Alfalfa, as a high-quality forage resource, has high nutritional value. Due to the high phenotypic similarity among its varieties and the susceptibility to environmental influences, challenges are encountered in variety identification and breeding. In this study, 23 simple sequence repeat (SSR) markers were screened to distinguish 49 alfalfa varieties, among which 21 SSR markers showed polymorphic fragments. The results indicated that these 21 markers were highly polymorphic, with an average of 5.91 alleles per SSR marker locus and an average polymorphic information content (PIC) of 0.66, suggesting a strong discriminatory efficiency. The results of a population genetic diversity analysis showed that there was a relatively high level of genetic diversity among the tested materials. The analysis of molecular variance (AMOVA) results indicated that the genetic variation within the population of the 49 alfalfa germplasm samples was the main source of the total variation. The results of genetic distance and genetic identity analyses showed that the genetic relationship between population 1 and population 4 was the most distant, while the relationship between population 2 and population 3 was the closest. The cluster analysis results showed that samples S16 and S55 formed a separate branch; that is, there were two main genetic subgroups. These results confirm that SSR markers are effective tools for genetic characterization and precise discrimination of alfalfa varieties and have important application values in breeding, variety registration, and germplasm resource conservation.

Saline–alkali land is widely distributed worldwide, and poses significant challenges to agricultural productivity and ecological restoration, particularly in the Qaidam Basin. This study investigates the effects of intercropping and mixed sowing systems of oats (Avena sativa L.) and forage peas (Pisum sativum L.) on hay yield and soil chemical fertility in mildly saline–alkali soils of the Qaidam Basin. Through a comprehensive analysis of hay yield, soil chemical properties, and enzyme activities under different sowing methods (mixed sowing, intercropping, and monoculture) and row spacings (30, 25, 20 and 15 cm), an optimal planting pattern was identified. The 25 cm intercropping treatment produced the highest amount of fresh biomass (2242 kg hm⁻¹), with an increase ranging from 3.17% to 70.44% compared to other treatments. Additionally, this treatment led to significant reductions in soil pH and electrical conductivity (by 3.87–8.31% and 5.13–6.05%, respectively), while enhancing organic matter content and enzyme activities. The intercropping system also demonstrated higher ammonium nitrogen and available phosphorus contents compared to the mixed sowing system. Structural equation modeling revealed that row spacing indirectly influenced both hay yield and enzyme activities, with the 25 cm row spacing proving to be the most effective. A comprehensive evaluation using the TOPSIS model further affirmed that the 25 cm intercropping system significantly enhanced hay yield, soil chemical properties, and enzyme activities, making it the most suitable planting pattern for sustainable land management in the study area. Therefore, the 25 cm intercropping model not only optimizes hay yield, but also improves soil quality and ecological functions in saline–alkali land, offering valuable insights and practical recommendations for the sustainable use of saline–alkali land in the Qaidam Basin.

(1) Background: This study used the cold-tolerant cultivar “Daye No. 3” (DY) and the cold-sensitive cultivar “Longdong” (LD) as plant materials to study the metabolic changes in plant hormones in alfalfa (Medicago sativa L.) under cold stress. (2) Methods: The targeted quantitative detection of phytohormones in alfalfa was carried out by liquid chromatography–tandem mass spectrometry (LC-MS/MS) technology. Principal component analysis (PCA), orthogonal signal correction, and partial least squares discriminant analysis (OPLS-DA) were used to investigate sample classification and screen differential metabolites. (3) Results: The results showed that 17 differential metabolites were detected. Seven metabolites showed common changes in the two cultivars after low-temperature stress induction. The levels of tryptamine, N-jasmonoylisoleucine, trans-zeatin riboside, isopentenyladenine riboside, cis-zeatin riboside, and gibberellin A7 were decreased, while N6-isopentenyladenine levels increased. In addition, compared with the LD variety, DY had more metabolite changes in response to low-temperature stress. Abscisic acid and trans-zeatin were elevated, whereas IAA-alanine, dihydrozeatin riboside, and indole-3-carboxaldehyde showed reduced concentrations. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis showed that differential plant hormones were more active in plant hormone signal transduction, zeatin biosynthesis, and tryptophan metabolism pathways. In addition, a total of 12 metabolites in these three pathways showed common changes under cold stress. (4) This study identified significant metabolomic differences between two alfalfa genotypes under stress. It highlighted key pathways and provided new insights into the metabolic changes of alfalfa under cold-stress conditions.

Summary: Dispersal is an important behaviour for nematodes. Entomopathogenic nematodes (EPN) are able to regulate plant-parasitic nematodes in the field. However, the mechanism for the interactions between two types of nematodes is not clearly known. The effects of 12 synthesised ascarosides, three EPN species (Steinernema carpocapsae All, Heterorhabditis bacteriophora H06 and H. indica LN2), and 15 symbiotic bacterial isolates from EPN on the dispersal of Meloidogyne incognita were investigated. The results revealed that M. incognita juveniles were repelled, to various degrees, by most of the tested ascarosides (especially ascr#9), three species of EPN, and by bacterial isolates (especially TT01 from H. bacteriophora TT01 and H06 from H. bacteriophora H06), compared with the controls. Ascr#9 was abundant in M. incognita juvenile-conditioned supernatant. This provides useful cues for elucidating the interaction mechanism between two nematode groups and establishing alternative techniques for the safe and effective control of root-knot nematodes.

This study aimed to clarify the effects of row spacing on forage yield, quality, and soil function in an oat-forage pea intercropping system in the high-altitude Qinghai-Tibet region. A two-year, multi-site field experiment was conducted in Hainan and Haixi Prefectures, in which DTOPSIS and structural equation modeling (SEM) were integrated to evaluate multiple objectives. The results indicated that the optimal row spacing differed between sites. In Hainan, a row spacing of 30 cm maximized forage yield (11,507.94 kg·ha− 1), representing a 12% increase compared with 25 cm spacing, although the soil quality index (SQI) declined by 9.67%. In Haixi, a 25 cm spacing enhanced forage yield (6,905.98 kg·ha− 1) and maintained a higher SQI than wider spacings. SEM analysis identified site-specific pathways linking row spacing, forage productivity, and soil function, and emphasized the presence of negative feedback mechanisms in nutrient-limited or arid environments. The findings suggest that optimal row spacing is region-specific, balancing trade-offs among yield, forage quality, and soil sustainability, and providing mechanistic insights for precision spatial management of alpine intercropping systems.