QTL mapping reveals malt barley quality improvement in two dryland environments associated with extended grain fill and seminal root traits

To achieve malt grade and receive full price, barley (Hordeum vulgare L.) crops must meet standards for certain quality traits including percent plump and protein. Terminal drought stress reduces quality and is projected to worsen in barley cultivation areas, underscoring the need for varieties that maintain good malt production with unreliable precipitation. The stay-green trait extends the grain fill phase between heading and maturity and has been linked to stable quality under dry conditions. However, this relationship can be inconsistent and is not well understood. To effectively leverage a longer grain fill phenotype for drought adaptation, a better grasp of its genetics and environmental interaction is needed. Stay-green root system differences have been observed and could be at play. We performed correlation and quantitative trait locus (QTL) analysis on grain fill duration, grain quality, and seminal root traits using a recombinant inbred line (RIL) population segregating for stay-green. Agronomic data were collected in four field trials at two distinct semiarid locations, and roots were measured in a greenhouse assay. Earlier heading and later maturity led to improved quality in both locations and more consistent quality between locations. Earlier heading had a greater influence on quality in the drier environment, while later maturity was more impactful in the less dry environment. We observed co-locations of seminal root trait QTLs with grain fill duration and grain quality. These QTLs lay the groundwork for further investigation into root phenotypes associated with stay-green and the deployment of these traits in breeding for drought adaptation. Extended grain fill improved and stabilized barley plump and protein quality for malting. Grain quality was more affected by heading in the drier location and by maturity where there was more moisture. Extended grain fill, early root development, and grain quality co-located at multiple QTLs. Seminal root-to-shoot length ratio co-located with a gene (HvNAM1) that affects protein, plump, and maturity.