摘要:

Growth ofB.polymyxaover a 72 hr. period was not significantly affected by the brown, fluorescent materials formed by the reaction between dextrose and protein constituents of the media. During the first 24 hr. after inoculation a slight inhibition was evident in autoclaved yeast extract media, and in casein hydrolyzate media to which additional amino acid – dextrose reaction products had been added, but the inhibitory effects were never marked and disappeared within 48 hr.

ISSN:1923-4287    

DOI:10.1139/cjr49c-023

出版商:NRC Research Press    

年代:1949

数据来源: NRC

摘要:

A saltant ofH.sativumdisappeared from six different soils in which it was cultured in the laboratory within four weeks, whereas the indigenous flora persisted for nine weeks. During this nine week period numbers of bacteria showed no obvious trend, but numbers of fungi decreased. When cultured in sterilized portions of the above soils, the saltant showed a downward trend in numbers in the nine week period, a trend that was more obvious in some cultures than in others. Twenty-two of 221 isolates of fungi from soil, grain, and air, 45 of 286 isolates ofStreptomyces, and 33 of 193 isolates of other bacteria produced evidence of antagonism to the saltant in spot inoculation studies. Filtrates prepared from two of the fungal isolates suppressed the growth of the saltant, as did also autoclaved portions of the nitrates. On the contrary, filtrates from three cultures of bacteria failed to suppress growth of the saltant, even though cultures of the bacteria did. The same 22 fungal isolates and 25 of theStreptomyces, when introduced separately into sterile soil along with the saltant, reduced the disease rating of barley seedlings below that produced by the saltant alone. The direct-count method of estimating numbers of spores of the saltant in a suspension was found to be reliable. Estimates based on the direct count were significantly greater than those made by the plate method. Estimates based on numbers of the saltant developing on potato dextrose agar containing small amounts of sterile soil were smaller than those made on the same medium without the soil. Even though the soil in the medium changed the pH of the medium, the difference in pH was considered not to be the primary factor in producing the lower estimates. Soil, either natural or heat sterilized, would contain the thermostable filterable substance or substances found to be produced by two species of fungi and probably produced by other species, likewise normally present in soil.

ISSN:1923-4287    

DOI:10.1139/cjr49c-024

出版商:NRC Research Press    

年代:1949

数据来源: NRC

摘要:

In southern Ontario rootrot of sugar beets may be caused byAphanomyces cochlioidesDrechs.,Pythium aphanidermatum(Edson) Fitz.,Pythium ultimumTrow, orRhizoctonia solaniKuehn. The distribution of these fungi was found to be limited to soil type rather than to locality,A.cochlioidesthus being found in the clay soils andP.aphanidermatumonly in the sand loam. They were not present in the subsoil and were most abundant in the top two or three inches of surface soil.A.cochlioides, which was found for the first time in Canada in 1946, causes the so-called blackroot of sugar beets, and is the most economically important pathogen encountered. Blackroot appears either as an early acute attack or a later chronic one, but the acute phase is of major importance and occurs in epiphytotics during seedling development, usually when the beet is from two to five weeks old. Weather records and experiments have shown that serious disease outbreaks only occur when moisture is abundant and soil temperature exceeds 60° F. Susceptibility is sharply correlated with the developmental rhythm of the seedling and ends when the cortex of the hypocotyl is sloughed off.A.cochlioidesis homothallic, attacks the hypocotyl of the beet, and develops in the intercellular spaces of the cortex. It will not grow at relative humidities of less than 99% and this sensitivity to all but extremely high humidity is believed to limit its parasitic activity. Microbiological studies indicated that the number of organisms in the rhizosphere of diseased sugar beet roots is much larger than in that of healthy beet roots. Since parallel rhizosphere responses followed local artificial killing of roots, they are believed to be due in part at least to the utilization of necrotic tissues or substances released on their breakdown. Streptomycin, but not penicillin, was effective in controlling rootrot in greenhouse experiments. Control with Arasan is achieved in part through a direct fungicidal action, but the evidence suggests that it may be due to a shift in the microbiological balance of the soil flora unfavorable to the pathogen.

ISSN:1923-4287    

DOI:10.1139/cjr49c-025

出版商:NRC Research Press    

年代:1949

数据来源: NRC

摘要:

An investigation of decay in western hemlock (Tsuga heterophylla(Raf.) Sarg.) and fir (mainlyAbies amabilis(Loud.) Forb.) in the Juan de Fuca forest region of British Columbia has shown that the major organisms causing root and butt rots are the same in both species. These arePoria subacida(Peck) Sacc.,Fomes annosus(Fr.) Cke.,Armillaria melleaVahl ex Fr.,Polyporus sulphureusBull. ex Fr., andP.circinatusFr. Those organisms causing trunk rots of western hemlock, in decreasing order of importance, areFomes pinicola(Sw.) Cke.,F.Pini(Thore) Lloyd,Stereum abietinumPers.,Fomes Hartigii(Allesch.) Sacc. and Trav., andHydnumsp. (H.abietis). These same organisms causing trunk rots of fir, in decreasing order of importance, areFomes pinicola,Stereum abietinum,Hydnumsp. (H.abietis),Fomes Pini, andFomes Hartigii. The logs of 963 western hemlock were analyzed in detail. Maximum periodic volume increment was reached between 225 and 275 years of age. Maximum periodic volume increment was reached between 275 and 325 years of age in the 719 fir that were analyzed. Scars were the most frequent avenue of entrance for infection. In 59% of the cases of infection studied the fungus had entered through wounds.

