Screening and identification of Bacillus megaterium TA-4 and its effect on the activities of tomato defense enzymes
[Objective]This study was conducted to screen biological control bacteria with indoleacetic acid(IAA)producing ability and explore the potential of growth-promoting ability.[Method]In the present study,the plate-counting and Salkowski colorimetric methods were used to screen growth-promoting bacteria with IAA producing ability from the fumigated tomato soil.After identified the bacterium with the best IAA production,pot experiments were used to determine the tomato growth promotion effect of the strain and its effects on the activities of defense enzymes.[Result]The results showed that the largest amount of IAA produced by TA-4 was 39.0 µg/mL.TA-4 was identified as Bacillus megaterium according to the results of colony morphology,physiological and biochemical and molecular biological technology.In the pot experiments,the effects of TA-4 bio-organic fertilizer on the activities of defense enzymes of tomato plants including phenylalanine ammonia lyase(PAL),polyphenol oxidase(PPO)and peroxidase(POD)were explored.The results also showed that,at 30 days after treatment,2%TA-4 bio-organic fertilizer notably enhanced tomato growth.Compared with the non-treated control,the application of TA-4 bio-organic fertilizer significantly increased the plant height,stem diameter,fresh weight and dry weight of tomato plants by 58.7%,27.3%,53.2%and 70.6%,respectively.Meanwhile,the activities of defense enzymes including PAL,PPO and POD in tomato plants significantly increased compared to that of the non-treated control,which effectively enhanced the plant growth and induced host resistance in the tomato against adverse environments.[Conclusion]The results of this study determined the effects of TA-4 on the plant growth and activities of tomato defense enzymes,providing a theoretical basis for the research and development of new bio-organic fertilizers.
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