The processes of plant adaptation to stressful environments are controlled and regulated by multiple genes (Pardo and VanBuren, 2021; Zhang et al., 2022). Functional characterization of these genes is helpful to understand how grass and forage plants adapt to stressful environments and selected genes can be used for breeding grass, forage and crop plant cultivars with improved stress tolerance. Jiang et al. characterized a novel transcriptional regulator HbERF6 that regulates the HbCIPK2-coordinated pathway conferring salt tolerance in a halophytic grass Hordeum brevisubulatum. Zhou et al. constructed a high-density genetic map and localized grazing-tolerant QTLs in Medicago falcata L. Wang et al. identified LjHDZ7 encoding a 40 HD-Zip transcription factor from Lotus japonicas and the overexpression of LjHDZ7 increased plant salt tolerance. The overexpression of abscisic acid-insensitive gene (ABI4) from Medicago truncatula by Li et al. enhanced the content of endogenous ABA in plants and improved plant cold tolerance. Guan et al. found that Zoysia japonica ZjNOL promotes chlorophyll degradation and senescence and negatively affects the integrity and function of the photosystem.

Numerous structurally different metabolites are produced in plants in response to various stressful environments (Kim et al., 2007; Kim et al., 2017). Li et al. found that caffeic acid O-methyltransferase gene CrCOMT from Carex rigescens conferred melatonin-mediated drought tolerance in plants. Differential responses of four white clover genotypes to salt stress associated with root growth, endogenous polyamines metabolism, and sodium/potassium accumulation and transport were identified by Li et al. Yu et al. identified 90 uridine diphosphate glycosyltransferase (UGT) members in ten evolutionary groups that are likely related to secondary metabolites in alfalfa (Medicago sativa L.). Li et al. found that the flexible response of a large number of genes and metabolites endows Poa crymophila with robust cold and drought tolerance. Yang et al. demonstrated that genotypic-specific reprogramming and crosstalk of various plant hormones are crucial for root growth and salt tolerance of bermudagrass (Cynodon dactylon). Lin et al. found that Leymus chinensis adapts to degraded soil environments by changing its metabolic pathways and root exudate components. Overexpression of Pennisetum purpureum CCoAOMT encoding caffeoyl-CoA O-methyltransferase by Song et al. contributes to lignin deposition and drought tolerance by promoting the accumulation of flavonoids in transgenic plants.

Root-associated microbes can improve plant growth, and offer the potential to increase plant tolerance to stressful environments (Saijo and Loo, 2020; Vries et al., 2020). Mei et al. found that the planting of alfalfa can promote the proliferation of specific beneficial microbiota groups in the soil. Wang et al. demonstrated that Bacillus amyloliquefaciens GB03 augmented tall fescue growth by regulating phytohormone and nutrient homeostasis under nitrogen deficiency condition. Hou et al. found that Bacillus atrophaeus WZYH01 and Planococcus soli WZYH02 improved salt tolerance of maize (Zea mays L.). Zhang et al. demonstrated that inoculation of Elymus nutans with arbuscular mycorrhizal fungi Funneliformis mosseae improved the uptake of nutrients and induced the resistance to grasshopper attack. Pan et al. found that root exudates and rhizosphere soil bacterial relationships of Nitraria tangutorum are linked to k-strategist bacterial community under salt stress. Wei et al. demonstrated that salt-tolerant endophytic bacterium Enterobacter ludwigii B30 enhance bermudagrass growth under salt stress by modulating plant physiology and changing rhizosphere and root bacterial community.

Recent significant progress in omics techniques (transcriptomics, genomics, proteomics, and metabolomics) have helped to deeply understand the molecular insights into multiple stress tolerance of plants (Singhal et al., 2021). Salt tolerance in alfalfa is associated with regulation of ionic homeostasis, antioxidative enzymes and fatty acid metabolism at both transcriptional and physiological level (Li et al.). Transcriptomic profiling by Chen et al. showed the role of 24-epibrassinolide in alleviating salt stress damage in tall fescue (Festuca arundinacea). A transcriptome analysis by Dong et al. revealed the molecular regulatory mechanisms of leaf senescence in Medicago truncatula under alkaline stress. Another transcriptome analysis by Li et al. revealed the molecular response mechanism of high-resistant and low-resistant alfalfa varieties to Verticillium alfalfa. A combined analysis of the transcriptome and proteome by Ming et al. revealed the mechanisms underlying the enhanced salt tolerance by the protein disulfide isomerase gene (ZmPDI) in Zoysia matrella [L.] Merr. An integrated analysis of small RNAs, transcriptome and degradome sequencing by Fan et al. revealed the drought stress network in Agropyron mongolicum. A series integrated analyses in Medicago truncatula in response to salt stress by An et al. revealed multiple differentially expressed coding and non-coding RNAs, including mRNAs, lncRNAs, circRNAs, and miRNAs, and they identified multiple DEmRNA and ceRNA interaction pairs that function in many pathways of salt stress responses.

Overall, the articles collected on this Research Topic represent a substantial contribution to fill gaps in knowledge of the roles of complex signaling transduction pathways in grass and forage plants in response to various stressful environments. Moreover, the stress tolerance-related genes, beneficial natural metabolites, and root-associated microbes identified are valuable resources not only for grass and forage plants, but also for other crops. Jiuxin and Liebao reviewed the research progress of turfgrass resistance breeding, analyzed the bottlenecks of turfgrass resistance breeding, and put forward the strategies to cope with the bottlenecks, which will be useful to guide turfgrass breeding for stress tolerance.

J-LZ and JZ prepared the draft. JZ, M-FC, SG, K-HW and J-LZ revised the manuscript. All authors approved the final version of the manuscript and approved it for publication.