Extended grain fill stabilizes malt barley quality across variable environments and nitrogen inputs

Barley (Hordeum vulgare L.) intended for malting must meet quality standards for producers to receive premium prices. In semiarid climates, variable weather can reduce grain quality and lead to over- or underfertilization, further compromising economic returns. The stay-green trait may support producers’ attainment of malt quality standards across variable environments and nitrogen (N) inputs by sustaining photosynthesis during grain filling through earlier heading and or delayed senescence. We identified three barley cultivars carrying distinct combinations of stay-green-associated quantitative trait loci (QTLs), with Buzz and MT Endurance exhibiting extended grain fill relative to the cultivar Hockett. This study evaluated whether variation in N response among the cultivars could be attributed to their stay-green-associated QTL combinations and resulting effects on malt quality. Cultivars were grown under four N treatments across four locations from 2019 to 2023. Extended grain fill in Buzz and MT Endurance improved the attainability of producer market traits, particularly in trials with elevated temperatures, reduced precipitation, and overfertilization. Under these conditions, Hockett exceeded grain protein thresholds and failed to meet kernel plumpness standards, whereas the extended grain fill cultivars maintained acceptable protein concentrations and higher plumpness. These responses were associated with stay-green-associated QTLs, which shift the balance toward starch accumulation during grain filling and help maintain malt quality under variable N and environmental conditions. These findings provide a basis for further investigation into how stay-green traits and their associated QTLs enhance the starch-to-protein ratio, enabling barley to maintain key producer market traits under elevated N and environmental stress.

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