Soil salinization is a global environmental issue and a significant abiotic stress that threatens crop production. Root-associated rhizosphere microbiota play a pivotal role in enhancing plant tolerance to abiotic stresses. However, limited information is available concerning the specific variations in rhizosphere microbiota driven by different plant genotypes (varieties) in response to varying levels of salinity stress. In this study, we compared the growth performance of three alfalfa varieties with varying salt tolerance levels in soils with different degrees of salinization. High-throughput 16S rRNA and ITS sequencing were employed to analyze the rhizosphere microbial communities. Undoubtedly, the increasing salinity significantly inhibited alfalfa growth and reduced rhizosphere microbial diversity. However, intriguingly, salt-tolerant varieties exhibited relatively lower susceptibility to salinity, maintaining more stable rhizosphere bacterial community structure, whereas the reverse was observed for salt-sensitive varieties. Bacillus emerged as the dominant species in alfalfa's adaptation to salinity stress, constituting 21.20% of the shared bacterial genera among the three varieties. The higher abundance of Bacillus, Ensifer, and Pseudomonas in the rhizosphere of salt-tolerant alfalfa varieties is crucial in determining their elevated salt tolerance. As salinity levels increased, salt-sensitive varieties gradually accumulated a substantial population of pathogenic fungi, such as Fusarium and Rhizoctonia. Furthermore, rhizosphere bacteria of salt-tolerant varieties exhibited increased activity in various metabolic pathways, including biosynthesis of secondary metabolites, carbon metabolism, and biosynthesis of amino acids. It is suggested that salt-tolerant alfalfa varieties can provide more carbon sources to the rhizosphere, enriching more effective plant growth-promoting bacteria (PGPB) such as Pseudomonas to mitigate salinity stress. In conclusion, our results highlight the variety-mediated enrichment of rhizosphere microbiota in response to salinity stress, confirming that the high-abundance enrichment of specific dominant rhizosphere microbes and their vital roles play a significant role in conferring high salt adaptability to these varieties.

Excessive use of chemical fertilizers in agriculture has become a major global source of pollution, leading to issues such as soil compaction, reduced fertility, eutrophication of water bodies, and air pollution. To address these challenges, the application of biofertilizers, such as rhizobial inoculants, has gradually become an effective, low-cost, and sustainable solution. In this study, the variety Trifolium ambiguum Bieb. (Mengnong clover No. 1) was used as the test material, and two rhizobial strains (R1 and R2) were employed for field inoculation trials. In April 2022, Caucasian clover was planted in an experimental field at Inner Mongolia Agricultural University. Each plot measured 3 m × 4 m and was arranged in a completely randomized design with three replications. In the regreening stage of 2023, rhizobial inoculation treatments were applied, with a control group included for comparison. This research examined the effects of rhizobial inoculation on the growth indicators of Caucasian clover, soil physicochemical properties, soil enzyme activities, and soil microbial communities. The results showed that rhizobial treatment increased the plant height and yield of Caucasian clover, improved soil physicochemical properties and enzyme activities, and positively affected soil microbial diversity and abundance. These changes enhanced soil fertility and optimized microbial community structure, promoting plant growth. The inoculation effect of strain R1 was superior to R2. In conclusion, rhizobial inoculants R1 and R2 can serve as effective biofertilizers for agricultural production.

Plants have evolved a series of inducible or constitutive defense mechanisms in response to herbivore attack. Constitutive plant defenses are morphological and biochemical traits of the plants themselves, regardless of the presence of herbivores. We bred an alfalfa variety (Caoyuan No.4) with high thrips resistance, but the mechanisms underlying Caoyuan No.4 resistance to thrips are not well understood. To explore the constitutive defense of Caoyuan No.4, the morphological and biochemical traits associated with constitutive defense to thrips in alfalfa were analyzed using a thrips-susceptible alfalfa accession (Caoyuan No.2) as a control. The results showed that Caoyuan No.4 had thicker palisade tissue and parenchyma tissue, wider collenchyma, phloem, cambium and lignin layer, and smaller epidermal cells and stomatal aperture compared to Caoyuan No.2. Moreover, Caoyuan No.4 showed more non-glandular trichomes in both leaves and stems, but less glandular trichomes and more wax in stems. In addition, the results of the widely targeted metabolomics analysis showed that metabolites related to flavonoid, isoflavonoid, flavone and flavonol biosynthesis, as well as cysteine and methionine metabolism, differed between CaoyuanNo.2 and Caoyuan No.4. These findings shed new light on the constitutive insect defense of plants associated with physical or biochemical traits and may provide convenient markers for breeding thrips-resistant alfalfa cultivars.

