Genetic control of barb/trichome formation on barley awns and stigmata – or, why does cultivated barley need rough awns?

• Applicant: Professor Dr. Nils Stein
• Subject Area: Plant Breeding and Plant Pathology
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 428798945

Barley awns are rough because they are coated with highly silicified barbs. Rough awns are known to cause hazards for the human respiratory tract during grain harvest as well as for the digestive tract of some ruminants and other animals when foraging on barley. The trait is controlled by a few major genetic loci and breeding for barbless awns, or smooth awns, is relatively easy achievable. Because of a correlation of smooth awns with reduced stigma hairiness, which is often associated with reduced fertility in barley, however, rough awn remained the predominant form of cultivated barley.We have recently cloned a major gene Raw1 controlling awn roughness in barley and based on GWAS and bi-parental mapping we have delimited a second locus in a promising region for gene-cloning on barley chromosome 7HS.We aim to isolate the second locus by state-of-the-art genomics-based positional cloning and perform gene function analysis of both cloned awn roughness genes. Knowing both genes that were under natural selection and by exploiting the pan-genome and genetic diversity resources under development in my group at IPK, it will be possible to track the selection/domestication history of the trait awn roughness and test its linkage/correlation with stigma hairiness and fertility and thus provide the knowledge of future breeding for smooth awn phenotypes without yield penalty through reduced fertility. The project aims at revealing the genetic basis of awn roughness in barley as well as its correlation to stigma hairiness, which is influencing fertility and yield. The following objectives will be adressed:• Genetic mapping and cloning of the functional gene of the newly identified smooth awn locus on barley chromosome 7HS (Raw7HS);• Functional validation of the newly isolated gene Raw7HS by TILLING and site-directed mutagenesis;• Functional validation of Raw1 control of awn roughness and stigma hairiness through site-directed mutagenesis;• Reveal natural diversity and signatures of selection at the Raw1 and Raw7HS loci; • Test for functional linkage between barb formation and stigma hairiness through systematic phenotyping of rough, smooth and semi-smooth accessions from a natural diversity collection;• Phenotypic and genotypic (Raw1 and Raw7HS) characterisation of a panel of independently induced smooth / semi-smooth mutants to reveal their allelic state.• Establish genetic crosses between raw1 and raw7HS genotypes and the panel of induced mutants to test for cumulative or epistatic interactions and to establish mapping populations for further gene isolations in (a) subsequent project(s).

• DFG Programme: Research Grants