Tea’s drought-defense gene offers a new route to climate-resilient breeding
image: Haplotype analysis of CsAGD6 and its association with drought resistance in tea germplasms. (A) Haplotype structure and frequency of CsAGD6 based on SNPs in the promoter and coding regions; (B) Regional LD block analysis; (C) Genomic structure of CsAGD6 and distribution of major SNP loci; (D) Haplotype network diagrams and frequency pie charts showing the distribution of promoter (Hap-P) and coding region (Hap-C) haplotypes; (E) Phenotypic comparison of major haplotypes under drought stress; (F) Relative expression levels of CsAGD6 in representative tea accessions from Hap-C1 and Hap-C2. Different letters indicate significant differences at P < 0.05.
Credit: Horticulture Research
Drought is becoming a growing threat to tea production, reducing both yield and quality as water shortages intensify under climate change. In a new study, researchers identified a key gene, CsAGD6, that helps tea plants cope with drought stress and maintain better physiological performance. By combining genome-wide association analysis with expression profiling and functional experiments, the team showed that CsAGD6 supports drought tolerance by protecting photosynthetic activity and cellular stability. They also identified favorable natural variants of the gene and developed a practical molecular marker that can help breeders detect drought-tolerant tea germplasm earlier and more efficiently.
Tea plants are especially vulnerable to prolonged water deficit, which can suppress photosynthesis, disturb metabolism, and damage cell membranes. Although recent multi-omics studies have revealed many drought-responsive pathways in tea, the genetic basis of drought tolerance has remained difficult to resolve because the trait is controlled by multiple interacting factors. Traditional evaluation methods often rely on single physiological indicators and may not fully capture a plant’s overall drought performance. At the same time, genome-wide association studies have been widely used in other crops to dissect complex traits, but comparable work on drought resistance in tea has lagged behind. Based on these challenges, in-depth research on the genetic determinants of drought tolerance in tea plant is needed.
Researchers from Qingdao Agricultural University, together with colleagues from the Tea Research Institute of the Shandong Academy of Agricultural Sciences and the Rizhao Academy of Agricultural Sciences, published (DOI: 10.1093/hr/uhaf320) the study on November 21, 2025, in Horticulture Research, reporting that CsAGD6 is a drought-responsive gene that improves tea plant tolerance and can be converted into a useful marker for breeding.
To find the genetic signals behind drought resistance, the team evaluated 11 physiological traits in 115 diverse tea accessions exposed to drought and built a comprehensive drought-resistance index known as the D-value. They observed that drought generally reduced photosynthetic traits such as net photosynthetic rate, stomatal conductance, transpiration, leaf relative water content, and Fv/Fm, while increasing malondialdehyde, a marker of oxidative damage. Using whole-genome resequencing and GWAS, the researchers identified 79 associated SNPs, including 67 highly significant loci, and narrowed the search to four candidate genes. Among them, CsAGD6 stood out because it was strongly induced under drought stress. Functional tests then confirmed its role: silencing CsAGD6 increased oxidative damage and reduced chlorophyll and photosynthetic efficiency, while overexpressing it produced the opposite effect. The team further showed that favorable haplotypes, Hap-P1 and Hap-C1, were associated with stronger drought tolerance and higher CsAGD6 expression. Finally, they developed a KASP marker targeting chr10:206216541 (C/T), which effectively distinguished drought-tolerant genotypes and showed promise for early screening in tea breeding.
“This study does more than identify another drought-related signal,” the researchers suggest through their results. It connects field-relevant physiological traits, natural genetic variation, and functional validation into a single breeding framework. By showing that CsAGD6 helps preserve membrane stability and photosynthetic machinery under water deficit, the work also expands scientific understanding of ARF-GAP proteins, which had previously been linked more often to growth and trafficking processes than to abiotic stress adaptation in tea. In this sense, the study offers both a mechanistic insight and a practical breeding entry point.
The implications are significant for tea improvement under climate pressure. Because tea is a perennial crop with a long breeding cycle, early molecular screening is especially valuable. The newly developed CsAGD6-based marker could help breeders identify promising drought-tolerant germplasm before lengthy field evaluation, saving time and improving selection efficiency. More broadly, the study provides a genetic framework for developing more resilient tea cultivars that can better withstand increasingly erratic rainfall and water scarcity. With further validation in larger populations, this discovery may become an important tool for sustaining tea production in a warming world.
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References
DOI
Original Source URL
https://doi.org/10.1093/hr/uhaf320
Funding information
This work was funded by the National Natural Science Foundation of China (No. 32272767).
About Horticulture Research
Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2023. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.