Beoordeling van lijnzaad opBotrytis
With a summary: Judging flax seed for Botrytis
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Gedurende de laatste jaren wordt internationaal veel aandacht geschonken aan deBotrytis-aantasting van lijnzaad. Voor routine-onderzoek van lijnzaadmonsters wordt in verscheidene landen de voorkeur gegeven aan de agarmethode, terwijl in Nederland van ouds de filtreerpapier-proef in het donker wordt gebruikt.
In het onderhavige onderzoek werden de filtreerpapier-proef in het licht, de filtreerpapier-proef in het donker en de agar-methode ter bepaling van deze infectie vergeleken met betrekking tot de resultaten van grondproeven. Daarbij bleek, dat deze drie methoden ten opzichte van de grondproeven vrijwel even nauwkeurig zijn, maar dat de achteruitgang van de infectie tijdens de bewaring van geïnfecteerd zaad beter tot uitdrukking komt in de filtreerpapier-methoden dan in de agar-methode.
De oude werkwijze van het Proefstation heeft belangrijke nadelen, o.a. dat hij onbevredigend is voor de meeste andere lijnzaadschimmels. De agar-methode blijkt ook belangrijke nadelen te hebben. In de toekomst zal worden overgegaan op de filtreerpapier-methode in het licht.
In the examination of flax seed for infection withBotrytis cinerea, different methods are used in different countries. Since there is, as yet, no internationally accepted standard method, it was thought desirable to compare the results obtained with various routine methods now in use.
In this investigation 61 samples of flax seed were tested for the fungus by three methods, viz. the malt agar method, the blotter method in darkness and the blotter method in light. The results obtained using these laboratory methods were compared with the figures for emergence andBotrytis percentage in soil tests at constant temperatures of 12° and 20°C. All methods were used simultaneously in early winter and again in spring after four month's storage in an unheated room.
Figs. 1 and 2 show the importance ofBotrytis under field conditions in the Netherlands and the prevalence of infection in the seed harvest over a period of years.
Table 1 shows the correlation-coefficient found between the figures forBotrytis infection determined with the laboratory methods and the emergence figures determined in soil tests. It would appear that the three laboratory methods are equally accurate, but that the soil test at 12°C, which is the more common temperature for flax sowings, is more reliable. The correlations are far higher for the fall determinations, which suggests that by spring the aged and declining infections become very sensitive to small variations in testing conditions.
Table 2 gives the average infection figures found for the 61 samples by the different methods. It will be seen that they are highest for the agar method and lowest for the blotter method in light. The decline of the seed-borne inoculum during storage is best revealed by the blotter test in light, somewhat less by the blotter test in darkness, and very badly by the agar test.
Especially when a weak or weakened pathogen is concerned it is scientifically preferable to use a method in which the infection is estimated from parasitic development on the growing seedling. In seed testing practice, however, the first samples are usually examined several months before, and the last ones during or even after normal sowing time. This makes a method desirable which does not reflect the aging very strongly, such as the agar-method. The results of the agar test are quickly available, but the method has practical disadvantages. For example, it is cumbersome to handle 40 glass dishes of 10 seeds per sample, and it requires absolute sterility, which is difficult to fulfil whereRhizopus and similar fungi are prevalent air- and seed-borne contaminants.
ForBotrytis the old blotter method in darkness is fairly satisfactory, but for other seed-borne flax fungi — which in Holland are far less common — it is unsatisfactory. In past years, therefore, the blotter method in light has frequently been used beside it.
The agar method does not seem attractive. For that reason the Dutch Seed Testing Station intends to adopt the blotter method in light for flax health investigation. For the purpose glass germinators with fluorescent light will be constructed.
It will be understood from the preceding that any choice of a routine method of health investigation for flax seed will to some extent be arbitrary, and markedly dependent on local circumstances, such as equipment, experience, and requirements. Such a choice cannot but be subjective. Though international standardization of certain testing methods is a modern aim and should be welcomed, it does not seem desirable to push it so far that certain methods are made internationally obligatory for certain infections. In stead it might be studied what is the level of the results obtained with different methods for the same disease.
KeywordsSoil Test Agar Method Flax Seed Blotter Method Health Investigation
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