Author
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Casler, Michael |
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Submitted to: Crop Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 4/2/2018 Publication Date: 6/21/2018 Citation: Casler, M.D. 2018. Adjustment of biomass yield to a dry matter basis in switchgrass breeding: A necessity or a nuisance? Crop Science. 58:1624-1631. Interpretive Summary: Development of dedicated energy crops requires intensive breeding, selection, and evaluation to increase the yield of biomass and make these crops economically and environmentally sustainable. Breeding, selection, and evaluation requires high labor inputs and intensive efforts in the narrow time window between killing frost and the first snowfalls. This study investigated the elimination of the dry-matter estimation and adjustment process as a mechanism to increase selection intensity and selection pressure and increase the rate of gain for biomass yield. Elimination of labor required for collecting and weighing samples for dry-matter determination would allow breeders to triple population sizes and to increase the rate of gain for biomass yield by 17%. These results will be of interest to breeders of any energy grass species, where the focus of the program is on increasing biomass yield. Technical Abstract: Increases in biomass yield of switchgrass have been achieved, the rate of gain has been slow and would benefit from improved efficiency of selection methods. Dry matter (DM) determinations at the time of harvest are a traditional method to adjust plot mass to a dry-matter basis. The purpose of this study was to determine if DM determinations in switchgrass yield evaluations are necessary or unnecessary. Data from 219 trial-years of 11 published experiments were used to evaluate the value of DM adjustment. Heritability for fresh matter yield (FMY) and dry biomass yield (DBY) were similar and the genetic correlation between these two traits was >0.8 for 96.7% of the trial-years. The direct effect of FMY on DBY was 3 to 4× greater than the direct effect of DM concentration. Because DM determination requires a larger field crew at the time of harvest, use of FMY as a selection criterion requires significantly less labor than DBY at harvest time. Tripling the number of families evaluated and eliminating the DM step would increase the expected genetic gain for DBY by 17%. However, decreasing the number of replicates per family while eliminating the DM step would undermine the gains in efficiency due to reduced heritability for FMY. While the risk of using FMY is low, achieving this increase in efficiency requires a serious commitment to evaluating a very large number of replicated families in each generation, an effort that may be beyond the ability and scope of most breeding programs. |
