Study On The Effect Of Ag-antibiotic 211 On Rice And Its Induced Resistance Mechanism

Rice,as a staple food for about 60% of people,is one of the most important food crops in China,So ensuring the safe and the stable production of rice has an important impact on the economic development of our country.Ag-antibiotic 211 is an active substance produced by Streptomyces JD211,which has inhibitory effects on various plant pathogenic fungi.In this paper,the mechanism of rice yield-promoting and resistance to sheath blight was analyzed by spraying Ag-antibiotic 211 on susceptible rice varieties.The results were as follows:(1)Rice seeds were treated with Ag-antibiotic 211 and Germination percentage,soluble sugar,protein content and root activity were measured.The results showed that suitable concentration of Ag-antibiotic 211 can increase seed germination rate,soluble protein content and root activity,and decrease soluble sugar content.The germination rate was 11.11% higher than that of the control at the concentration of0.99?g/m Lfor 72 h,and the root activity of 0.40?g/m L treated group was 447mg/g.Fw,It is 41.5% higher than the control group.(2)Spraying Ag-antibiotic 211 in seedling stage,Growing stage(three-leaf and one-heart stage)and returning green stage,respectively,to study the effect of Ag-antibiotic 211 on promoting and strengthening seedling growth of rice,and spraying Ag-antibiotic 211 on rice at heading stage to study its effect on the yield of rice.The results showed that the treatment concentration of 62 ?g/m L was the best.The stem width,leaf width,root number,white root number,root length,fresh weight and dry weight of rice were higher than the blank value at three stages.The full grain weight,full grain weight per hole,yield of 12 holes and total grain number per panicle were 26.67,10.55,137.48 g and 152.75 grains,respectively,which were significantly different from those of CK(p < 0.05).The yield increased by 31.59%.The results showed that Ag-antibiotic 211 had obvious effect on promoting seedling growth and increasing yield of rice.(3)The effect of Ag-antibiotic 211 on rice resistance to sheath blight in five stages was studied.It was found that at low concentration,the effect of Ag-antibiotic211 on rice sheath blight resistance was obvious at seedling stage,turning green stage and heading stage,and the effect of Ag-antibiotic 211 on rice sheath blight resistance at low concentration was obvious.When the concentration of Ag-antibiotic 211 was62 ?g/m L,the effect was the best,the infection rate and disease index were lower,and the relative effect of induced resistance was the highest,which reached 68.57%.The optimum concentration of resistance to rice sheath blight at tillering stage and seed setting stage was 124 ?g/m L and 62 ?g/m L,respectively.It was selected that the concentration of Ag-antibiotic 211 was 62 ?g/m L and the best treatment period was the turning green stage of rice.The duration of resistance to sheath blight was studied.The control effect of Ag-antibiotic 211 on sheath blight increased with the increase of action time,reached the maximum value at 96 h,and then decreased slightly.Therelative effect of Jinggangmycin was consistent with that of Ag-antibiotic 211,and the control effect of Jinggangmycin on sheath blight could be sustained for more than 7days.The resistance to sheath blight was induced by Ag-antibiotic 211 pairs of rice leaves in the green returning stage,heading stage and seed setting stage.Compared with the blank control,the disease index was significantly decreased and the relative effect of induced resistance was improved.The concentration of Ag-antibiotic 211 was 7.75?g /m L and 15.5 ?g/m L respectively.