摘要:

The antagonism of a number of bacteria, actinomycetes and fungi toBotrytis cinereain pure culture on lettuce extract agar has been investigated. A considerable number were antagonistic at 25° C., a few showed antagonism at 15° C. and a limited number grew and were active at 5° C.Certain of these organisms were able to control rot of detached lettuce leaves when inoculated before or simultaneously withB. cinerea.The latter is unable to penetrate areas of dead tissue colonized by selected antagonists.Control of rot was also obtained when leaves of growing plants were similarly inoculated.Substantial control of disease occurred when young potted plants in frames were sprayed with suspensions of selected antagonists in 1.0 % glucose solution.The practicability of this method of control is discuss

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1951.tb07797.x

出版商:Blackwell Publishing Ltd    

年代:1951

数据来源: WILEY

摘要:

The antagonism of a number of bacteria, actinomycetes and fungi in pure culture on soil extract agar has been investigated. A considerable number of each of the three groups were highly antagonistic at 25° C., fewer were active at 15° C. and only a very limited number were effective at 5° C.In greenhouse experiments damping‐off of lettuce seedlings was substantially controlled by selected antagonists in sterile sand, soil or in sand/soil mixtures. Under similar conditions in unsterile soil, forms highly antagonistic in pure culture were generally ineffective in controlling disease. In one experiment control of disease in natural soil was obtained by the use of soil amendments, the effect being enhanced by the inoculation of one of these amendments with suspensions of antagonists.Attempts to control disease in the field by the use of soil amendments are described. In one year a substantial increase in the stand of healthy seedlings was obtained with certain treatm

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1951.tb07798.x

出版商:Blackwell Publishing Ltd    

年代:1951

数据来源: WILEY

摘要:

Potato tubers infected withPhytophthora infestansin the field produce abnormal amounts of liquid which often appear on the surface of tubers kept in a saturated atmosphere. Under these conditions a soft rot, associated with bacteria, develops.Healthy tubers artificially infected with pure cultures ofP. infestansproduce a similar liquid and, if further inoculated with pure cultures of certain bacteria, develop a wet rot which spreads if the bacteria are pathogenic or is confined to the zone of fungal invasion if the bacteria are saprophytes.Sap extracted fromPhytophthora‐infected tissue contains more sugar and has a greater osmotic pressure than sap extracted from healthy tissue. Thus, water may be withdrawn from healthy tissue which would result in the infected tissue containing more liquid than does the healthy tissu

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1951.tb07799.x

出版商:Blackwell Publishing Ltd    

年代:1951

数据来源: WILEY

摘要:

Laboratory experiments showed that gram (Cicer arietinum) could be infected byCorynebacterium fascians.Parallel tests on sweet peas and gram confirmed the existence of host specificity among strains of the pathogen, and of differences in host susceptibility towards a given strain. Adventitious root formation appeared as a new, though rare, sign of infection. Inoculation of aerial dormant buds invariably caused infection whereas cotyledonary bud inoculation often failed. Sporing bacteria antagonistic toC. fasciansin culture media were isolated from soil, but they failed to exert their influence in infection experiments in sand.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1951.tb07800.x

出版商:Blackwell Publishing Ltd    

年代:1951

数据来源: WILEY

摘要:

The effectiveness in nitrogen fixation of fifty‐four strains of the clover nodule organism has been tested on red, white and alsike clover in aseptic tube‐culture by comparing the nitrogen content of nodulated plants grown on nitrogen‐free medium against that of non‐nodulated plants grown on media with and without nitrate‐nitrogen. The performance of the strains was to a considerable degree consistent on all three hosts. Minor changes were shown but for the most part did not exceed the experimental error. Thus in respect of these three clovers there is no marked host species effect. Seed inoculants or naturally occurring strains effective on one species are likely to be effective on the othe

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1951.tb07801.x

出版商:Blackwell Publishing Ltd    

年代:1951

数据来源: WILEY

摘要:

