Genetic analysis of yield and quality traits in switchgrass based on population crosses

Authors: Edme, Serge; Mitchell, Robert - Rob

Submitted to: Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/29/2021
Publication Date: 11/2/2021
Citation: Edme, S.J., Mitchell, R. 2021. Genetic analysis of yield and quality traits in switchgrass based on population crosses. Agronomy. 11(11):2220. https://doi.org/10.3390/agronomy11112220.
DOI: https://doi.org/10.3390/agronomy11112220

Interpretive Summary: To develop better cultivars with high biomass and ethanol yield in switchgrass requires gaining knowledge of the mode of inheritance of the characteristics used in breeding and selection. The inheritance is mostly governed by what is called general combining ability or GCA and specific combining ability or SCA, which are used as indicators of the way the parents pass genes to their progeny. Some crosses were made between different populations of switchgrass, called lowland and upland and tested in Nebraska to evaluate biomass yield, digestibility, lignin content, and ethanol yield. The relative importance of GCA and SCA was estimated and it was found that SCA was more relevant than GCA for all traits examined and contributed 20 to 57% to the total variation in the progeny. GCA was implicated in the genetic control of biomass and ethanol yield (but to a lesser degree than SCA) and not in the control of digestibility and lignin content. Moreover, to increase biomass yield, specific parents have to be used as females and not as males. Based on these results, strategies were developed and proposed to improve switchgrass populations for forage and bioenergy.

Technical Abstract: Obtaining greater genetic gains, particularly for biomass yield, requires a good understanding of the gene action governing the inheritance of traits with economic importance in switchgrass (Panicum virgatum L.). Individual genotypes from three different accessions were crossed in single-pair matings with reciprocals to assess the relative importance of additive to nonadditive genetic variation and the potential of using inter-ecotypic crosses to improve dry matter yield (DMY), in vitro dry matter digestibility (IVDMD), lignin content (ADL and KL), and ethanol yield (ETOH), Crosses and four reference populations were planted in a randomized complete block design with eight replications of single family-rows plots, with five-plants each and 1m spacings. A linear mixed model was applied as per the restricted maximum likelihood method, integrated with a pedigree tracing back to the original founders of these parental populations, and augmented with the designation of four genetic groups. Variation due to SCA (specific combining ability) was predominant for all traits, contributing from 20% to 57% of the total phenotypic variation and with Baker’s ratios (GCA/SCA) varying from 0.003 to 0.67. Heritability values calculated at the fullsib-family mean level were moderate to very high. Variation due to GCA (general combining ability) was detected with a lesser significance for DMY and ETOH. A reciprocal GCA effect was present in the form of maternal inheritance for DMY, suggesting the use of the highest biomass-yielding parent as female in inter-ecotypic breeding. Selecting and deploying fullsib families, deploying clonal hybrids, and adopting an introgression breeding approach are all possibilities available to switchgrass breeders to exploit the complementary genes from this germplasm and capitalize on the non-additive genetic variation present in these crosses.