Preliminary Study On Effect And Mechanism Of Hydrogen Sulfide Alleviating Fusarium Head Blight In Wheat Seedlings

Fusarium head blight(FHB)is a climatic soil-borne fungal disease that seriously threatens wheat production,mainly caused by the infection of Fusarium graminearum(F.graminearum).FHB occurs on wheat spikes,stem bases,and roots,which can lead to complete losses of grain yield during severe epidemics.In addition,mycotoxins produced by pathogens in infected grains are seriously harmful to the health of humans and animals,that become one of the most concerned safety issues of human food and animal feed.In China,FHB mainly occurs in the wheat areas where the flowering period is rainy.The annual incidence area exceeds 80 million Mu,and the annual prevention area exceeds 150 million Mu.As the global climate warms,extreme weather occurs frequently,the occurrence range of FHB has the trend of northward expansion and westward movement.Therefore,the FHB causes huge economic losses in the world every year.Hydrogen sulphide(H2S),a crucial gas signal molecule,has been reported to be involved in various processes related to development and adversity responses in plants.However,the effects and regulatory mechanism of H2S in controlling FHB in wheat have not been clarified.In this study,sodium hydrosulfide(NaHS)was used as the H2S donor.Through concentration gradient experiments,it was reported that H2S released from low-concentration NaHS solution significantly alleviated the symptoms of wheat FHB.On the one hand,low concentrations of H2S alleviated FHB by participating in the resistance against F.graminearum in wheat;On the other hand,low concentrations of H2S exerted its antifungal effect by influencing various aspects of fungal development,including inhibition of spore germination and retardation mycelial growth.Through experimental exploration,the main research results are as follows:1.The results of the inoculation test showed that the exogenous application of NaHS could effectively control the development of wheat FHB in both the seedling stage and the flowering stage,and 0.3 mmol/L was confirmed as the optimal concentration.Experiments indicated that H2S or HS’,rather than other derivatives,promoted the role of NaHS in heightening FHB resistance in wheat.Based on the coleoptile inoculation method,under the condition of FHB stress,the disease index of the 0.3 mmol NaHS treatment group was greatly reduced,and the disease control effect was as high as 85.60%.Meanwhile,through gel electrophoresis and qPCR analysis,the number of F.graminearum at the seedlings stem base of this subgroup was significantly reduced,and the relative content of fungal DNA was almost zero.Growth indicators of wheat seedlings were tested,and the results showed that NaHS treatment reduced the negative effects of FHB.Under stress conditions,the plant height,fresh weight and dry weight of wheat in the 0.3 mmol/L NaHS treatment subgroup increased by 4.98%,12.30%and 8.40%,respectively.2.In vivo,our experiments showed that exogenous application of H2S significantly improved the resistance of wheat seedlings.Under the condition of FHB stress,compared with the control group,the levels of hydrogen peroxide(H2O2)and malondialdehyde(MDA)in the NaHS treatment group were decreased by 51.90%and 42.90%,respectively,at 36 h after inoculation;In addition,H2S treatment enhanced the activities of antioxidant enzymes(SOD,POD,APX and CAT),thereby H2S enhanced the resistance of wheat to F.graminearum by reducing intracellular oxidative damage.Meanwhile,the activities of defence-related enzymes(PPO and PAL)and the relative expressions levels of SA associated genes(NPR1.3),JA associated genes(LOX2 and AOS2)and defence-related genes(PR1.1,PR2,PR3,and PR4),were all dramatically upregulated,thereby H2S enhanced the resistance of wheat to F.graminearum by enhancing the defense mechanism.3.In vitro,our result showed that H2S was toxic to F.graminearum,including inhibiting mycelial growth and spore germination,revealing that H2S exerted its antifungal effect.0.075 mM NaHS inhibited spore germination by 78.7%.After 3 days of 0.3 mM NaHS treatment,F.graminearum spores could not germinate for 15 days.In addition,by adding sulfate to the PDA,the bacteriostatic effect of sulfur was excluded,indicating that H2S itself has a strong bactericidal effect.Taken together,the findings demonstrated the potential value of H2S in mitigating the adverse effects induced by F.graminearum and advanced the current knowledge regarding the molecular mechanisms in wheat.In this context,given the beneficial effects of exogenous treatment with H2S to mitigate the negative impact of various types of abiotic stress,H2S could potentially be used as a biotechnological application in agriculture.Nanoparticles with the capacity to release H2S under controlled conditions will need to be researched and developed in the future.