Stems are more important to forage quality than leaves in alfalfa. To understand lignin formation at different stages in alfalfa, lignin distribution, anatomical characteristics and transcriptome profile were employed using two alfalfa cultivars. The results showed that the in vitro true digestibility (IVTD) of stems in WL168 was significantly higher than that of Zhungeer, along with the significantly lower neutral detergent fiber (NDF), acid detergent fiber (ADF) and lignin contents. In addition, Zhungeer exhibited increased staining of the xylem areas in the stems of different developmental stages compared to WL168. Interestingly, the stems of WL168 appeared intracellular space from the stage 3, while Zhungeer did not. The comparative transcriptome analysis showed that a total of 1993 genes were differentially expressed in the stem between the cultivars, with a higher number of expressed genes in the stage 4. Of the differentially expressed genes, starch and sucrose metabolism as well as phenylpropanoid biosynthesis pathways were the most significantly enriched pathways. Furthermore, expression of genes involved in lignin biosynthesis such as PAL, 4CL, HCT, CAD, COMT and POD coincides with the anatomic characteristics and lignin accumulation. These results may help elucidate the regulatory mechanisms of lignin biosynthesis and improve forage quality in alfalfa.

Background: To accelerate the establishment of a genetic improvement system for Onobrychis viciaefolia Scop. by cultivating haploid plants and producing pure parental material. Methods: We endeavored to set up the Onobrychis viciaefolia Scop. anther culture system, examine the suitable anther pre-treatment method and the factors influencing medium type and hormone ratio during anther regeneration. Result: The regenerative capacity of intact anthers was preserved by 48h low temperature (4°C) medium treatment. Or the broken anthers were obtained when the regenerated grass was budding and preserved in the medium after 48 hours of low temperature treatment; callus induction was based on MS and the callus rate was 18.33% when 1.0 mg/L 2,4-D + 0.75 mg/L 6-BA + 0.8 mg/L NAA + 2.0 mg/L KT was added. With N6 as the basic medium, the addition of 2.0 mg/L 2,4-D + 0.75 mg/L 6-BA + 0.4 mg/L NAA + 0.5 mg/L KT resulted in a healing rate of 16.19%; the addition of 0.5 mg/L 6-BA + 1.0 mg/L KT to the MS medium resulted in a differentiation rate of 68%; during the construction of the anther histoponic system, browning and waterlogging of the healing tissues and vitrification of the seedlings hindered the formation of regenerated plants.

Plant-derived volatile organic compounds (VOCs) are widely used as insect attractants for population monitoring, offering an efficient and eco-friendly approach to pest management. Since thrips are the dominant pest species in alfalfa (Medicago sativa) crops, alfalfa volatiles produced in the presence of Odontothrips loti and compounds with attractive potential to both O. loti and Frankliniella occidentalis were investigated. Using gas chromatography–mass spectrometry (GC-MS), 96 VOCs were identified from seven alfalfa cultivars with varying levels of thrips resistance with and without damage by O. loti. Eleven volatiles were selected for Y-tube olfactometer assays. The semiochemical p-Menth-8-en-2-one, which was suppressed in alfalfa subject O. loti damage, significantly attracted both O. loti and F. occidentalis in Y-olfactometer bioassays; the response rates were 2.05~3.07 times compared to control (p < 0.05). Further experiments confirmed p-Menth-8-en-2-one, dispensed through PE (Polyethylene) vials, was the most effective lure material with the concentrations of 10 ng/μL. This study demonstrated that the alfalfa-derived volatile p-Menth-8-en-2-one, shows significant attraction to thrips, which can be utilized for monitoring and management of odontothrips loti and frankliniella occidentalis.