Abstract

Soft rot disease of Amorphorallus konjac, an important and potentially destructive corms disease, is caused by Pectobacterium species. Now, the conventional methods of controlling the disease include the breeding variety and the chemical control, but the effects are uncomfortable. The aim of this study was to screen antagonistic bacteria for soft rot disease and optimize its fermentation conditions. The antagonistic bacterium (strain C12) confirmed Bacillus subtilis by the identification of Biolog system and analysis of 16S rDNA gene sequence. Antimicrobial spectrum of the strain C12 was determined by growth rate method, which could restrain the growth of 12 pathogens. The fermentation conditions of the strain C12 were studied by using the single-factor method. The optimal fermentation conditions for antagonistic bacteria were as follow: Medium initial pH 7.0, the fermentation temperature 31°C, the quantity of medium 50 mL in a 250 mL flask, the inoculation volume 2.5%, the incubation time 22 h and the rotation speed 180 rpm, the glucose as carbon source and yeast as nitrogen source. The fermentation liquor of the strain C12 was twice than the streptomycin in control effect of pot experiment. The research provides reference for controlling soft rot disease of A. konjac. The findings suggested that the strain C12 could be exploited as a biocontrol agent for soft rot pathogens.

Key words: Soft rot disease, antagonistic bacteria, characterization, fermentation condition, optimization.

Abbreviation

P.c.c, Pectobacterium carotovorasub sp. Carotovora; PCR, polymerase chain reaction; BLAST, Basic Alignment Search Tool; DO, dissolved oxygen.