Study On Antifungal Activity And Mechanism Of Nanochitin On Wheat Stem Rot Pathogen

Nanochitin whiskers(NC)synthesized by acidic hydrolysis are cationic crystalline rod-like nanoparticles with strong biological activity against fungal pathogens.NC has been recognized as plant growth regulators and growth stimulants to promote plant growth,increase crop yield and quality;as an elicitors to induce plant defense against plant diseases.NC can be used in plant protection and plant disease control.Wheat is an important food crop in the world.Wheat stem base rot and scab caused by F.graminearum will cause immeasurable economic losses to wheat yield and quality.In this study,shrimp origin chitin was used as a material,F.graminearum causing wheat root rot disease was used as target pathogen to investigate the effects of NC on pathogenicity of F.graminearum as well as molecular mechanisms.NC was prepared by hydrolysis in 3 M HCl at 90℃ for 1.5 h.Within 3 times repeat of hydrolysis at same condition and purified by dialysis against deionized water followed by ultrasonication,the resulted product of nanochitin was 95 nm in size with a Zeta potential and conductivity of+47.2 mV,and 813 uS/cm,respectively,measured by dynamic light scattering method.Different application methods and concentrations of NC suspensions have different effects on F.graminearum,the effect of four concentrations of NC suspensions of 250,500,750 and 1000 mg/L on the colony diameter of F.graminearum was determined by spraying,coating and mixing,the effect of spraying NC suspension at 250 mg/L was most obvious.The effect of NC on the hyphae structure of F.graminearum was observed by magnifying 100 times under microscope,which resulted in the increase of cavities and decrease of large particles.RNA-Seq results were analyzed by single nucleotide polymorphism(SNP),alternative splicing(AS)events,enrichment analysis,the results showed that NC increased the probability of single nucleotide polymorphisms and alternative splicing events,up-regulated biometabolism,degradation,and synthesis within F.graminearum,membrane-bounded organelle,nucleus and interacelluar membrane-bounded organelle gene expression and affect the pathogenicity of F.graminearum,with the greatest effect on the nucleus.It can also be seen that NC treatment of F.graminearum significantly affected the biosynthesis of secondary metabolites,biosynthesis of antibiotics and carbon metabolism.NC also promoted pyruvate metabolism,tryptophan metabolism and propanoate metabolism.The differentially expressed gene from RNA-Seq of F.graminearum treated with NC was validated by q-PCR.It can be concluded that NC increases the occurrence of single nucleotide polymorphisms and alternative splicing events in F.graminearum,and differentially expressed genes play an important role in reducing the pathogenicity of F.gramineae.The conclusions obtained in this paper have important reference value for the future study of NC mechanism,and also have guiding significance for the application of the NC in agriculture.