Sunflower is valued as an oilseed crop and as a resilient plant that can grow where many crops struggle. Yet salt in soil still threatens seed germination, early seedling growth, and future yield, especially as agriculture increasingly turns to marginal land. A new study traces this problem to a specific genetic control point in sunflower. By combining high-throughput phenotyping with genome-wide analysis and functional validation, researchers identified the HaCBF4 – HaHAK11 module as a positive regulator of salt tolerance. The work explains how young sunflower plants activate stress-response pathways under saline conditions and provides candidate genes that could support breeding of more salt-tolerant sunflower varieties.
Soil salinity is a growing threat to agriculture because excess salts disrupt water uptake, ion balance, photosynthesis, and normal plant development. Sunflower ( Helianthus annuus L.) is generally considered moderately salt tolerant, but different sunflower lines show wide variation in their ability to germinate and grow under saline conditions. Although genome-wide association study (GWAS) approaches have helped identify stress-related loci in crops, previous work in sunflower has often lacked high-resolution genetic variation data and detailed functional validation. Based on these challenges, there is a need to conduct deeper research into the genetic determinants that allow sunflower to respond to salt stress at the earliest growth stages.
Researchers from Hangzhou Normal University, South China Agricultural University, Xinjiang University, and the Xinjiang Academy of Agricultural Sciences published (DOI: 10.1093/hr/uhag081) the study on 4 March 2026 in Horticulture Research . The team analyzed 342 oilseed sunflower accessions under salt stress at the germination stage, combining high-throughput phenomics, whole-genome sequencing (WGS), genome-wide association study (GWAS), transcriptome analysis, and molecular assays. Their work identified a regulatory pathway in which C-repeat binding factor 4 (CBF4) activates high-affinity potassium transporter 11 (HAK11) to improve sunflower salt-stress tolerance.
The team first recorded 31 germination and seedling traits, including germination rate, germination index, germination energy, root length, water content, fresh weight, and dry weight. The panel included salt-tolerant, moderately salt-tolerant, and salt-sensitive accessions, giving the study a broad phenotypic base. Whole-genome sequencing generated a dense variation map, and GWAS detected 359 trait-associated single-nucleotide polymorphisms (SNPs) and 63 insertions/deletions (InDels), corresponding to 424 and 83 candidate genes, respectively. Among these candidates, HaCBF4 stood out because it was associated with germination energy and responded strongly to salt stress. Functional experiments showed that HaCBF4 localizes to the nucleus and acts as a positive regulator. When HaCBF4 was suppressed using virus-induced gene silencing (VIGS), plants lost water faster, accumulated more reactive oxygen species (ROS) and malondialdehyde (MDA), and suffered greater leaf damage after sodium chloride (NaCl) treatment. Transcriptome analysis then highlighted HaHAK11 as a downstream target. Yeast one-hybrid (Y1H), luciferase reporter, and electrophoretic mobility shift assay (EMSA) experiments showed that HaCBF4 binds the dehydration-responsive element (DRE) in the HaHAK11 promoter and activates its expression. Silencing HaHAK11 produced similar salt-sensitive traits and reduced the induction of known stress-response genes.
The authors said the study connects population-level genetic signals with a working molecular mechanism, moving beyond a list of candidate genes. They said the key advance is showing how HaCBF4, a stress-responsive transcription factor, directly activates HaHAK11 and then influences a wider set of salt-response genes, including DREB2B , LEA18 , P5CS2 , LEA1-A , MADS27 , and RAB18 . In their view, this regulatory module provides a clearer route from phenotype to gene discovery to breeding application, especially for improving seedling establishment under saline conditions.
The discovery offers practical genetic resources for breeding sunflower cultivars that can better establish seedlings in saline soils, an important step for using marginal land without adding pressure to high-quality farmland. The study also provides a transferable research pipeline for other crops: high-throughput phenotyping can reveal stress-related traits, WGS and GWAS can locate candidate genes, and molecular assays can confirm how those genes work. Future research can test whether HaHAK11 also contributes to sodium exclusion, potassium balance, or ROS signaling in field environments. These findings may support molecular markers, marker-assisted selection, or gene-editing strategies for salt-tolerant sunflower improvement.
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References
DOI
Original Source URL
https://doi.org/10.1093/hr/uhag081
Funding information
This work was supported by the Interdisciplinary Research Project of Hangzhou Normal University (2025JCXK01) and the Postdoctoral Research Startup Fund (4105C5022521521 to W.G.).
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.
Horticulture Research
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Integrating high-throughput phenomics and GWAS unravels the HaCBF4-HaHAK11 module to regulate salt stress tolerance in sunflower (Helianthus annuus L.)
4-Mar-2026
The authors declare that they have no competing interests.