摘要:

The vascular system of leaves of chrysanthemum plants inoculated withVerticillium dahliaewas invaded by mycelium before the appearance of visible wilt symptoms. After flower buds appeared a rapid rise in the number of propagules of fungus in the leaf was followed by a rise in severity of visible wilt symptom expression and conductivity of leaf exudate. Those portions of the leaf with the most advanced stages of wilt contained the greatest amounts of fungus. It is suggested that the mycelium within the leaf makes a significant contribution to the development of symptoms of wilt.

ISSN:0008-4026    

DOI:10.1139/b71-031

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The presence of Millipore filter discs on the agar medium resulted in more uniform, vigorous colonies of flax rust than were found when the colonies were grown directly on the agar surface. In addition, transferring and subculturing were greatly facilitated, and losses were greatly reduced.

ISSN:0008-4026    

DOI:10.1139/b71-032

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Two races ofCladosporium fulvum, hitherto not encountered from the Niagara Peninsula or adjacent areas of Ontario, Canada, are reported as races 11 and 12. They are described in terms of their infection capabilities on differential tomato hosts carrying theCf1,Cf2,Cf3, orCf4resistance genes. A tabular summary compares the infection capabilities of races 11 and 12 with those of four other presently availableC. fulvumraces on the differential hosts used for their characterization. Of the four resistance genes which have been incorporated in the various tomato cultivars onlyCf1andCf4appear to condition resistance to race 11 and onlyCf1to race 12. Results of inoculation studies withC. fulvumunder controlled conditions of light, temperature, and relative humidity are discussed. Comparative studies of their reaction to races 1 and 12 indicate that certain tomato cultivars reported to carry the Stirling Castle, orCf1, resistance no longer possess it and that additional resistance genes may be present in others.

ISSN:0008-4026    

DOI:10.1139/b71-033

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The serial section technique was used to delimit 0.5-mm regions of the root tip. Seven such sections numbered from the root tip backwards were examined to a total length of 3.5 mm.Developmental changes in the root tip cells of Marquis (spring) and Rideau (winter) wheats were closely correlated with sequential changes in the content of free sugars (sucrose, glucose, fructose, raffinose, and galactose), starch, and amylase. Specific varietal differences were observed both before and after vernalization.Spatially comparable root tip sections derived from previously vernalized grains revealed marked changes in the content of the sugars and starch. A shift in the starch–sugar equilibrium is noted with cellular development. For the most part, in Rideau wheat, the amount of these metabolites in any specific section derived from a vernalized root tip was more nearly comparable to the chronologically less mature tissue of the control roots, i.e. section 3 of the vernalized root compared more closely with section 2 of control roots.Amylase activity increased markedly after vernalization in the winter wheat but did not change in the spring wheat. Its activity could be directly correlated with changes in the amount of sucrose (not starch). Starch content increased in the more mature root tip cells of both varieties after vernalization.Sugar, amylase, and starch content were primarily a function of the developmental stage of the root tip cells, vernalization effected secondary smaller changes.

ISSN:0008-4026    

DOI:10.1139/b71-034

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Eighteen isolates ofPucciniawere compared for ability to grow as saprophytes. After incubation of uredospores until growth ceased, six isolates developed an extensive mycelium, nine isolates formed a limited mycelium, and three isolates produced only scant saprophytic hyphae.The following factors were tested for their effect on the growth ofP. graminis triticirace 126 Anz 6,7: inoculation from different uredosori; mode of application of the inoculum; density of the inoculum; composition of the medium. Using a dense inoculum it was found that yeast extract and peptone may be replaced by aspartic acid and a sulphur amino acid such as cysteine, and that glucose, fructose, mannose, or mannitol will substitute for sucrose as principal carbon source. However, no medium or method of inoculation was found to be completely reliable. A study of thinly seeded cultures showed that although 20–80% of sporelings could initiate saprophytic growth, only 3–6% eventually formed macroscopically visible colonies. It was found that frequencies of growth initiation and colony formation were highest on the thinnest layer of nutrient agar tested, and that sporelings mutually stimulated one another's growth. We conclude that the success of present culture techniques depends on an adequately high inoculum density, and other processes which are not understood.

ISSN:0008-4026    

DOI:10.1139/b71-035

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Tilopteris mertensii(Turn. in Sm.) Kütz. (order Tilopteridales, family Tilopteridaceae) is reported for the first time from Newfoundland. The record represents the third known locality for the species in North America. Newfoundland plants bore uninucleate monospores and plurilocular sporangia. Preliminary observations indicate that reproduction in Newfoundland is asexual, by direct germination of the monospores, with no apparent function of the motile spores.

ISSN:0008-4026    

DOI:10.1139/b71-036

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The production of new reproductive structures at the apex of successive percurrent proliferations is a common phenomenon in fungi. Successive sporangia and conidia in Phycomycetes, successive asci, conidia, phialides, and possibly 'gemmae' in Ascomycetes, and successive probasidia, basidia, and apparently urediniospores in Basidiomycetes, can be produced in this way. Examples of these are given from published accounts and some personal observations. Successive reproductive structures of various kinds are also formed on percurrent proliferations in 'green,' brown, and red algae. In the red algae successive antheridia can develop within empty ones by this method; it is concluded that such antheridia are not phialides. Successive gemmae in some mosses are formed terminally on percurrent proliferations.

ISSN:0008-4026    

DOI:10.1139/b71-037

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Interaction tests, using aster (Callistephus chinensisNees) as the host plant andMacrosteles fascifrons(Stål) as the vector, showed that infection with clover phyllody causal agent (CPCA) did not protect the plant against subsequent infection with a celery-infecting strain of aster yellows causal agent (AYCA), although symptom development was delayed. However, infection with AYCA prevented subsequent infection with CPCA. These interactions indicate that CPCA and AYCA are related. Both causal agents could be recovered from some dually infected plants.

ISSN:0008-4026    

DOI:10.1139/b71-038

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Light exerted an inhibitory effect on sporulation ofBremia lactucaeRegel on infected lettuce seedlings. Maximum sporulation was obtained in a dew chamber on seedlings exposed to a minimum of 6 h of darkness 7 days after inoculation. Continuous light applied at this time (2000 ft-c) prevented sporulation completely. If no dark period was allowed immediately after inoculation, there was an apparent inhibition of penetration and establishment of the parasite.

ISSN:0008-4026    

DOI:10.1139/b71-039

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Attempts were made to characterize the native auxins of citrus tissues. Paper chromatography with eight solvent systems and copartition followed by cochromatography with IAA-2-14C suggest that the auxin of citrus shoots is identical with IAA. This evidence is discussed and compared with other studies of auxin identification reported in the literature.

ISSN:0008-4026    

DOI:10.1139/b71-040

出版商:NRC Research Press    

年代:1971

数据来源: NRC