Genome-wide association mapping for tolerance to preharvest sprouting and low falling numbers in wheat

Authors: MARTINEZ, SHANTEL - Washington State University; GODOY, JAYFRED - Washington State University; HUANG, MENG - Washington State University; ZHANG, ZHIWU - Washington State University; CARTER, AARON - Washington State University; Garland-Campbell, Kimberly; Steber, Camille

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/25/2018
Publication Date: 2/14/2018
Citation: Martinez, S.A., Godoy, J., Huang, M., Zhang, Z., Carter, A.H., Garland Campbell, K.A., Steber, C.M. 2018. Genome-wide association mapping for tolerance to preharvest sprouting and low falling numbers in wheat. Frontiers in Plant Science. 9:141. https://doi.org/10.3389/fpls.2018.00141.
DOI: https://doi.org/10.3389/fpls.2018.00141

Interpretive Summary: Preharvest sprouting (PHS), the germination of grain on the mother plant under cool and wet conditions, is a recurring problem for wheat farmers worldwide. Wheat flour made from sprouted grain contains high levels of the enzyme alpha-amylase that digests starch resulting in cakes that fall and bread that fails to rise well. The wheat industry uses the Hagberg-Perten Falling Number (FN) test to detect this problem before the wheat is baked. FN determines how much a farmer’s wheat is discounted for sprout damage. Genetic tolerance to preharvest sprouting is associated with higher grain dormancy at maturity that reduces that change that germination will be initiated. Thus, breeding programs use germination-based assays such as the spike-wetting test to measure preharvest spouting susceptibility. Association mapping was performed in a panel of 469 soft white wheat lines from the U.S. Pacific Northwest. We identified 9 genes/loci called QFN.wsu associated with higher/better Falling Number and 34 genes/loci called QPHS.wsu associated with less germination in the spike-wetting test. This is the first study to map preharvest sprouting tolerance based on both Falling Number and germination.

Technical Abstract: Preharvest sprouting (PHS), the germination of grain on the mother plant under cool and wet conditions, is a recurring problem for wheat farmers worldwide. a-amylase enzyme produced during PHS degrades starch resulting in baked good with poor end-use quality. The Hagberg-Perten Falling Number (FN) test is used to measure this problem in the wheat industry, and determines how much a farmer’s wheat is discounted for PHS damage. PHS tolerance is associated with higher grain dormancy. Thus, breeding programs use germination-based assays such as the spike-wetting test to measure PHS susceptibility. Association mapping identified loci associated with PHS tolerance in U.S. Pacific Northwest germplasm based both on FN and on spike-wetting test data. The study was performed using a panel of 469 white winter wheat cultivars and elite breeding lines genotyped for 15,229 polymorphic markers using the 90k SNP Illumina iSelect array. Marker-trait associated were identified using the FarmCPU R package over five Washington state environments. Principal component was directly and kinship matrix was indirectly used to account for population structure. Nine loci associated with FN and 34 loci associated with PHS based on sprouting scores. None of the QFN.wsu loci were detected in multiple environments, whereas six of the 34 QPHS.wsu loci were detected in two of the five environments. There was no overlap between the QTN detected based on FN and PHS, and there was little correlation between the two traits. However, both traits appear to be PHS-related since 19 of the 34 QPHS.wsu loci and four of the nine QFN.wsu loci co-localized with previously published dormancy and PHS QTL. Loci identified in this study have the potential to improve marker-assisted selection for PHS tolerance.