摘要:

In an extensive experiment conducted under field conditions during four successive years, the symptoms of leaf roll of potatoes, as expressed by potato plants of various ages, were studied. Healthy plants of the varieties Netted Gem, Carter's Early Favorite, and Canus were graft-inoculated with infected scions from Canus at 10-day intervals from June 10 to September 15 and protected from viruliferous aphids by a lethal spray applied frequently. Infection of the plants was verified by the tuber-index method. On young plants leaf-roll symptoms were regularly severe and a high percentage of plants became infected. However, the severity of foliage symptoms and also the percentage of plants infected gradually decreased until about August 15. After this date the infected plants were healthy in appearance but the percentage of them actually infected continued to decline sharply. The data presented show that potato plants infected by the leaf-roll virus after midseason normally do not develop definite foliage symptoms of the leaf-roll disease and, therefore, cannot be detected by ordinary field inspection.

ISSN:0008-4026    

DOI:10.1139/b54-026

出版商:NRC Research Press    

年代:1954

数据来源: NRC

摘要:

Successful crops of wheat, oats, and barley were produced in a growth chamber in 60 days with light from fluorescent and incandescent bulbs at an intensity of 1200 to 1500 candle power. Full light was used for 18 hr. per day and a low intensity of incandescent light for the remaining six hour period. The experiments indicated that the light requirement of the oat crop is somewhat higher than for wheat and barley.

ISSN:0008-4026    

DOI:10.1139/b54-027

出版商:NRC Research Press    

年代:1954

数据来源: NRC

摘要:

The effect on ascospore formation in bakers' yeast of varying degrees of aeration and of oxygen, carbon dioxide, and nitrogen individually and in mixtures was studied. In the absence of carbon dioxide, ascospore formation was stimulated by concentrations of oxygen up to 12.0% but was depressed slightly at 41.1% and more so at 68.8% and at 100%. Carbon dioxide inhibited ascospore formation; very few were found when the carbon dioxide concentration was 25% or greater. Oxygen did not overcome the inhibitory effect of carbon dioxide. Ethyl alcohol vapor so markedly inhibited sporulation that ascospores were rarely observed in cultures exposed to the vapor from a 5% solution of ethyl alcohol. Ascospore formation was observed at. temperatures from 3.0 to 33.3 °C. Of two strains studied in one experiment, one showed highest sporulation at 24.0 °C. and the other at 27.5 °C. Cells exposed for 14 days to temperatures of 2.5, −3.5, and −18.0 °C, and cells multiplied at 37.5 °C, showed reduced sporulation at room temperature.

ISSN:0008-4026    

DOI:10.1139/b54-028

出版商:NRC Research Press    

年代:1954

数据来源: NRC

摘要:

A means of determining the thiram content of treated soil was developed, applying the paper disk bioassay technique withGlomerella cingulataas the test organism. It was found that thiram persisted in sandy soil for over two months but disappeared from compost soil within one week. Thiram treatment changed the microbiological balance in the soil, the number of bacteria being increased and the fungi decreased for some time. Thiram was shown to be selective in its action against fungi;PenicilliumandTrichoderma, being resistant, increased in number after soil treatment. Thiram treatment rendered soil more difficult to infest artificially withPythium ultimumand also prevented a natural increase in the population of damping-off organisms resulting from repeated cropping. This protection for seedlings persisted longer than did the fungicide in the soil.

ISSN:0008-4026    

DOI:10.1139/b54-029

出版商:NRC Research Press    

年代:1954

数据来源: NRC

摘要:

Prior to 1952, oat varieties with the Hajira type of resistance to all the known races of oat stem rust in North America, such varieties as Garry and Rodney, were thought to have identical rust resistance. In 1952, slight amounts of stem rust occurred in one field of Rodney. This rust was identical with race 7 except for its ability to attack Rodney and some sister strains. Other sister strains of Rodney as well as Garry were highly resistant to it. Therefore, Garry and Rodney, which derived their resistance from the same source, did not, as had been assumed, contain identical factors for rust resistance. The new rust strain was regarded as a biotype of race 7 and was designated race 7A. Studies were made onF3lines derived from crosses involving Hajira to determine the reaction of the plants to stem rust races, including race 7A. These studies indicate that resistance to the various rust races is conditioned by three genes. GeneA(present in varieties such as Richland, Vanguard, Ajax, and Green Russian) conditions resistance to races 1, 2, 3, 5, 7, 7A, and 12. A second geneB(present in varieties such as Canuck and Rodney) conditions resistance to races 1, 2, 3, 5, 7, and 12 but is not effective against race 7A. A third geneCconditions resistance to races 4, 6, 8, 10, 11, and 13. Varieties such as Rodney, Canuck, and R.L. 1225 presumably contain genesBandC, whereas varieties such as Garry and R.L. 1574 contain genesA,B, andC.

ISSN:0008-4026    

DOI:10.1139/b54-030

出版商:NRC Research Press    

年代:1954

数据来源: NRC

摘要:

A series of experiments were carried out over a period of three years in which plants ofAvena sativavar. Tama were grown in nutrient solutions which provided variations in iron and manganese concentrations, calcium concentration, and pH. The experiments were conducted under a wide range of growing conditions as regards light intensity and temperature control. The aim of the work was to furnish information regarding the factors associated with the development of the symptoms of gray speck disease. The experimental results indicated that under otherwise favorable culture conditions, manganese deficiency alone will produce gray speck symptoms. Inoculation of the cultures with root material from plants bearing gray speck symptoms had no effect whatever on the incidence of the disease. Variations in the pH of the culture solutions did not affect the development of gray speck symptoms, but the symptoms appeared later in cultures containing a high concentration of calcium than in cultures containing a low concentration of this metal.

ISSN:0008-4026    

DOI:10.1139/b54-031

出版商:NRC Research Press    

年代:1954

数据来源: NRC