Abstract
BackgroundCommon bunt (caused by Tilletia caries and T. foetida) has been considered as a major disease in wheat (Triticum aestivum) following rust (Puccinia spp.) in the Near East and is economically important in the Great Plains, USA. Despite the fact that it can be easily controlled using seed treatment with fungicides, fungicides often cannot or may not be used in organic and low-input fields. Planting common bunt resistant genotypes is an alternative.ResultsTo identify resistance genes for Nebraska common bunt race, the global set of differential lines were inoculated. Nine differential lines carrying nine different genes had 0% infected heads and seemed to be resistant to Nebraska race. To understand the genetic basis of the resistance in Nebraska winter wheat, a set of 330 genotypes were inoculated and evaluated under field conditions in two locations. Out of the 330 genotypes, 62 genotypes had different degrees of resistance. Moreover, plant height, chlorophyll content and days to heading were scored in both locations. Using genome-wide association study, 123 SNPs located on fourteen chromosomes were identified to be associated with the resistance. Different degrees of linkage disequilibrium was found among the significant SNPs and they explained 1.00 to 9.00% of the phenotypic variance, indicating the presence of many minor QTLs controlling the resistance.ConclusionBased on the chromosomal location of some of the known genes, some SNPs may be associated with Bt1, Bt6, Bt11 and Bt12 resistance loci. The remaining significant SNPs may be novel alleles that were not reported previously. Common bunt resistance seems to be an independent trait as no correlation was found between a number of infected heads and chlorophyll content, days to heading or plant height.
Highlights
IntroductionCommon bunt (caused by Tilletia caries and T. foetida) has been considered as a major disease in wheat (Triticum aestivum) following rust (Puccinia spp.) in the Near East and is economically important in the Great Plains, USA
Common bunt has been considered as a major disease in wheat (Triticum aestivum) following rust (Puccinia spp.) in the Near East and is economically important in the Great Plains, USA
The objectives of this study are: 1) identify genes that are resistant to the Nebraska race of common bunt using 14 differential lines, 2) screen a set of 330 Nebraska winter wheat lines for resistance to common bunt in multiple locations, 3) identify alleles/genomic regions associated with common bunt resistance using genome-wide association study (GWAS), and 4) study the correlation of common bunt resistance and agronomic traits which could possibly be used as a selection criterion
Summary
Common bunt (caused by Tilletia caries and T. foetida) has been considered as a major disease in wheat (Triticum aestivum) following rust (Puccinia spp.) in the Near East and is economically important in the Great Plains, USA. Occasionally the formation of bunt balls can occur only in the last spike formed on the plant and only in a few of the florets [1] To overcome these limitations in the direct assessment of common bunt resistance, marker-assisted selection (MAS) could be used. Genotyping-by-sequencing usually generates a lot of SNP markers that cover large genomic regions in a cost-effective manner [6, 7]. Those genome-wide SNPs could be utilized in different genomics studies including genome-wide association study (GWAS), genomic selection, and genetic diversity studies. To detect alleles associated with target traits using GWAS, 100–500 individuals and codominant markers (SSR or SNP) are highly recommended for the analysis [9]
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