ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1951.tb07807.x

出版商:Blackwell Publishing Ltd    

年代:1951

数据来源: WILEY

摘要:

A method is described for assessing the systemic activity of compounds in checking the infection of broad bean (Vicia faba) by the fungiBotrytis cinereaorB. fabae.Treatment consisted in allowing the roots of young seedlings to stand in a solution containing 10 p.p.m. of the chemical for 2–3 weeks. The plants, together with controls, were then inoculated and when symptoms had had time to develop, the degree of chocolate spot infection was assessed. Several methods of disease assessment were examined and are critically discussed.Certain phenoxyalkylcarboxylic acids tested by this method consistently gave a reduction in the mean size of fungus lesions on the bean leaves, clearly indicating systemic fungicidal action. The most promising substances were 2:4:6‐trichlorophenoxyacetic, pentachlorophenoxyacetic and pentachlorophenoxyisobutyric acids. Further experiments with these compounds involving soil treatment, stem injection and spray application are described, and in most cases systemic fungicidal activity was clearly demonstrated. Certain compounds caused visible damage to the plants or resulted in a reduction in growth.The results presented indicate that phenoxy acids can be fairly readily translocated in bean plants and that they tend to accumulate in actively growing tissues. It is considered unlikely, however, that they persist for long periods in plant tissue.In the soil, the compounds appeared to remain effective for a considerable time, particularly the less soluble pentachloro acids, suggesting that soil application might provide a safe and useful method of treatm

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1951.tb07808.x

出版商:Blackwell Publishing Ltd    

年代:1951

数据来源: WILEY

摘要:

Metallic mercury and mercury compounds in the soil retard the growth of plants. The development of mosses and lichens is inhibited, and experimental evidence shows that the growth of toadstools on turf and the activity of ascomycetes is retarded by mercury.In vitro, mercury has no fungicidal action but the rate of growth of hyphae is reduced by mercury vapour.The lack of fungicidal properties of mercury and its good performance in controlling certain soil‐borne diseases are reconciled by assuming that a differential retardation disturbs the relationships necessary for infection. This assumption is supported by diagrams which treat the rates of growth of the parasite and the host as population characteristics normally distribute

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1951.tb07809.x

出版商:Blackwell Publishing Ltd    

年代:1951

数据来源: WILEY

摘要:

An internal fungal mycelium between the epidermis and cross‐layer cells in normal wheat grains is shown to consist of extracellular septate hyphae forming a network on the inner surface of the epidermis, whose cells are occasionally penetrated. The mycelium, which is first observed at a comparatively late stage of maturation of the grain, usually remains as a loose network, although sclerotia and plate‐like structures suggestive of drought forms are occasionally present. These appearances support the view, derived from comparison of the drying rates of grain under various climatic conditions, that the spread of the subepidermal mycelium is finally restricted by desiccation beneath the epidermis during the drying out of the ripening grain.Cultures from surface‐sterilized grains of Bersée wheat have shown that the most common subepidermal fungus isAlternaria tenuis(in 64.4% of the grains). Bacteria (28.8%),Mycogonesp. (?) (7.7%),Cladosporium herbarum(5.8%),Pullularia pullulans(4.8%),Fusariumsp. (1.9%),Botrytis cinerea(1.9%) andStemphylium botryosum(0.9%) were also isolated.The subepidermal mycelium apparently arises either from systemic infection of the wheat plant or from fungal spores and hyphae present on the outside of the developing grains and among the dead floral

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1951.tb07810.x

出版商:Blackwell Publishing Ltd    

年代:1951

数据来源: WILEY

摘要:

For the study of deposition of air‐borne particles on plant and trap surfaces a small wind tunnel has been constructed giving turbulent or streamline flow up to about 10 m./sec. The efficiency with which cylinders of from 0.018 to 2.0cm. diameter, coated with glycerine jelly, catchLycopodiumspores at wind speeds over the range 1–10 m./sec. has been measured experimentally with a Cascade Impactor, operated iso‐kinetically, as standard. Efficiency has been found to increase as wind speed increases, and as cylinder diameter decreases. Similar effects have been observed in the field. Efficiencies observed are lower than predicted by Sell and Glauert, but agree well with those predicted by Langmuir and Blodgett, except with the narrowest cylinders. The standard vertical sticky traps used in routine trappings of fungus spores, pollen, and crop‐protectant sprays and dusts have a low trapping eff

