Isolation and Identification of a Benzoic Acid-degrading Bacterium and Its Effect on Growth of Flue-cured Tobacco

In order to reduce adverse effects of continuous cropping on yield and quality to some extent, as well as growth and development of flue-cured tobacco, the authors isolated a benzoic acid decompositon strain from the root exudate of tobacco by plate screening and shaker rescreening. The strain was identified as Aspergillus according to rDNA-ITS and sequence analysis, culture characteristics and morphological characteristics. The results showed that the strain could grow normally in the 0-800 μmol/L benzoic acid concentration range in 15 days. To certain extent the strain’s growth was constrained in the 800-1600 μmol/L benzoic acid concentration range. When using benzoic acid as the sole carbon source at the concentration of 800 μmol/L, dry weight and degradation rate of the strain reached the maximum on LBA medium. The dry weight of the strain was 0.765 g and the degradation rate was 19.98%. The degradation of the strain reached the highest rate which was 8.5 mg/d on the ninth day. To some extent, application of the degradation strain could reduce the the hazard of benzoic acid in root exudates of flue-cured tobacco. The degradation strain can reduce the toxic effect of root exudates in a pot experiment, it then can potentially be used to degrade the self poison substance to overcome the continuous cropping obstacle.