There is confusion as to whether theSclerotiniaonVicia fabais a normal strain ofSclerotinia trifoliorumas found on clover and related legumes or a distinct variety (var.fabae). Pathologically the two fungi appear to be the same, and field observations indicate that beans in the rotation may aggravate the incidence of clover rot. A re‐investigation of the morphology of the two fungi is made to assess the status of var.fabae.The two fungi could not be distinguished by apothecial characters or cultural behaviour. Ascospore measurements confirm the existence ofS. trifoliorumvar.fabae, although 5.trifoliorumproper also occurs on beans. Var.fabaehas not been found on any legume besides beans. Isolates from trefoil and sainfoin agree in spore size withS. trifoliorumon clover.When isolates ofS. trifoliorumare co‐inoculated on the same Petri plate, they either do not react, or react to form a ‘demarcation line’. Although a demarcation line is assumed to imply a genetic difference, non‐reaction does not necessarily imply genetic identity. Non‐reaction and the formation of a demarcation line also occur when var.fabaestrains are co‐inoculated together. When an isolate ofS. trifoliorumis co‐inoculated with an isolate of S.trifoliorum var. fabaean ‘incompatibility line’ is formed. Use can be made of this fact in identification.On the basis of co‐inoculations 5.trifoliorumandS. trifoliorumvar.fabaeare both shown to constitute a diverse range of biotypes. Segregation of biotypes in the ascus as a result of heterokaryosis in the ascus‐initial is demonstrated. The view is expressed that heterokaryosis is the mechanism underlying the pro

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1951.tb07802.x

出版商:Blackwell Publishing Ltd    

年代:1951

数据来源: WILEY

摘要:

The loss of total carbohydrate (sugars and starch) per cent of residual dry matter (dry matter less total carbohydrate) during a period of darkness from leaves of sugar‐beet plants infected with yellows virus was as great as that from the leaves of healthy plants. The conclusion of previous workers, based on the results of the Sachs iodine test for starch and the occurrence of ‘phloem gummosis’ in infected plants, that starch accumulates in infected leaves because translocation is prevented by blockage of the sieve‐tubes, is therefore incorrect.Older leaves of infected plants had a higher content of reducing sugars and sucrose, and usually but not invariably of starch, both at the beginning and end of the dark period, than comparable leaves of healthy plants. By far the greater part of the increase was in reducing sugars. In leaves taken in late September from infected plants growing in the field, 20 % or more of the total dry matter was present as reducing sugars. The reducing sugars in both healthy and yellows‐infected leaves were shown by paper chromatography to be glucose and fructose in approximately equal amounts.Accumulation of carbohydrate in infected leaves is probably not a passive consequence of differences in carbohydrate production, distribution and utilization, but is attributable to changes in the physiology of the cells of the leaf.The carbohydrate content of sugar‐beet leaves was little affected by infection with beet mosaic virus.Yellows‐infected leaves had a lower water content per cent of fresh weight than healthy leaves. This was accounted for by the higher carbohydrate content of infected leaves, for the ratio of water: residual dry matter was not affected by infection or was slightly reduced. This implies that hydration was independent of carbohy

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1951.tb07803.x

出版商:Blackwell Publishing Ltd    

年代:1951

数据来源: WILEY

摘要:

Two species of wild oats,Avena fatuaandA. ludoviciana, and two varieties of cultivated oats for comparison, were grown to maturity in pots of manganese‐deficient soil with and without added manganese.A. ludovicianashowed different leaf symptoms of manganese deficiency fromA. fatuaand the cultivated varieties. In other respects wild and cultivated oats were similar in their responses to the level of manganese supply, though differences were observed in the severity of the effects. These are summarized in Table 6. The relative susceptibility to manganese deficiency of the wild and cultivated oats differed according to the effect considered. The total dry weight at harvest is an integration of all the preceding effects on growth and is therefore presumably the best single criterion for determining susceptibility to manganese deficiency. On the basis of per cent loss of total dry weight at harvest due to lack of manganese,A. fatuais judged less susceptible andA. ludovicianamore susceptible than the two cultivated varieties and no distinction can be made between the latter.The most interesting differences between wild and cultivated oats in response to the level of manganese supply occurred in seed production. Manganese‐deficient wild oats showed a smaller reduction in the number of seeds formed but a greater reduction in the size and manganese content of individual seeds than the cultivated varieties.Manganese deficiency lowered the percentage of viable seeds and the percentage of dormant seeds produced by bothA. fatuaandA. ludovici

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1951.tb07804.x

出版商:Blackwell Publishing Ltd    

年代:1951

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1951.tb07805.x

出版商:Blackwell Publishing Ltd    

年代:1951

数据来源: WILEY

摘要:

Book reviewed in this article:Reports of the Forest Products Research BoardField Trials II: The Analysts of Covariance.Iodine and Plant Life: Annotated Bibliography

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1951.tb07806.x

出版商:Blackwell Publishing Ltd    

年代:1951

数据来源: WILEY