Roepke's werk op het gebied van de toegepaste entomologie voor het voormalig Nederlandsch Oost Indië

Ohne Zusammenfassung     

Bestaat er een verband tusschen het voorkomen van black heart en het optreden van virusziekten bij den aardappel?

Summary Biourge andSokal have claimed: firstly: Black heart is not caused by lack of oxygen, followed by suffocation of central part of the tuber, but it results from attack byBacillus mesentericus vulgatus;Flugge) andBacillus mesentericus ruber (Globig); Secondly: Tubers suffering from black heart develop plants suffering from the diseases, which have been ascribed to viruses. Therefore it is not necessary to suppose the existance of viruses. This type of disease is caused by the bacilli mentioned. Sanitation of the plants can be performed by keeping the tubers during 48 hours at 42 centigrades. The tubers withstanding this heating without turning black develop virus-free plants. The present author however has, in controlling experimentally the work of the writers mentioned above, not been able to detect any relation between the occurrence of black heart in the tubers and of viroses in the sprouts. Sensibility for black heart proved to be more dependent on the climate and the soil, than on hereditary characters of the potato variety. Between the melanine-value (as aimed byHaehn) and the intensity of black heart, thus far no correlation has been found by the present author.     

De stichting het Phytopathologisch Laboratorium „Willie Commelin Scholten”

Ohne Zusammenfassung

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With a summary: The foundation Phytopathological Laboratory Willie Commelin Scholten

     

Over de vatbaarheid van niet-kruisbloemige planten voor het zoösporangium-stadium vanPlasmodiophora brassicae Woron

Samenvatting en bespreking Een vijftiental plantensoorten werd onderzocht op vatbaarheid voor het zoösporangium-stadium vanP. brassicae. Hiervan werdenTrifolium pratense, Reseda odorata enLolium perenne in zeer geringe mate, enPapaver rhoeas iets sterker aangetast. De mate van aantasting van deze laatste was echter nog aanzienlijk minder dan van als vergelijkingsobject gebruikte bloemkoolplantjes. Gezien deze resultaten is het niet waarschijnlijk, dat niet-cruciferen enigermate kunnen bijdragen tot de instandhouding of vermeerdering van de schimmel bij afwezigheid van kruisbloemigen. Evenmin is er reden te veronderstellen, dat niet-cruciferen als vangplanten voor het uitroeien van de rustsporen van groot practisch belang kunnen zijn.Summary Webb's (1949) discovery of zoosporangia ofP. brassicae in non-crucifers raises the question of further means of multiplication and survival in the soil (MacFarlane, 1952). Perhaps the fungus can maintain itself in successive generations of zoosporangia in root hairs of these plants. From there it might in turn infect crucifers and produce a fresh crop of resting spores. This must be kept in mind when considering the possibility of eradicating the fungus from the soil by growing non-crucifers which stimulate the resting spores to germinate. If survival in root hairs were important, plants for this purpose would need to resist the zoosporangial stage as well as stimulate spore germination.In the present study a number of non-crucifers was tested for susceptibility to the zoosporangial stage by a method already described (Kole, 1955). In addition, the rate of infection of susceptible non-crucifers was compared with that of cabbage grown under the same conditions. Of seven non-crucifers, not tested before, onlyTrifolium pratense became infected.MacFaralane's findings of non-cruciferous hosts were confirmed forPapaver rhoeas, Reseda odorata andLolium perenne (Table 1). In all the susceptible non-crucifers exceptPapaver rhoeas, infection was very sligth. There were more infections onPapaver rhoeas than on the other non-crucifers but fewer than on cabbage, which was heavily infected. On the basis of these results it is not thought that the occurrence of non-cruciferous hosts ofP. brassicae will generally be of great practical importance.     

De stichtingen: Het centraal Bureau voor Schimmel Cultures en het Phytopathologisch Laboratorium „Willie Commelin Scholten”

Summary In this paper a short survey of the history of the Central Bureau of Fungus Cultures at Baarn is given and some of its activities, especially those in relation with plant pathology, are mentioned.     

Waarnemingen over het gedrag van zoösporen uit de zoösporangia vanOlpidium brassicae (wor.) dang

Summary The zoosporangial zoospores ofOlpidium brassicae are uniflagellate (fig. 1). Observations with a phase contrast microscope on living zoospores in watermounts showed that biflagellate zoospores resulted from zoospore fusion. Further, specimens were found with more than two flagella (fig. 2 and 3). As at zoospore discharge only uniflagellate zoospores occur, it may be, assumed that zoospores with more than two flagella are also the result of zoospore fusion. As there may be an analogy betweenO. brassicae andO. viciae,Kusano's explanation of the occurrence of compound zoospores with more than two flagella is discussed.