meng.li@botany.ubc.ca; sean.formby@gmail.com; forum.bhanshali@terramera.com; lu.liu3@wsu.edu; gurcharn@ualberta.ca; annett@terramera.com; guus.bakkeren@agr.gc.ca;

Despite quarantine measures, new wheat rust fungal isolates enter Canada regularly, often from Mexico via the US by common airflows known as the Puccinia pathways. New incursions include mutated rust spores with changed virulence, aggressiveness, and sensitivities to fungicides. Evolved isolates can result in changed virulence towards current resistant wheat varieties and can be caused by mutated or lost avirulence effectors or nuclear haplotype exchange via hybridization.

Complementing rust disease control via genetic resistance occurs through fungicide application which has been estimated to cost on average $17.25 per acre annually in wheat fields on the Canadian Prairies. Even though fungicides are targeted to fungal pathogens, they have also been reported to trigger disease resistant effects on the host plant.

Therefore, our collaboration connecting industrial technology and wheat-rust research has developed an assay system combining plant genetics and fungicide plus formulation treatment on germinating urediniospores and detached or in-planta, infected leaves that allows for dramatic dose reductions of the synthetic fungicides Quadris and Proline often used for wheat leaf rust control.

To study the potential mode of actions (molecular mechanisms) of the commercial compounds, the effect of the supplement, and to identify potential biomarkers for diagnosing virulence-reducing and defense-enhancing responses in both fungus and wheat host, comparative transcriptomic analyses were carried out.

By comparing groups of leaf rust fungus and wheat transcripts, differentially expressing genes were identified as potential diagnostic biomarkers indicating resistance or susceptibility, and as potential regulators of defense responses as annotated by gene ontology searches.

This new combinational treatment will generate significant cost savings, increase options available to producers as well as reduce negative environmental impacts of synthetic fungicides while improving crop yield and quality.