title: mlo-based powdery mildew resistance in hexaploid bread wheat generated by a non-transgenic TILLING approach.
abstract: Wheat is one of the most widely grown cereal crops in the world and is an important food grain source for humans. However, wheat yields can be reduced by many abiotic and biotic stress factors, including powdery mildew disease caused by Blumeria graminis f.sp. tritici (Bgt). Generating resistant varieties is thus a major effort in plant breeding. Here, we took advantage of the non-transgenic Targeting Induced Lesions IN Genomes (TILLING) technology to select partial loss-of-function alleles of TaMlo, the orthologue of the barley Mlo (Mildew resistance locus o) gene. Natural and induced loss-of-function alleles (mlo) of barley Mlo are known to confer durable broad-spectrum powdery mildew resistance, typically at the expense of pleiotropic phenotypes such as premature leaf senescence. We identified 16 missense mutations in the three wheat TaMlo homoeologues, TaMlo-A1, TaMlo-B1 and TaMlo-D1 that each lead to single amino acid exchanges. Using transient gene expression assays in barley single cells, we functionally analysed the different missense mutants and identified the most promising candidates affecting powdery mildew susceptibility. By stacking of selected mutant alleles we generated four independent lines with non-conservative mutations in each of the three TaMlo homoeologues. Homozygous triple mutant lines and surprisingly also some of the homozygous double mutant lines showed enhanced, yet incomplete, Bgt resistance without the occurrence of discernible pleiotropic phenotypes. These lines thus represent an important step towards the production of commercial non-transgenic, powdery mildew-resistant bread wheat varieties.
authors: Unit of Plant Molecular Cell Biology, Institute for Biology I, RWTH Aachen University, Aachen, Germany.
authors: Johanna
authors: J
authors: Acevedo-Garcia
authors: Unit of Plant Molecular Cell Biology, Institute for Biology I, RWTH Aachen University, Aachen, Germany.
authors: David
authors: D
authors: Spencer
authors: Unit of Plant Molecular Cell Biology, Institute for Biology I, RWTH Aachen University, Aachen, Germany.
authors: Hannah
authors: H
authors: Thieron
authors: Unit of Plant Molecular Cell Biology, Institute for Biology I, RWTH Aachen University, Aachen, Germany.
authors: Anja
authors: A
authors: Reinstädler
authors: Department of Plant Biology and Crop Science, Rothamsted Research, West Common, Harpenden, Hertfordshire, AL5 2JQ, UK.
authors: Kim
authors: K
authors: Hammond-Kosack
authors: Department of Plant Biology and Crop Science, Rothamsted Research, West Common, Harpenden, Hertfordshire, AL5 2JQ, UK.
authors: Andrew L
authors: AL
authors: Phillips
authors: Unit of Plant Molecular Cell Biology, Institute for Biology I, RWTH Aachen University, Aachen, Germany.
authors: Ralph
authors: R
authors: Panstruga
mesh_terms: D060467:Disease Resistance / Q000235:genetics / Q000502:physiology; D018745:Genome, Plant / Q000235:genetics; D010935:Plant Diseases / Q000235:genetics* / Q000382:microbiology*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000382:microbiology; D014908:Triticum / Q000235:genetics / Q000382:microbiology*
chemical_list: D010940:Plant Proteins
keywords: 
  Blumeria graminis
  ; 
  Mlo
  ; Targeting Induced Local Lesions in Genomes; hexaploid bread wheat; plant disease resistance; powdery mildew