Plant root - fungal pathogen interactions

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Plant roots provide a vital connection with the soil or growth substrate, ensuring uptake and conductance of nutrients and water. Many stresses reduce root growth, which negatively impacts plant growth and development. Pathogenic fungi can severely compromise root growth. These soil-inhabiting organisms penetrate roots, causing death through production of enzymes and toxins (pathogenesis). Knowledge of the factors affecting fungal pathogenesis and how plants can potentially defend against infection, via production of defense compounds, would provide valuable information. The information generated can be applied to reduce the negative impact of these fungi on food production. In this research, three important aspects of fungal x plant x environment interactions will be studied to understand pathogenesis. 1). How does transgene expression affect defense responses in carrot tissues and fungal pathogenesis ? We will evaluate effects of genes encoding peroxidase, NPR1 ( a signaling pathway modulator ) and carotenoids on different molecular, biochemical, and cellular responses in tissues. The levels of PR-proteins, active oxygen species and hydrogen peroxide, as well as lignin formation, will be determined. This will help identify the key defense responses in roots to pathogen challenge. 2). Can pathogenesis be mediated through dsRNA (mycovirus) infection ? Double-stranded RNA elements are known to affect fungal virulence. The effects of dsRNA on pathogenesis of Chalara elegans on carrot will be investigated, including the effects on virulence, fungal gene expression, and phenotype of strains with and without specific dsRNA elements. This should help identify the key fungal parameters involved in pathogenicity. 3). How does iron affect fungal pathogenesis on carrot ? While iron is an essential micronutrient for plant growth and for some fungi, effects on root infection by fungi have not been well researched. The effect of iron on fungal enzyme production, production of host defense compounds, and on pathogenesis, will be studied using Chalara elegans, an important root-infecting pathogen. The proposed research will provide valuable insight into plant root-fungal pathogen interactions and provide novel information.