC

摘要:

A new genus,Thysanophora, based onHaplographium penicillioidesRoum., is proposed. Two species are placed within the genus:Thysanophora penicillioides(Roum.) Kendrick comb. nov. is redescribed from 32 collections and isolations, andThysanophora longisporaKendrick sp. nov. is described from four collections on decaying needles ofTsuga canadensisand an isolation derived from one of these collections.

ISSN:0008-4026    

DOI:10.1139/b61-069

出版商:NRC Research Press    

年代:1961

数据来源: NRC

摘要:

Hormodendrum staurophorumsp. nov., a pleomorphic dematiaceous hyphomycete isolated from fallen needles ofPinus sylvestris, is described and illustrated.

ISSN:0008-4026    

DOI:10.1139/b61-070

出版商:NRC Research Press    

年代:1961

数据来源: NRC