Determination Of The Biocontrol Activity Of Two Spore Producing Bacteria And Analysis The Cocultivation Effect

Bacillus is an important biocontrol resource and has broad application prospects.In this study,two spore-producing bacteria were obtained from the soil,and their biocontrol potentials were measured.The two strains were mixed and cultured in order to obtain the possibility of the mixed fermentation of the two biocontrol bacteria for use in production.The main results of this study are as follows:1.Two strains of biocontrol bacteria were isolated and screened from farmland soil.They were identified by morphology and 16S rRNA molecular biology.The two strains were Bacillus amyloliquefaciens and Paenibacillus polymyxa respectively.They were named ZYBA17 and ZYPP19.2.B.amyloliquefaciens ZYBA17 and P.polymyxa ZYPP19 have good bacteriostatic effects on a variety of plant pathogenic fungi and bacteria,and the bacteriostatic rates against corn polar spot pathogen?Bipolaris maydis?have reached 78.21%and 80.15%,respectively.Using corn as an indicator plant,through pot experiments,it was found that ZYBA17 and ZYPP19 had a good growth promoting effect on corn.After treatment with ZYBA17 and ZYPP19,the growth indexes of corn such as plant height,stem thickness,leaf length,and leaf width were better than that of application of bacteria treatment.The effect of ZYBA17 and ZYPP19 on corn leaf spot disease was measured under in vitro conditions,and it was found that after treatment with ZYBA17 and ZYPP19 bacterial solution,the incidence of corn leaves was significantly reduced,and the control effect was 89.37%and 64.96%,respectively;microscopic examination revealed that ZYBA17 and ZYPP19 can inhibit the infection of corn leaves by pathogenic bacteria.ZYBA17 and ZYPP19 can dissolve phosphate.ZYBA17 and ZYPP19 are cultivated with inorganic phosphorus medium and organic phosphorus medium,which have phosphate-dissolving activity.The strain culture solution has orthophosphate increment and phosphatase activity;this strain can produce IAA in culture.After 3 days of cultivation,the IAA content was 1.362 mg/mL and 4.818 mg/mL,respectively,and after 5days of culture,the IAA content was 1.242 mg/mL and 2.547 mg/mL,respectively.3.The single-factor test method and orthogonal test method were used to determine the conditions of ZYBA17 and ZYPP19 mixed culture.When ZYBA17 and ZYPP19 were inoculated at a ratio of 2:1,the inoculation amount was 2%,the culture temperature was 25°C,and the initial pH was 7.The OD₆₀₀ value of the bacteria in the mixed culture for 72 h was the largest,and the mixed culture could obtain a larger amount of cultured bacteria.The best conditions for the two bacteria to obtain the best bacteriostatic effect were:ZYBA17 and ZYPP19 were inoculated at a ratio of 1:1,the amount of inoculation was 2%,the culture temperature was 34°C,and the initial pH was 5.In the growth-promoting pot test,after the mixed culture of the two strains of bacteria was treated,the growth index of corn was better than that of the control group,and it was better than that of ZYBA17 and ZYPP19 single bacteria.Bacterial mixed culture has a good effect on the growth of corn,and it is stronger than a single bacteria on the growth of corn.In the in vitro test of corn leaves,the leaves were treated with the mixed culture bacterial solution,and the mixed culture solution had a control effect on corn leaf spot disease of 94.71%,indicating that the mixed culture of two bacteria has a good control effect on corn leaf spot disease,and it has a stronger control effect on maize leaf spot than single bacteria.