摘要:

Five pathogenic species predominated among the numerous isolates ofFusariumobtained from diseased roots of alfalfa and sweet clover in Alberta. Of these, the closely related speciesF.avenaceum(Fr.) Sacc. andF.arthrosporioidesSherb. appear most important, because they occur commonly and can cause serious injury to the roots, both in the early spring and during the growing season.F.culmorum(W.G.Sm.) Sacc. is very virulent during the summer, but is apparently non-pathogenic in the early spring. At both timesF.Poae(Peck) Wr. andF.ScirpiLamb, et Fautr. var.acuminatum(Ell. et Ev.) Wr. usually behave as weak pathogens. With the exception ofF.avenaceumon alfalfa and sweet clover, andF.Scirpivar.acuminatumon alfalfa, these species have not been previously reported as occurring on the host plants indicated.Cardinal temperatures for growth in pure culture were:—F.avenaceumandF.arthrosporioides: − 2°, 24°, and 34 °C.;F.culmorum: 3°, 24° to 27°, and 34° to 36 °C.;F.Poae: −2°, 20° to 24°, and 32 °C.;F.Scirpivar.acuminatum: 1°, 24°, and 34 °C. All five species grew well at hydrogen ion concentrations ranging from pH 4.0 to 9.5. Carbon dioxide concentrations up to 20% had very little effect on the growth ofF.avenaceum,F.arthrosporioides, orF.Poae, but the higher concentrations retarded the growth ofF.culmorumandF.Scirpivar.acuminatum. The retarding effect of carbon dioxide was greater at 5 °C. than at room temperature.F.avenaceumproduced more infection at temperatures up to 24 °C. than at 27 °C. At 27 °C., infection was much lighter in dry soil than in moist soil.F.culmorumcaused severe damage at 18° to 27 °C., but did not attack the roots at low temperatures.F.avenaceumusually attacked roots of sweet clover more severely than those of alfalfa. All varieties of both hosts tested proved susceptible. In the absence of wounds,F.avenaceumreadily entered roots through the basal tissues of branch roots, or through lenticels. Variant forms of this pathogen, which occurred frequently in pure culture, proved decidedly less pathogenic than the original isolates.Alfalfa and sweet clover roots were attacked by an isolate ofF.avenaceumobtained from diseased roots ofVicia Americana,F.avenaceum,F.arthrosporioides, andF.culmorumfrom alfalfa and sweet clover proved pathogenic to roots ofTrifoliumspp. and to seedlings of wheat, oats, and barley. Certain isolates from the cereals were pathogenic to roots of alfalfa and sweet clover, and thus certain limits to crop rotation in reducing the root-rot damage caused by these pathogens are indicated.

ISSN:1923-4287    

DOI:10.1139/cjr37c-037

出版商:NRC Research Press    

年代:1937

数据来源: NRC

摘要:

Crossing technique is discussed with respect to coincidental flowering of parental plants, emasculation, bagging, tagging, marking, collection of pollen and pollination.Data are presented which demonstrate that stigmas of emasculated wheat florets retain their receptivity, and may be successfully pollinated, a week or more after the normal time of flowering. It is also shown that wheat andAgropyronpollen may be stored under room conditions for a day or two without appreciable reduction in viability. These points are discussed in relation to crossing technique.

ISSN:1923-4287    

DOI:10.1139/cjr37c-038

出版商:NRC Research Press    

年代:1937

数据来源: NRC

摘要:

Substances previously found to be highly toxic when applied to annuals as a spray were also found to be most toxic when added to culture solution. The results by the two methods, however, do not agree as far as the less poisonous chemicals are concerned, certain substances being comparatively more toxic in culture solution than as a spray, andvice versa. These discrepancies can be explained by the fact that the dosage in culture solution was varied by adjusting the concentration, whereas in the spraying test it was varied by altering the volume of spray.The time between treatment and death of the plant generally decreases as the dosage is increased over a limited dosage range, but varies with different chemicals, and appears to be independent of their inherent toxicity.The size of the plant is seriously reduced at dosages that produce no mortality. The final weight, however, was unsatisfactory as a criterion of toxicity since it was extremely variable. The interfering factors affecting the final weight were taken into account by computing the relative growth rate. The curve relating growth rate and dosage is slightly concave upwards when the dosage is plotted on an arithmetical scale and linear when plotted on a logarithmic scale. The position and slope of the line depends on the chemical. The standard error of duplicate tests increases as the growth rate decreases. On the average, complete mortality occurred at a growth rate of − 2.44% per day under the conditions of these experiments, but this is subject to variation due to differences between duplicates, chemicals, and series (plants grown at different times).Analyses of the culture solutions containing chlorates showed that the amount of chlorate taken up by the plant increased with the concentration present in the culture solution. Nevertheless, only a small, relatively constant proportion of the chlorate present was taken up by the plant at all concentrations.

ISSN:1923-4287    

DOI:10.1139/cjr37c-039

出版商:NRC Research Press    

年代:1937

数据来源: NRC

摘要:

In all plant species tested, increasing concentrations of phytohormones produced responses falling on a physiologic curve from minimum through optimum to maximum which, if exceeded, led to injury and death. Indolyl-acetic acid, its butyric and propionic homologues, naphthylacetic acid, their salts, and mixtures gave similar results. Treating seeds with hormones incorporated in adsorbent dust stimulated both root and top growth markedly, with less danger of overdosage than in solution treatment. Dosages equivalent to 50 to 250 mg. per acre applied as dilute solutions to soil growing young lettuce and tomato plants covered the optimum range of stimulation to growth. Dust treatment of cuttings proved very convenient and successful in inducing rooting, the plants again showing a wider range of tolerance to dusts than to solutions. Fermentation of sugar by yeast responded to hormone stimulation. Various practical applications are discussed.

ISSN:1923-4287    

DOI:10.1139/cjr37c-040

出版商:NRC Research Press    

年代:1937

数据来源: NRC