Eastern redbud (Cercis canadensis L.) is a popular small landscape tree. In the two most recent U.S. Department of Agriculture (USDA) Censuses of Horticultural Specialties, redbud was the fifth most valuable deciduous flowering tree in the United States. As reported in the USDA Censuses of Horticultural Specialties, economic value of redbuds increased from ≈21.8 million in 2009 to 28.4 million in 2019 (USDA-NASS, 2009; USDA-NASS, 2015; USDA-NASS, 2020). Eastern redbud is widely used in landscaping because of its moderate size and wide adaptability (Werner and Snelling, 2010). Mature redbud can range from small shrubs to medium trees, grow in full sun to shade, and are hardy from USDA zones 4 to 9 (Kidwell-Slak and Pooler, 2018; Raulston, 1990). Their showy early spring flowers and heart-shaped foliage also contribute to their popularity (Kidwell-Slak and Pooler, 2018).
Diverse morphologies in eastern redbud have been used in breeding for increasing their ornamental value and diversifying landscaping utility (Roberts et al., 2015). Popular traits like leaf color mutations (purple, gold, variegated), double flowers, compact growth, and weeping architecture are found in many current cultivars (Kidwell-Slak and Pooler, 2018). The inheritance and allelism of many of these popular traits have been studied (Roberts et al., 2015). For example, Roberts et al. (2015) demonstrated that purple leaves of ‘Ruby Falls’, ‘Forest Pansy’, and ‘Greswan’ were all controlled by the same recessive allele (pl1). Two nonallelic weeping genes were reported; the weeping gene of ‘Covey’ and ‘Ruby Falls’ (wp1), and the weeping gene of ‘Traveller’ (C. canadensis var. texensis) (Roberts et al., 2015).
Compact redbud cultivars are popular in the market because of their ability to fill specific landscape niches (Fantz and Woody, 2005). ‘Ace of Hearts’ and ‘Little Woody’ are nonweeping, compact cultivars released in 2005 that were selected from a bulked seed population that originated from Morganton Nursery (Morganton, NC) and do not have clear pedigrees (Fantz and Woody, 2005). ‘Ace of Hearts’ is a popular compact cultivar with a dome-shaped canopy and small, heart-shaped leaves (Fantz and Woody, 2005). Although its unique compact form is a valuable ornamental trait, the inheritance of compact growth habit is unclear. Understanding its inheritance will assist breeders using the compact trait in future breeding efforts.
In this research, hybrid families, including F1, F2, and reciprocal backcross families of ‘Ruby Falls’ (noncompact/weeping architecture/purple leaf) × ‘Ace of Hearts’ (compact/nonweeping architecture/green leaf) were created and used to 1) study the inheritance of the compact trait derived from ‘Ace of Hearts’, and 2) investigate linkage relationships between the genes controlling compactness, weeping, and purple leaves.
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