Isolation, Identification And Characterization Of Benzoic Acid-degrading Bacterium From Tomato Rhizosphere

Tomatoes plant in all over the world because of its nutrition and unique taste.As the continuous cultivation of tomato,continuous cropping obstacle phenomenon becomes more and more serious,and restricts the development of tomato industry.Therefore,the study of how to mitigate the obstacles of continuous cropping of tomato is of important practical significance.Autointoxication is one of the main reasons of continuous cropping obstacles of tomatoes,Autotoxin can inhibit plant growth and development.Therefore,reducing the concentration of autotoxin will be able to effectively alleviate the continuous cropping obstacles.The aims of this experiment is to select the strains can degrade the benzoic acid(BA),and choose the bacterial strain to identification and evaluation of degradation capability.Finally,this experiment test the bacteria colonization and mitigation effect of continuous cropping obstacles on tomato by pot experiments.Results are as follows.(1)85 degradation strains of benzoic acid were obtained from tomato rhizosphere soil.And the experiment determined the degradation capability to benzoic acid by shake flask experiment.A strain(TA-4)from those strains which had a degradation rate as high as93.58% to phlorizin within 24 h.The bacterium was identified as Pseudomonas nitroreducens using the morphological,biochemical and molecular methods.(2)We optimized fermentation conditions of the strain in the experiment.Results of response surface showed that the optimal conditions was 0.97 g/L initial BA concentration,7.34 initial pH of medium and 30.45℃ of culture temperature.Under which,TA-4 degraded97.62%BA in hydroponic nutrient solutions at 18 h.(3)The pot experiment: we use two kinds of soil,vermiculite and soil(already have not planted tomato).And we set 4 treatments,and treatments are respectively control,+BA,+TA-4,+BA+TA-4.We observed effects of exogenous benzoic acid on growth of tomato.The results show exogenous benzoic acid reduce biomass of tomato plants.TA-4 relieves the inhibition caused by BA.(4)The results the pot experiment show activities of APX,CAT,SOD were decreased andactivities of urease,alkaline phosphatase,sucrose and catalase were also decreased after adding BA.After inoculating TA-4,the enzymes activities and soil microbial consortia structure were improved.TA-4 were conducive to the growth of tomato plants.