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United States Department of Agriculture

Agricultural Research Service

Research Project: Biology and Biological Control of Root Diseases of Wheat, Barley and Biofuel Brassicas

Location: Root Disease and Biological Control Research

Title: Pre-Breeding for root rot resistance using root morphology traits

Authors
item Mahoney, Aaron -
item Okubara, Patricia
item Hulbert, S -

Submitted to: WSU Dryland Field Day Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: May 20, 2014
Publication Date: July 20, 2014
Citation: Mahoney, A., Okubara, P.A., Hulbert, S. 2014. Pre-Breeding for root rot resistance using root morphology traits. WSU Dryland Field Day Abstracts. 14-1. Pg. 29.

Technical Abstract: Root rot caused by the fungal pathogen Rhizoctonia solani can be a major yield-limiting disease in minimal tillage or direct-seeded cereal production systems. Reduced tillage greatly influences the plant residue retained on the soil surfaces. This retained residue (green bridge) provides increased disease pressure from R. solani, but chemical fungicides are not cost-effective. Currently, no resistance in the Triticum germplasm has been identified to this soil-borne pathogen. By identifying and transferring natural resistance using the genetic diversity of ‘synthetic hexaploid’ and natural landraces of wheat into commercial varieties, we will greatly improve this problem. The objectives of our study are to (i) identify root rot resistance in synthetic and landrace accessions of wheat; (ii) transfer this resistance into the Pacific Northwest (PNW) commercial spring wheat cultivar, Louise; and (iii) identify the phenotypic and genetic markers associated with this resistance. To identify resistance, approximately 400 accessions of wheat were evaluated in greenhouse and field assays with high levels of disease pressure. Six accessions were identified having reduced stunting under heavy disease pressure. These six accessions consisted of four synthetic (SYN 30, SYN 172, SYN 182, and SYN 201), one synthetic-derived (SPCB 3104), and one landrace (AUS28451); all have all been crossed at least once to the cv. Louise. In the past year, two large BC1 (two crosses into Louise) derived populations (SPCB 3104 and SYN 172) were evaluated for the second time in our field assays in spring of 2013. These evaluations consisted of planting the individuals into a “green” and “clean” field assay. The green planting consisted of direct-seeding into cool, wet, soils whose plots were chemically sprayed 2-3 days prior to planting (green bridge with high disease pressure). These individuals were compared to those grown in clean soil which was sprayed four weeks prior to planting (no green bridge, low disease pressure). Individual seedlings were evaluated for stunting four weeks after planting. From these evaluations BC2-derived lines were made in the field and have been advanced in the greenhouse. This spring, we will be screening BC1F6 individuals of SYN30 in a green and clean field assay, and backcrosses will be conducted in the field. We have begun evaluating a new mapping population, (AUS28451 by Louise) in a green and clean field assay. AUS28451 is a soil nematode resistant landrace of wheat that we have evaluated in greenhouse and field trials and showed real promise for R. solani resistance. We have continued advancing the best lines from the remaining 2 synthetic populations and have made BC2-derived lines. We will begin screening BC2 lines (three crosses to Louise) for SYN182, SYN 201, 3104, and SYN 172 individuals in greenhouse assays. Finally, using genetic markers from these populations we will identify quantitative trait loci that can be used to transfer this resistance and identify root morphology traits in the best advanced backcrossed lines. Our cooperators are Tim Paulitz and Deven See.

Last Modified: 10/25/2014
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