Research Objective
To develop a stain-based bioassay to distinguish between viable and non-viable resting spores; to conduct a high throughput screen of 50,000 small molecules to identify those that can induce zoospore emergence; to validate candidate compounds identified from the screen and assess their efficacy using plant assays.
Aphanomyces euteiches is an oomycete plant pathogen that is the causative agent of Aphanomyces root rot (ARR) in pulse crops (Wu et al. 2018). Primarily affecting peas and lentils, crop yield loses due to ARR pose a significant economic threat to pulse crop production in Saskatchewan due to limited disease prevention and treatment options (Chatterton et al. 2019; Karppinen et al. 2020). Acting as the primary inoculum source in the soil, the resting spore structure of A. euteiches is highly resistant and has been reported to remain viable in the soil for over ten years (Billard et al., 2019; Pfender & Hagedorn, 1983). In the presence of root exudates from host plants, the resting spores are capable of germination and subsequent release of short-lived motile zoospores which can swim and encyst on the surface of host roots and cause infection (Billard et al., 2019). As the longevity of resting spores acts as the primary challenge in preventing crop cultivation in infected fields, methods are required to reduce the amount of viable inoculum in the soil. As such, exploring small molecules capable of pre-germinating resting spores prior to sowing host crops could greatly reduce pathogen infection and propagation. Methods for harvesting spores as well as a staining method to facilitate the identification of viable and non-viable spores were explored.