Tea tree (Camellia sinensis) is among the most vital beverage crops globally. The size of tea buds not only impacts the yield and quality of fresh leaves but also influences the compatibility of various tea types. In a recent study, the Chinese Academy of Agricultural Sciences gathered images of apical buds at the one-bud, two-leaf stage from 280 representative tea lines. Their analysis of genetic diversity revealed that the length, width, circumference, and area of tea buds followed a normal distribution. A comparative transcriptome analysis of extreme bud sizes demonstrated a significant negative correlation between the expression levels of four substances. nox genes also showed a relationship with tea bud size, indicating that CsKNOX6 could be a key gene regulating tea bud size negatively.
The tea plant stands out as one of the world’s leading beverage crops, cultivated in over 60 countries and consumed by more than 2 billion people globally.
In premium tea production, leaves are typically harvested based on criteria including one bud, one leaf per bud, and two leaves per bud.
Tea bud size not only significantly impacts the yield and quality of fresh leaves but is also closely linked to the processing potential of tea.
Various tea types have different shapes and specific requirements for bud and leaf size.
Research into the molecular mechanisms governing tea bud and leaf size has historically been sparse, hindering genetic improvement efforts.
Understanding the genetic regulatory frameworks of tea bud size is crucial for enhancing tea plant varieties and boosting yield.
In the study led by Dr. Jiedan Chen, the dimensions—length, width, circumference, and area—of buds were quantified across 280 diverse tea strains.
These traits exhibited continuous variation with high heritability, indicating robust genetic control.
Comparative transcriptome analysis of accessions with extreme bud sizes identified four candidate class I KNOX transcription factors that had significantly elevated expression in cultivars with smaller buds.
Among these, genome-wide association mapping is emphasizing CsKNOX6 as a likely pivotal regulatory gene.
CsKNOX6 is located on chromosome 10, with its sequence indicating nuclear localization, aligning with its role in transcription regulation.
To validate its functionality, researchers modelled CsKNOX6 in the plant Arabidopsis.
Transgenic plants exhibited abnormal shoot development, yielding significantly smaller leaves, with leaf area reduced to just 13% of wild-type levels.
This functional evidence substantiates the conclusion that CsKNOX6 serves as a negative regulator of bud and leaf size.
“Bud size is a critical attribute for both agricultural productivity and the quality of tea in the market,” scientists shared.
“Identifying CsKNOX6 creates direct genetic targets for selective breeding, including marker-driven improvements.”
“Although functional tests in Arabidopsis provide substantial support, future gene editing or transgenic validation in tea plants will be vital to confirm regulatory mechanisms in these perennial woody species.”
“This discovery paves the way for precision breeding strategies that enhance yield, consistency, and suitability of tea varieties.”
Identifying CsKNOX6 opens new possibilities for developing tea varieties with optimized bud sizes for various production goals, including premium hand-picked teas or high-yield mechanical harvesting.
This gene can be integrated into molecular breeding programs via SNP marker selection or gene editing approaches to fine-tune developmental growth.
A paper detailing this discovery was published in the journal horticultural research.
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Shuran Zhang et al. 2025. Integration of digital phenotyping, GWAS, and transcriptome analysis reveals key genes for tea plant bud size (Camellia sinensis). horticultural research 12(6):uhaf051; doi: 10.1093/hr/uhaf051
Source: www.sci.news
