A novel way to identify specific powdery mildew resistance genes in hybrid barley cultivars

Antonín Dreiseitl

doi:10.1038/s41598-020-75978-7

Abstract

Powdery mildew, a common cereal disease caused by the fungus Blumeria graminis, is a major limiting factor of barley production and genetic resistance is the most appropriate protection against it. To aid the breeding of new cultivars and their marketing, resistance genes can be postulated in homogeneous accessions. Although hybrid cultivars (F1) should be homogeneous, they are often not genetically uniform, especially if more than two genotypes are involved in their seed production or due to undesirable self-pollination, out-crossing and mechanical admixtures. To overcome these problems the accepted method of postulating specific resistance genes based on comparing response type arrays (RTAs) of genetically homogeneous cultivars with RTAs of standard genotypes was substituted by analysing the frequency of response types to clusters of pathogen isolates in segregating F2 generations. This method combines a genetic and phytopathological approach for identifying resistance genes. To assess its applicability six hybrid cultivars were screened and from three to seven with a total of 14 resistance genes were found. Two genes were newly located at the Mla locus and their heritability determined. In addition, three unknown dominant genes were detected. This novel, comprehensive and efficient method to identifying resistance genes in hybrid cultivars can also be applied in other cereals and crops.

Highlights

Powdery mildew, a common cereal disease caused by the fungus Blumeria graminis, is a major limiting factor of barley production and genetic resistance is the most appropriate protection against it
Each of the six tables relating to the screened cultivars has 55 columns and ca. 40–80 lines and these tables are presented in Supplementary Dataset S_1
Resistance tests of this cultivar were done on one leaf segment grown from 25 ears derived from separate plants and subsequently on five segments from a further 25 ears, making a total of 150 leaf segments individually inoculated with each of 52 isolates

Summary

Introduction

A common cereal disease caused by the fungus Blumeria graminis, is a major limiting factor of barley production and genetic resistance is the most appropriate protection against it. Hybrid cultivars (F1) should be homogeneous, they are often not genetically uniform, especially if more than two genotypes are involved in their seed production or due to undesirable self-pollination, out-crossing and mechanical admixtures To overcome these problems the accepted method of postulating specific resistance genes based on comparing response type arrays (RTAs) of genetically homogeneous cultivars with RTAs of standard genotypes was substituted by analysing the frequency of response types to clusters of pathogen isolates in segregating F2 generations. Barley and wheat genomes have already been well-characterised and can be readily modified with CRISPR techniques4 This method could be used to select suitable parents for making crosses between those with high combining ability and achieve higher and more stable yields. Considering varietal resistance itself, selected cultivars carrying resistance genes, including those present in hybrid cultivars, can be used as differentials for studying pathogen populations and combined with virulence frequency data. Almost all current barley cultivars contain one or more specific g enes and when looking for partial r esistance specific genes that mask minor resistance genes must be overcome with

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