ISSN:1923-4287    

DOI:10.1139/cjr49c-026

出版商:NRC Research Press    

年代:1949

数据来源: NRC

摘要:

Fatuoid, steriloid, and subfatuoid oats and speltoid, compactoid, and subnormal wheats arise by mutation which in most cases can clearly be shown to be a chromosome aberration. In all three segregation-types of speltoids, Series α, β, and γ, deficiency is definitely established. It ranges from the whole of one particular chromosome, designated C, down to a segment of C too small to be established microscopically, with certainty, at metaphase but still determinable genetically as a deficiency and not a single gene mutation. In the oat mutants there are similar deficiencies but the range apparently extends below the present limit of both cytological and genetic determination. At this point it naturally cannot yet definitely be differentiated from gene mutation, though no evidence favors the latter alternative. In compactoid and subnormal wheats duplication of the whole C chromosome or of its major arm is involved. Natural crossing, particularly between wild and cultivated oats, complicates the problems and is of practical agricultural significance. A distinction can, however, almost invariably be drawn between such hybrids and the mutants. The origin of the mutants and their survival and peculiar genetic behavior are all bound up with the polyploid nature of cultivated oats and wheat. This particularly affects the viability of deficient gametes. The frequency with which different types of gametes are formed is determined by meiotic behavior, which is dependent upon the particular aberrant constitution or the mutant in question; the decree of deficiency or duplication in the gametes affects their selective functioning. All these factors, together with the usual differential between ovules and pollen in the functioning of aberrant gametes, determine the diverse segregation ratios that may be obtained from phenotypically similar mutants.

ISSN:1923-4287    

DOI:10.1139/cjr49c-027

出版商:NRC Research Press    

年代:1949

数据来源: NRC

摘要:

The bearded speltoids that are found in beardless varieties ofTriticum vulgareare usually segregates from heterozygous speltoids that have arisen through mutational loss of two genes, or gene complexes, that normally determine the glume and, to a lesser extent, the lemma and rachis characteristics that predominantly differentiateT.vulgarefromT.spelta, which is possibly one of its ancestors. These "vulgare" genes are epistatic to genes that in their absence determine indurated, sharply and heavily keeled glumes and bearded lemmas closely resembling those ofT.spelta. The two "vulgare genes" are both on one chromosome ("C" or "IX"); the hypostatic "spelta" or speltoid genes are probably multiple and have not yet been definitely located.The "vulgare" genes or gene complexes may be lost independently, giving (after segregation) "part-mutations", i.e. beardless speltoids or bearded normals, or they may be lost together, giving the "total mutation" i.e. bearded speltoid. The mutations that produce the "part-mutants" are necessarily segmental changes, but the total mutants may arise through either segmental or whole chromosome loss.Loss of an entire C chromosome gives a β het speltoid which, on selfing, gives normal, het speltoid, and bearded speltoid offspring in a ratio varying about the mode 1:5: few. These β bearded speltoids are dwarf, sterile nullisomics having only 20 pairs of chromosomes, 20II– –, in place of the 21IInormal forT.vulgare. The characteristic β Series ratio and its variations are mainly determined by the frequency with which the unpaired C of a β het speltoid is left out of the gynospore nuclei during meiosis and by the lower functioning of 20-chromosome pollen. Zygotic elimination plays a minor role.Deletion of an appreciable interstitial segment, or the whole, of the long arm of C produces γ het speltoids which on selfing give normals, het speltoids, and speltoids in ratios near 1:1: few. If the segment deleted involves both gene complexes the speltoid segregates are bearded and more or less dwarfed and partially sterile. If it does not involve the beard "inhibitor" they are beardless. The γ ratio is determined largely by the lower functioning of pollen carrying the deletion.Deletion of a segment of C too small to be established definitely at metaphase but genetically determinable as of not less than about 30 cross-over units in length gives α het speltoids that segregate normals, het speltoids, and bearded speltoids in ratios approaching 1:2:1 and all segregates are of normal size and fertile. Evidently this deletion does not materially affect pollen functioning.Hybridization and polyploidy have been involved in the evolution ofT.vulgareand it is the latter which permits the functioning of gametes bearing deficient chromosome complements and the survival of aberrant types that would be unlikely to exist in a diploid species. The hybrid ancestry accounts for quantitative chromosome changes being able to produce forms that closely resemble ancestral or related species, and also for the fact that crosses between varieties ofT.vulgareor of closely related species can produce forms that may be phenotypically indistinguishable (or nearly so) from the mutants.

ISSN:1923-4287    

DOI:10.1139/cjr49c-028

出版商:NRC Research Press    

年代:1949

数据来源: NRC