Researchers have identified a key gene, CsKNOX6, that directly regulates bud size in tea plants (Camellia sinensis ), opening the door to more efficient breeding programs for improved yield and quality. This discovery, published in Horticulture Research, provides a genetic target for fine-tuning tea cultivars to meet diverse production goals, from premium hand-plucked teas to high-yield mechanical harvesting.
The Importance of Bud Size in Tea Production
Tea is one of the world’s most consumed beverages, cultivated across over 60 countries. The size of tea buds—typically harvested as “one bud and two leaves”—directly impacts both the quantity and quality of fresh leaves. Different tea types require specific bud and leaf sizes for optimal processing. For years, limited understanding of the molecular mechanisms controlling bud size has hindered genetic improvement efforts.
Identifying CsKNOX6 as a Key Regulator
A team led by Dr. Jiedan Chen at the Tea Research Institute of the Chinese Academy of Agricultural Sciences analyzed the genetic diversity of 280 tea accessions, quantifying bud length, width, and area. Their research revealed strong genetic control over bud size, with traits displaying normal distribution and high heritability. Comparative transcriptomic analysis of tea plants with extreme bud sizes identified four KNOX genes with significantly higher expression in smaller-bud varieties. Genome-wide association mapping then pinpointed CsKNOX6 as the most likely key regulator.
Functional Validation in Arabidopsis
To confirm the role of CsKNOX6, researchers overexpressed the gene in Arabidopsis thaliana, a model plant. Transgenic Arabidopsis displayed stunted shoot development and dramatically reduced leaf size—leaf area shrank to just 13% of wild-type levels. This functional evidence supports the conclusion that CsKNOX6 acts as a negative regulator of bud and leaf size.
Implications for Breeding and Future Research
The discovery of CsKNOX6 provides a direct genetic target for selective breeding. While functional testing in Arabidopsis offers strong support, future validation in tea plants through gene editing or transgenic approaches will be essential. This discovery lays the groundwork for precision breeding strategies to improve yield, uniformity, and suitability of tea cultivars. The gene can be integrated into molecular breeding programs through SNP marker selection or gene-editing approaches to fine-tune developmental growth.
“Bud size is a critical trait for both agronomic productivity and market quality in tea,” the scientists concluded.
This breakthrough offers new opportunities for developing tea varieties with optimized bud size for different production goals, from premium hand-plucked teas to high-yield mechanical harvesting.
Reference: Zhang, S., et al. (2025). Integration of digital phenotyping, GWAS, and transcriptomic analysis revealed a key gene for bud size in tea plant (Camellia sinensis ). Horticulture Research, 12 (6), uhaf051. doi: 10.1093/hr/uhaf051
