A strategy to breed low-protein barley with acceptable kernel color and diastatic power

Grain protein content is an important malt quality trait in barley (Hordeum vulgare L.). A source of low-protein used by the North Dakota six-rowed barley breeding program has been the cultivar Karl. No cultivars with Karl in their pedigree have been released from this program because all low-protein lines have had unacceptably dark kernel color, low diastatic power (DP), or both. The objective of this study was to determine why low-protein cultivars with acceptable kernel color, DP, and grain protein content have not been developed and to suggest a strategy to breed such cultivars. To fulfill these objectives, the following grain protein content, kernel color, and DP data were collected from three crosses: broad-sense heritability estimates, expected and observed gains from selection, genetic: correlations between the three traits, and the correlated response of a trait when selecting for another trait. Low to medium heritability estimates for all traits, low genetic correlation between traits, and the small expected correlated changes in DP when selecting for decreased grain protein content or a brighter kernel color suggest it should be possible to identify low-protein lines with acceptable kernel color and DP. Using independent culling, DP of selected lines in all crosses was similar when either grain protein content or kernel color was the first trait selected; therefore, either trait could be used as the primary selection trait. A strategy for developing low-protein cultivars with acceptable kernel color and DP would be to use independent culling in F-2:3 Or F-3:4 families in which grain protein content or kernel color would be the first trait and DP would be the last trait selected. The population size needed to select such lines needs to be greater than the 100 to 200 F-2:3 Or F-3:4 families currently used by the North Dakota six-rowed barley breeding program.