Inheritance of Secondary Morphological Traits for Among‐and‐Within‐Family Selection in Upland Tetraploid Switchgrass

Abstract

Major efforts are currently being undertaken to improve biomass yield in switchgrass. Among‐and‐within‐family selection has been proposed as an efficient selection scheme to increase rates of genetic gain. The objectives of this study were to estimate the heritability of three yield‐related traits (plant height, tiller count, and flowering date) and evaluate the suitability of those traits as within‐family‐selection criteria. Divergent selections of parents were made for each trait from an upland‐tetraploid population developed for use in temperate North America. Progeny from these selections were used to estimate narrow‐sense heritability by both parent–progeny regression and response to selection. Moderate heritability (0.41) was estimated for plant height but was greater for selection of increased height. Heritability for tiller count was low overall (0.06), with greater values observed for reduced tillering selections. Flowering date was estimated to have high heritability (0.75) overall in both selection directions. Plant height and flowering date both appear heritable on a spaced‐plant basis and may be effective selection criteria for within‐family selection. The relative value of among‐and‐within‐family selection within a practical breeding program will vary depending on what selection criteria are used and the timing of selections.

Breeding for Biomass Yield in Switchgrass Using Surrogate Measures of Yield

“…Heading date was scored on each individual plant in every row and defined as the calendar date on which approximately 50% of the panicles were fully emerged from the boot. Anthesis date was determined on parental spaced plants for 2 years, defined as the calendar date on which approximately 50% of the panicles reached anthesis [6].…”

“…These correlations imply that these traits could be used as indirect selection criteria to either speed up the breeding process or to increase selection intensity per generation, potentially increasing the rate of gain for biomass yield. While there is some evidence that these potential indirect selection criteria may have positive genetic correlations with sward-plot biomass yield [10], the only results to date have demonstrated a nearzero genetic correlation for all vigor-related or tillering traits [6]. Indeed, divergent selection for several of these traits failed to generate any correlated responses in sward-plot biomass yield [11].…”

“…Phenotypic selection of individual plants with the greatest amount of biomass is very effective on relatively raw and unimproved germplasm [2][3][4], easily allowing breeders to discard plants with low vigor, tillering, or whole-plant biomass. However, the genetic correlation between spaced-plant biomass and sward-plot biomass yield diminishes to near zero for elite and highly improved germplasm [6]. Any use of sward-plot evaluation increases both time and funding costs.…”

QTL Mapping for Reproductive Maturity in Lowland Switchgrass Populations

“…Bhandari et al (2011) observed heritability estimates for heading date were larger based on full-sib families than on half-sib families, suggesting dominant gene effect or epistasis likely played an important role. Investigating on upland switchgrass half-sib families, Price and Casler (2014) reported high narrow-sense and realized heritability estimates for flowering time. They recommended flowering time should be used as an effective secondary trait to biomass yield for within-family selection.…”

“…Price and Casler (2014) correctly indicated successful field-based selection for late flowering requires large spaced-plant nurseries to assure sufficient variation, and large amounts of time to accurately measure flowering date in the field. If molecular markers are identified to be significantly linked to the genetic variation of reproductive maturity, markerassisted selection could be used as an alternative in the development of later maturing germplasm.…”