Grain‐Filling Duration and Yield in Spring Barley1

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Abstract
Several studies of various crop species have suggested the possibility of identifying an optimum grain‐filling duration for improving grain yield. Accordingly, a research program on grainfilling duration and its relationship to grain yield in barley (Hordeum vulgare L.) was initiated at the University of Minnesota, St. Paul in 1970. Two and three cycles of crossing and selection were used to incorporate variability for grain‐filling duration into improved genetic backgrounds. Ultimately, lines from four populations were grown in field trials in 1979, 1980, and 1982 to study the relationship between grain‐filling duration and grain yield. These lines were selected to assure diversity for grainfilling duration, while having similar maturity. Significant differences among genotypes for grain‐filling duration were found in all populations. Long duration lines spent an average of 3 to 7 days longer in the grain‐filling period than short duration lines. Although grain‐filling duration varied with environment, the long and short duration classes remained distinct. In spite of the consistent differences in grain‐filling duration there was no significant association between grain‐filling duration and yield in these populations. Failure to detect a yield advantage due to differences in grain‐filling duration in lines with similar maturity suggests that any advantage derived from alteration of the grain‐filling period may have been outweighed by the coincident change in length of the vegetative period. Genetic differences among lines for traits other than grain‐filling duration, such as synchrony of anthesis, may have limited our ability to find an association between grain‐filling duration and yield. Based on our research, selection for an optimum grain‐filling duration to improve grain yield does not appear to be a worth while objective for upper midwestern‐type barleys.