Genome‐wide association study for spot blotch resistance in Afghan wheat germplasm

Abstract

Spot blotch (SB), caused by Bipolaris sorokiniana, is a devastating disease of wheat globally, especially in South Asia and South America. Understanding the genetics of resistance to SB is important for developing breeding strategies to improve resistance. A panel of 301 genotypes from Afghanistan was phenotyped over two crop seasons using a mixture of virulent B. sorokiniana isolates and genotyped using DArTSeq to obtain genome‐wide markers. Fifty genotypes (16.6%) showed disease scores less than the resistant control. Principal component analysis using the genotypic data clustered the genotypes into five different groups. Among models used for genome‐wide association mapping, the multilocus mixed model, and fixed and random model circulating probability unification algorithms were most effective in identifying significant marker‐trait associations (MTA). Twenty‐five MTAs at p ≤ .001 were identified on chromosomes 1A, 1B, 1D, 2B, 2D, 3A, 3B, 4A, 5A, 5B, 6A, 7A, and 7D, indicating the quantitative nature of resistance to SB. Phenotypic variation explained by these markers ranged from 2.0% to 17.7%, and genomic regions on the chromosomes 1D, 2D, 3A, 3B, 4A, 5A, and 5B coincided with loci identified in previous studies. Three single nucleotide polymorphism (SNP) markers on chromosomes 1B (SNP 1113207) and 5A (SNPs 5411867 and 998276) were significant in both crop seasons as well as in the combined analysis across seasons. Marker 5411867 is close to Vrn‐A1, shown to be associated with SB in previous studies. Furthermore, among known SB resistance genes, Sb2 on chromosome 5B was predicted to be significant in this panel.

New QTLs for Spot Blotch Disease Resistance in Wheat (Triticum aestivum L.) Using Genome-Wide Association Mapping

“…It is noteworthy that the SNP marker S1B_636840957 on chromosome 1B was associated with spot blotch severity, where the annotation study revealed that S1B_636840957 is close to transmembrane protein, which regulates fungal development and pathogenicity via the MAPK module ( Gu et al, 2015 ). Another significant marker S1D_8983568 accounted for 24.0% of the allelic effect, consistent with the earlier studies ( Bainsla et al, 2020 ). However, the QTL reported in our study and Bainsla et al (2020) was more than 83 Mb apart at chromosome 1D.…”

“…Another significant marker S1D_8983568 accounted for 24.0% of the allelic effect, consistent with the earlier studies ( Bainsla et al, 2020 ). However, the QTL reported in our study and Bainsla et al (2020) was more than 83 Mb apart at chromosome 1D.…”

“…Stay-green has been reported to be associated with spot blotch disease resistance ( Joshi et al, 2007a ; Rosyara et al, 2008 ). The present results and other independent studies also indicated the importance of this chromosome region in spot blotch disease resistance ( Joshi et al, 2007a ; Rosyara et al, 2008 ; Bainsla et al, 2020 ).…”

“…The present study not only reports the region on 1A elucidating up to 18.8% of phenotypic variation but also provides insight on the markers S1A_497201550 and S1A_497201682 by gene annotation. The previous studies ( Adhikari et al, 2012 ; Jamil et al, 2018 ; Bainsla et al, 2020 ) on spot blotch reported the chromosomal region on 1A explained 2.1–10% of phenotypic variation. Both SNP markers (S1A_497201550 and S1A_497201682) were associated with LURP-one-like protein that mediates resistance by coordinated transcriptional upregulation of plant defense genes ( Knoth et al, 2009 ).…”

Genetics of resistance to common root rot (spot blotch),Fusariumcrown rot, and sharp eyespot in wheat

“…A recent study phenotyped 301 Afghan wheat germplasms and found that approximately 15% of them exhibited lower disease scores than the resistant control. A subsequent GWAS approach identified twenty-five marker-trait associations on more than twelve chromosomes, including previously identified Vrn-A1 and Sb2/Tsn1 loci [43].…”