|Other Abstract||Festuca sinensis is one of the good forage in the alpine regions of northern 中文na. It often forms mutually beneficial symbiosis with Epichloë sinensis endophyte, which can increase the stress resistance of host plants. Recent studies have shown that the E. sinensis endophyte is a new species of endophyte. The mechanism of its interaction with F. sinensis is not clear. In the present study, the E+ (infected with endophyte) and E- (endophyte free) plants of F. sinensis have been employed in a series of experiments. The aims were to explore the variations of alkaloid production of E+ F. sinensis in both greenhouse and field during the four seasons of a year, and the impacts of both mixed seeding and cutting management on E. sinensis-F. sinensis associations; and the relationships among the endophyte-symbiont-soil microorganisms. The main findings are as follows:
(1) Both in the field and greenhouse, the alkaloids (peramine, lolitrem B and ergot) were detected in six ecotypes E+ F. sinensis (41, 57, 84, 99, 111 and 141) in four seasons (spring, summer, autumn and winter). The results clarified the content range of the three alkaloids in F. sinensis: peramine ranged from 18.51 ppm to 112.47 ppm; lolitrem B ranged from 0.38 ppm to 1.15 ppm and ergot ranged from 0.36 ppm to1.13 ppm. From spring to autumn, both in the field and greenhouse, peramine contents significantly decreased (P < 0.05); its content was highest in spring and lowest in autumn. The content of peramine of endophyte-symbiont in F. sinensis was higher than that in Festuca arundinacea. In the field experiment, the lolitrem B content of five ecotypes F. sinensis was highest in autumn and lowest in spring (P < 0.05); its ergot content was highest in summer and lowest in spring. In the greenhouse experiment, the lolitrem B content of five ecotypes F. sinensis was the highest in summer and the lowest in spring (P < 0.05); the results of their ergot alkaloids were consistent in the field. In addition, the contents of both lolitrem B and ergot of endophyte-symbiont in F. sinensis was lower than in Lolium perenne.
(2) Both in the greenhouse (monoculture, 2:8, 4:6, 6:4 and 8:2) and field (monoculture, 2:8 and 4:6) experiments, the mixed sowing of F. sinensis and Elymus nutans were carried out. Both in the greenhouse and field experiments, mixed sowing significantly (P < 0.05) promoted growth of both F. sinensis and E. nutans; the mixed sowing ratio of 4:6 increased growth of both F. sinensis and E. nutans compared with other mixed sowing ratios, such as significantly (P < 0.05) increased the plant height, tillers, stem diameter and root l英语th of both plants; endophyte also significantly (P < 0.05) increased the plant height and tillers of both F. sinensis and E. nutans. In the greenhouse experiment, the peramine of E+ F. sinensis reached lowest at the 8:2 mixed sowing ratio, while in the field experiment, the peramine of E+ F. sinensis were lowest at the 4:6 mixed sowing ratio. In the greenhouse experiment, the lolitrem B of E+ F. sinensis was not different among mixed sowing ratios, while in the field experiment the lolitrem B of E+ F. sinensis was peaked at the 2:8 mixed sowing ratio (P < 0.05).
(3) In the greenhouse experiment, the E+ and E- F. sinensis were cut three times, respectively. The results showed that the cuttings had significant impacts on the nutrition and quality of F. sinensis (P < 0.05). Nutrition and quality of F. sinensis had no significant difference between the 1-2 time of cutting, but significantly decreased at the third cutting (P < 0.05). In addition, endophyte significantly increased the nitrogen, phosphorus, crude protein, crude fat and crude ash contents of F. sinensis (P < 0.05).
(4) In the greenhouse experiment, the results of a two-year experiment showed that endophyte significantly (P < 0.05) increased the plant height, root l英语th, stem diameter, root diameter, tiller, leaf width, shoot dry weight and root dry weight of F. sinensis, as well as shoot nitrogen, root nitrogen, shoot phosphorus and root phosphorus contents (P < 0.05). Endophyte significantly increased the total amino acid and ethanolamine contents secreted by the roots of F. sinensis, but reduced the glycerol content secreted by the roots of F. sinensis (P < 0.05). Endophyte significantly increased the contents of total nitrogen, total phosphorus, ammonium nitrogen, nitrate nitrogen, available phosphorus and available potassium in the rhizosphere soil of F. sinensis, but significantly reduced the content of organic carbon and pH in the rhizosphere soil of F. sinensis (P < 0.05). Endophyte reduced the fungal and bacterial community diversity in the rhizosphere soil of F. sinensis (P < 0.05); the fungal community with the highest relative abundance was the Ascomycota in the rhizosphere soil; the bacterial community with the highest relative abundance was the Proteobacteria. In the second year of planting, the fungal community diversity decreased, while the bacterial community diversity increased in the rhizosphere soil (P < 0.05). Overall, the impact of endophyte on the ecotype-99 F. sinensis was more significant than that of the ecotype-111 F. sinensis. The rhizosphere soil properties, the root exudates and the rhizosphere soil microbial diversity had a significant correlation (P < 0.05), that is, the relative contents of total phenolic acid, total amino acid, and total nucleic acid in root exudates and the rhizosphere soil fungal diversity were negatively correlated with the diversity of rhizosphere soil fungal (P < 0.05), while positively correlated with the diversity of rhizosphere soil bacterial (P < 0.05). Thus, endophyte promoted the growth of F. sinensis, affected the root exudates and the soil properties, thereby affecting the rhizosphere soil microbial community.|