摘要:

Tobacco etch is one of the most prevalent and injurious viruses on sweet peppers in southern Ontario. The virus occurs in several strains. Detailed descriptions of symptoms produced by etch on sweet, hot, and semihot varieties of peppers are described. Symptoms on the pepper fruits have been observed chiefly on the sweet types. The widespread occurrence of etch in peppers is attributed to the prevalence of the vectorMyzus persicaeSulz. Possible sources of etch that may give rise to epidemics on pepper and tobacco crops in southern Ontario are discussed.

ISSN:0008-4026    

DOI:10.1139/b54-011

出版商:NRC Research Press    

年代:1954

数据来源: NRC

摘要:

The effectiveness of methyl bromide (Dowfume MC-2, 98% methyl bromide and 2% chloropicrin) as a fumigant for controlling diseases in seedbed soils used for the production of vegetable seedlings under glass was studied. A differential response of the microfloral components of a sandy loam compost soil to the lethal action of methyl bromide was observed. In general, fungi were destroyed at lower concentrations than were bacteria and actinomycetes. Of the pathogenic fungi tested,Fusarium oxysporumf.niveumand aFusariumsp. causing root decay of onion seedlings were found to be the most resistant to the lethal action of methyl bromide. Whereas the former was destroyed by a dosage of. per 100 cu. ft. in sandy loam soil and the latter by a dosage of 2 lb. in muck soil,Pythiumsp.Rhizoctonia solani, and several other pathogenic fungi were destroyed by a much lower dosage, namely, that of. per 100 cu. ft. Bacteria showed a broader range of variability than the fungi in their tolerance of methyl bromide. WhereasXanthomonas vesicatoriaandRhizobium trifoliiwere destroyed at dosages of 1–2 lb. per 100 cu. ft.,Pseudomonas tomatooccurring in shallow lesions on tomato fruits and several spore-forming bacteria occurring in the soil were not destroyed at dosages of 4 lb. per 100 cu. ft. The benefits derived from the fumigation of a sandy loam compost soil with methyl bromide were reflected not only in the freedom of vegetable seedlings from disease but also in their increased and uniform growth. Some vegetables showed greater growth in fumigated than in steam-sterilized soil, whereas others showed the opposite effect.

ISSN:0008-4026    

DOI:10.1139/b54-012

出版商:NRC Research Press    

年代:1954

数据来源: NRC

摘要:

The genusDurandiella, founded onPeziza fraxiniSchw., includes a group of inoperculate Discomycetes occurring on twigs and branches of woody plants. The apothecia are flat, black, very hard in consistency, and have eight-spored asci with filiform ascospores. All of the species have subfiliform conidia of similar form, but the form of the conidial fruiting body varies in different species. Nine species are included in the genus of which two are described as new species, and new combinations are created for five.

ISSN:0008-4026    

DOI:10.1139/b54-013

出版商:NRC Research Press    

年代:1954

数据来源: NRC

摘要:

An investigation of western hemlock (Tsuga heterophylla(Raf.) Sarg.) in the Upper Columbia region has shown that decay losses are excessive, amounting to 52 and 74% in terms of cubic and board foot computations respectively. The logs of 833 hemlock on 36 sample plots located in mature timber were analyzed in detail. Twenty-six decay-producing fungi have been isolated. Sixty-two per cent of the total decay was attributed toEchinodontium tinctoriumEll. & Ever. and 25% toFomes pini(Thore) Lloyd. Considerable variation in the fungi responsible for decay was encountered intraregionally. Stand defect losses varied from 38 to 71%. Some of this variation could be predicted on the basis of the site index determinations of hemlock. Relative to the total incidence and importance of decay,Echinodontium tinctoriumdecreased andFomes piniincreased in significance with increasing site quality. Sporophores, scars, dead tops, large rotten branches, swollen knots, frost cracks, forked trees, and trunk infections of mistletoe were classed as indicators of significance in relation to hidden defect. Living trees, classed as Suspect or Residual depending on the presence or absence of one or more reliable indicators of defect, were found to differ appreciably in average defect. Within each of the preceding classes decay increased progressively with increasing diameter and decreasing site quality. Immature hemlock was found to be susceptible to appreciable decay and mature stands reached an advanced stage of deterioration at 250 years. Multiple correlation analyses between percentage of decay, site, age, and the relative percentage of Residual trees weighted by volume permitted an estimate of total stand defect within ± 7%.

ISSN:0008-4026    

DOI:10.1139/b54-014

出版商:NRC Research Press    

年代:1954

数据来源: NRC

摘要:

Gnomonia fructicola(Arnaud) Fall was isolated from strawberries growing in various localities in Ontario and Quebec. This fungus was found to be capable of causing serious damage to strawberries under certain environmental conditions. The disease occurs on fruits, peduncles, and leaf petioles and blades. On the leaves, the first symptoms are numerous pin-point lesions which enlarge and coalesce, and finally cover large areas of the blades or entirely girdle the petioles. The fungus was found to enter the stomata of artificially inoculated leaf blades. In the host, the fungus tends to follow the vascular elements along which the pycnidia and perithecia are usually formed. Pathogenicity ofG.fructicolawas compared with that of leaf blight, leaf scorch, and leaf spot of the strawberry. It was demonstrated that, under the conditions described, it was capable of causing as much damage as any of the three diseases. The results obtained from nutritional experiments indicate that high concentrations of dextrose suppress, whereas those of starch, cellulose, and pectin favor the growth and reproduction ofG.fructicola.

