A nested association mapping population identifies multiple small effect QTL conferring resistance against net blotch (Pyrenophora teres f. teres) in wild barley

Abstract

The net form of net blotch caused by the necrotrophic fungus Pyrenophora teres f. teres is a major disease of barley, causing high yield losses and reduced malting and feed quality. Exploiting the allelic richness of wild barley proved to be a valuable tool to broaden the genetic base of resistance of modern elite cultivars. In this study, a SNP-based nested association mapping (NAM) study was conducted to map QTL for P. teres resistance in the barley population HEB-25 comprising 1,420 lines derived from BC1S3 generation. By scoring the percentage of infected leaf area followed by calculation of the average ordinate (AO) and scoring of the reaction type (RT) in two-year field trials a large variability of net blotch resistance across and within families of HEB-25 was observed. Genotype response to net blotch infection showed a range of 48.2% for AO (0.9–49.1%) and 6.4 for RT (2.2–8.6). NAM based on 5,715 informative SNPs resulted in the identification of 24 QTL for resistance against net blotch. Out of these, six QTL are considered novel showing no correspondence to previously reported QTL for net blotch resistance. Overall, variation of net blotch resistance in HEB-25 turned out to be controlled by small effect QTL. Results indicate the presence of alleles in HEB-25 differing in their effect on net blotch resistance. Results provide valuable information regarding the genetic architecture of the complex barley-P. teres f. teres interaction as well as for the improvement of net blotch resistance of elite barley cultivars.

SNPs associated with barley resistance to isolates of Pyrenophora teres f. teres

“…We suggest that seedling resistance to the newly studied isolates P3.4.0 and K5.1 is conferred in Siberian barley germplasm by the previously known locus found on chromosome 1H by Grewal et al (2012) [10] and Afanasenko et al (2014) [2]. In addition, chromosome 1H is known to carry another locus at approximately 40 cM from this one, described by Amezrou et al (2018) [8] and Vatter et al [18] (Table 5).…”

“…The locus associated with resistance to the S10.2 isolate included one suggestive SNP (JHI-Hv50k-2016-74407) mapped in the interval 23.3-23.8 cM. We suggest that seedling resistance to the S10.2 isolate is conferred by a previously known locus mapped earlier by Wonneberger et al (2017) [7] and Vatter et al (2017) [18] (Table 5). The locus on chromosome 2H revealed for the P3.4.0 isolate included 7 SNPs and was expanded between JHI-Hv50k-2016-104508 and JHI-Hv50k-2016-104859 markers located in the interval 71.0-74.1 cM.…”

“…The genomic regions associated with resistance of barley to P. teres f. teres have been found on all barley chromosomes [3,[5][6][7][8][9][10][11][12][13][14][15][16][17][18] using both linkage mapping in biparental mapping populations and association mapping (AM). Some QTLs provide resistance during whole ontogenesis, such as QRpt6 on chromosome 6H, determining both seedling and adult resistance to the net form of net blotch [5].…”

Barley yield formation under abiotic stress depends on the interplay between flowering time genes and environmental cues

“…Wild barley accessions, in particular H. v. ssp. spontaneum, the progenitor of cultivated barley have been used to improve disease resistance 24,82 and abiotic stress tolerance 22,69,83,84 , as well as plant developmental traits 18,20,25 and quality traits 82,85,86 . The successful use of wild relatives to increase grain yield of barley has not been reported frequently, some exceptions are available 69,87,88 .…”

“…The usefulness of wild germplasm for future breeding has often been emphasized [14][15][16] , mostly as a source to improve biotic resistance and abiotic stress tolerance rather than to directly increase grain yield 17 . Recent studies in wild barley indicate the existence of vast phenological variation for important agronomic traits [18][19][20][21][22][23][24][25] .…”