Clubroot Development Research Articles

Role of Primary and Secondary Zoospores ofPlasmodiophora brassicaein the Development of Clubroot in Chinese Cabbage

Role of Primary and Secondary Zoospores of<i>Plasmodiophora brassicae</i>in the Development of Clubroot in Chinese Cabbage

Translocation of 14C‐labelled assimilates in cabbage during club root development

SUMMARYThe effects of infection of root systems by Plasmodiophora brassicae on the translocation of 14C‐labelled assimilates from the first and third leaves of cabbage seedlings were investigated. During the early phases of Plasmodium development, there were small differences in the distribution patterns of 14C‐labelled assimilate between healthy and infected seedlings. At the end of growth of plasmodia and during resting spore formation, both first and third leaves exported more assimilates than corresponding leaves of healthy seedlings. When the infected roots were dissected into various regions after exposure of the fed leaves to 14CO2, more assimilate accumulated in the club root region than in any other part.

INFLUENCE OF SOIL MOISTURE, SOIL pH, AND LIMING SOURCES ON THE INCIDENCE OF CLUBROOT, THE GERMINATION AND GROWTH OF CABBAGE PRODUCED IN MINERAL AND ORGANIC SOILS UNDER CONTROLLED CONDITIONS

Under growth chamber conditions, the influence of soil moisture, soil pH, and liming sources on the germination, yield and infection of cabbage by Plasmodiophora brassicae Wor. was studied in artificially infested mineral and organic soils. Clubroot infection occurred at moisture levels as low as 9 and 60% in the mineral and organic soils, respectively. The growth of cabbage and the reduction of the incidence of clubroot were more dependent on liming source than on soil pH. Soil pH adjustment to effect complete clubroot control was invariably deleterious to cabbage growth. It was established for the organic soil that the effect of calcium hydroxide was important in correcting soil acidity as well as supplying calcium as an essential plant nutrient for cabbage. In addition, there was evidence that correction of the soil acidity favored clubroot development, but simultaneously the Ca ion had an inhibitory effect on the disease organism. On the mineral soil, Mg sources producing a soil pH not normally considered deleterious to plants affected the germination and ultimate yield of cabbage.

Carbohydrate composition and activity of invertase in infected cabbage root tissues during club root development

Carbohydrate composition and activity of invertase in infected cabbage root tissues during club root development

Translocation of Sugars Into Infected Cabbage Tissues During Clubroot Development

Sucrose, glucose, and inositol were the major sugars in cabbage hypocotyls infected by Plasmodiophora brassicae and in noninfected hypocotyls, based on paper, thin-layer, and gas-liquid chromatography. Small amounts of trehalose were tentatively identified in extracts from noninfected hypocotyls, whereas up to 20x this level occurred in extracts from infected hypocotyls. Inositol declined in the infected hypocotyls while glucose increased to about 4x the level in noninfected hypocotyls. Fructose and mannose concentrations increased about 2-fold in the diseased hypocotyls, whereas the galactose concentration was about one-third that of noninfected hypocotyls.Translocation of (14)CO(2) sugar photosynthates into infected hypocotyls was more rapid than that into noninfected hypocotyls. The infected tissues also exported less sugar than the non-infected tissues. Sucrose was the major sugar translocated into the hypocotyls of both infected and noninfected plants.