Genome size, ploidy levels, and development of novel SSR primer to evaluate genetic diversity of Corylopsis Siebold & Zucc, germplasm collections

Authors: LATTIER, JASON - High Point University; BALLARD, HARVEY - Ohio University; Kramer, Matthew; Pooler, Margaret

Submitted to: Genetic Resources and Crop Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/6/2022
Publication Date: 4/14/2022
Citation: Lattier, J., Ballard, H., Kramer, M.H., Pooler, M.R. 2022. Genome size, ploidy levels, and genetic diversity of Corylopsis germplasm collections. Genetic Resources and Crop Evolution. https://doi.org/10.1007/s10722-022-01371-0.
DOI: https://doi.org/10.1007/s10722-022-01371-0

Interpretive Summary: Winterhazels (Corylopsis species) are a genus of flowering shrubs that are planted in the landscape for their showy fragrant spring flowers, fall foliage, and general resistance to disease and pest problems. Despite their value in ornamental landscapes, there are relatively few cultivars of this genus, and little basic information that would assist with breeding, such as genome size, chromosome numbers (ploidy) among species, and genetic relationships among taxa. ARS scientists at the U.S. National Arboretum led an investigation that determined ploidy, genome size, and genetic relationships among hundreds of Corylopsis accessions representing 14 taxa from collections throughout the U.S. They confirmed a ploidy series between and within species that included diploid, tetraploid, pentaploid, and hexaploid individuals. In addition, the team developed robust genetic markers for this genus that were used to determine genetic relationships among taxa. This will be useful across the genus to make decisions about species identity, collection management, or breeding targets.

Technical Abstract: Corylopsis is a genus of flowering shrubs with few cultivars and little information on genome size, ploidy levels, and genetic relationships among taxa. The United States National Arboretum and collaborating gardens in North America maintain a diverse germplasm collection of Corylopsis including cultivated and wild-collected taxa. The objectives of this study were to determine genome size, ploidy, and genetic diversity in Corylopsis. Flow cytometry revealed a ploidy series of diploid, tetraploid, pentaploid, and hexaploid taxa in Corylopsis with 2C genome sizes ranging from 1.9 pg to 5.7 pg. Representative taxa were selected for root tip cytology, revealing diploid (C. platypetala), tetraploid (C. gotoana), pentaploid (unnamed hybrid selection), and hexaploid (C. willmottiae) taxa. Seventeen genomic simple sequence repeat markers were developed and used to determine the genetic diversity of Corylopsis. These markers had an average of 7.4 alleles per locus with a range of three to 17 alleles. A dendrogram was generated by unweighted pair group method with arithmetic mean (UPGMA) cluster analysis using the Jaccard similarity coef'cient to visualize genetic relationships and ploidy series within taxa. Information gained from this study will further breeding efforts and aid management of germplasm collections of Corylopsis.