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.

Ensiling forage under low-temperature conditions often leads to poor fermentation and nutrient losses. This study evaluated the effects of a cold-tolerant Pediococcus pentosaceus OL77 strain on oat silage. Silages were prepared with or without Pediococcus pentosaceus inoculation (1 × 10⁵ cfu/g FM). After 90 days, OL77-treated silage showed markedly higher lactic acid (45.83 vs. 30.51 g/kg DM), lower pH (3.88 vs. 4.443), and better preservation of WSC (64.68 vs. 47.60 g/kg DM) and crude protein (89.26 vs. 65.52 g/kg DM) than the control. Microbial analysis revealed accelerated colonization by Pediococcus, reduced bacterial diversity, and faster stabilization of the fermentation process. Functional predictions indicated enhanced carbohydrate and energy metabolism. These findings demonstrate that OL77 can effectively improve fermentation quality and nutrient preservation of oat silage under low-temperature conditions, offering a practical inoculant option for cold regions.