ISSN:0008-4026    

DOI:10.1139/b54-015

出版商:NRC Research Press    

年代:1954

数据来源: NRC

摘要:

The chromosome numbers of three introduced species ofCentaureaare here reported:C.diffusaLam., 2n = 18;C.maculosa, Lam., 2n = 36;C.repensL., 2n = 26. The chromosome counts ofC.diffusaand ofC.maculosa, which are here reported for the first time, help to clarify a taxonomic problem. A pappus is usually lacking on the achenes ofC.diffusabut is present on those ofC.maculosa. As a result, plants ofC.diffusawith a short pappus have been considered to be possible hybrids between these species. Three such plants here studied had the diploid chromosome number 18, rather than the triploid number to be expected in such a hybrid. Examination of pollen of suspected hybrid specimens shows that the percentage of normal pollen is high. This fact also supports the belief that plants ofC.diffusawith a short pappus on the achene are not hybrids withC.maculosa.

ISSN:0008-4026    

DOI:10.1139/b54-016

出版商:NRC Research Press    

年代:1954

数据来源: NRC

摘要:

Seven thin coal seams from the uppermost Cretaceous strata (Brazeau) of Western Alberta are investigated with the purpose of revealing the existence of classifiable fossil spores and pollens which may be significant as index units in stratigraphic differentiation. Thirty-four microfossils are classified, described, and illustrated. Relationships to previously known macrofossils or modern plants are suggested. One spore is bryophytic, nine are pteridophytic in affiliation, and one microfossil type possibly represents a fungal spore. Twelve pollens show gymnosperm relationship, and 11 fall within the Angiospermae. A distributional pattern indicates occurrences and associations of 14 microfossils occurring in frequencies of 5% or greater within the coals. Differences between the Brazeau macro- and microflora are evalutated in terms of applicability to stratigraphic definition.

ISSN:0008-4026    

DOI:10.1139/b54-017

出版商:NRC Research Press    

年代:1954

数据来源: NRC

摘要:

Two trips were made from Montreal, Que., to London, England, in June and August, 1951, and samples of bacteria and fungi were obtained throughout the flight using quantitative and qualitative methods. Three sampling methods were used, employing the McGill G.E. and slit samplers and a filter. Plates were used, supplemented by silicone slides in the slit sampler. Bacteria varied from 0.0 to 0.05 per cu. ft. in polar air and 0.03-0.9 per cu. ft. for tropical air over the ocean in June. Fungi in polar air ranged from 0.1 to 0.9 per cu. ft. and from 0.2 to 9.0 per cu. ft. in tropical air in June. There was very little difference in the June, and August flights as far as viable organisms were concerned. Fungus spores showed striking differences in air masses. Polar air over the ocean had a maximum of 3.9 per cu. ft. in August whereas tropical air had a maximum of 15.1 per cu. ft. in June. Over land in August a maximum of 361.4 fungus spores per cu. ft. was obtained in tropical air over eastern Canada.Cladosporiumwas the commonest fungus, withAlternaria,Pullularia, yeasts,Penicillium,Botrytis, andStemphyliummost numerous among 27 types. Of the 4991 colonies the above occurred as 82.3, 2.6, 2.3, 2.1, 1.6, 1.5, and 1.1% of the total.Micrococci,Sarcina, Gram negative rods, Gram positive pleomorphic rods, and aerobic sporeformers occurred as 41.4, 4.3, 20.4, and 33.2% in June and 13.2, 20.7, 37.0, and 29.0% of the total in August.

ISSN:0008-4026    

DOI:10.1139/b54-018

出版商:NRC Research Press    

年代:1954

数据来源: NRC

摘要:

Germinating sporidia ofPuccinia coronataCorda f. sp.secalisPeturs. were examined cytologically during mitotic nuclear division to determine the chromosome number. Studies at metaphase and anaphase revealed a haploid number of three chromosomes in this rust. The possibility of a polyploid series in the genusPucciniais discussed.

ISSN:0008-4026    

DOI:10.1139/b54-019

出版商:NRC Research Press    

年代:1954

数据来源: NRC

摘要:

Evidence is presented to prove that stunting of clovers in Essex County, Ontario, in 1952 was caused by root parasitizing strains ofRhizoctonia solaniKühn (Corticium solani(Prill. & Del.) Bourd. & Galz.). Typical symptoms of stunt were reproduced in greenhouse tests with isolates of this fungus but the isolates varied in their pathogenicity to red clover, alfalfa, sweet clover, and alsike clover.

ISSN:0008-4026    

DOI:10.1139/b54-020

出版商:NRC Research Press    

年代:1954

数据来源: NRC