Background Due to its strong abiotic stress tolerance, common vetch is widely cultivated as a green manure and forage crop in grass and crop rotation systems. The comprehensive molecular mechanisms activated in common vetch during cold adaptation remain unknown. Results We investigated physiological responses and transcriptome profiles of cold-sensitive (Lanjian No. 1) and cold-tolerant (Lanjian No. 3) cultivars during cold acclimation to explore the molecular mechanisms of cold acclimation. In total, 2681 and 2352 differentially expressed genes (DEGs) were identified in Lanjian No. 1 and Lanjian No. 3, respectively; 7532 DEGs were identified in both lines. DEGs involved in “plant hormone signal transduction” were significantly enriched during cold treatment, and 115 DEGs involved in cold-processed hormone signal transduction were identified. Common vetch increased the level of indoleacetic acid (IAA) by upregulating the transcriptional regulator Aux/IAA and downregulating GH3, endowing it with stronger cold tolerance. An auxin-related DEG was overexpressed in yeast and shown to possess a biological function conferring cold tolerance. Conclusion This study identifies specific genes involved in Ca2+ signaling, redox regulation, circadian clock, plant hormones, and transcription factors whose transcriptional differentiation during cold acclimation may improve cold tolerance and contributes to the understanding of common and unique molecular mechanisms of cold acclimation in common vetch. The candidate genes identified here also provide valuable resources for further functional genomic and breeding studies.

Alfalfa (Medicago sativa L.), an important perennial legume forage crop with high nutritional value and forage yield, is widely used in animal husbandry. However, it is very sensitive to aluminum, which severely limits its growth in acidic soils. In this study, we analyzed the genotype variation of each agronomic trait in 44 alfalfa varieties in two acidic soil environments. Then, analysis of variance (ANOVA) of the variance components was performed using the Residual Maximum Likelihood (REML). The best linear unbiased predictor analysis was used to obtain the mean trait of each variety, and the mean values were used to construct the mean matrix of varieties × traits and interaction analysis of varieties × years. The results showed that there was significant (P < 0.05) genotypic variation for each trait of the 44 varieties and the genetic diversity was abundant. The average repeatability (R value) of interannual plant height (PH), stem thickness (ST), number of branches (NS), fresh weight (FW), total fresh weight (TFW), and total dry weight (TDW) was high (0.21–0.34), whereas the genetics were relatively stable. PH, NS, FW, TFW, and dry weight (DW) were positively correlated (P < 0.01) with TDW. Six alfalfa varieties (Algonquin, Xinjiang daye, Trifecta, Vernal, WL354HQ, and Boja) with excellent TDW and TFW were identified in different years, environmental regions, and climatic altitudes. Our research results can provide suggestions and critical information regarding the future improvement and development of new alfalfa strains and varieties that are resistant to acidic soil conditions.

Common vetch (Vicia sativa) is an important forage and green manure crop that is widely cultivated around the world. However, the large number of subspecies and accessions of common vetch has made taxonomic research on this species difficult. Pollen morphology data can provide important evidence in the study of plant phylogeny. Therefore, in this research, light microscopy and scanning electron microscopy were used to observe seven morphological traits of pollens from 22 common vetch accessions, and residual maximum likelihood and pattern analysis was conducted. The results showed that the pollen grains of the 22 accessions were all monad pollen and the polar view revealed three-lobed circular and triangular shapes, while the equatorial view mainly revealed an oblate shape; only one accession showed an oblate spherical shape. All accessions were 3-zonocolporate and the colpus length extended close to the poles. The polar axis length was (19.39 ± 0.97)–(42.12 ± 0.76) μm and the equatorial axis length was (35.97 ± 1.27)–(45.25 ± 0.81) μm. We found that qualitative traits of pollen shape, aperture polar view and ornamentation were highly stable. Among them, polar axis length, equatorial axis length and colpus length and width had significant differences among the accessions. The ratios of the equatorial and polar axes had significant differences among the subspecies. This trait information could be used for the classification and identification of common vetch accessions and subspecies.

Numerous studies have shown that plant microRNAs (miRNAs) play key roles in plant growth and development, as well as in response to biotic and abiotic stresses; however, the role of miRNA in legumes under aluminum (Al) stress have rarely been reported. Therefore, here, we aimed to investigate the role of miRNAs in and their mechanism of Al tolerance in legumes. To this end, we sequenced a 12-strand-specific library of Medicago truncatula under Al stress. A total of 195.80 M clean reads were obtained, and 876 miRNAs were identified, of which, 673 were known miRNAs and 203 were unknown. A total of 55 miRNAs and their corresponding 2,502 target genes were differentially expressed at various time points during Al stress. Further analysis revealed that mtr-miR156g-3p was the only miRNA that was significantly upregulated at all time points under Al stress and could directly regulate the expression of genes associated with root cell growth. Three miRNAs, novel_miR_135, novel_miR_182, and novel_miR_36, simultaneously regulated the expression of four Al-tolerant transcription factors, GRAS, MYB, WRKY, and bHLH, at an early stage of Al stress, indicating a response to Al stress. In addition, legume-specific miR2119 and miR5213 were involved in the tolerance mechanism to Al stress by regulating F-box proteins that have protective effects against stress. Our results contribute to an improved understanding of the role of miRNAs in Al stress in legumes and provide a basis for studying the molecular mechanisms of Al stress regulation.

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