摘要:

Bacillus larvaediffers from most nitrate-reducing species in its ability to accumulate nitrite in nutrient solutions containing but small amounts of nitrate (0.001%). Most nitrate-reducing organisms show no accumulation of nitrite at this concentration owing to assimilation of nitrate or disappearance of nitrite through reduction or assimilation. With many nitrate-reducing bacteria disappearance of nitrite keeps pace with nitrite formation only up to a certain concentration, varying with the organism, above which nitrite may accumulate.The ability ofB.larvaeto accumulate nitrite in semi-solid carrot or turnip extract media with no added nitrate is of considerable aid in the cultural test for this organism. Of five other organisms concerned with brood disease or occurring as contaminants in comb, which were grown in association withB.larvae, none showed interference with accumulation of nitrite by the latter exceptB.orpheus. With this species a positive nitrite test was dependent on the relative development of the organisms,B.larvaeexerting a certain antagonistic action. None of the eight species of bacteria tested prevented recognition of growth ofB.larvaein the semi-solid medium.

ISSN:1923-4287    

DOI:10.1139/cjr37c-006

出版商:NRC Research Press    

年代:1937

数据来源: NRC

摘要:

This paper is an account of an investigation into the identity of a hitherto undescribed mosaic disease of President potato. Both a mild and a severe form of the disease were observed, but both forms were characterized by a yellow mottling not found in the previously reported potato mosaics.The mild form of the disease has been shown to be caused by a single virus, while the severe form is due to a combination of this virus and one of the vein-banding" group. Because of the yellow color associated with the symptoms produced on a number of host plants, the name "yellow mottle" is proposed for the newly described virus.The "yellow mottle" virus of President mosaic has been compared with the "mottle" and "ringspot" viruses from rugose mosaic, both as to behavior under certain physical and chemical tests and with respect to the symptomatological reaction of a number of solanaceous host plants.Tabulated results of the differential property studies are given, and descriptions of the symptoms caused by each of the three viruses on eight different host plants are presented.From these studies it is concluded that the newly described "yellow mottle" virus is distinct from both "mottle" and "ringspot", but it is closely related to the "X-virus" or "latent virus" group.

ISSN:1923-4287    

DOI:10.1139/cjr37c-007

出版商:NRC Research Press    

年代:1937

数据来源: NRC

摘要:

Four physiologic forms of the imperfect fungusCladosporium fulvumCooke, causal agent of the leaf mold disease of tomatoes, have been differentiated by differences in pathogenicity. Cultural studies likewise have shown that this species is a composite of physiologic forms.Saltant strains of differing degrees of stability have been isolated repeatedly from cultures arising from single one-celled spores. Since each cell of a conidium contains a single nucleus, these saltant strains are considered to arise as a result of mutations, in the broad sense of the term.Four main classes of reaction toC.fulvumhave been defined: complete susceptibility, two types of partial resistance, and immunity.The reaction between pure lines of host and parasite is plastic. Environmentally conditioned variations in each of the four reaction types have been described. Of such variations the seasonal fluctuations in the reaction ofLyco-persicum esculentumvar. Stirling Castle to Form 1 are outstanding. It has been shown that the failure of the expression of the inherent resistance of this variety during midwinter at Toronto is due largely to the reduced light experience of plants grown at this time, while the failure of such plants to support sporulation is caused by the low relative humidity then prevalent in the greenhouses.The genetics of the three types of resistance was fully analyzed. The Red Currant tomato,L.pimpinellifolium, carries, in addition to the dominant factor for immunity, an independently segregating dominant factor which, in the absence of the immunity factor, governs resistance to all four forms ofC.fulvum. The resistance of Stirling Castle to Forms 1 and 3 has been shown to be due to another dominant factor.Conspicuous among the genetic factors in the host which modify the main reaction types is the recessive lutescence factor in the homozygous condition. Its most striking effect is the production, on genetically immune individuals, of small inconspicuous infection spots whose increase in size is arrested very soon after symptoms appear.As a result of linkage studies the three resistance factors have been located in MacArthur's (12) chromosome maps of the tomato.The conflicting reports concerning the resistance of esculentum tomato varieties toC.fulvumare discussed in the light of physiologic specialization and of a plastic host reaction.

ISSN:1923-4287    

DOI:10.1139/cjr37c-008

出版商:NRC Research Press    

年代:1937

数据来源: NRC