Malting quality and preharvest sprouting traits are genetically correlated in spring malting barley

Authors: ROONEY, TRAVIS - Cornell University; SWEENEY, DANIEL - Cornell University; KUNZE, KARL - Cornell University; SORRELLS, MARK - Cornell University; Walling, Jason

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/19/2022
Publication Date: 3/13/2023
Citation: Rooney, T.E., Sweeney, D.W., Kunze, K.H., Sorrells, M.E., Walling, J.G. 2023. Malting quality and preharvest sprouting traits are genetically correlated in spring malting barley. Theoretical and Applied Genetics. 136. Article 59. https://doi.org/10.1007/s00122-023-04257-6.
DOI: https://doi.org/10.1007/s00122-023-04257-6

Interpretive Summary: Traditionally, North American malting barley is grown in regions of western U.S. and Canada with dry environments during harvest that typically results in a high quality and sound grain that meets the quality specification of brewers, distillers and maltsters. However increased interested in malting barley has pushed it to non-traditional growing regions that witness high humidity and rain during harvest, resulting in presprouted grain of poor quality and in turn, a significant economic loss to the producer. The way to fight presprout is through seed dormancy (failure to germinate under normal condition). However too much dormancy means that the barley must after-ripen for months before it can be malted and thus fails to meet the malt house processing timelines. Here we examined the relationship between genetic factors that make a grain resistant to presprouting and how these factors might affect malt quality. We screened hundreds of barley lines for genes that might contribute to presprouting, we developed populations that were predicted to be presprout resistant, we tested the sprouting capacity of these line and then measured the malt quality using 10 different metrics. We are proud to report that our results demonstrate that producing high quality malt with sufficient resistance to presprout is not only possible but also within the logistical limitations (time from field to malting) of a working malt house.

Technical Abstract: Expansion of malting barley production into non-traditional growing regions and erratic weather has increased the demand for pre-harvest sprouting (PHS) resistant, high quality malting barley cultivars. This is hindered by the relatively unknown relationships between PHS resistance and malting quality. Here we present a three-year study of malting quality as it relates to germination at different after-ripening durations post physiological maturity (PM). Malting quality traits alpha amylase (AA) and free amino nitrogen (FAN), and germination rate at six days post PM shared a common genetic association with a SNP in HvMKK3 on chromosome 5H in the Seed Dormancy 2 (SD2) region responsible for PHS susceptibility. Soluble protein (SP) and soluble over total protein (S/T) both shared a common association with a marker in the SD2 region, but the most significant association was not with the causative mutation in HvMKK3. Significant genetic correlations were detected between PHS resistance and the malting quality traits AA, FAN, SP, S/T, both within and across HvMKK3 allelic groups. High quality adjunct malt related to PHS susceptibility and selection for PHS resistance led to a correlated response in several malting quality traits. Results suggest pleiotropy of HvMKK3 on malting quality traits and that classic “Canadian-style” malt is caused by a PHS susceptible allele of HvMKK3. PHS susceptibility appears to benefit the production of malt intended for adjunct brewing, while PHS resistance is compatible with all-malt brewing specifications. Correlations of germination rate to malting quality traits indicate its potential for use as a secondary trait in selection.