摘要:

Seedling leaves of Khapli wheat—a variety highly resistant to physiologic races of wheat stem rust prevalent in North America—became susceptible to stem rust a few days after they had been sprayed with DDT (1 oz. in 5 gal. water). The response to DDT was highly specific, as only one other of the resistant wheats tested (Arnautka) showed any indication of susceptibility consequent on spraying. Specificity of response was also indicated by the development of marked chlorosis on leaves of some varieties, whereas other varieties remained unaffected.

ISSN:1923-4287    

DOI:10.1139/cjr46c-004

出版商:NRC Research Press    

年代:1946

数据来源: NRC

摘要:

During the period 1919 to 1944, 65 physiologic races were identified from a total of 4543 isolates derived from uredial collections ofPuccinia graminisPers. var.TriticiErikss. & Henn. Forty-nine races were obtained in the Prairie Provinces from a study of 3475 isolates; 40 in Eastern Canada from 1013 isolates, and 12 in British Columbia from 55 isolates. During this period, the predominant races have shown notable fluctuations in their prevalence. Races 36, 17, and 21 were the most common races until shortly after 1930 and were largely responsible for the severe rust losses suffered by Marquis and other common wheats during the decade preceding that year. Races 34 and 49 were collected frequently from 1927 to about 1935. All of these races diminished greatly in their prevalence between 1930 and 1936, whereas race 56, which was first collected in Canada in 1931, has become the predominant race since 1934. It was this race that played a major part in the stem rust epiphytotic of 1935. Another recent change in the racial population was a recrudescence in 1940 of race17, which for several previous years had been of minor importance. In 1941 this race challenged the pre-eminent position of race 56 but receded again in succeeding years to minor significance.The distribution of races is somewhat similar but not identical in different parts of Canada. Races 36 and 21 have been relatively more common in the Prairie Provinces than in Eastern Canada, while the contrary is true of race 38. Only about a dozen of the 65 races collected in Canada have thus far assumed much economic importance, a few others may be considered of minor significance, but at least two-thirds of the races have been found only occasionally and have, for reasons not fully understood, failed to gain even a limited distribution.A comparison of the number of physiologic races collected in Eastern Canada and the Prairie Provinces, respectively, has indicated a somewhat greater variety of physiologic races in the former region, a condition that may perhaps be explained by the presence of the common barberry in many localities in Eastern Canada.

ISSN:1923-4287    

DOI:10.1139/cjr46c-005

出版商:NRC Research Press    

年代:1946

数据来源: NRC

摘要:

The spore-forming bacterium,Bacillus polymyxa, was found to occur widely in Alberta soils. All isolates obtained from the soil, together with several from other sources, proved capable of rotting potato tubers when introduced through wounds under conditions of abundant moisture and high temperature.In these studies pure cultures ofBacillus polymyxarotted potato slices at temperatures from 20 °C. to 45 °C. and whole tubers at temperatures from 30 °C. to 45 °C. but caused no damage below the minimum temperatures mentioned.Though potato tubers and other vegetables that are formed in the soil probably often come in contact withBacillus polymyxa, they are not likely to be rotted by it except when temperature and other factors are favourable. In general, soil temperatures in the field in Alberta are not conducive to the decay of potatoes by this organism, but those near the soil surface may on occasion reach favourable levels. The fact thatB.polymyxacan be isolated quite frequently from rotted stored potatoes indicates that it is of some importance as a cause of decay in harvested potatoes. If, however, recommended storage temperatures are maintained in the storage quarters no damage from this organism should occur there.

ISSN:1923-4287    

DOI:10.1139/cjr46c-006

出版商:NRC Research Press    

年代:1946

数据来源: NRC

摘要:

The soluble carbohydrates were extracted, by means of hot water, from dried ground roots ofTaraxacum kok-saghyzRod. that had been extracted previously with acetone and benzene. A cleared portion of the extract served for the determination of hexose and, after invertase hydrolysis, sucrose. Another portion was subjected to mild acid hydrolysis before clearing, and served for the determination of total reducing value, whence fructosans, as inulin, were calculated. Separation of the free reducing sugars and sucrose from the fructosans by ethanol extraction proved unsatisfactory. Analyses of 171 one-year old roots from six crosses gave the following average values expressed as per cent dry weight: hexose 1.6, sucrose 4.7, and inulin 41. The analytical data suggest the possibility of selecting and breeding for strains of kok-saghyz capable of high carbohydrate production.

ISSN:1923-4287    

DOI:10.1139/cjr46c-007

出版商:NRC Research Press    

年代:1946

数据来源: NRC