Abstract
Crown rot (CR), caused by various Fusarium species, is a major disease in many cereal-growing regions worldwide. Fusarium culmorum is one of the most important species, which can cause significant yield losses in wheat. A set of 126 advanced International Maize and Wheat Improvement Center (CIMMYT) spring bread wheat lines were phenotyped against CR for field crown, greenhouse crown and stem, and growth room crown resistance scores. Of these, 107 lines were genotyped using Diversity Array Technology (DArT) markers to identify quantitative trait loci linked to CR resistance by genome-wide association study. Results of the population structure analysis grouped the accessions into three sub-groups. Genome wide linkage disequilibrium was large and declined on average within 20 cM (centi-Morgan) in the panel. General linear model (GLM), mixed linear model (MLM), and naïve models were tested for each CR score and the best model was selected based on quarantine-quarantine plots. Three marker-trait associations (MTAs) were identified linked to CR resistance; two of these on chromosome 3B were associated with field crown scores, each explaining 11.4% of the phenotypic variation and the third MTA on chromosome 2D was associated with greenhouse stem score and explained 11.6% of the phenotypic variation. Together, these newly identified loci provide opportunity for wheat breeders to exploit in enhancing CR resistance via marker-assisted selection or deployment in genomic selection in wheat breeding programs.
Highlights
Bread wheat (Triticum aestivum L.) is one of the most important cereal crops
Crown rot (CR) is mostly caused by Fusarium pseudograminearum, but F. culmorum has been shown to cause significant reductions in wheat yields, both species are considered economically important [8,9]
The 126 spring bread wheat accessions were classified into three groups according to their CR resistant reactions under growth room, greenhouse, and field conditions (Figure 1, Table S1)
Summary
Bread wheat (Triticum aestivum L.) is one of the most important cereal crops. It is an allohexaploid (2n = 6x = 42, AABBDD) originated from the result of a rare natural hybridization between tetraploid emmer wheat (AABB, T. dicoccoides) and the diploid wild goat grass (DD, Aegilops tauschii) around. GWAS utilizes linkage disequilibrium to dissect the genetic architecture of complex traits by correlating phenotypes to genotypes [18,19] It has been utilized successfully in wheat to identify QTL linked to many important agronomic traits such as flowering time, plant height, grain yield, milling quality and disease resistance [18,20,21,22,23,24,25,26,27,28]. A candidate gene-based association study reported association of mitogen-activated protein kinase (MAPK) HOG1 gene with aggressiveness and deoxynivalenol (DON) production, explaining 10.29 and 6.05% of the genotypic variance, respectively [35] This present study aims to improve resistance of spring bread wheat to F. culmorum with the following objectives: (i) analyze resistance responses of spring bread wheat accessions to F. culmorum, and (ii) use GWAS to identify novel genomic loci conferring resistance to F. culmorum
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