Sodium selenite seed priming improves seed germination, seedling growth and rhizosphere microbial community structure of Sugar Beet (Beta vulgaris L.) under salt stress

This study deeply explored the multiple impacts of sodium selenite priming on the germination, growth, physiology, and rhizosphere microbial community of sugar beet seeds under salt stress. The results showed that salt stress had a significant inhibitory effect on the germination and growth of sugar beet seeds and seedlings. Using sodium selenite as a seed priming agent to soak sugar beet seeds, the experiment found that low-concentration sodium selenite soaking could significantly improve the germination and growth of sugar beet seeds and seedlings under salt stress, but when the sodium selenite concentration was too high (such as 40 μM), it had an inhibitory effect on the germination and growth of sugar beet seeds and seedlings. In addition, sodium selenite seed soaking could increase the contents of chlorophyll and carotenoids, maintain ion balance, increase the content of soluble sugar and soluble protein, maintain cell elasticity and cell membrane stability, and improve the plant's resistance to salt stress. Salt stress led to a significant increase in the content of malondialdehyde (MDA) in sugar beet seedling leaves, and after sodium selenite soaking, the MDA content could be significantly reduced, reducing the accumulation of reactive oxygen species (ROS) and lipid peroxidation of cell membranes. At the same time, it could increase the activities of antioxidant enzymes (SOD, POD, CAT, and APX), promote the clearance of intracellular ROS, and protect plants from oxidative damage. Low-concentration sodium selenite soaking could increase the richness and diversity of the rhizosphere bacterial community of sugar beets under salt stress. Different concentrations of sodium selenite soaking would lead to different enriched bacteria in the microbial community. Microorganisms might interact with plants, participate in plant growth and development, maintain species diversity and community structure stability, and thus improve the salt tolerance of sugar beets. Sodium selenite soaking made the differential species in each group different, and they might be important species for maintaining the health of saline-alkali soil, but their specific functions still needed further research. As a priming agent, sodium selenite still needed further in-depth research on the specific molecular mechanism of improving plant salt tolerance. In the future, multi-year field trials could be carried out to verify its effect in actual production, and the use concentration of sodium selenite could be further optimized to better play its role in improving the salt tolerance and yield of sugar beets, providing new ideas and methods for improving the cultivation and production of sugar beets.本研究深入探究了亚硒酸钠（sodium selenite）种子引发对盐胁迫下甜菜种子萌发、生长、生理特性及根际微生物群落的多重影响。结果表明，盐胁迫对甜菜种子及幼苗的萌发与生长具有显著抑制作用。本实验采用亚硒酸钠作为种子引发剂浸种甜菜种子后发现，低浓度亚硒酸钠浸种可显著改善盐胁迫下甜菜种子与幼苗的萌发及生长状况，但当亚硒酸钠浓度过高（如40 μM）时，反而会抑制甜菜种子及幼苗的萌发与生长。此外，亚硒酸钠浸种可提升叶绿素与类胡萝卜素含量，维持离子平衡，增加可溶性糖与可溶性蛋白含量，保持细胞弹性及细胞膜稳定性，从而提高植株的盐胁迫抗性。盐胁迫会导致甜菜幼苗叶片内丙二醛（MDA，malondialdehyde）含量显著升高，经亚硒酸钠浸种后，丙二醛含量可显著降低，减少活性氧（ROS，reactive oxygen species）积累与细胞膜脂质过氧化。同时，其可提升抗氧化酶（SOD、POD、CAT及APX）活性，促进细胞内活性氧的清除，保护植株免受氧化损伤。低浓度亚硒酸钠浸种可提升盐胁迫下甜菜根际细菌群落的丰富度与多样性。不同浓度的亚硒酸钠浸种会使微生物群落中富集的菌种存在差异。微生物可与植物产生相互作用，参与植物生长发育过程，维持物种多样性与群落结构稳定性，进而提升甜菜的耐盐性。亚硒酸钠浸种使各组的差异物种各不相同，它们或为维持盐碱地健康的关键物种，但其具体功能仍需进一步研究。作为一种种子引发剂，亚硒酸钠提升植物耐盐性的具体分子机制仍有待深入探究。未来可开展多年田间试验以验证其在实际生产中的应用效果，并进一步优化亚硒酸钠的使用浓度，以更好地发挥其在提升甜菜耐盐性与产量中的作用，为甜菜栽培与生产改良提供新思路与新方法。