Drought severely limits the growth and development of oat (Avena sativa) seedlings. As an osmotic regulator simulating a drought environment, Polyethylene glycol (PEG) has been widely linked in response to plant drought tolerance. However, the underlying mechanism of oats’ response to PEG stress is still largely unknown. Here, we investigated the physiological and transcriptome variables of the drought-resistant oat variety DA92-2F6, and the drought-susceptible variety Longyan 3 under 15% PEG-6000 drought stress to better understand the underlying drought tolerance molecular mechanisms. The physiological results showed that except for the cell membrane permeability, the antioxidant enzyme, osmotic adjustment substance, and photosynthetic efficiency were significantly higher in the DA92-2F6 after 7 d stress. Further, 12 cDNA libraries and 123,223 unigenes were obtained by RNA-seq. A total of 33,857 differentially expressed genes (DEGs) were detected, of which two co-upregulated and three co-downregulated in four comparisons. We highlighted an analysis of the DEGs in phytohormone signal transduction pathway. The auxin, cytokinin, and brassinosteroid signaling pathways, were suppressed in Longyan 3, while abscisic acid and jasmonic acid signaling pathways were mainly activated in DA92-2F6 under drought stress. The upregulated of PP2C, ABF, SNRK2, GID1, JAZ, and MYC2 genes may enhance the drought tolerance of DA92-2F6. Taken together, these results provided a new transcript resource for the drought tolerance improvement and a reference for oat drought resistance molecular breeding.

Red clover (Trifolium pratense L.) is used as forage and contains a high level of isoflavonoids. Although isoflavonoids in red clover were discovered a long time ago, the transcriptional regulation of isoflavonoid biosynthesis is virtually unknown because of the lack of accurate and comprehensive characterization of the transcriptome. Here, we used a combination of long-read (PacBio Iso-Seq) and short-read (Illumina) RNAseq sequencing to develop a more comprehensive full-length transcriptome in four tissues (root, stem, leaf, and flower) and to identify transcription factors possibly involved in isoflavonoid biosynthesis in red clover. Overall, we obtained 50,922 isoforms, including 19,860 known genes and 2817 novel isoforms based on the annotation of RefGen Tp_v2.0. We also found 1843 long non-coding RNAs, 1625 fusion genes, and 34,612 alternatively spliced events, with some transcript isoforms validated experimentally. A total of 16,734 differentially expressed genes were identified in the four tissues, including 43 isoflavonoid-biosynthesis-related genes, such as stem-specific expressed TpPAL, TpC4H, and Tp4CL and root-specific expressed TpCHS, TpCHI1, and TpIFS. Further, weighted gene co-expression network analysis and a targeted compound assay were combined to investigate the association between the isoflavonoid content and the transcription factors expression in the four tissues. Twelve transcription factors were identified as key genes for isoflavonoid biosynthesis. Among these transcription factors, the overexpression of TpMYB30 or TpRSM1-2 significantly increased the isoflavonoid content in tobacco. In particular, the glycitin was increased by 50–100 times in the plants overexpressing TpRSM1-2, in comparison to that in the WT plants. Our study provides a comprehensive and accurate annotation of the red clover transcriptome and candidate genes to improve isoflavonoid biosynthesis and accelerate research into molecular breeding in red clover or other crops.

To evaluate the effects of temperature and lactic acid bacteria (LAB) inoculants on oat silage in Loess Plateau of China, oat was harvested at dough stage, inoculated without (Control) or with LAB inoculants Synlac I (SLI, Lactobacillus plantarum and Pedioccocus acidilactici) and a selected strain HT1 (L. rhamnosus) and ensiled at 25°C (T25), 35°C (T35) and 45°C (T45). The fermentation quality was measured after 60 d of ensiling and the aerobic exposure was conducted at 30°C for 9 d. The results showed that control silage (stored at 25°C) had better fermentation quality than that ensiled at 35°C or 45°C. High temperature of 45°C resulted in sharp decreases in LAB counts and lactic acid concentration and increases in pH and NH3-N concentration in the control group. Inoculation improved the fermentation quality, and HT1 was more effective than SLI at 35°C and 45°C, while SLI showed better performance at 25°C. All silages displayed mild fluctuation for all treatments at the first 3 d of aerobic exposure, and significant differences were observed among treatments after that. Both control and inoculated silages stored at 25°C showed a sharp pH increase, while HT1 treated silages stored at 35°C and 45°C maintained stable pH and better fermentation quality during the aerobic exposure. In conclusion, SLI was suitable for oat silage fermentation at normal atmospheric temperature (25°C), while HT1 was more effective in improving DM recovery, fermentation quality and aerobic stability of oat silage at high temperature during summer in the Loess Plateau of China.

Chemical mutagenesis coupled with molecular marker analysis is an efficient strategy for accelerating crop improvement and creating crop genetic diversity, yet optimized protocols and comprehensive evaluations chemical mutagenesis-assisted forage oats traits improvement and breeding understudied. This study aimed to assess sodium azide (SA)-induced mutagenesis in two oat varieties (Everleaf and 709) by characterizing phenotypic and molecular variations, identifying tissue-specific mutation patterns, and establishing efficient treatment parameters for breeding. SA treatment at > 10 mmol·L⁻1 caused severe germination inhibition (lethality > 60%) but maximized phenotypic variation (CV up to 90.80% for panicle traits). By phenotypic screening, out of 767 (M2-M3) mutants, a total of six categories of mutant phenotypes were identified: leaf traits were most frequently altered (1.02%), followed by seeds (0.39%). M2 mutation frequencies reached 17.9–23.73%. SSR markers revealed high polymorphism (60–100% polymorphic sites, PIC 0.27–0.80), amplifying 3–9 alleles/locus. Multivariate analyses (PCA, UPGMA, and STRUCTURE) grouped 293 mutants into four genetically distinct clusters, confirming genome-wide diversity. SA induces extensive and diverse heritable phenotypic and molecular variations in oats, with mutation spectra showing tissue-specific trends. The mutant libraries and polymorphic SSR markers developed provide a valuable resource for oat breeding and functional genomics. This work establishes a protocol for SA mutagenesis in oats and delivers mutant germplasm with broad applicability in trait improvement and genetic research.