Role of effector-sensitivity gene interactions and durability of quantitative resistance to septoria nodorum blotch in Eastern U.S. wheat

Authors: Cowger, Christina; Ward, Brian; Brown-Guedira, Gina; BROWN, JAMES - John Innes Center

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/31/2020
Publication Date: 3/6/2020
Citation: Cowger, C., Ward, B.P., Brown Guedira, G.L., Brown, J.K. 2020. Role of effector-sensitivity gene interactions and durability of quantitative resistance to septoria nodorum blotch in Eastern U.S. wheat. Frontiers in Plant Science. 11:155. https://doi.org/10.3389/fpls.2020.00155.
DOI: https://doi.org/10.3389/fpls.2020.00155

Interpretive Summary: Septoria nodorum blotch (SNB) is a disease caused by the fungus Parastagonospora nodorum in wheat. The fungus produces small molecules called necrotrophic effectors that are specifically recognized by the products of matching sensitivity genes in wheat. This recognition can create greater susceptibility in wheat. Yet much remains to be learned about the effect of these interactions on actual wheat resistance levels in the field. There is mixed evidence on whether breeding programs have selected against the sensitivity genes because of their role in increasing susceptibility. The U.S. Atlantic seaboard is an ideal place to study SNB in the field because there are no other important wheat leaf blights. The USDA Eastern SNB Nursery has provided many years of data from the field on resistance of cultivars that are typical of eastern soft winter wheat. Molecular markers are also available for many of these cultivars. In this perspective article, we review the evidence that in this eastern region of the U.S., the partial resistance of wheat cultivars to SNB is durable, and interactions between necrotrophic effectors and wheat sensitivity genes do not play an important role in resistance or susceptibility. This conclusion is discussed in light of information from other parts of the world.

Technical Abstract: Important advances have been made in understanding the relationship of necrotrophic effectors (NE) and host sensitivity (Snn) genes in the Parastagonospora nodorum-wheat pathosystem. Yet much remains to be learned about the role of these interactions in determining wheat resistance levels in the field, and there is mixed evidence on whether breeding programs have selected against Snn genes due to their role in conferring susceptibility. SNB occurs ubiquitously in the U.S. Atlantic seaboard, and the environment is especially well suited to field studies of resistance to natural SNB populations, as there are no other important wheat leaf blights. Insights into the nature of SNB resistance have been gleaned from multi-year data on phenotypes and markers in cultivars representative of the region’s germplasm. In this perspective article, we review the evidence that in this eastern region of the U.S., wheat cultivars have durable quantitative SNB resistance and NE-Snn interactions are of limited importance. This conclusion is discussed in light of the relevant available information from other parts of the world.