Identification of Novel Quantitative Trait Loci Linked to Crown Rot Resistance in Spring Wheat

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.

Dissecting the Genetic Complexity of Fusarium Crown Rot Resistance in Wheat

“…For example, more numbers of resistant accessions were recorded under GR compared to GH, as GR has minimal environmental effect. Similar to our finding, Erginbas-Orakci et al 19 , confirmed that FCR disease development is comparatively higher in GR compared to GH and field 19 . Mitter et al 32 , reported a significant role of environment on FCR disease development at multiple environment 32 .…”

“…The process of effective recombination events in A and B genomes might have resulted from the historical development of hexaploid wheat and its domestication process 2,33 . Consistent with our previous findings, A and B genomes have higher polymorphism than D genome 19,24 . Würschum et al 34 reported similar finding of few SNPs to be located on the D genome of 172 European winter wheat cultivars 34 .…”

“…Therefore, understanding the complexity of FCR infection and disease development, and their interaction with environment will be crucial for further progress. Various screening approaches have previously been tested and colonized grain method was identified as the most reliable method 19 . Standard wheat "check lines" with known resistance/susceptibility to F. culmorum were included into the trials to evaluate the response of the diverse wheat populations.…”

“…GWAS utilizes linkage disequilibrium to dissect the genetic architecture of complex traits by correlating phenotypes to genotypes. It has been used earlier to identify QTLs that are involved in plant responses to soil borne pathogens in a large set of unrelated wheat accessions 19,24 . Detection of QTLs tightly linked to gene/s that control FCR resistance are the pre-requisite for marker assisted breeding.…”

“…Another major QTL, Fhb1, conferring resistance to FHB caused by the closely related pathogen F. graminearum, was found on chromosome 3BS (Qfhs.ndsu) in spring wheat [15][16][17][18] . Recently, Erginbas-Orakci et al 19 reported two QTLs on chromosomes 3BS linked to FCR resistance in a CIMMYT spring wheat mapping panel under green house conditions 19 . However, since breeding FCR resistance into wheat is a complex process, so far no durable FCR resistant wheat varieties are available.…”