Salt tolerance characterization and genome-wide association study of Gossypium barbadense accessions reveal salinity-adaptive variations

Huazu Li¹Shuhui Wang^1,2Zhengning Zheng¹Yue Sun³Yifei Han⁴Mengyu Xing¹Tianxu Zhang¹Wenlong Mo^1,2Binbin Cai¹Jinghan Yin^1,2Jiajie Qian^1,2Uzair Muhammad¹Wei Li^5,6Daojun Yuan⁷Jinhong Chen²Shuijin Zhu^1,2*Tianlun Zhao^1,2*

• ¹College of Agriculture and Biotechnology, Zhejiang University, Hangzhou, China
• ²Hainan Institute of Zhejiang University, Sanya, China
• ³Zhejiang Agricultural Technical Extension Center, Hangzhou, China
• ⁴Institute of Crop and Nuclear Technology Utilization, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
• ⁵Zhengzhou Research Base, State Key Laboratory of Cotton Bio-breeding and Integrated Utilization, School of Agricultural Sciences, Zhengzhou, China
• ⁶Chinese Academy of Agricultural Sciences State Key Laboratory of Cotton Bio-breeding and Integrated Utilization, Anyang, China
• ⁷National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, China

As a globally important cash crop, Gossypium barbadense has the high-quality fiber for textile industry. However, it experiences substantial growth reduction and yield limitations under salt stress, rendering the elucidation of its salt tolerance mechanisms imperative for breeding initiatives. Here, we performed population structure analysis on 240 globally distributed G. barbadense accessions, resolving four distinct subpopulations (G1-G4) with G1 comprising exclusively non-Xinjiang (China) accessions. Seedling-stage salt stress screening identified 23 highly salt-tolerant genotypes exhibiting divergent phenotypic responses. A genome-wide association study (GWAS) identified multiple significant single nucleotide polymorphism (SNP) loci associated with salt tolerance, with the most prominent signal localized to chromosome D02. Virus-induced gene silencing (VIGS) of Gbar_D02G014670 (GbXTH27) exacerbated salt-induced wilting phenotypes and significantly decreased antioxidant enzyme activities. Functional characterization demonstrated that GbXTH27 could enhance salt tolerance in G. barbadense by regulating antioxidant capacity and facilitating osmotic adjustment substance accumulation. This research provides valuable molecular markers and theoretical foundations for genetic improvement and breeding of salt-tolerant G. barbadense cultivars, while also offering insights into salt stress response mechanisms applicable to other crops.