Soybean cyst nematode (SCN, Heterodera glycine) is a serious damaging disease in soybean worldwide, thus resulting in severe yield losses. MicroRNA408 (miR408) is an ancient and highly conserved miRNA involved in regulating plant growth, development, biotic and abiotic stress response. Here, we analyzed the evolution of miR408 in plants and verified four miR408 members in Glycine max. In the current research, highly upregulated gma-miR408 expressing was detected during nematode migration and syncytium formation response to soybean cyst nematode infection. Overexpressing and silencing miR408 vectors were transformed to soybean to confirm its potential role in plant and nematode interaction. Significant variations were observed in the MAPK signaling pathway with low OXI1, PR1, and wounding of the overexpressing lines. Overexpressing miR408 could negatively regulate soybean resistance to SCN by suppressing reactive oxygen species accumulation. Conversely, silencing miR408 positively regulates soybean resistance to SCN. Overall, gma-miR408 enhances soybean cyst nematode susceptibility by suppressing reactive oxygen species accumulation.

Water scarcity and soil hypoxia are major constraints to forage productivity in arid regions. This study investigated the effects of subsurface drip irrigation with micro-nano bubble oxygenated water (MNBO) on the rhizosphere environment, root physiology, growth, and quality of alfalfa ( Medicago sativa L. cv. ‘Caoyuan No. 2’) under field conditions in Inner Mongolia. A full factorial experimental design was employed, combining three irrigation levels (20, 25, and 30 mm) and three dissolved oxygen concentrations (1.8, 5.0, and 8.2 mg/L). Structural equation modeling (SEM) was applied to quantify the direct and indirect effects of irrigation and oxygenation on yield formation pathways. Results demonstrated that MNBO irrigation significantly improved soil enzyme activities (catalase by 15–28%; urease by 18–32%), microbial abundance (bacteria, fungi, actinomycetes), and root vitality (27.9–103.6%), thereby promoting plant growth and yield. The optimal treatment (25 mm irrigation with 5.0 mg/L DO) increased dry matter yield by 8.3–30.1%, crude protein by 11.2–11.5%, and crude fat by 18.8–27.6% compared to conventional practices. Structural equation modeling revealed that yield improvement was primarily mediated through enhanced soil biological activity and root functionality, rather than direct irrigation effects. These findings provide a scientifically robust irrigation strategy that synergistically enhances water use efficiency and root zone aeration, offering significant potential to support sustainable forage production in water-limited ecosystems.