Rheological Hardness Index for Assessing Hardness of Hexaploids and Durums.

Kernel hardness of cereal grains is a fundamental phenotype, and various protocols for its characterization have been proposed. Although, from different perspectives, each has proved useful, these methods do not directly address the rheological (fracturing) response of a grain when subjected to compression. Such information is hidden in the individual crush response profiles (iCRPs) obtained by measuring the response of individual grains to crushing on an SKCS 4100 device. Here, the appropriateness and utility of rheological phenotypes, based on single‐kernel measurements, are demonstrated by proposing and validating a new wheat grain hardness phenotype, the rheological hardness index (RHI). It is defined in terms of the rheological phenotype phases (RPPs) of the averaged CRPs (aCRPs) obtained by averaging a large number of iCRPs. The utility of RHI is illustrated by showing how it provides improved insight about the differences in brittleness and compactness of grains from different wheat varieties. This investigation highlights the opportunity that the RPP of the aCRPs represent for obtaining specific quantitative phenotypes for the study of hardness in cereal grains. In particular, successful plant breeding relies on segregating a breeding population into appropriate end‐use categories, for which RHI has a potential role to play. [ABSTRACT FROM AUTHOR]