Induction Of Resistance Against Rice Blast Disease By A New Polyene Macrolide Antibiotic Ag-antibiotic 702 And Its Induced

Rice blast caused by Magnaporthe oryzae is one of the three major diseases that threaten the global rice growing area.In recent years,through the induction by various biological and abiotic stresses can activate the plant's own immune system,enhance plant resistance,to achieve the purpose of agricultural production on disease and pest control is widely studied.Agricultural antibiotic 702(Ag-antibiotic 702)is a new polyene macrolide antibiotic produced by our laboratory separation of the Streptomyces sp.702 from the soil.In this paper,Ag-antibiotic 702 and rice were the experimental materials.First,in order to explore the rice blast resistance,induced by Ag-antibiotic 702,the effect of resistance blast induced by different concentration Ag-antibiotic 702 on rice and the effect of resistance to blast resistance induced by rice in different growth stages and continuous duration of resistance blast on rice and the defense of different pathogens were studied.Secondly,in order to explore the rice blast resistance mechanism induced by Ag-antibiotic 702,the effects of membrane lipid peroxidation and active oxygen scavenging system and the metabolism of phenolic compounds and disease-related protein activity and antibacterial active substance in rice leaves was studied.In order to explore the resistance of rice blast resistance induced by Ag-antibiotic 702 and its induced resistance mechanism,this paper used Ag-antibiotic 702 as the experimental group,spraying Jinggangmycin as positive control,distilled water as negative control.First,At three-leaf and one-heart stage of rice,5?g / mL,10?g / mL,15?g / mL,20?g / mL,30?g / mL and 40?g / mL Ag-antibiotic 702 were sprayed on rice leaves to screenthe optimum concentration of rice blast resistance induced byAg-antibiotic 702,.And then,the best growth period of rice blast resistance induced by Ag-antibiotic 702 was determated in the seed sprouts,seedling stage(leaf stage),into a seedling(4th leaf stage),turning green,tillering,booting and seed of seven different growth stage.The duration of the rice blast resistance was determated after sprayed with rice blast fungus spore at 24 h,48 h,72 h,96 h,120 h and 144 h,respectively.And the defensive study on different pathogens of rice induced by Ag-antibiotic 702.According to the above test results,when three-leaf and one-heart stage of rice,15?g/mL Ag-antibiotic 702 was sprayed,while 15?g/mL Jinggangmycin and distilled water were sprayed as positive control and negative control,respectively.The changes of membrane lipid peroxidation and active oxygen scavenging system(five antioxidant enzyme(SOD,POD,PPO,CAT and PAL)activities and malondialdehyde(MDA)content)and the metabolism of phenolic compounds(two antioxidant enzyme(PAL,PPO)and four phenolic compounds(HRGP,falconoid,Total phenolics,lignin)and disease-related protein activity(three enzyme(?-1,3-glucanase exochitinase and endochitinase)and total protein contents)and antibacterial active substance in the second leaf of each treatment group were determined every 24 hourswithin 168 h post spraying.The results are as follows:1)Six kinds of concentrations Ag-antibiotic 702 all can induce rice blast resistance,and 15?g/m L was the optimum concentration.three-leaf and one-heart stage of rice is the best induced period,the effect of the induced resistance reached 56.56%.The duration of the rice blast resistance could reach 144 h,and the best time of the rice blast resistance was 48h-96 h.And,Ag-antibiotic 702 can effectively improve rice resistance to rice blast,sheath blight and bacterial blight,the effects of resistance were 59.7%,58.25% and 49.36%,respectively.2)The study on the membrane lipid peroxidation and reactive oxygen scavenging system showed that the content of MDA and the activities of five kinds of antioxidant enzymes were improved by the treatment of Ag-antibiotic 702,Jinggangmycin and inoculated pathogens treatment.Among them,MDA content and SOD,CAT and POD activities of Ag-antibiotic 702 treatment were significantly higher in the early stage than that in the inoculated pathogens treatment.APX and LOX activity of Ag-antibiotic 702 treatment increased speed and peak height were stronger than inoculated pathogens treatment.The induction effect of the Ag-antibiotic 702 treatment can reach or exceed the treatment of Jinggangmycin.3)The study of phenolic metabolism in rice leaves showed that,compared with the blank control group,the activity of phenylalanine ammonia lyase(PAL),polyphenol oxidase(PPO),flavonoids and total phenolics of Ag-antibiotic 702 treatment were significantly higher than that of inoculated pathogens treatment.And,there is little difference with treatment of Jinggangmycin.Lignin and hydroxyproline glycoprotein(HGRP)were significantly higher than those of inoculated pathogens treatment,and the effect was better than that of Jinggangmycin.4)The study of disease-related protein activity in rice leaves showed that,compared with the blank control group,both Ag-antibiotic 702 and Jinggangmycin could significantly increase the total protein content and the activities of?-1,3-glucanase exochitinase and endochitinase in rice leaves,and the effect of of Ag-antibiotics 702 treatment Which is better than Jinggangmycin.5)The study of the production of corresponding antimicrobial active substances induced by Ag-antibiotic 702 in rice leaves showed that,compared with the blank control,the rice leaf extract substances induced by Ag-antibiotic 702 had a significant inhibitory effect on the spore germination of Magnaporthe oryzae.The maximum inhibitory effect at 168 h was 46.64%,this time higher than the negative control 53.57%.Ag-antibiotic 702 can enhance the resistance of rice blast by significantly increase antimicrobial active substances in rice leaves.(Campesterol,Stigmasterol,gamma.-Sitosterol,9,12-Octadecadienoic acid,2,4-Di-tert-butylphenol,9,12,15-Octadecatrienoic acid,Tetradecanoic acid,Undecane and n-Hexadecanoic acid)In summary,Ag-antibiotic 702 can significantly improve the resistance to rice blast disease,and has a positive induction in related metabolic of rice blast resistance.Ag-antibiotic 702 can induction Disease-related physiological defense mechanisms,such as,induce allergic reactions and enhance antioxidant enzyme activity,improve the activity of the disease-related phenolic substances and metabolic enzymes,increase the activity of disease-related protein,and increase the accumulation of antimicrobial substances in rice leaves,to prevent rice blast fungus infections,invasion and spread.