Mutations in the HvMKK3 and HvAlaAT1 genes affect barley preharvest sprouting and after-ripened seed dormancy

Authors: VETCH, JUSTIN - Montana State University; Walling, Jason; SHERMAN, JAMIE - Montana State University; MARTIN, JOHN - Montana State University; GIROUX, MICHAEL - Montana State University

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/16/2020
Publication Date: 4/22/2020
Citation: Vetch, J., Walling, J.G., Sherman, J., Martin, J., Giroux, M. 2020. Mutations in the HvMKK3 and HvAlaAT1 genes affect barley preharvest sprouting and after-ripened seed dormancy. Crop Science. 1-10. https://doi.org/10.1002/csc2.20178.
DOI: https://doi.org/10.1002/csc2.20178

Interpretive Summary: Preharvest Sprouting (PHS) is a problem in cereal crops that results in reduction in grain quality coming out of the field. In barley, growers trying to obtain premium prices on their malting barley must meet strict grain quality parameters set required by maltsters and other buyers. Barley that exhibits signs of preharvest sprouting is relegated to feed quality and must be sold at a reduced price. Therefore, preharvest sprouting presents a tangible risk to growers considering malting barley as crop. Since the main physiological cause of preharvest sprouting in cereals is the absence or reduced effect of grain dormancy, we sought to identify those genetic elements that might increase levels of dormancy, and in turn, reduce the incidence of preharvest sprouting in fields. The manuscript submitted presents our findings that highlight the effect of 3 genes that have been shown to modulate dormancy levels at different stages of seed ripening. We fully sequenced 3 genes shown to affect grain dormancy and screened hundreds of barley varieties to evaluate the effect of these genes on reducing or increasing dormancy. The impact of this work bolsters our understanding of the genes involved in modulating dormancy and/or precocious germination. The information presented will be valuable for subsequent marker development that will provide breeders with tools to screen for varieties with improved PHS resistance.

Technical Abstract: Preharvest sprouting (PHS) is a natural phenomenon that negatively impacts various crops across the globe when late season rainfall causes seeds to germinate prior to harvest. Prevention of PHS in small grains such as barley and wheat is of particular importance due to the large acreage devoted to them. Barley (Hordeum vulgare) is the fourth most grown cereal crop and is often susceptible to PHS damage, which limits the regions in which barley can be grown without heavy losses. PHS damage could be mitigated by incorporation of genetic alleles that impart desired levels of dormancy at specific times in grain maturity, ideally high dormancy at harvest with a fast loss of dormancy upon after-ripening. Toward this goal, 114 barley varieties were assessed for dormancy at physiological maturity and in after-ripened grains. Three genes previously associated with dormancy in barley or wheat (HvAlaAT1, HvMKK3, and HvMFT) were sequenced from all lines and assessed for allelic diversity. The resulting alleles were assessed for association with dormancy at each of the maturity time points. In total, seven missense mutations were discovered across the three genes. It was observed that a single missense mutation in HvAlaAT1 (L214F) is associated with loss of dormancy in after-ripened grain while a single missense mutation in HvMKK3 (E165Q) is associated with a large loss of dormancy starting around physiological maturity. This study demonstrates that different genes are associated with dormancy at different time points in grain maturity, which may allow for selective breeding of specific dormancy time periods.