Plant architecture strongly influences both agronomic performance and ornamental quality. Prostrate growth habit, characterized by low stature and outward-spreading branches, improves resistance to lodging and environmental stress while enhancing ground-cover potential. Although this trait has been investigated in crops such as rice and peanut, its genetic regulation in chrysanthemum—an economically important ornamental plant—remains largely unexplored. Traditional breeding is further complicated by polyploidy, high heterozygosity, and long breeding cycles. Advances in high-density genetic mapping and quantitative trait locus (QTL) analysis offer new opportunities to dissect complex traits in polyploid species. Based on these challenges, in-depth genetic and functional studies are needed to clarify how prostrate growth habit is formed and inherited.

In a study published (DOI: 10.1093/hr/uhaf129) on 21 May 2025 in Horticulture Research, scientists from Beijing Forestry University investigated the genetic basis of prostrate growth habit in chrysanthemum using interspecific hybrids between a creeping wild species and an erect relative. By constructing high-density genetic linkage maps and analyzing multiple growth-related traits over several years, the team identified key genomic regions associated with plant architecture. Subsequent physiological measurements and transgenic experiments revealed a candidate gene that plays a central role in shaping creeping growth.

The researchers crossed prostrate-type Chrysanthemum yantaiense with erect-type C. indicum to generate a large hybrid population for genetic analysis. Five architecture-related traits—including plant height, crown width, creeping index, branch angle, and overall growth habit—were evaluated over four consecutive years, revealing continuous variation and high heritability. Using genotyping-by-sequencing, the team constructed high-density genetic linkage maps containing thousands of SNP markers.

QTL mapping identified more than one hundred loci associated with prostrate growth-related traits, among which four stable QTL regions consistently appeared across years and traits. Notably, a major QTL on a specific linkage group explained up to 20% of phenotypic variation and was validated using kompetitive allele-specific PCR (KASP) markers in multiple populations.

Comparative genomic analyses narrowed this region to 44 candidate genes, with one gene encoding a D-type cyclin emerging as a strong candidate. Physiological assays showed elevated cytokinin levels in prostrate plants, while gene expression analyses revealed higher transcript abundance of this cyclin gene in creeping stems. Transgenic overexpression in both Arabidopsis and cultivated chrysanthemum confirmed its role in reducing plant height, increasing lateral spread, and promoting prostrate growth.

“The most exciting aspect of this work is that we connected long-term field phenotyping with functional gene validation,” said one of the corresponding authors. “Prostrate growth is a complex trait influenced by both genetics and hormones, and our results show that a single key regulator can coordinate cell division and plant architecture. This not only deepens our understanding of how growth habit evolves in wild species, but also demonstrates how modern genetic tools can overcome the challenges of breeding in polyploid ornamental plants.”

The findings have important implications for ornamental plant breeding and landscape design. The identified molecular markers enable marker-assisted selection, allowing breeders to efficiently introduce prostrate growth habit into elite chrysanthemum cultivars without lengthy field screening. Ground-cover chrysanthemums developed using this approach could reduce maintenance costs, improve landscape resilience, and support low-carbon urban greening. More broadly, the study provides a framework for dissecting complex architectural traits in polyploid species and highlights how integrating genomics, physiology, and functional validation can accelerate the development of climate-resilient and resource-efficient ornamental plants.