Preliminary Study On Mechanism Of Induced Systemic Resistance To Pepper By Serratia Plymuthica A21-4

S.plymuthica A21-4 is a biocontrol bacteria to phytophthora capsici.A21-4 can produce macrolide antibiotic to resistant infection of Pathogen such as phytophthora capsici(Shen,2004).Otherwise,A21-4 has significant control effect to pepper phytophthora blight,and it can induce pepper systemic resistance,it means that soaking pepper roots with A21-4 can enhance disease resistance of the leaves in spatial segregation and show the resistance to Phytophthora capsici in pepper leaves.In order to further explore mechanism Induced Systemic Resistance by A21-4,this paper studied the changes of activity enzymes related to defense response,the signal transduction pathway of induced systemic resistance by A21-4,and the plant promoting effect of A21-4,activity of promoting growth by A21-4,for laying the foundation of a new broad spectrum biological pesticide.Results were as follows:1.The control effects of A21-4 was measured by means of space isolation inoculating.Consequently,A21-4 induced pepper phytophthora blight that can arise 75.53;A21-4 was able to induce cucumber resistance to Erysiphe necrtor,the control can get 47.62%;soaking pepper roots with A21-4,in vitriol inoculate Botrytis cinerea in cucumber leaf,control can reach 77.78.2.Analyze the influence of defense enzymes in the process of A21-4 inducing pepper to produce ISR,It turned out that after induction,activity of all four enzyme has went up evidently,improved 57.14%?46.77%?64.16% and 35.99% respectively,especially PAL and PPO played a key role in the process of A21-4 inducible resistance.And A21-4 improved the activity of PAL and PPO higher with phytophthora capsici.3.In order to analyzes the effect of PR protein induced by A21-4,we tested the activity of ?-l,3-glueanas and Chitinase.A21-4 can improve the activity of ?-l,3-glueanas and Chitinase;the activity of ?-l,3-glueanas reached peak at the sixth day,it increase by 76.66%;the activity of Chitinase reach peak at the seventh day,it increase by 276.05%.A21-4 can induct over-expression of Chitinase gene Ca Chi and PR4 gene by RT-PCR and Real-time PCR,increased 104 times and 32 times respectively.4.While Different expression of inducible resistance signal transduction related genes has been tested by RT-PCR and Real-time PCR.The results show that A21-4 inducts the over-expression of gene NPR1 and expression of key defense genes PR1 in SA signal transduction pathway.Meanwhile,the expression quantity of JA/ET signal transduction pathway modify gene PDF1.2 inducted by A21-4 has declined,compared with control it increase.Showing that A21-4 inducting pepper resisting pepper phytophthora blight is being realized by SA signal transduction pathway.It is needed further research to prove coordinated expression of SA signal transduction pathway and JA/ET signal transduction pathway come true.5.A21-4 had a positive effect on the growth of pepper and other crops.After soaking A21-4,all growth indicators of pepper and tomato rosed,and cucumber height in seedling stage and overground dry and fresh weight have increase apparently.The activity of A21-4 about promoting growth is tested,it is found that A21-4 can resolve Inorganic phosphorus and organic phosphorus secrete heteroauxin and siderophores,has the activity of Chitinase and cellulase.While the activity of A21-4 extracellular enzyme will affect the growth of A21-4.