Breeding barley for intensive and sustainable agriculture, powdery mildew (Blumeria graminis) resistance in elite spring barley

Helmy Youssef1, Mathias R. Gemmer1, Denise Weidenbach2, Doreen Neumeister1, Daniela Nowara3, Andreas Maurer1, Victor Korzun4, Anja Hannemann5, Günther Schweizer6, Ralph Hückelhoven7, Patrick Schweizer3*), Ulrich Schaffrath2, Ernesto Igartua8, Ana M Casas8, Luigi Cattivelli9, Alessandro Tondelli9, Thomas Schmutzer1, Andreas Maurer1, Klaus Pillen1

1**Institute of Agricultural and Nutritional Sciences, Chair of Plant Breeding, Martin Luther University Halle-

   Wittenberg, Betty-Heimann-Str. 3, 06120 Halle, Germany.

2**Department of Plant Physiology, RWTH Aachen University, 52056 Aachen, Germany.

3**Plant Reproductive Biology, Leibniz Institute of Plant Genetics and Crop Plant Research, 06466 Stadt Seeland/OT

     Gatersleben, Germany.

4**Cereals Biotechnology, KWS LOCHOW GMBH, 37574 Einbeck, Germany.

5**Saatzucht Josef Breun GmbH & Co. KG, Amselweg 1, D-91074 Herzogenaurach, Germany.

6**Biotechnologie der Pflanzenzüchtung, Bayerische Landesanstalt für Landwirtschaft, Am Gereuth 8, 85354 Freising,

     Germany.

7**Center of Life and Food Sciences Weihenstephan, Technische Universität München, 85350 Freising, Germany.

8**Department of Genetics and Plant Production, Aula Dei Experimental Station, EEAD-CSIC, Avenida Montañana,

     1005, 50059, Zaragoza, Spain.

9**CREA Research Centre for Genomics and Bioinformatics, Via San Protaso 302, Fiorenzuola d'Arda, 29017, Italy.

helmy.mohamed-youssef-ibrahim@landw.uni-halle.de

Abstract

One of the major diseases negatively affecting barley (Hordeum vulgare L.) yield is powdery mildew (Blumeria graminis f.sp. hordei, Bgh). Bgh is causing yield losses of up to 50 %. It was found that the most common and stable Bgh resistance is based on the mildew resistance locus o (mlo). The recessive mlo allele is effective against most of the known isolates of the pathogen. In our previous screens, we selected a number of potential Bgh resistance donor genes which are involved in cell wall formation. These donor genes, HvCSLH1 (cellulose synthase-like gene), HsGER4d (germin-like gene), HvCSLD2 (cellulose synthase-like gene D), HvCS (chorismate synthase), unknown protein, HvLSD1a (Lesion Simulating Disease 1a) and HvWIR1a (wheat induced resistance 1a), derived from exotic land races and wild barley accessions. These genes were introgressed into the spring barley cultivar KWS-Bambina, which is lacking mlo resistance. The donor genes were stacked through intercrossing and backcrossing, resulting in progeny simultaneously carrying between zero and three new resistance genes. The resulting genotypes were screened for resistance against the barley diseases powdery mildew, leaf rust, net blotch, scald, cereal blast and spot blotch in the field in 2014 (in Germany) and in 2020 and 2021 (in Germany, Spain and Italy).

We observed strong Bgh resistance showing that stacking of multiple resistance genes is important to quantitatively enhance disease resistance. The lines with stacked resistance alleles exhibited a significantly increased resistance against Bgh compared to lines with no or only one resistance allele. Notably, out of the selected donors we found that donors; HOR3036, HOR2932 and S42-L124 were evaluated with high tolerance than KWS Bambina, they showed clear resistance effect in average. We conclude that the stacking of the selected resistance genes; HvCSLH1, CSLD and CS proved to be a promising strategy in barley breeding to improve resistance against Bgh and other barley diseases.

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Keywords: Barley, Blumeria graminis, Disease resistance, Mlo, Powdery mildew resistance, Stacking.