Background: Artificial inoculation of Epichloë endophytes into elite forage germplasm aims to establish beneficial symbioses for developing high-yield, high-quality, and stress-tolerant cultivars, but host specificity of the fungi often causes compatibility issues in non-natural hosts. Methods: The E. bromicola isolated from native wild barley was inoculated into cultivated wild barley (Hordeum brevisubulatum) and cultivated barley (Hordeum valgare), forming Hb+Eb and Hv+Eb. The NHb+Eb (native wild barley naturally infected with E. bromicola) served as a control. We analyzed fungal colonization patterns and symbiotic gene regulation to clarify the compatibility between E. bromicola and non-natural hosts. Results: Compared with NHb+Eb and Hb+Eb, E. bromicola in Hv+Eb showed obvious hyphal vacuolization. E. bromicola colonization altered host trichome morphology and induced stomatal closure. Correspondingly, expression of the siderophore biosynthesis gene sidN and the NADPH oxidase complex genes (NoxA, NoxB, NoxR, RacA) was significantly lower (p < 0.05) in Hv+Eb than in Hb+Eb and NHb+Eb. Conclusions: This study reveals that the incompatibility between cultivated barley and E. bromicola is characterized by altered hyphal morphology, which is linked to the downregulation of sidN and Nox. These findings provide a critical theoretical foundation for developing highly compatible cereal-Epichloë germplasms.

Cultivated grasslands provide an important strategy for reducing pressure on degraded natural grasslands and increasing high-quality forage supply. However, how stand-age-related variation affects belowground–aboveground coordination and forage production in cultivated Leymus chinensis remains unclear. Here, we compared a natural L. chinensis stand (NL) with 3-, 4-, and 5-year-old cultivated ‘Zhongke No. 1’ stands by integrating plant trait measurements, biomass assessment, nutrient analysis, forage quality evaluation, correlation analysis, and structural equation modeling. (1) Compared with NL, cultivated stands generally showed greater vegetative growth and aboveground biomass, lower fiber concentrations, and higher soluble sugar concentration and relative feed value. (2) Root and aboveground traits exhibited distinct stand-age-related patterns, with the 3Y stand showing greater root exploration traits, the 4Y stand achieving the highest aboveground biomass (4.61 t/hm²), and the 5Y stand exhibiting greater root thickening and ramet density. (3) Carbon, nitrogen, and phosphorus concentrations varied among stand ages, indicating shifts in nutrient status during stand development. (4) Correlation analysis and PLS-SEM revealed that root architecture, nutrient status, and aboveground morphology were closely associated with forage yield and quality variation. These findings highlight the importance of stand-age-dependent belowground–aboveground coordination for optimizing the management and utilization of cultivated L. chinensis grasslands.

Low soil fertility caused by organic matter deficit severely restricts crop productivity in sandy lands. To investigate the effects of organic matter addition on plant yield and soil productivity in sandy areas, a two-factor randomized block field experiment was conducted using oat (Avena sativa) with five ratios (7:3, 3:2, 1:1, 2:3, 3:7; w:w) and five application rates (0, 5, 10, 15, and 20, t·ha⁻¹) of peat powder and fermented manure in the Horqin Sandy Land, which is a typical agro-pastoral ecotone in northern China. Application of combined peat powder and fermented manure significantly increased oat yield, and the fertilization rate exerted a stronger effect on oat yield than the mixing ratio of the two organic materials. Furthermore, organic fertilization significantly increased the relative abundances of microorganisms, improved soil C, N and P contents, and enhanced the activities of urease, invertase, and catalase. The combination of an application rate of 20 t·ha⁻¹ and a 3:2 peat-powder-to-fermented-manure ratio represents a promising fertilization regime among treatments tested for oat cultivation in this region, given its highest aboveground dry-matter yield. Collectively, these findings show that rational combined application of fermented manure and peat powder in sandy land can significantly increase soil enzyme activities and optimize soil nutrient stoichiometry, and is positively correlated with rhizosphere microbial community composition and oat yield.