Octoploids show enhanced salt tolerance through chromosome doubling in Switchgrass (Panicum virgatum L.)

Abstract Background Polyploid plants often exhibit enhanced stress tolerance. Switchgrass is a perennial rhizomatous bunchgrass that is considered ideal for cultivation in marginal lands, including sites with saline soil. In this study, we investigated the physiological responses and transcriptome changes of octoploid and tetraploid of switchgrass (Panicum virgatum L. ‘Alamo’) under salt stress.Results We found that autoploid 8× switchgrass had enhanced salt tolerance compared with the amphidiploid 4× precursor as indicated by physiological and phenotypic traits. Octoploids had increased salt tolerance by significantly changes to the osmoregulatory and antioxidant systems. The salt-treated 8× Alamo plants showed greater K+ accumulation and an increase in the K+/Na+ ratio. Root transcriptome analysis for octoploid and tetraploid plants with or without salt stress revealed that 302 upregulated and 546 downregulated differentially expressed genes were enriched in genes involved in plant hormone signal transduction pathways, and were specifically associated with the auxin, cytokinin, abscisic acid, and ethylene pathways. Weighted gene co-expression network analysis detected four significant salt stress-related modules.Conclusions This study explored the changes in the osmoregulatory system, inorganic ions, antioxidant enzyme system, and the root transcriptome in response to salt stress in 8× and 4× Alamo switchgrass. The results enhance knowledge of the salt tolerance of artificially induced homologous polyploid plants, and provide experimental and sequencing data to aid research on the short-term adaptability and breeding of salt-tolerant biofuel plants.