Temporal genetic relationships between growth, development, and malting quality in winter barley (Hordeum vulgare) using aerial imagery

Grain characteristics are the cumulative product of growth and development throughout the growing season. In barley (Hordeum vulgare), these traits determine the grain's value for malting purposes. The ability to accurately predict the genetic merit for malting quality is of great interest for barley breeding programs. Same-season selection on malting quality traits is nearly impossible due to the costly, destructive, time-intensive, malting, and testing procedures. This study examined the temporal relationships of growth and development with grain quality measures through genetic correlations of vegetative indices and end-use traits. Normalized difference vegetation index (NDVI) calculated from aerial imagery is rapid to collect and models photosynthesis and vegetative growth. Malting quality, agronomic traits, and NDVI were measured in 385 lines of two-row winter barley breeding germplasm across 2 years. Genetic and residual correlations between malt quality and agronomic traits from bivariate genomic prediction models point to environmental variation due to field heterogeneity and batch malting effects. The reliability of NDVI was high during fall growth, reduced during spring vegetative growth, and increased again after flowering. Heading date was positively correlated (mean ) with NDVI during heading, but genetic correlations between NDVI and other traits were not consistent across environments. Multi-trait models using NDVI as the secondary trait were fit for each end-use trait. Compared to single-trait genomic prediction models, multi-trait genomic prediction models increased predictive abilities by an average of 0.04 across multiple traits and environments. However, NDVI was not found to be effective as an economic secondary trait for selection of malting quality traits.

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