Deciphering salt stress adaptation in octoploid broomcorn millet (Panicum miliaceum L.): For sustainable agricultural development in saline-alkaline soils.

Saline-alkali soil is one of the major challenges in global agricultural production, significantly affecting crop growth and yield. Polyploid plants often exhibit stronger salt tolerance. However, the specific mechanisms by which polyploid broomcorn millet adapts to salt stress remain unclear. This study used tetraploid and octoploid broomcorn millet as experimental materials to explore their response mechanisms under 120 mM salt stress. The results indicated that octoploid broomcorn millet exhibited stronger antioxidant capacity under salt stress, with lower malondialdehyde (MDA) content in the leaves, and a significant increase in soluble sugars and proline (Pro) content. In contrast, the tetraploid broomcorn millet displayed tighter stomatal closure, leading to reduced carbon dioxide assimilation. Additionally, salt stress inhibited auxin signal transduction in tetraploid broomcorn millet, greatly hindering its growth, but had a lesser inhibitory effect on octoploid broomcorn millet. Under salt stress, the abscisic acid (ABA) induced antioxidant and starch degradation pathways were promoted in octoploid broomcorn millet, while the glycolysis pathway was inhibited. Consequently, octoploid broomcorn millet has stronger osmoregulatory capacity and adaptability to salt stress. This study provides a reference for research on the salt tolerance mechanisms of polyploid broomcorn millet and offers a new theoretical basis and practical support for sustainable agricultural development in saline-alkali soils.