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 (Ho rdeum vulgare L.). A source of low-protein used by the North Dakota si x-rowed barley breeding program has been the cultivar Karl. No cultiva rs with Karl in their pedigree have been released from this program be cause all low-protein lines have had unacceptably dark kernel color, l ow diastatic power (DP), or both. The objective of this study was to d etermine why low-protein cultivars with acceptable kernel color, DP, a nd grain protein content have not been developed and to suggest a stra tegy to breed such cultivars. To fulfill these objectives, the followi ng grain protein content, kernel color, and DP data were collected fro m three crosses: broad-sense heritability estimates, expected and obse rved gains from selection, genetic: correlations between the three tra its, and the correlated response of a trait when selecting for another trait. Low to medium heritability estimates for all traits, low genet ic correlation between traits, and the small expected correlated chang es in DP when selecting for decreased grain protein content or a brigh ter 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 pro tein 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 w hich grain protein content or kernel color would be the first trait an d DP would be the last trait selected. The population size needed to s elect 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 breedin g program.