Inducted Resistance Study Of Actinomycetes 769 Against Magnaporthe Grisea

Strain 769(Streptomyces ahygroscopicus gongzhulingensis n.var.Ruan.et Zhang.1974),which was isolated from a soil sample in 1974,was an effective antagonistic Streptomyces sp.on different plant pathogens.We discussed the application of strain 769 in rice blast control.Fermentation medium and fermentation conditions were optimized in flask.The inhibition spectrum of strain 769 and the stability of fermentation production were studied.The defense enzymes(Catalase,CAT;Peroxidase,POD; Phenylalanine ammonialyase,PAL) activity was analyzed of the treated rice leaves with different concentration of 769 fermentation production and different growth periods.The study not only develops the new areas of strain 769 but also provides certain theory basis and the technical support for this old antagonistic strain.In this study,we optimized the fermentation culture media to enhance 769 fermentation effect,and we chose a basic media by compared with the six common media,then we optimized the carbon source,nitrogen source and mineral salts in base of the basic media.In the end,we got the optimum combination of medium through quadrate experiment and the optimal component was soybean powder 2.0%,corn powder 1.50%, sucrose 1.0%,beef extract 0.60%,CaCO₃ 0.3%,(NH₄)₂ SO₄0.3%,NaCl 0.3%,MgSO₄ 0.1%,KH₂PO₄ 0.02%,FeSO₄ 0.01%.In this research,we also optimized the fermentation condition to enhance 769 fermentation effect,we optimized some parameters in the base of the optimum medium in shake-flash,and they included:original pH,original value,temperature,rotation speed,amount of inoculation et al.The optimum fermentation parameters were as follows:culture temperature 28℃,initiation pH 6.72,and seed age 28 hours,inoculation volume 4%,70 ml liquid medium in 250 ml flake,180 rmin^-1,and 72 hours in shaker. The best inhibition rate achieved 87.75%,compared to initial screening the result to be higher than 20%.We had a conclusion about the inhibition spectrum of strain 769 fermentation production;it not only has good activity to Magnaporthe grisea but also have some activity to Colletotrichum coccodes,Peronospora manschurica,Aspergillus niculans,Fulvia fulva,Botrytis cinerea,Gibberella zeae and Fusarium graminearum et al.Through the study on 769 fermentation production's pH stability and thermostability,the research indicated that the fermentation production had good stability in acid and alkali environment,only in extremely sour and alkali conditions,the activity decreased.When the temperature achieved 100℃,the inhibition rate decreased along with time extension,this demonstrates that fermentation production's thermostability is not very stable in high temperature,has little changes in lower tempareture.Effects of 769 fermentation production on rice leaves defense enzymes were detected:all of the original fermentation fluid,10 times dilution,20 times dilution fermentation fluid can induce the expression of these defense enzymes respectively in rice leaves for CAT,POD and PAL.The optimum concentration is original fermentation fluid.769 fermentation production could decrease CAT activity,increace the activity of POD and PAL.The results showed that the induction of POD,PAL expression in rice leaves was positively related to fermentation production treatment,and could be used as the indicators of rice resistance.