Genome-Wide Association Study for Powdery Mildew and Rusts Adult Plant Resistance in European Spring Barley from Polish Gene Bank

Jerzy H Czembor,Elzbieta Czembor,Nathan S Watson-Haigh,Radoslaw Suchecki

doi:10.3390/agronomy12010007

Abstract

Rusts and powdery mildew are diseases that have a major effect on yield loss in barley. Adult Plant Resistance (APR) is a post-seedling resistance mechanism and its expression is influenced by many factors, including host susceptibility and weather conditions, as well as the timing and severity of disease outbreaks. There are two mechanisms associated with APR: non-hypersensitive and minor gene APR. In this study, 431 European barley accessions were evaluated phenotypically over 2 years (2018–2019) under field conditions, scoring APR to powdery mildew (PM), barley brown rust (BBR), and stem rust (SR), and genotypically using DArTseq. Accessions were grouped into sub-collections by cultivation period (group A—cultivated prior 1985, B—cultivated after 1985, and C—Polish landraces) and by European country of origin or European region. GWAS was conducted for PM, BBR, and SR, and scored at the heading (HA) and milky-waxy (MW) seed stages in 2019 and maximum scores across all replicates were obtained 2018–2019. Disease severity was sufficient to differentiate the collection according to cultivation time and country of origin and to determine SNPs. Overall, the GWAS analysis identified 73 marker–trait associations (MTAs) with these traits. For PM resistance, we identified five MTAs at both the HA stage and when considering the maximal disease score across both growth stages and both years. One marker (3432490-28-T/C) was shared between these two traits; it is located on chromosome 4H. For BBR resistance, six MTAs at HA and one MTA at the MW stage in 2019 and seven MTAs, when considering the maximal disease score across both growth stages and both years, were identified. Of the 48 markers identified as being associated with SR resistance, 12 were on chromosome 7H, 1 was in the telomeric region of the short arm, and 7 were in the telomeric region of the long arm. Rpg1 has previously been mapped to 7HS. The results of this study will be used to create a Polish Gene Bank platform for precise breeding programs. The resistant genotypes and MTA markers will serve as a valuable resource for breeding for PM, BBR, and SR resistance in barley.

Highlights

Barley (Hordeum vulgare L.) is an economically important cereal crop that is known to be dry, cold, salt-tolerant, and well adapted to low-input environmental conditions and changing climates [1,2]
The collection of 431 accessions evaluated under field conditions for powdery mildew (PM), barley brown rust (BBR), and barley stem rust (SR) was grouped into sub-collections according to cultivation time and country of origin
An analysis of the genome-wide association study (GWAS) for resistance to powdery mildew (PM), stem rust (SR), and barley brown rust (BBR) at the HA and MW stages in 2019 and for maximum scores across all the replicates during 2018–2019 indicate 73 markers associated with these traits

Summary

Introduction

Barley (Hordeum vulgare L.) is an economically important cereal crop that is known to be dry, cold, salt-tolerant, and well adapted to low-input environmental conditions and changing climates [1,2]. It is cultivated at high altitudes, commonly under rainfed conditions. Almost half of the world’s barley growing area is in Europe, including Poland, where it is ranked second in terms of the most cultivated crop after wheat. It is used for livestock feed, malt, and foods. Domestic Polish barley supply has fluctuated substantially in recent years, it tended to decline from 1969–2018 [4]

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