Physiological Changes Associated with Three Cycles of Recurrent Selection for Grain Yield Improvement in Oats1

Abstract

Recurrent selection has been successful in cross‐pollinated crops for some time, but only recently has it been utilized in self‐pollinated crops. The original parents and the third cycle parental selections of a recurrent selection program for grain yield in spring oat (Avena sativa L.) were compared in a field study. Possible yield‐related traits were also measured to assess correlated responses. The latter included a growth analysis of the genotypes to enable a post facto assessment of changes in plant growth in response to selection for grain yield. Grain yield was increased 12% during the three cycles of selection, with increases in kernel number (8%) and kernel weight (3%) being the most noteworthy yield component responses. Heading and maturity were delayed about 2 days, but the grain‐filling period duration remained constant. The rate of grain filling increased 12%, whereas vegetative growth rate during the linear, preanthesis phase did not increase significantly in response to selection for grain yield. The ratio of grain to vegetative growth rates was higher for cycle 3 genotypes, suggesting that a greater proportion of assimilate was distributed to reproductive growth by the advanced cycle selections. Harvest index values did not change. These results suggest that increasing biomass may be necessary to achieve future grain yield increases, and that more attention should be given to grain‐filling rates than to vegetative growth rates.