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  • Author or Editor: Joseph H. Kirkbride Jr x
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The genus Chionanthus (Oleaceae Hoffmans. & Link) includes deciduous or evergreen trees and shrubs distributed widely in tropical and sub-tropical areas, including a few temperate species. Although Chionanthus species are planted as ornamental garden plants and commercialized for natural products, genetic information for Chionanthus spp. is lacking. We created microsatellite-enriched libraries of Chionanthus retusus Lindl. & Paxton, assembled 1072 contigs, and detected 1010 repeats. The frequency of the repeats decreased with the increase in repeat length, and the most abundant motifs were: AG, AC, AAG, ACC, AT, and ACTC. We screened 384 markers on 12 accessions of four related taxa that included C. retusus, Chionanthus virginicus L., Chionanthus pygmaeus Small, and Osmanthus americanus (L.) Benth. & Hook. A total of 195 simple sequence repeat (SSR) markers amplified and discriminated six accessions of C. retusus and 57 SSR markers amplified and discriminated across the four Oleaceae species screened. To identify the best markers to use in future experiments, the “Unique Pattern Informative Combination” (UPIC) values were calculated for all the markers and the 100 markers that were most effective are reported here. The percentage of heterozygous loci across the 384 markers was lowest for C. retusus (29.3%) and highest for O. americanus (68.9%). The SSR markers developed here could assist in taxonomy and hybridization investigations for breeding programs and authentication of varieties used as medicinal plants.

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The genus Chionanthus, known as fringetrees, is a member of the olive family (Oleaceae). Chionanthus virginicus is an understory tree or shrub with a wide range in forests of the eastern United States and is used as an ornamental tree that is known to be free of insects and disease in the wild. The species is tolerant of a wide range of environmental conditions, and there is interest in developing new cultivars with improved horticultural traits, such as tree form or upright growth habit and superior flowering display that are widely adapted. To identify genepools in the native range of C. virginicus for use in breeding programs, the genetic diversity and population structure were assessed for 274 individuals from 12 locations in four states (Florida, Maryland, North Carolina, and Texas) using 26 simple sequence repeats (SSRs). An average of 12.54 alleles/locus were detected, allelic richness averaged 2.80. Genetic differentiation was 0.11, indicating moderate differentiation among subpopulations. Despite the high genetic diversity and low population differentiation, Bayesian clustering analysis identified six genetic groups that match the geographic distribution of collection sites. Analysis of molecular variance indicated that most (82%) of the variation is explained within individuals, and 11% and 7% of the variation is due to differences among individuals within populations and among populations. Analysis of isolation by distance across all samples showed a weak positive relationship between geographic distance and genetic distance. The C. virginicus samples analyzed in this study indicate there is sufficient diversity for germplasm collection for use in breeding programs. Given the relatively moderate genetic differentiation, there are not likely to be unique islands of genetic diversity that may be missed when gathering parental materials for a breeding program

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