Breeding for biomass yield in switchgrass using surrogate measures of yield

Authors: Casler, Michael; RAMSTEIN, GUILLAUME - University Of Wisconsin

Submitted to: BioEnergy Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/10/2017
Publication Date: 2/1/2018
Citation: Casler, M.D., Ramstein, G.P. 2018. Breeding for biomass yield in switchgrass using surrogate measures of yield. BioEnergy Research. 11:1-12. doi: https://doi.org/10.1007/s12155-017-9867-y.
DOI: https://doi.org/10.1007/s12155-017-9867-y

Interpretive Summary: Development of switchgrass as a dedicated biomass crop for conversion to energy requires substantial increases in biomass yield. Most efforts to breed for increased biomass yield are based on some form of indirect selection criterion because direct measurement of biomass yield is difficult and time-consuming. The objective of this paper is to evaluate and compare the expected efficiency of several indirect measures of breeding value for improving biomass yield of switchgrass. The most common form of indirect selection is to measure biomass of plants that are planted on a spacing that eliminates competition between plants, or to select plants for later flowering time. While both of these are effective, they are less efficient than taking the time and effort to conduct plot trials to measure biomass yield on realistically sown plots. Genomic selection, using DNA markers from the entire genome, was the only indirect selection criterion of clear value for improving the rate of gain for biomass yield per se. Using genomic selection, it is expected that rates of gain can be doubled or tripled, depending on population size. These results will be of potential value to all breeders and geneticists working on energy grasses.

Technical Abstract: Development of switchgrass (Panicum virgatum L.) as a dedicated biomass crop for conversion to energy requires substantial increases in biomass yield. Most efforts to breed for increased biomass yield are based on some form of indirect selection. The objective of this paper is to evaluate and compare the expected efficiency of several indirect measures of breeding value for improving sward-plot biomass yield of switchgrass. Sward-plot biomass yield, row-plot biomass, and spaced-plant biomass were measured on 144 half-sib families or their maternal parents from the WS4U-C2 breeding population of upland switchgrass. Heading date was also scored on row plots, and anthesis date was scored on spaced plants. Use of any of these indirect selection criteria was expected to be less efficient than direct selection for biomass yield measured on sward plots, when expressed as genetic gain per year. Combining any of these indirect selection criteria with half-sib family selection for biomass yield resulted in increases in efficiency of 14 to 36%, but this could only be achieved at a very large cost of measuring phenotype on literally thousands of plants that would eventually have no chance of being selected because they were derived from inferior families. Genomic prediction methods offered the best solution to increase breeding efficiency by reducing average cycle time, increasing selection intensity, and placing selection pressure on all additive genetic variance within the population. Use of genomic selection methods is expected to double or triple genetic gains over field-based half-sib family selection.