(4)In order to clarify the mechanism of resistance of rice to sheath blight induced by Ag-antibiotic 211,The spraying concentration of 62 ?g/m LAg-antibiotic211,Jinggangmycin and the same amount of distilled water during the green-turning stage,inoculated with Rhizoctonia solani at different time after induction.The third leaf was collected and the scavenging enzyme activity of reactive oxygen species and phenolic substances were determined respectively.The results showed that the total phenol content in the leaves of rice treated with different Ag-antibiotic 211 was significantly higher than that of the control at the middle stage of the experiment,the PPO at the later stage and the PAL at the different stages,and the treatment of Jinggangmycin could achieve the similar effect.At 72 h,the flavonoid content of Ag-antibiotic 211+Rhizoctonia solani treatment group reached its peak,which was39.6%,42.81% and 91.97% higher than that of Jinggangmycin +Rhizoctonia solani,CK+ Rhizoctonia solani and blank treatment groups.The lignin content reached the maximum value of 1214.97 ?g/g.Fw at 168 h,which was 45.06% and 66.38% higher than that of CK+Rhizoctonia solani and blank treatment respectively.The results showed that Ag-antibiotic 211 could increase the activities of PPO and PAL,and produce total phenols,flavonoids,lignin and other phenolic substances in the leaves of rice,so as to improve the disease resistance of rice.The CAT and SOD in the leaves increased first and then decreased,which were significantly higher than those of the control in the middle period of the test.At 120 h,the APX of Rhizoctonia solani treated with Ag-antibiotic 211 was 10.99,3.32 times higher than that of blank control(CK),CK+Rhizoctonia solani,and the MDA content reached the minimum value of11.59 ?mol/g.Fw,at 144 h,which was 43.85% less than that of blank treatment.POD was superior to other treatment groups in the late stage of treatment.The content of MDA in the leaves of rice treated with Ag-antibiotic 211 decreased significantly,and both CAT,SOD and APX increased,indicating that Ag-antibiotic 211 could decrease membrane lipid peroxidation and enhance the ability of active oxygen scavenging system.It provides a basis for studying the mechanism of resistance to rice sheath blight induced by Ag-antibiotic 211.(5)The effects of Ag-antibiotic 211 on disease course-related proteins and resistant substances in rice leaves were further studied.The results showed that proline,glutathione,chitinase,?-1,3-glucanase and soluble protein in rice leaves were higher than those in control.After 96 h treatment,the ?-1,3-glucanase activities of Ag-antibiotic 211 +Rhizoctonia solani treatment group were 36.84% and 10.48%higher than that of the blank(CK+Rhizoctonia solani),respectively.After 144 hours,the proline content in the control group was higher than that in the control group by 41.41%.The treatment of Ag-antibiotic 211+Rhizoctonia solani could reach or slightly higher than that of Jinggangmycin Rhizoctonia solani.The resistance substances and disease course-related proteins of Rhizoctonia solani inoculated with Rhizoctonia solani were significantly higher than those inoculated only with Rhizoctonia solaniand blank control after induction of Ag-antibiotic 211,which indicated that Ag-antibiotic 211 could induce rice to produce and accumulate resistance-related substances and resist rice sheath blight.The extract of rice leaf had obvious inhibitory effect on Rhizoctonia solani.It was found that the extract of rice leaf that determined by GC-MS was inoculated with Rhizoctonia solani,methyl linolenic acid,methyll linoleic acid,dibutyl phthalate after treatment with Ag-antibiotic 211.The contents of Phytol,methyl palmitate and2,4-Di-tert-butylphenol were higher than those of blank control and CK+Rhizoctonia solani treatment(except for methyl palmitate on the 4th day).The results showed that the resistance of rice to Rhizoctonia solani induced by Ag-antibiotic 211 was closely related to the related antibacterial and stress-resistant small molecular substances in rice.In conclusion,Ag-antibiotic 211 can increase seed germination rate,promote seedling growth and increase yield,induce rice resistance to Rhizoctonia solani,increase the activity of related resistance enzymes and stress resistance,and increase the germination rate of rice,and improve the resistance index of rice to Rhizoctonia solani.Ag-antibiotic 211,which was used to deal with rice,can improve the activity of rice-related resistance enzymes and induce a large number of resistant substances in rice,thus reducing the infection degree of Rhizoctonia solani to rice.The physiological and biochemical mechanism of Ag-antibiotic 211 was revealed,which provided a theoretical basis for the application of secondary metabolites produced by biocontrol bacteria in agricultural disease resistance and increased production.It was of great significance to ensure the safety and stable development of grain crops in China.