Thesis (M.S.)--Wisconsin. / Includes bibliographical references.

Presented as Thesis (Ph. D.)--University of Wisconsin--Madison, 1934. / Caption title. From Journal of agricultural research, vol. 49, no. 7 (Oct. 1, 1934). "This study was carried out under the cooperative support of the Division of Fruit and Vegetable Crops and Diseases, Bureau of Plant Industry, U.S. Dept. of Agriculture, and the Dept. of Plant Pathology, College of Agriculture, University of Wisconsin."--Foot-note, p. 607. "Literature cited": p. 623-624.

Thesis (M.Sc.)--University of Alberta, 2010. / Title from PDF file main screen (viewed on May 3, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science in Plant Science, Department of Agricultural, Food and Nutritional Science, University of Alberta. Includes bibliographical references.

No description available.

Clubroot (casual agent Plasmodiophora brassicae Woronin,) is a major disease of crucifers, liming is the traditionally applied control method. This project aimed to identify effects of calcium and pH, in isolation, on host invasion and pathogen development. Nitrogen and boron were investigated as potential control agents in order to develop an integrated nutrient control treatment effective at high inoculum pressures. Chinese cabbage seedlings Brassica oleracea ssp. pekinensis cv. Granaat,) were grown in acid washed sand or peat: sand composts containing various concentrations of nutrients and P. brassicae propagules. pH was varied and concentrations of calcium, nitrogen and boron were raised for specific periods of the host parasite cycle. Assessments of infection number and sporogenesis in the root hair were made 10-16 days after inoculation. Clubbing symptoms, host dry weights and mineral contents of root and leat tissue were assessed at 30 days. Infection was reduced by separate increases of pH to 7.2 and calcium to 55mel-1. Sporogenesis of root hair infections was inhibited by pH 7.2, 55mel-1 calcium and 6.4ppm boron. Suppression of clubbing by pH 7.2, 55mel-1 calcium and 60mel-1 nitrate was effected 0-14 days after inoculation, applications of such inhibitory treatments later than 14 days were ineffective. In contrast 6.4ppm boron applied over 0-14 and 14-30 day periods actively reduced clubbing. Nitrate, boron pH treatments controlling clubroot were non-phytotoxic. Control due to pH7.2 may in part be attributed to enhanced uptake of calcium into host plants at higher pH. Suppressive nutrients applied at pH7.2 and calcium applied with boron showed synergistically enhanced control of clubroot when compared with single treatments. A non-phytotoxic nutrient containing intermediate levels of calcium (30mel-1), nitrate (30mel-1) and boron (6.4ppm) at pH7.2 reduced disease index from 100% to 3% in plants subject to heavy inoculum pressures. An integrated control treatment for clubroot was thus demonstrated.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1968. / Typescript. Vita. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1968. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

No description available.

Management of clubroot caused by the soil-borne biotrophic plant protist Plasmodiophora brassicae on canola and other Brassica crops is an important challenge to producers. Studies on the interaction of pH and temperature on root hair infection (RHI) and clubroot symptom development in canola roots revealed that high levels of clubroot can occur under optimum temperature, moisture and spore load, even at alkaline pH of 7.5. Clubroot was suppressed at all temperatures at pH 8.0, but not totally eliminated. The occurrence of maximum levels of root hair infection and clubroot development (RHI = 61%, Clubroot incidence (CI) & Disease severity index (DSI) = 100%) at temperatures of 20° and 25°C and pH of 5.0 to 6.5 was confirmed. The efficacy of biofungicides against P. brassicae was influenced by pathogen load, host, growth media and its properties. Drench application of Serenade and Prestop were moderately effective in reducing clubroot levels in canola (Brassica napus L. and B. rapa L.) and to a lesser extent in Shanghai pak choy (B. rapa L. ssp. Chinensis (Rupr.) var. communis Tsen and Lee). The mean clubroot incidence and severity caused by Pathotype 3 was found to be slightly higher than that of Pathotype 6. Clubroot level increased with increase in soil bulk density.

The aim of this project was to develop treatments that would be able to reduce the survival of clubroot spores in field soil and protect the roots of young transplants against infection. The project focused on using combinations of treatments which integrate novel and existing controls with emphasis placed on the sustainable use of waste materials, plant materials and bioactives. A wide range of treatments were screened individually and in combination under glasshouse and field conditions, e.g. fungicides, nutritional amendments, companion planting, plant saponins and biocontrol agents. Many of these treatments were able to reduce clubroot severity to varying degrees. Glasshouse treatments were more successful at controlling disease than those applied in the field. The most effective treatments - when applied correctly - contained calcium, e.g. lime as calcium oxide or LimeX (a by-product of the sugarbeet processing industry), and crushed scallop and whelk shells (a by-product of the fishing industry). Whilst the effects of calcium and pH on clubroot are not new, growers need to think more in terms of dose of calcium applied in the field rather than just pH, and also, the time of addition of lime to soil before planting needs serious consideration as it may be optimal to apply lime less than two weeks before transplanting. Experimental results have shown that soil microflora plays a major role in the development of clubroot disease and that the membrane potential of growing roots may be one of the most important factors in preventing P. brassicae from entering plant roots and causing disease due to the effect that calcium and pH have on clubroot control. The experiments have also shown that there are interactions between treatments such as fungicides, limes, soil nutritional level and soil microflora at controlling disease and some treatments may reduce the effectiveness of other treatments at controlling disease. Another factor that is known to affect the effectiveness of treatments at controlling clubroot is the initial spore load in the soil. Therefore, an additional aim of the project was to develop a rapid, quantitative PCR based diagnostic test that could measure the level of clubroot spores directly from soil. Plasmodiophora brassicae DNA was successfully extracted and amplified from artificially inoculated soils and from naturally infested field soils using real-time PCR with selected sets of primers and probes. Many different types of soil DNA extraction methods were tested and standard curves relating to different levels of spore inoculum were created. This project has generated useful information as to why there are contradictory results in clubroot research about the effect of various treatments at controlling clubroot. This information may also be the basis of practical advice to brassica growers on best practices to use to achieve optimal clubroot control in the field. Options in relation to new sustainable control treatments are discussed in the light of the results from both glasshouse and field experiments. These involve planting brassicas on raised beds and applying treatments strategically around the root zone. LimeX 70 or powdered calcium oxide were demonstrated to be the most optimal lime treatments for control, and a split application of Perlka (granular calcium cyanamide) may prove to be a consistently effective method for controlling clubroot.