The relation was studied between black vessel disease of beet and factors influencing the condition of the soil. Field observations demonstrated that the disease occurred exclusively on sandy soils and that wet and cool weather during May and June encouraged the disease.The virulence was studied of several strains of Pythium irregulare and one strain of P. debaryanum. All these strains could cause damping-off but only a few strains of P. irregulare could cause black vessel disease. Toxic metabolites of the fungus, secreted in the lateral roots and transported through the waterconducting tissues, caused the symptoms of black vessel disease. A correlation could be demonstrated between the pathogenicity of the different strains and the toxicity of their staling products.The amount of nutrients in the soil had no influence on the severity of the disease but acid soil (pH 7.1-4.9) encouraged the disease.The influence of the temperature was clearest at a moisture content of 20-50 % of the moisture-holding capacity of the soil, the disease being more severe at a higher temperature.There was a positive correlation between severity of the disease and moisture content of the soil.
|Qualification||Doctor of Philosophy|
|Award date||13 Apr 1951|
|Place of Publication||Wageningen|
|Publication status||Published - 1951|
- plant pathogenic fungi
- fodder beet