The Antibacterial Mechanism Of MgONPs To Ralstonia Solanacearum And Its Control Effect On Tobacco Bacterial Wilt

As an important mineral element,magnesium,involved in biological and non-biological plant defense and metabolic activity,plays an important role in plant growth.Owning their higher specific surface area,better physical and chemical properties,such as small size effect,nanometer materials have better antibacterial ability than the conventional materials.With the development of science and technology,nanotechnology is becoming a new tool to control crop diseases.Bacterial wilt,caused by the infection of Ralstonia solanacearum(R.solanacearum),is a disease that has devastating effects on tobacco production,but there is short of effective control method.This paper preliminarily discussed the antibacterial mechanism of nanometer magnesia(MgONPs)to plant pathogen R.solanacearum,its prevention to the bacterial wilt and its impact on plant growth.This paper provided the basis for the application of MgONPs in crop disease control,and proposed a new train of thought for tobacco bacterial wilt control.The main work of this research is as follows:1.Characterize MgONPs and preliminarily tested its antibacterial activity against the R.solanacearum.MgONPs was characterized by dynamic light scattering(DLS),transmission electron microscopy(TEM),SEM and Zeta,and the results showed that the average particle size of MgONPs was 50 to 100 nm.The minimum inhibitory concentration(MIC)and the minimum bactericidal concentration(MBC)of MgONPs were 200 and 250mg/L,respectively,while the normal magnesia(bulk MgO)was 500 and 600mg/L.The classic colony counting method and growth curve analysis showed that MgONPs has better antimicrobial property than the bulk MgO,and both with concentration-dependence.2.Study the toxicity mechanism of MgONPs to the R.solanacearum.MgONPs adsorbed on the surface of R.solanacearum by using SEM and TEM,and the bacterial cell structure was seriously damaged,which indicated that MgONPs could produce physical damage to the bacterial cell membrane,and membranous rupture also caused the leakage of cytoplasm,further restrained bacterial motility and biofilm formation ability;Meantime,it was observed that the accumulation of ROS could be an important cause of DNA damage by MgONPs.3.Study the effects of MgONPs on tobacco growth and development.The results showed that MgONPs had no inhibitory effect on the germination of tobacco seeds which proved that it had no toxic effect on the seeds,and it also had nopromotion effect in comparison with the clear water;The results of determination of the influence of tobacco seedling growth showed that tobacco root length and plant height were significantly improved after 30 d when drenched and treated with 50mg/L-250 mg/L of the MgONPs suspension compared with water.It was detected that MgONPs were absorbed by plants and transported to various parts of the plant through vascular bundles,which promoted the increase of chlorophyll content,enhanced photosynthesis,and increased relative water content.Using SEM and paraffin sections observed that cells of tobacco leaves and the palisade tissue increased when treated with MgONPs.To sum up,MgONPs is beneficial to the healthy growth of plants,and can be used as a green and efficient antibacterial agent to prevent and control crop diseases.4.Investigate the effect of MgONPs on tobacco bacterial wilt.Pot experiment showed that inhibition effect of MgONPs on tobacco bacterial wilt was better in early infection of phytopathogen than the later period.Disease index was 62.5 0of 250 mg/L MgONPs in 21 th days,250 mg/L bulk MgO was 93.20,and the control index was 98.50;Field trials showed that compared with control,the incidence of tobacco bacterial wilt were reduced by 38.83% and 13.06% when treated with MgONPs and bulk MgO;Both MgONPs and bulk MgO have promoted tobacco growing according to the experimental results,especially leaf length,leaf width,leaf area index which are greater than that of bulk MgO and control in the stages of rosette,budding and mature during tobacco period.The results showed that MgONPs could control tobacco diseases safely and effectively.