Antifangalactivity Of Two Biocontrolagents Against Tobacco Black Shank And Its Characteristics Research

The microorganism were separated from the health plants in the differents place of Henan province, and two biocontrol strains were separated from the microorganism, we studied their antifangal activity, rhizosphere colonization characteristics, fermentation conditions and applying technology, for the biocontrol of tobacoo black shank disease laid a foundation.1. the screening of the biocontrol strains and the research of its characteristics 871 strains were separated from 116 plant and soil samples collected from different places in Henan province, there are 61 strains have antifangal activity, K9-3 and L14-2 were the best strains which inhibited tobacco black shank. In vitro experiment, K9-3 and L14-2 both inhibited the grows of mycelium, the form of zoosporangium, the release of zoospore and the germinate of cystospores. In pot experiment, they prevented and controlled tobacco black shank significantly, the control effect to be 77.78% and 96.29%. In addition, K9-3and L14-2 both have rhizosphere colonization ability, in laboratory, their colonization density in the root of tobacco were 1.30×105 cfu/cm and 7.0×104 cfu/cm. In pot experiment, their colonization density in the root of tobacco kept in the 106cfu/g above, and in the rhizosphere soil, the colonization density had downtrend in protophase, but kept a level in 7 days, and 21days after transplant, the colonization density kept in the 5×104 cfu/g above.2. Identification of the biocontrol strains Through morphological and physiological characteristics and 16SrDNA sequence analysis,K9-3 was Serratia plymuthica, L14-2 was Pseudomonas chlororaphis.3. Applying technology research of K9-3 and L14-2 In order to explore the applying technology of K9-3 and L14-2, the study researched the control efficiency and rhizosphere colonization density in different concentrations, application process and period of the two strains. In pot experiment, the control efficiency of 109cfu/mL and 108cfu/mL of the two strains were remarkable, the control efficiency of 109cfu/mL and 108cfu/mL of K9-3 were reached 78.14% and 77.78%, the control efficiency of 109cfu/mL and 108cfu/mL of L14-2 were reached 96.38% and 95.93%. Dipping roots in the transplanting of tobacco, the control efficiency of the two strains were significant, which were up to 59.68% and 69.35%, on the basis of dipping roots, perfusion treatment after transplanting of tobacco will increase their control efficiency, which were up to 66.13% and 83.87%.4. The optimization of fermentation conditions of K9-3 and L14-2 Through orthogonal test, optimize the conditions of cultivate and nutrition of K9-3 and L14-2. The fermentation condition of K9-3 was in the temperature of 30℃, rotate speed of 150 r/min, tongqiliang of 40%, pH of 8 cultivate 32h, its carbon source was Glycerol 1%, nitrogen source was yeast extract 0.1% and inorganic salt K2HPO45mmol/L. The fermentation condition of L14-2 was in the temperature of 30℃, rotate speed of 160 r/min, tongqiliang of 50%, pH of 7.5 cultivate 36h, its carbon source was Glycerol 1%, nitrogen source was peptone 0.1% and inorganic salt K2HPO45mmol/L.