Abstract:

A strain of Streptomyces ciscaucasicus SS9-1 was isolated from rhizosphere soil samples of Aconitum pendulum Busch in our laboratory before. The antifungal activity test showed that the strain SS9-1 had a good inhibitory effect on Botrytis cinerea, the pathogen of tomato gray mold. In order to further improve its antifungal effect on tomato gray mold, the fermentation medium formula and fermentation conditions of SS9-1 were optimized by single factor test and orthogonal test. Then the fermentation filtrate was tested for its antifungal effect and pot control efficiency on tomato gray mold. The results showed that the optimal fermentation medium of strain SS9-1 was as follows: starch soluble 4%, KNO₃ 1%, yeast extract powder 0.25%, NaCl 0.2%, MnCl₂·4H₂O 0.002%. The optimum fermentation conditions were as follows: liquid volume 150 mL, inoculation rate 3%, initial pH 8.0, fermentation temperature28℃, fermentation time 7 d. Plate confrontation test showed that the mycelium of B. cinerea was swelled and deformed after being affected by the fermentation filtrate. It also had a strong inhibitory effect on the germination of B. cinerea spores, and the germination inhibition rates of were 97.83% and 96.07% after 12h and 24h of treatment, respectively. In addition, in the pot experiment, the control efficiency of the fermentation filtrate of strain SS9-1 reached 98.43%, which was obviously higher than that of the pesticide control, 40% pyrimethanil SC 500 times dilution. After the fermentation filtrate was diluted 50 times, the control efficiency was still 71.11%. In conclusion, the strain SS9-1 has a good biological control effect on tomato gray mold, and has the application value and potential as a biocontrol agent.

Key words:

Streptomyces; tomato gray mold, fermentation conditions optimization, biological control