The Rose Genetics & Breeding Program
Rose Research
Roses are among the most important ornamental crops worldwide. In the US, rose growers produced ~25 million bushes worth $168 million in 2019, contributing to a direct economic impact of ~$777 million on the US economy. Besides this substantial economic importance, roses and other ornamentals also promote human well-being and increase property values. the US as shrubbery numbered ~25 million and were estimated to be worth ~$168 million. At the base of the rose industry is a broad array of cultivars (>37,000) developed through breeding, mostly in the private sector. Cultivated roses are a complex of tetraploid, triploid, and/or diploid interspecific hybrids with a wide range of flower shapes, colors, fragrances, plant architectures, and classes. This multitude of species, ploidy levels, geographic adaptation requirements, and the various end-uses of roses make variety development particularly challenging.
The development of varieties has traditionally been a long-term process with limited use of genomic technologies. Nevertheless, genomic tools have been developed. These include genome sequence assemblies, genotyping platforms, computational tools that can deal with polyploidy in linkage and quantitative trait (QTL) mapping, genome-wide association studies (GWAS), genomic prediction, and ploidy and aneuploidy determination.
Several studies and surveys have demonstrated that consumers demand carefree cultivars that are tolerant to biotic and abiotic stresses, and possess superior ornamental quality. In the Southeastern US, the target environment for this research, the greatest challenge is to combine high ornamental value with adaptation to humid subtropical climates, characterized by intense heat stress in the summer and high levels of humidity that foster disease. Thus, the incorporation of particular resistances to rose genotypes, especially to the black spot fungus (Diplocarpon rosae. [Lib.] Wolf), powdery mildew (Sphaerotheca pannosa Wallr. [ex Fr.] Lev), rust (Phragmidium spp.), Cercospora leaf spot (Cercospora rosicola Pass.), and rose rosette disease caused by the Rose rosette emaravirus (Emaravirus rosae) is greatly desired.
In this context, the program has made significant inroads to unveil the genetic basis of field-based resistance to various diseases and traits of ornamental value using genetic mapping-based methods. The research suggests that disease resistance and other traits are uder complex genetic control, with multiple factors of varying effects regulating them. Genetic improvement of these polygenic traits through marker-assisted selection (MAS) alone will not be feasible. Thus, our attention has now shifted to explore and implementing genomic prediction methods, which use of loci distributed throughout the genome to capture and use alleles of all effect sizes. We currently utilize genomic prediction for parental selection, and we are working toward establishing a system for seedling selection.
