The Responses Of Achnatherum Inebrians-Epichlo(?) Endophyte Symbiont To Blumeria Graminis

Achnatherum inebrians is a perennial bunchgrass that is becoming increasingly common in north and northwest alpine and subalpine grasslands in China.The associations between grasses and Epichlo(?) endophytes are considered in general to be mutualistic.Nearly all A.inebrians plants growing in these grasslands are host to an Epichlo(?) sp.In this study,the growth,physiological,biochemical and transcriptome differences of endophyte-infected(EI)and endophyte-free(EF)A.inebrians plants inoculated with(P+)and uninoculated with(P-)Blumeria graminis were systematically compared by greenhouse experiments combined with physiological and biochemical methods and molecular biological methods.And the mechanism of improving the disease resistance of grass by endophyte was revealed.In order to provide theoretical support for the creation of new resistant grass species and further scientific and reasonable utilization of A.inebrians,the response process of A.inebrians-E.gansuensis symbiont to B.graminis,was determined.The main results are as follows:(1)The powdery mildew incidence and disease severity of EI and EF plants increased significantly with inoculation time.Compared with EF plants,the incidence and disease severity of EI plants were significantly(P<0.05)decreased by 20% and19%,respectively.The aboveground biomass of EI and EF plants were significantly decreased(P<0.05)by inoculation with B.graminis,and the biomass of aboveground grassland was significantly increased(P<0.05)by infection with E.gansuensis under both P+ and P-.(2)The content of salicylic acid(SA)in EF leaves was significantly(P<0.05)decreased by inoculation with B.graminis,but had no effect on the content of jasmonic acid(JA)in EF leaves.Epichlo(?) endophyte infection significantly(P<0.05)increased the SA content in plant leaves,and significantly(P<0.05)decreased the JA content.When Epichlo(?) endophyte and B.graminis coexisted,the content of SA and JA in leaves of A.inebrians was significantly increased and decreased(P<0.05),respectively.Leaf epidermal wax of EI and EF plants is composed of hydrocarbons,esters,alcohols,etc,and the main group is hydrocarbon.The fatty acid content of EF plants at 1,2 and3 months was significantly(P<0.05)higher than that of EI plants.(3)The Epichlo(?) endophyte enhanced the expression levels of plant genes of synthesis and response to the SA hormone(ICS,SA-binding protein 2 and PAL).The pathogen B.graminis partly downregulated the expression of some PAL family genes involved in the SA biosynthesis,and JA-defence responses were also activated by the pathogen(several genes coding for JAZ proteins were downregulated).The elevated expression of SA-related genes coding for putative plant enzymes with anti-fungal activities(TGA,PR1,subtilase and MLO)promoted by the endophyte may explain the enhanced resistance to the pathogen.Some key genes involved in biosynthesis of unsaturated fatty acid,fatty acid elongation,wax biosynthesis,ABC transporters and protein transport(ABCB subfamily,ACX,acyl-ACP,KCS,FAR,CER1,BIP and SEC61 A family genes)in leaf wax synthesis pathway were differentially expressed in different treatments of A.inebrians.