摘要:

An account is given of the results of studies on the physiologic specialization ofPuccinia graminis AvenaeErikss. and Henn. in Canada since the inception of the work. Twelve physiologic races were identified from 2586 isolates studied during the period 1921 to 1943. The annual surveys of the prevalence of physiologic races during this period show that each year races 1, 2, and 5 have comprised the bulk of the oat stem rust in all parts of Canada. The predominance of these races has been greatest in the three Prairie Provinces, where barberry is virtually non-existent. In regions where barberry is present, other races of greater range of pathogenicity have been found more frequently than in these three provinces. The occurrence of such races, however, was sporadic until 1943, in which year races 8, 10, and 11 attained a wide distribution, apparently traceable to wind-borne urediospores from the south. There is evidence that the strains of these races present in 1943 remain in the uredial stage for much longer periods than do strains of the same races collected in previous years—a fact that may have favoured their spread in this year.The role of barberry in the origination of generally virulent physiologic races is discussed. The possibility that such races may also originate by mutation is suggested by spontaneous pathogenic changes that occurred, in the greenhouse, in a culture of race 3 that gave rise to several cultures of race 7.The effect of environment on the identification of physiologic races is demonstrated by the seasonal influences on the reaction of the variety Sevnothree to races 1 and 11. On this variety the characteristic type 1 is frequently replaced, in summer, by type x.Experiments on the influence of temperature on the reaction of adult oat plants to stem rust showed that a constant temperature of about 80° F. does not appreciably affect the reaction of White Tartar and Richland, or of other varieties with the same type of resistance, but is capable of breaking down the resistance of certain varieties derived from the crosses Hajira × Joanette, Hajira × Banner, and Victoria × (Hajira × Banner).

ISSN:1923-4287    

DOI:10.1139/cjr44c-017

出版商:NRC Research Press    

年代:1944

数据来源: NRC

摘要:

Seven species ofAlternaria, of which six are definitely pathogenic, have been isolated from agricultural seeds. Cruciferous plants are attacked by three distinct species;A.Brassicae(Berk.) Sacc.,A.oleraceaMilbr., andA.Raphanin. sp. The latter has been isolated only from radish seeds. Two species occur on carrots,A.Dauci(Kühn) n. comb., andA.radicinaMeier, Drechsler, and Eddy. A species close toA.Daucihas been isolated from flax and is described asA.linicolan. sp. The nameA.tenuisauct. is used to include the generally saprophytic forms that have been isolated from seeds of a wide variety of plants. They exhibit many variations in cultural characters, spore markings, etc., but all have spores falling within the range 20–50 × 10–16 μ.

ISSN:1923-4287    

DOI:10.1139/cjr44c-018

出版商:NRC Research Press    

年代:1944

数据来源: NRC

摘要:

Factors affecting the fermentation of 15% wheat mashes by strains ofBacillus polymyxa, under laboratory conditions, were studied with a view of obtaining maximum yields of 2,3 butanediol, a compound that can be converted to butadiene, an essential precursor of synthetic rubber. Neither the nature of the inoculating medium nor the age of the inoculum affected the fermentation but small amounts (0.5%) of the inoculum lowered the yield. Increasing the surface of the fermentation mixture resulted in improved yields of the diol as did the addition of yeast extract. Different strains varied markedly in fermentative ability; of 82 strains tested, 10 gave excellent results (over 3% diol). Combinations of two strains (phage-susceptible and phage-resistant) also gave satisfactory yields but mixtures of 5 or 10 caused a sharp drop in diol production. Low-grade, low-quality wheat samples were as satisfactory as samples of high-grade wheat in diol yield capacity. Elevator screenings were capable of being fermented byA.polymyxaalthough low yields were obtained, owing, undoubtedly, to the low starch content of these materials. However, since screenings command a low price on the market, it may be economically practical to consider their utilization for butanediol production.

ISSN:1923-4287    

DOI:10.1139/cjr44c-019

出版商:NRC Research Press    

年代:1944

数据来源: NRC

摘要:

A procedure is described that resulted in the isolation of a number of phages against various strains ofBacillus polymyxa. Out of 82 strains tested, 63 were lysed completely and 6 partially. The phages produced plaques that were separated into eight morphological groups. No special relationship between susceptibility to phage and yield of butanediol was noted.Temperature studies indicated that these phages were very sensitive, being inactivated by an exposure of 30 min. at 55 °C. They were shown to be transmitted through the bacterial spore and under these conditions resisted a temperature of 80 °C. for 60 min.Eight out of 50 strains tested were lysogenic.Phage was capable of almost completely stopping the fermentation of wheat mashes by susceptible strains. Certain resistant cultures gave good yields in the presence of active phage. Mixing resistant and susceptible strains resulted in lowered yields; however, a good fermentation was obtained in the presence of phage by combining three resistant strains. Even in the absence of phage, a mixture of five strains was not favourable, probably as a result of antibiotic effects among the individual strains. Secondary cultures differed markedly in nature of growth and spore-producing capacity from primary strains and were, on the whole, poorer diol producers.It was suggested that under ordinary conditions in the factory, proper sterilization of equipment and materials, aseptic technique, and use of well-tested non-lysogenic strains are adequate precautions against this bacterial virus.

ISSN:1923-4287    

DOI:10.1139/cjr44c-020

出版商:NRC Research Press    

年代:1944

数据来源: NRC

摘要:

A new species ofAleurodiscusis described and designatedAleurodiscus canadensis. The basidia of this fungus are regularly two-spored, but occasionally basidia bearing three spores or rarely one spore are encountered. From the cultural and cytological evidence presented the normal life cycle may be described as follows. The cells of the subhymenium are dikaryotic with clamp connections. The young basidia are at first binucleate. Following karyogamy the fusion nucleus undergoes reduction division producing the usual tetrad of nuclei. Each spore of the two-spored basidium receives two of the four daughter nuclei. The two nuclei in these spores undergo further division while the spore is still attached or shortly after discharge, so that the mature spore contains four nuclei. Such a spore is capable of producing a mycelium bearing clamp connections. Although the majority of the spores produce mycelia with clamp connections, a spore may occasionally develop a mycelium that does not bear clamps. When such exceptional mycelia are mated in compatible combinations, dikaryotic mycelia with clamp connections are obtained. From the mating of a number of these exceptional haplonts the heterothallic and bipolar relationship is made evident. Although complete cytological information on the spores that give rise to these exceptional haploid mycelia is lacking, it is probable that these spores are originally uninucleate and that this results from the distribution of the four nuclei in a three-spored basidium in such a way that one spore receives two nuclei and the other two spores one nucleus each. The two nuceli that migrate into the normal spore, therefore, probably bear allelomorphic inter-fertility factors. If this species can be considered homothallic, the homothallism is a different type from that found in species that complete their life cycle from the development of a single uninucleate spore. The necessity for such a distinction is stressed.

ISSN:1923-4287    

DOI:10.1139/cjr44c-021

出版商:NRC Research Press    

年代:1944

数据来源: NRC