Molecular characterization of doubled haploid lines derived from different cycles of the Iowa Stiff Stalk Synthetic (BSSS) maize population

Authors: LEDESMA, ALEJANDRO - Iowa State University; SALES RIBEIRO, FERNANDO AUGUST - Iowa State University; UBERTI, ALISON - Iowa State University; Edwards, Jode; HEARNE, SARAH - International Maize & Wheat Improvement Center (CIMMYT); FREI, URSULA - Iowa State University; LUBBERSTEDT, THOMAS - Iowa State University

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/10/2023
Publication Date: 7/27/2023
Citation: Ledesma, A., Sales Ribeiro, F., Uberti, A., Edwards, J.W., Hearne, S., Frei, U., Lubberstedt, T. 2023. Molecular characterization of doubled haploid lines derived from different cycles of the Iowa Stiff Stalk Synthetic (BSSS) maize population. Frontiers in Plant Science. 14. https://doi.org/10.3389/fpls.2023.1226072.
DOI: https://doi.org/10.3389/fpls.2023.1226072

Interpretive Summary: Genetic diversity among maize hybrids in the U.S. has declined rapidly and continues to decline. In the present study, maize doubled haploid (DH) lines were characterized to obtain a better understanding of the genetic effects of long-term intensive maize breeding and to explore novel methods to potentially recover lost genetic diversity. The study showed that intensive breeding reduced diversity as expected, but much of the original diversity could be recovered by outcrossing back to the original population. The diversity and genetic properties of the cross to the unselected base population provide a method to recover lost diversity and enable the use genetic mapping to identify specific genetic regions targeted by breeders during selection. This study will benefit breeders who are trying to enhance rates of genetic gain and consumers of improved maize hybrids.

Technical Abstract: Molecular characterization of a given set of maize germplasm could be useful for understanding the use of the assembled germplasm for further improvement in a breeding program, such as analyzing genetic diversity, selecting a parental line, assigning heterotic groups, creating a core set of germplasm and/or performing association analysis for traits of interest. In this study, we used single nucleotide polymorphism (SNP) markers to assess the genetic variability in a set of doubled haploid (DH) lines derived from the unselected Iowa Stiff Stalk Synthetic (BSSS) maize population, denoted as C0 (BSSS(R)C0), the seventeenth cycle of reciprocal recurrent selection in BSSS (BSSS(R)C17), denoted as C17 and the cross between BSSS(R)C0 and BSSS(R)C17 denoted as C0/C17. With the aim to explore if we have potentially lost diversity from C0 to C17 derived DH lines and observe whether useful genetic variation in C0 was left behind during the selection process since C0 could be a reservoir of genetic diversity that could be untapped using DH technology. Additionally, we quantify the contribution of the BSSS progenitors in each set of DH lines. The molecular characterization analysis confirmed the apparent separation and the loss of genetic variability from C0 to C17 through the recurrent selection process. Some of the progenitors had a higher genetic contribution in C0 compared with C0/C17 and C17 derived DH lines. Although genetic drift can explain most of the genetic structure genome-wide, phenotypic data provide evidence that selection has altered favorable allele frequencies in the BSSS maize population through the reciprocal recurrent selection program.