Study On The Endophytic Potential Of Sclerotinia Sclerotiorum In Brachypodium Distachyon And Induced Resistance To Fusarium Head Blight

Sclerotinia sclerotiorum is a schizotrophic fungus.On the one hand it can infect many important dicotyledon cash crops as pathogenic fungi,on the other hand it can exist in wheat as an endophytic fungi.In this paper,the model plant Brachypodium distachyon-S.sclerotiorum is used as the research system to systematically study the endophytic growth of S.sclerotiorum and its influence on the growth and disease resistance of S.sclerotiorum,and initially explore its molecular mechanism.The main results obtained are as follows:By Laser Scanning Confocal Microscope(LSCM),it was confirmed that both the wild-type strain 1980 and the attenuated strain DT-8 containing fungal virus Ss HADV-1could be observed in the intracellular and intercellular spaces of the roots and leaves of the B.distachyon.Moreover,the mycelia invading from the root can further extend to the whole body of B.distachyon for endogenous growth.Endophytic growth of S.sclerotiorum in B.distachyon plants.Endophytic fungi promoted the growth of B.distachyon.The plant height,panicle number and panicle weight of B.distachyon were increased to some extent by mycelium of strain 1980 and DT-8.The plant height,panicle number and panicle weight of B.distachyon treated by strain 1980 were increased respectively by 15.84% and 30.94%.The plant height and ear weight increased respectively by 9.35% and 16.02% under the treatment of DT-8.Endophytic fungi improved the disease resistance of B.distachyon.The plant resistance to scab could be significantly improved by treating the seeds of B.distachyon with the strains of 1980 and DT-8.After 3 days of artificial inoculation of Fusarium graminearum PH-1 in the flowering stage of the culture room,the resistance increased respectively by 23.57% and 41.99% for 6 hours and 12 hours of seed dressing treatment by1980.After 6 h and 12 h treatment with strain DT-8 seed dressing,the resistance increased respectively by 25.94% and 48.51%.Molecular mechanism of endogenous enhancement of disease resistance of B.distachyon.The early immune response detection and RNA-seq analysis of B.distachyon seedlings showed that endogenous growth of S.sclerotiorum activated the early immune response of B.distachyon seedlings,resulting in increased associated genes involved in redox reactions of defense pathways and carbohydrate synthesis pathways involved in plant growth and development.The differential expression of these genes provided the basis for the study of resistance improvement and growth promotion mechanism of B.distachyon.In order to explore how S.sclerotiorum as an endogenous fungi in B.distachyon could promote growth and improve resistance to scab,we tested the PTI response of B.distachyon seedlings and analyzed the RNA-seq sequencing.The analysis results showed that S.sclerotiorum as an endogenous fungi activated the early immune response of B.distachyon and the expression of associated genes such as REDOX pathway and carbohydrate synthesis pathway.These differentially expressed genes provide clues for the study of the growth promotion mechanism and the improvement of resistance to scab in B.distachyon.In conclusion,this study confirmed that S.sclerotiorum can endogenically grow in B.distachyon.On the one hand,the expression of genes involved in defense response in B.distachyon plants is activated to enhance the resistance of plants to F.graminearum.On the other hand,by activating the expression of genes related to carbohydrate synthesis pathway and other metabolic pathways,the growth of B.distachyon was promoted and the yield was further increased.