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.
Highlights
Soft rot disease is one of the destructive diseases of vegetables
Determination of the antifungal spectrum The antifungal spectrum of the antagonistic bacteria strains C12 was determined by growth rate method (Table 1)
The inhibition rate was greater than 90% of the strawberry root rot (Rhizoctonia solani) and Fusarium Wilt of watermelon (Fusarium oxysporum f.sp. niveum)
Summary
It causes a greater total loss of produce than any other bacterial disease. The disease can be found on crops in the field, in transit, in storage and during marketing, and results in great economic losses (Bhat et al, 2010). The disease is conventionally controlled by cultivation measures (such as crop rotation, intercropping) and chemical control (Ronald et al, 2004). Chemical control is usually inappropriate because pathogens can develop resistance and pesticides can pollute the environment. It was reported that Pseudomonas fluorescens (Hendawy et al, 1998), Lysobacter enzymogenes (Folman et al, 2003), Erwinia carotovora subsp. Betavasculorum Ecb168 (Costa and Joyce, 1994), E. carotovora subsp. Carotovora Ecc 32 (Seo et al, 2004) and Streptomyces (Zamanian et al, 2005) and so on could restrain the Pectobacterium carotovorasub sp. Koch ex N.E.Br. (Araceae) originates in South East Asia
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