Isolation,Identification And Biocontrol Characteristics Of Bacillus Spp.

Bacillus spp.exists widely in the atmosphere,soil,water and other environments.It can prevent plant from diseases.At the same time,the metabolites produced by Bacillus spp.can also promote growth of plants.The advantages of its stable activity has made Bacillus become the ideal bacteria for biocontrol.In this study,Bacillus strains were used to conduct their effects on both promoting and preventing plant disease.The main results are as follows:（1）After isolation and purification,a total of 40 strains were obtained from the soil samples,along with 4 strains of tobacco leaf surface.According to physiological and biochemical characteristics and 16S rDNA sequence analysis,the results were as follows:strain B1-3,B2-4,JF435 and Q2-5 were B.altitudinis.Strain B1-2,B1-5,B2-1 and B3-5were B.aryabhattai.Strain Q1-12 was B.atrophaeus.Strain B1-4 was B.cereus.Strain Q1-8,Q2-2 were B.megaterium.Strain 154 was B.pacificus,Strain Q1-11,Q1-3,Q1-6,Q1-4 and Q2-1 were B.paralicheniformis.Strain I-6 and Q1-1 were B.siamensis.Strain Q2-4 was B.subtilis subsp.Subtilis.Strain Q1-5 was B.thuringiensis.Strain B2-5 and Q1-9 were B.toyonensis.Strain B1-1 and Q2-3 were B.wiedmannii.Strain Q1-10 was B.zhangzhouensis.Strain B2-2 and g201 were Brevibacterium frigoritolerans.Strain B3-1,B3-2,B3-3,B3-4,B3-6,Q1-2,Q1-7,Q3-1,Q3-2,Q3-3,Q3-4,Q3-5,Q3-6 and Q3-7 were B.Tequilensis.Strain B2-3 was Paenibacillus illinoisensis.（2）44 strains of bacteria were tested for the inhibition of plant pathogenic fungi and the ability to produce protease,cellulase,IAA,NH₃,siderophores,EPS and to solubilize phosphorus,potassium.The research showed that strain B3-1,B3-2,B3-3,B3-4,Q1-1,Q1-2,Q1-3,Q1-7,Q1-12,Q2-4,Q3-1,Q3-2,Q3-3,Q3-4,Q3-5,Q3-6,Q3-7 and I-6 had good inhibitory effect on pathogenic fungi,strain B1-3 and Q1-12 had the strongest ability of proteolysis.Strain Q3-1 had the strongest ability to degrade cellulose.Strain B3-5 and Q1-8had the strongest ability of producing IAA.Strain Q2-3 producing ammonia was the strongest.Strain B3-2 producing iron carrier has the strongest ability.Strain Q1-4,Q1-6,Q1-8 and Q3-4had the strongest ability of secreting ESP.Strain B2-4 solubilizing phosphorus was the strongest.Only the strain Q1-7 and Q3-1 had the ability of potassium solution.Only B2-3,B2-4 and Q1-12 strains had the ability of nitrogen fixation.（3）The 37 strains with better biological characteristics were fermented.Comparing seed germination rate,seedling height,root length,dry weight and fresh weight of the fermentation treated and CK.It was found that strain B2-2,Q1-3,Q1-12,Q3-3,Q3-4,Q3-7 and 154 have different effects on cucumber growth promotion（P<0.01）.The average germination rate of the seeds treated with strains B2-2 and Q1-12 was as high as 93%.The average root length of the seeds treated with strains Q1-3 and Q3-4 was 2.67 and 2.01 times that of CK.The average dry weight of the seedlings treated with the strains Q1-12,Q3-3 and 154 was 2.43 times 2.10times and 1.90 times of CK.（4）In the biocontrol of Botrytis cinerea,a total of 17 strains on the isolated cucumber leaves had significant effects（P<0.01）,which were B1-5,B2-3,B3-4,Q1-2,Q1-3,Q1-4,Q1-12,Q2-4,Q3-1,Q3-2,Q3-3,Q3-4,Q3-5,Q3-7,154,JF435 and I-6.Among them,strain Q1-3 had the highest control effect,reaching 97.30%.These strains selected were further used to carry out a pot experiment.The results showed that 7 strains had outstanding control effects（P<0.01）,which were I-6,B3-4,Q1-12,Q3-3,Q3-4,Q3-5 and Q3-7.Strain I-6 had the best control effect,almost reached 100%.The control effect of strain Q3-7 was 86.36%.The control effect of strain Q1-12,Q3-5,Q3-4,B3-4 and Q3-3 were 76.14%,72.73%,70.45%,64.77%and 64.77%.（5）The activity of four defense enzymes–PAL,CAT,POD and SOD,which in cucumber leaves induced by 7 strains were determined by colorimetric method.The results showed that the activities of these four defensive enzymes were significantly higher than those of CK.After the induction of strain Q3-5,the POD activity peaked at 230U·FW·g^-1·min^-1at 96 h,which was 7.67 times of CK.After induction by strain Q3-4,PAL activity peaked at 380 U·FW·g^-1·min^-1at 72 h,which was 7.6 times of CK.After being induced by strain Q3-7,the CAT activity peaked at 1340 U·FW·g^-1·min^-1at 96 h,which was3.44 times of CK.After induction by strain Q3-3,SOD activity peaked at 1641.72U·FW·g^-1·min^-1at 96 h,which was 2.96 times of CK.