Every time a combine harvester strips barley from the field, some grains get crushed or lost because the plant clings too tightly to its straw. This project aims to find the genes that control how easily barley grains separate from the stalk—a trait called threshability—and to understand why wild relatives of barley shatter their seed heads in different ways. The problem is practical: older barley varieties and some wild species are hard to thresh, leading to damaged grain and wasted harvest. The genes controlling threshability in barley are unknown, and it is unclear whether the same molecular mechanism governs both the natural shattering of wild grasses and the artificial threshing of domesticated crops. The researcher will compare an easy-threshing barley cultivar with a hard-to-thresh line carrying a chromosome from wild barley, identify the cellular structures where breakage occurs, and pinpoint the responsible genes. If successful, this work could give breeders the tools to develop barley varieties that thresh cleanly without damaging the grain, reducing post-harvest losses. It will also reveal the genetic switch that determines whether a wild Triticeae grass shatters at the rachis or the rachilla, laying groundwork for breeding forage crops and for harnessing wild species in barley and wheat improvement. A third project will establish a gene-editing pipeline for wild barley species, enabling future fundamental studies of evolution and genetics across the Triticeae.
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Barley is an important cereal crop for the brewing industry, animal feed and human food. Domestication of barley led to a non-shattering (non-brittle) rachis, facilitating grain harvesting by farmers. However, the edible part of the grain needs to be further separated from the straw after harvesting, a process called threshing. Thus, easy threshability has been selected during crop improvement. In barley, the genes underlying threshability remains unknown. Barley belongs to a group of grasses called the Triticeae, which contains other economically important cereals such as wheat, rye and various forage crops. Shattering in wild grasses, including Triticeae, ensures seed dispersal and establishment of offspring. In the Triticeae, shattering occurs either in the inflorescence stalk (the rachis), as in barley and wheat, or in the floral stalk (the rachilla). Rachis shattering is controlled by two known genes in barley, while the genes controlling rachilla shattering are unknown. It is therefore unclear whether the rachis and rachilla shattering are controlled by the same or distinct mechanisms, and what determines the switch of the two positions. In addition, it is unknown whether threshing is controlled by the same molecular mechanism as shattering. This fellowship aims to (1) investigate and compare the genetic basis of shattering and threshing in the Triticeae, (2) uncover the molecular switch responsible for the differentiation between rachis and rachilla shattering, and (3) develop a transformation pipeline necessary for studying wild Triticeae species. Particularly, I propose three projects focusing on threshability, shattering diversity and transformation tool development. Project 1 aims to investigate threshability by comparing an easy-threshing barley cultivar with its hard-to-thresh derivative line that carries a specific chromosome region from wild barley. I will characterise the cellular structures where threshing occurs and identify the gene(s) controlling this trait. Threshability can be a problem particularly in some older barley cultivars, leading to grain damage. The outcome of this research will shed light on this crucial trait and will provide key elements to improve threshability in barley reducing losses during post-harvest operations. Project 2 aims to compare many wild Triticeae species that shatter either in the rachis or rachilla. Shattering occurs in specialised cell layers forming an inherent weak layer for breakage. I will perform detailed cellular characterisation and identify genes that are highly expressed in these cell layers and compare across Triticeae species. I will test if the known shattering genes in barley play a role in determining the two different shattering positions. Project 2 will reveal the shattering mechanisms and key genes that differentiate rachis and rachilla shattering within Triticeae. This research will lay groundwork for breeding forage crops in the Triticeae and harnessing the potential of wild Triticeae species in barley and wheat breeding. Project 3 will capitalise on recent advances in technology using plant developmental genes to substantially improve methods for editing genes in various species and cultivars. I will apply these cutting-edge technologies to establish an efficient transformation pipeline for wild Hordeum species. Mutants of candidate shattering and threshability genes will be generated and characterised. The outcome of this project will pave the way for new avenues of evolutionary and genetic studies in Hordeum species. The developed transformation pipeline can be adapted to other barley cultivars and landraces, and thus providing valuable tools for the barley research community.
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