| Elymus tangutorum is a perennial grass of the tribe Triticeae in the family Poaceae,and provides high quality forage for animal production in northwest China.It forms a mutually beneficial symbiosis with the endophyte Epichlo? bromicola.Previous studies had shown that elevation had influences on the symbiont,but there was a need for further research.In this study,66 sampling sites from 13 counties in Gansu and Qinghai provinces with different elevations were used to provide data for study,and the relevant climate and soil information was collected and collated.Through collection from the wild,laboratory experiments,and the combination of conventional techniques and molecular biology techniques,the relationship between elevation and the biological characteristics of the endophytic symbiont of E.tangutorum was studied,in order to provide theoretical support for the scientific and optimal use of the endophyte symbiont of E.tangutorum.The main results are as follows:1.The endophyte infection decreased with increasing elevation.The frequency of endophyte infection of E.tangutorum at the study sites ranged from 0 to 100%,with100% endophyte infection frequency recorded at six sites,and 0% infection recorded at 11 sites.The hyphal density was 1?6.3 per mm cross section,and maximum and minimum values were recorded in samples collected at 2100 m(Ping'an,Qinghai)and3920 m(Guinan,Qinghai),respectively.The endophyte infection frequency and hyphal density decreased gradually with increasing elevation(P<0.001).The endophyte infection was significantly positively correlated with the mean daily temperature of the sampling sites(P<0.05),while the mean annual precipitation was negatively correlated with endophyte infection(P<0.05).The contribution rate of the mean daily temperature reached more than 72%.2.Elevation had no significant effect on the biological characteristics of endophyte strains isolated from E.tangutorum,but had a significant effect on endophyte genetic diversity.Based on their morphological and molecular characteristics,endophyte strains isolated from E.tangutorum were identified as Epichlo? bromicola.For a temperature range of 5?30°C with 5°C increments,the endophyte colony diameter was determined,and was increased with collection elevation at 5?(P>0.05).Under warmer other growth conditions,colony diameters did not vary significantly with the increased elevation of collection(P>0.05).Except for the haplotype diversity of per A and combination sequences,genetic diversity indices decreased significantly with increasing elevation of collection(P<0.05).Mean daily temperature,soil organic carbon content and total soil nitrogen content of collection sites were the main factors affecting endophyte genetic diversity.3.The remainder of biomass between endophyte infected(E+)and endophyte free(E–)plants increased with increasing elevation.For E+ and E– E.tangutorum,plant heights ranged from(64.70?97.40)cm and(63.50?97.75)cm,respectively;tiller numbers ranged from(1?5.8)and(1?6.1)per plant,respectively;the above ground biomass values were(0.81?5.45)g/plant and(0.83?5.76)g/plant,respectively,and the thousand seed weight values were(1.61?3.64)g and(2.11?4.25)g,respectively.Interestingly,the remainder between E+ and E– plants increased with increasing elevation,and the remainder between E+ and E– height and E+ and E– aboveground biomass became significant at higher elevation(P<0.05).The lower mean daily temperature and higher mean annual precipitation were the main factors that caused the higher biomass remainder between E+ and E–.4.At higher elevation,E+ plants had higher crude protein content than E– plants.For E+ and E– plants,respectively,ranges for crude protein content were(7.37%?12.76%)and(7.19%?12.82%);ranges for acid detergent fiber were(35.16%?53.47%)and(41.42%?55.58%);and for neutral detergent fiber were(67.53%?78.96%)and(65.29%?78.01%).Crude protein,acid detergent fiber and neutral detergent fiber contents of E+ plants were significantly higher than those of E–plants at 60.86%,17.39% and 17.39% of studied sites,respectively(P<0.05).The remainders in crude protein content between E+ and E– increased with increasing elevation(P<0.05),while the remainders in neutral detergent fiber and acid detergent fiber between E+ and E– plants decreased with increasing elevation(P>0.05).Higher mean daily temperature was not conducive to increase in crude protein content,but did promote the accumulation of fiber content in E+ plants.In E+ and E– plants,respectively,ranges for total digestible nutrients were(100.69%?101.31%)and(100.63%?100.82%),ranges for digestible dry matter were(88.50%?88.63%)and(88.49%?88.58%),ranges for dry matter intake were(152.38% ?161.07%)and(152.49%?162.33%),and ranges for relative forage value were(104.26%?122.02%)and(105.55%?126.53%).The levels of total digestible nutrients,digestible dry matter,dry matter intake,and relative forage value of E+ plants were significantly higher than those of E– in 60.87%,34.78%,21.74% and 39.13% sites,respectively(P<0.05).The remainder in total digestible nutrients of E+ and E– plants decreased with increasing elevation(P<0.001),while the remainder below than 0 only in 3 sites.Mean daily temperature was extremely significant with the remainders in total digestible nutrients of E+ and E– plants(P<0.01).5.The concentrations of ergine and peramine alkaloids varied significantly with elevation(P<0.05),but the concentration of ergonovine showed no significant elevational trend(P<0.05).Across all sites for the study,the concentration ranges of ergonovine,ergine and peramine alkaloids were,respectively,(0.47?0.84)?g/g,(0.35?1.49)?g/g and(9.18?13.00)?g/g.Fitted cubic regression curves describing an arc-pattern across the elevational series were statistically significant for ergine and peramine concentrations(P<0.05),while higher elevation is not conducive to the production of alkaloids.The higher peramine concentration was linked to higher mean daily temperature and lower mean precipitation,while the lower ergine concentration was linked to higher mean daily temperature.In conclusion,this study of relationship between elevation and the biological characteristics of the E.bromicola-E.tangutorum symbiosis indicated that high elevation was not conducive to the symbiosis,the growth of the endophyte,the maintenance of endophyte genetic diversity or the production of endophyte alkaloids,but endophyte–infected E.tangutorum plants generally had higher biomass and crude protien content than E– plants at the same elevation.The study assessed the relationship between elevation and the biological characteristics of the endophytic symbiont of E.tangutorum,and provide theoretical support for the scientific and optimal use of this endophyte symbiont. |
PDF Full Text Request