Breeding for Biomass Yield in Switchgrass Using Surrogate Measures of Yield

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.

Comparison of Representative and Custom Methods of Generating Core Subsets of a Carrot Germplasm Collection

“…The upper bound of predictive ability is set by the narrow-sense heritability for each trait (h 2 ), which is 0.60 for canopy height and 0.35 for harsh flavor. However, even relatively low levels of accuracy around 0.2 to 0.3, similar to those found here, can have utility in a breeding program if the use of genomic predictions allows the breeder to effectively evaluate larger populations sizes or reduce the breeding cycle time (Heffner et al, 2010;Casler and Ramstein, 2018). Genetic representativeness of core sets.…”

“…Therefore, this result is not unexpected but calls into question the utility of the core collection strategy for developing predictive models. However, even relatively low levels of accuracy around 0.2 to 0.3, similar to those found here, can have utility in a breeding program if the use of genomic predictions allows the breeder to effectively evaluate larger populations sizes or reduce the breeding cycle time (Heffner et al, 2010;Casler and Ramstein, 2018). In most cases, the training population is considerably larger than the core collection strategies we tested here.…”

Adjustment of Biomass Yield to a Dry Matter Basis in Switchgrass Breeding: A Necessity or a Nuisance?

“…In the breeding and selection phases of the program, where ranking of the best genotypes is the principal goal, absolute values and accurate values are of little concern to breeders. This would include field trials of half-sib families, as described by Casler (2010) and Casler and Ramstein (2017), and as referenced in Fig. 5.…”

“…Predicted genetic gains were computed for several scenarios based on the idea that use of FMY as the selection criterion would allow for higher population sizes and selection intensities than DBY, owing to the elimination of DM determinations at harvest time. Genotype × environment interactions were ignored in these computations for two reasons: (i) the WS4U population did not display any significant genotype × environment interactions (Casler, 2010; Casler and Ramstein, 2017), and (ii) the concept of genotype × environment interactions is not germane to the arguments presented here and would unnecessarily complicate the computations and discussion.…”

Comparison of space‐plant versus sward plot selection in thickspike wheatgrass (Elymus lanceolatus)

“…In most cases the entities developing rangeland revegetation plant materials have limited resources and are attempting to improve many unrelated plant species simultaneously. Additionally, the inefficiency of space plant evaluation has only been shown in the recent past (Casler & Ramstein, ; Robins & Jensen, ; Waldron et al., ), is more important for some traits than others (Sykes, Allen, DeSantis, Saxton, & Benelli, ), and is not absolute (Bhandari, Fasoula, & Bouton, ).…”