The Differential Responses Of The Near-isogenic Lines Of Qtl Fhb1 With Major Effect On Fhb Resistance To Abscisic Acid In Wheat

Fusarium head blight(FHB),caused by Fusarium graminearum(Fg),is one of the most dangerous diseases of wheat and epidemic in all over the world.This disease mainly damages the ear of wheat,prompting the discoloration and shrinkage of grains,resulting in grain losses and even crop failures.Abscisic acid belongs to sesquiterpenoid compounds,and is involved in plant-pathogen interactions extensively.In this thesis,the responses of the two wheat near-isogenic lines,NIL-R75 and NIL-S98 contrasting in FHB resistance due to the QTL Fhb1 with major effect to ABA and its metabolic inhibitor triazole were investigated.During the anthesis period,these two lines were inoculated with Fg0865 strains,and then were sprayed with ABA,triazole and tween20(control),by tphenotypic evaluation and transcriptome sequencing,the potential effects of these chemicals in wheat-Fg interactions.The S4800-? field emission scanning electron microscope was used to study the impacts of ABA,triazole and tween20 on the growth and cell morphology of Fg strains.The experimental results showed that the hypha densely arranged and intertwined together and were consistent in size with no significant differences between treatments,indicating the growth and cell morphology of Fg strains were not affected by ABA,triazole and tween20.Fourier transform infrared spectroscopy was then used to determine whether these chemicals altered the patterns of the carbohydrates,lipids,proteins,nucleic acids and other biological macromolecules of strains.The results revealed that the mycelium under the three treatments appeared feature patterns,indicating that the growth and virulence of strains might not be affected by ABA,triazole and tween20.The spore suspension was inoculated onto NIL-R75 and NIL-S98 using a single floret inoculation method,and immediately after inoculation,these two near-isogenic lines were sprayed with ABA,Triazole and Tween20,respectively to observe differences in FHB severity and ABA content by LCQ Deca XP max liquid chromatography-mass spectrometry,and we found that with the higher ABA content,NIL-R75 showed the lower FHB severity,whereas ABA content and FHB severity of NIL-S98 were not significantly affected by the treatments,indicating that the endogenous ABA may regulate,directly or indirectly,the expression of resistance-related genes for FHB,and ABA signaling pathway might be invovled in the FHB resistances mediated by Fhbl.CYP707A1 is one of the key genes invovled in ABA metabolism and was cloned in NIL-R75 and NIL-S98.Monopolymorphism in sequence were observed in the target gene between these two lines,thus CYP707A1 gene may not be the candidate gene of Fhbl.RNA was extracted from samples of different treatments of near-isogenic lines for transcriptome sequencing,totally 543,145,840 raw reads were detected,and 472,840,356 clean reads were filtered through screening,and 574,927 Unigenes were assembled,with the average length of 631 bp.Ninety five out of 64,048 differentially expressed genes were identified were assigned to Fhbl locus on 3BS chromosome of wheat,and these genes of interest were annotated in Nr,Nt,KEGG and Pathway databases.The results of this study provided more information on undertanding the potential mechanisms underlying the FHB resistance mediated by Fhb1,and will be helpful for screening and cloning the candidate genes of Fhb1.