Using Exogenous Endophytic Fungi to Improve Seed Germination and Seedling Development of Oat under Water Stress

【Objective】 Seed germination and its subsequent seedling development underpin the ultimate yield, but they are prone to water stress. This paper studies the feasibility and effectiveness of using exogenous endophytic fungi to boost germination of oat (Avena sativa L.) seed and its seedling development under drought conditions. 【Method】 Oat seeds were treated with tap water (WW); water stress in the petri dishes was created by adding 12% of PEG-6000 to the water. The Czapek medium was used as the control (CK). The seeds were inoculated by endophytic fungi O-2 (Fusarium equiseti) and O-66 (Alternaria pomicola), respectively. In each treatment, we measured seed germination and the subsequent seedling growth, morphology, and physiological traits of the roots. 【Result】 Successful colonization of the exogenous endophytic fungi O-2 and O-66 was identified in the oat roots. Drought stress significantly inhibited seed germination, but inoculation with endophytic fungi O-2 and O-66 increased the germination rate. Notably, inoculation with fungus O-66 significantly increased the germination rate and seedling development by 44.68% and 41.18%, respectively, compared to CK. The endophytic fungi also promoted radicle and germ elongation, which were 1.15 to 1.36 times and 1.18 to 1.42 times that of CK, respectively. In hydroponic culture, all endophytic fungi enhanced plant height, dry matter accumulation, and root index of the oat seedlings. O-66 inoculation resulted in a 23.67% increase in plant height and a 39.58% increase in canopy dry weight. Additionally, inoculation also increased root dry weight, total root length, projected root area, total root surface area, total root volume and root tips significantly by 33.72%, 20.40%, 35.47%, 31.84%, 36.94% and 59.24%, compared to CK. Inoculation with endophytic fungi increased root activity, and elevated SOD, POD, and CAT enzymes by 25.97% to 30.48%, 14.26% to 20.47% and 37.46% to 45.72%, respectively. Compared to CK, inoculation reduced the content of MDA (malondialdehyde), a marker of oxidative stress, by 9.27% to 10.33%. 【Conclusion】 Inoculating the oat seeds by exogenous endophytic fungi can effectively alleviate drought stress to their germination and the subsequent seedling development, especially when inoculated with the fungus O-66. These results provide valuable insight into the use of endophytic fungi to mitigate drought stress to seed germination and improve crop growth.