Polycomb group (PcG) proteins, which are important epigenetic regulators, play essential roles in the regulatory networks involved in plant growth, development, and environmental stress responses. Currently, as far as we know, no comprehensive and systematic study has been carried out on the PcG family in Medicago truncatula. In the present study, we identified 64 PcG genes with distinct gene structures from the M. truncatula genome. All of the PcG genes were distributed unevenly over eight chromosomes, of which 26 genes underwent gene duplication. The prediction of protein interaction network indicated that 34 M. truncatula PcG proteins exhibited protein–protein interactions, and MtMSI1;4 and MtVRN2 had the largest number of protein–protein interactions. Based on phylogenetic analysis, we divided 375 PcG proteins from 27 species into three groups and nine subgroups. Group I and Group III were composed of five components from the PRC1 complex, and Group II was composed of four components from the PRC2 complex. Additionally, we found that seven PcG proteins in M. truncatula were closely related to the corresponding proteins of Cicer arietinum. Syntenic analysis revealed that PcG proteins had evolved more conservatively in dicots than in monocots. M. truncatula had the most collinearity relationships with Glycine max (36 genes), while collinearity with three monocots was rare (eight genes). The analysis of various types of expression data suggested that PcG genes were involved in the regulation and response process of M. truncatula in multiple developmental stages, in different tissues, and for various environmental stimuli. Meanwhile, many differentially expressed genes (DEGs) were identified in the RNA-seq data, which had potential research value in further studies on gene function verification. These findings provide novel and detailed information on the M. truncatula PcG family, and in the future it would be helpful to carry out related research on the PcG family in other legumes.

Both Avena sativa and Avena nuda, which are highly valued for their use in food and fodder, demonstrate considerable potential in the management of saline-alkali soils. This study aimed to establish a foundation for the selection of salt-tolerant oat cultivars by assessing the impact of varying salt concentrations (0, 50, 100, 150, and 200 mmol L⁻¹) on agronomic traits, photosynthetic characteristics, physiological and biochemical properties, and leaf anatomical structures in both covered oat cultivars and naked oat cultivars. The measured parameters indicate the level of salt tolerance in Avena sativa and Avena nuda, which is influenced by both salt concentration and cultivar. Both Avena sativa and Avena nuda demonstrate strong adaptation to mild and moderate salt stress conditions. However, Avena sativa exhibits a significantly greater capacity to withstand severe salt stress compared to Avena nuda. Affinity function analysis ranked the cultivars’ salt tolerance as follows: ‘Qinghai 444’ > ‘Mengyan No. 1’ > ‘Baiyan No. 18’ > ‘Qingyin No. 3’. These results suggest that the selection of oat cultivars for salinity improvement should be tailored to the specific salinity levels present in different regions.