| Maize stem rot is mainly caused by Pythium and Fusarium fungi,also known as bacterial wilt.The pathogen infects maize through the damaged parts of maize root or stem,its expansion and infection process all occur in the maize plant,the incubation period is generally about 7 days,once the disease without any control measures.At present,the commonly used control measure is chemical control,although the effect is fast,but the residue seriously pollutes the environment.In contrast,microbial control has many advantages,such as strong stress resistance,wide bacteriostatic spectrum and high safety.A broad-spectrum antagonistic strain OR2-30 was screened from 156 strains of bacteria in our group,which could improve the resistance of maize to stem rot pathogen in response to maize root recruitment,but its biocontrol mechanism was not clear.In this study,Fusarium graminearum was used as the target,the bacteriostatic substances of OR2-30 were identified by matrix-assisted laser desorption ionization flight mass spectrometry(MALDI-TOF-MS),and its bacteriostatic mechanism was studied.This study provides a theoretical basis for the development of microbial agents with independent intellectual property rights and is of great significance in the prevention and control of maize diseases.The main results are as follows:1.The inhibitory effect of OR2-30 suspension and its secondary metabolites on Fusarium graminearum was determined by plate confrontation method.It was confirmed that OR2-30 inhibited Fusarium graminearum by secreting lipopeptide compounds,and the inhibition rate was 73%.At the same time,the types of lipopeptide compounds from Bacillus amylolyticus OR2-30 were identified by MALDI-TOF-MS,and it was confirmed that OR2-30 only produced Iturin.2.The effects of OR2-30 lipopeptide compounds on spore production and spore germination of Fusarium graminearum were determined by routine fungal biomass determination method.It was confirmed that OR2-30 lipopeptide compound could inhibit the sporulation and spore germination of Fusarium graminearum.When the concentration of lipopeptide reached 0.6mg/mL,the inhibition rate of spore production reached 96.27%.When the concentration was 1.8 mg/mL,the germination rate of spores was only 7%,and the inhibition rate was 74.14%.At the same time,the morphology of conidia and hyphae of Fusarium graminearum was observed by microscope and scanning electron microscope.It was found that the lipopeptide compound of OR2-30 could destroy the morphology of mycelium and conidia of Fusarium graminearum.3.ROS detection kit was used to further detect the active oxygen accumulation of OR2-30 lipopeptide compounds on Fusarium graminearum mycelia.It was confirmed that OR2-30 lipopeptide compounds induced a large amount of ROS accumulation in Fusarium graminearum hyphae.At the same time,the activity of mycelium was detected by fluorescein diacetate and propidium iodide double fluorescence staining,which confirmed that OR2-30 lipopeptide compound caused the death of Fusarium graminearum mycelium.4.To further detect the effect of OR2-30 lipopeptide compounds on the pathogenicity of Fusarium graminearum,the conidia of Fusarium graminearum treated with OR2-30 lipopeptide compounds were used to infect maize seedlings.It was found that the disease spot of Fusarium graminearum infected maize seedlings decreased with the increase of lipopeptide concentration,which confirmed that OR2-30 lipopeptide compounds could reduce the pathogenicity of Fusarium graminearum. |
PDF Full Text Request