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Article|23 Mar 2022|OPEN
Genome-wide association study and genomic prediction of white rust resistance in USDA GRIN spinach germplasm 
Ainong Shi1 , , Gehendra Bhattarai1 , Haizheng Xiong1 , Carlos A. Avila2 , , Chunda Feng3 , Bo Liu3 , Vijay Joshi4 , Larry Stein4 , , Beiquan Mou5 , , Lindsey J. du Toit6 , and James C. Correll,3 ,
1Department of Horticulture, University of Arkansas, Fayetteville, AR 72701, USA
2Department of Horticultural Sciences, Texas A&M AgriLife Research and Extension Center, Weslaco, TX 78596, USA
3Department of Plant Pathology, University of Arkansas, Fayetteville, AR 72701, USA
4Texas A&M AgriLife Research and Extension Center, Uvalde, TX 77801, USA
5Crop Improvement and Protection Research Unit, USDA-ARS, Salinas, CA 93905, USA
6Washington State University, Mount Vernon, WA 98273, USA
*Corresponding author. E-mail: ashi@uark.edu,Carlos.Avila@ag.tamu.edu,larrystein@tamu.edu,beiquan.mou@usda.gov,dutoit@wsu.edu,jcorrell@uark.edu

Horticulture Research 9,
Article number: uhac069 (2022)
doi: https://doi.org/10.1093/hr/uhac069
Views: 21

Received: 22 Nov 2021
Accepted: 09 Mar 2022
Published online: 23 Mar 2022

Abstract

White rust, caused by Albugo occidentalis, is one of the major yield-limiting diseases of spinach (Spinacia oleracea) in some major commercial production areas, particularly in southern Texas in the United States. The use of host resistance is the most economical and environment-friendly approach to managing white rust in spinach production. The objectives of this study were to conduct a genome-wide associating study (GWAS), to identify single nucleotide polymorphism (SNP) markers associated with white rust resistance in spinach, and to perform genomic prediction (GP) to estimate the prediction accuracy (PA). A GWAS panel of 346 USDA (US Dept. of Agriculture) germplasm accessions was phenotyped for white rust resistance under field conditions and GWAS was performed using 13 235 whole-genome resequencing (WGR) generated SNPs. Nine SNPs, chr2_53 049 132, chr3_58 479 501, chr3_95 114 909, chr4_9 176 069, chr4_17 807 168, chr4_83 938 338, chr4_87 601 768, chr6_1 877 096, and chr6_31 287 118, located on chromosomes 2, 3, 4, and 6 were associated with white rust resistance in this GWAS panel. Four scenarios were tested for PA using Pearson’s correlation coefficient (r) between the genomic estimation breeding value (GEBV) and the observed values: (1) different ratios between the training set and testing set (fold), (2) different GP models, (3) different SNP numbers in three different SNP sets, and (4) the use of GWAS-derived significant SNP markers. The results indicated that a 2- to 10-fold difference in the various GP models had similar, although not identical, averaged r values in each SNP set; using GWAS-derived significant SNP markers would increase PA with a high r-value up to 0.84. The SNP markers and the high PA can provide valuable information for breeders to improve spinach by marker-assisted selection (MAS) and genomic selection (GS).