Interactions of soil nutrient environment, pathogenesis and host resistance

Abstract

Host plants and soil borne pathogens that attack them exist within an ecological matrix populated by numerous microbial species that may influence the access of pathogenesis. These events are moderated by physical and chemical components of the soil. The impact of inorganic and organic nutrients on pathogenesis and the development of host resistance are discussed in this review using two host – pathogen combinations as examples. Calcium, boron, nitrogen and pH have been demonstrated to affect the processes of resting spore germination, host invasion and colonisation in the Plasmodiophora brassicae-Brassica combination that results in clubroot disease. Organic nutrients that have associated biostimulant properties have been demonstrated to influence the development of Pythium ultimum-Brassica combination that results in damping-off disease. This latter combination is affected by the presence of antagonistic microbial flora as demonstrated by increased ATP, extra-cellular enzyme and siderophore production. In both examples there are indications of the manner by which host resistance to pathogenesis may be enhanced by changes to the nutrient status surrounding host plants. These effects are discussed in relation to the development of integrated control strategies that permit disease control with minimal environmental impact.