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Article|09 Nov 2023|OPEN
Two haplotype-resolved genomes reveal important flower traits in bigleaf hydrangea (Hydrangea macrophylla) and insights into Asterid evolution
Xingbo Wu1,2 , Sheron A. Simpson3 , Ramey C. Youngblood4 , Xiaofen F. Liu3 , Brian E. Scheff ler3 , Timothy A. Rinehart5 and Lisa W. Alexander6 , , Amanda M. Hulse-Kemp,2,7 ,
1Department of Environmental Horticulture, Tropical Research and Education Center, University of Florida, Homestead, FL 33031, United States
2Genomics and Bioinformatics Research Unit, USDA-ARS, Raleigh, NC 27695, United States
3Genomics and Bioinformatics Research Unit, USDA-ARS, Stoneville, MS 38776, United States
4Institute for Genomics, Biocomputing and Biotechnology, Mississippi State University, Starkville, MS 39762, United States
5Crop Production and Protection, USDA-ARS, Beltsville, MD 20705, United States
6Floral and Nursery Plants Research Unit, U.S. National Arboretum, USDA-ARS, McMinnville, TN 37110, United States
7Department of Crop and Soil Sciences, North Carolina State University, Raleigh, NC 27695, United States
*Corresponding author. E-mail:,

Horticulture Research 11,
Article number: uhad217 (2024)
Views: 41

Received: 21 Aug 2023
Accepted: 07 Oct 2023
Published online: 09 Nov 2023


The Hydrangea genus belongs to the Hydrangeaceae family, in the Cornales order of flowering plants, which early diverged among the Asterids, and includes several species that are commonly used ornamental plants. Of them, Hydrangea macrophylla is one of the most valuable species in the nursery trade, yet few genomic resources are available for this crop or closely related Asterid species. Two high-quality haplotype-resolved reference genomes of hydrangea cultivars ‘Veitchii’ and ‘Endless Summer’ [highest quality at 2.22 gigabase pairs (Gb), 396 contigs, N50 22.8 megabase pairs (Mb)] were assembled and scaffolded into the expected 18 pseudochromosomes. Utilizing the newly developed high-quality reference genomes along with high-quality genomes of other related flowering plants, nuclear data were found to support a single divergence point in the Asterids clade where both the Cornales and Ericales diverged from the euasterids. Genetic mapping with an F1 hybrid population demonstrated the power of linkage mapping combined with the new genomic resources to identify the gene for inflorescence shape, CYP78A5 located on chromosome 4, and a novel gene, BAM3 located on chromosome 17, for causing double flower. Resources developed in this study will not only help to accelerate hydrangea genetic improvement but also contribute to understanding the largest group of flowering plants, the Asterids.