Improving sunflower resistance to the necrotrophic fungal pathogens Sclerotinia and Phomopsis

Authors: Underwood, William; Misar, Christopher; Overlander-Chen, Megan; SHARMA-POUDEL, ROSHAN - North Dakota State University; PAHL, JESSE - North Dakota State University

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 1/8/2020
Publication Date: N/A
Citation: N/A

Interpretive Summary: Sclerotinia sclerotiorium, Diaporthe helianthi, and Diaporthe gulyae are fungal pathogens causing damaging diseases and yield loss on sunflower in the US. Currently, sunflower producers have limited options for managing these important diseases due to lack of sufficient genetic resistance in commercial sunflower hybrids and limited efficacy of chemical control measures. Sclerotinia sclerotiorum causes white mold diseases on many crop plants, including three distinct diseases on cultivated sunflower: head rot, basal stalk rot, and mid-stalk rot. The related fungal species Diaporthe helianthi and Diaporthe gulyae are the causal agents of Phomopsis stem canker, a disease that has increased in prevalence in the US over the past decade. Resistance to these important sunflower diseases is genetically complex and the mechanisms conferring resistance are poorly understood. In this presentation, I will give an overview of our current efforts to uncover the molecular, genetic and physiological basis for resistance to these diseases and to develop knowledge to improve deployment of genetic resistance in commercial sunflower hybrids.

Technical Abstract: Our understanding of the basis for quantitative disease resistance to necrotrophic phytopathogens is currently limited. Similarly, the extent of genetic and pathogenic variation among isolates of the sunflower pathogens Sclerotinia sclerotiorum and Diaporthe helianthi and the mechanisms used by these pathogens to cause disease are poorly understood. Our efforts toward improving sunflower resistance to these important diseases are focused in two main areas: 1) Characterizing mechanisms of sunflower quantitative resistance to S. sclerotiorum and Diaporthe spp. and identifying the underlying genes; 2) Investigating the virulence strategies used by S. sclerotiorum and D. helianthi to successfully colonize sunflower. In this presentation, I will summarize progress on projects to identify sunflower lines with high levels of Sclerotinia basal stalk rot resistance and characterize resistance mechanisms, to define mechanisms of resistance to Phomopsis stem canker caused by Diaporthe helianthi in sunflower germplasm resources, and to evaluate genetic and pathogenic variation among Diaporthe helianthi isolates.