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1951.tb07811.x

出版商:Blackwell Publishing Ltd    

年代:1951

数据来源: WILEY

摘要:

Different strains of cucumber mosaic virus differ in their host range, symptoms caused, virulence towards different plants, transmissibility by aphids, dilution end‐point and thermal inactivation point.There are seasonal variations in the susceptibility of some host species; French bean is apparently immune during the summer but during the winter produces countable local lesions suitable for quantitative assays.Different host species differ in the ease with which cucumber mosaic virus is transmitted to and from them; systemic infection in beet rarely occurs unless the virus is introduced into young tissues. Inhibitors of infectivity in sap of sugar beet andPhytolaccasp. make mechanical transmission from these to other hosts difficult; the inhibitors interfere less with the infection of hosts in which they occur than with the infection of tobacco.Cucumber mosaic virus has a low temperature coefficient of thermal inactivation and much infectivity is destroyed by heating at temperatures below the thermal inactivation point.Myzus persicae(Sulz.) is a more efficient vector thanM. ornatusLaing which is more efficient thanMacrosiphum euphorbiae(Thomas); although individual aphids can cause more than one infection, most cease to be infective in feeding periods of from one to five minute

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1951.tb07812.x

出版商:Blackwell Publishing Ltd    

年代:1951

数据来源: WILEY

摘要:

From the time of first feeding on plants infected with strawberry virus 3, 10–19 days elapsed beforeCapitophorus fragariaebecame infective, a longer ‘latent period’ than any previously recorded for an aphid‐transmitted virus. The time taken for aphids to develop infectivity after leaving infected plants decreased with increasing duration of the infection feed. Aphids which had fed for 16 days on an infected plant caused infection in the first day of test

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1951.tb07813.x

出版商:Blackwell Publishing Ltd    

年代:1951

数据来源: WILEY

摘要:

The incidence of yellows virus in sugar‐beet crops was reduced by increasing the density of plant population. The variations in plant population were obtained by differences in row width and singling distance. The differences in susceptibility between large‐ and small‐topped varieties, and between early and late sown crops, could not be attributed solely to differences in plant size. It is suggested that close planting would increase the yields of sugar beet and reduce the losses caused by yellows virus. Roguing infected plants during the early part of the growing season did not reduce the incidence of di

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1951.tb07814.x

出版商:Blackwell Publishing Ltd    

年代:1951

数据来源: WILEY

摘要:

Tobacco veinal necrosis virus is serologically related to potato virusesYandC.It does not protect tobacco,Nicotiana glutinosa, or potato plants from infection by them, and tobacco andN. glutinosaplants infected with either virusYorCare still susceptible to it. There is some evidence that it does not multiply normally in potato plants infected with virusYand that it is sometimes suppressed in such plants.The possession of antigenic groups in common with virusesYandCis considered to justify identifying tobacco veinal necrosis virus as a strain of virusY, and to be of greater taxonomic significance than failure to protect plants against other strains. A further difference from other strains is that it is more virulent towards tobacco than towards potato.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1951.tb07815.x

出版商:Blackwell Publishing Ltd    

年代:1951

数据来源: WILEY

摘要:

Batches of potato plants in pots were placed in the field for limited periods among plants infected with potato virusYand leaf roll virus. Some of the potted plants were surrounded by sticky boards which prevented apterous aphids from reaching them. Almost as many plants within the boards as without became infected, indicating that most of the spread of virus was by winged aphids.Apterae were probably responsible for spreading the viruses throughout a hill after one or more stems were infected. They may carry infection to neighbouring plants, but most of these will have been infected already by alatae.The number of plants contracting infection was unaffected by watering.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1951.tb07816.x

出版商:Blackwell Publishing Ltd    

年代:1951

数据来源: WILEY