| Root-rot disease, also called dry-rot disease, was a serious disease of the cultivated Atractylodes macrocephala Koidz. The rhizomes of diseased plants would turn to be swollen and decayed with a brown colour at the cutting interface of the rhizomes. Finally, the disease led the plant to die, resulting in a remarkable loss to the farmers.A suspicious pathogen of the root-rot disease was isolated from the root tissue of the diseased Atractylodes macrocephala Koidz and four antagonistic bacteria strains were also isolated from the rhizosphere soil of the healthy Atractylodes macrocephala Koidz which was culviated in Jurong, the major cultivation place in Jiangsu Province. The fungus was identified as a species of Fusarium and named as Fusarium sp. FO14 by combining the morphology of the asexual spores and the analysis of its ITS sequence. The isolate with best anti Fusarium sp. FO14 activity was chosen for the further study. It was identified as Bacillus and named as Bacilllus sp. BS14 by combining the physiological, biochemical characters and the analysis of the 16S rDNA sequence. The antifungal activity against some other plant pathogen was also studied.A strain FS14 producing red pigment was also isolated from the stem of the diseased plant during the isolation of the pathogen of root-rot disease of Atractylodes macrocephala Koidz. Combined with the traditional physiological and biochemical characterization and the analysis of the 16s rDNA sequence, the isolate was named as Serratia sp. FS14.. The isolate could grow in a wide pH range from pH 4 to pH 10 and could grow in LB medium with 0-10% sodium chloride. Surprisingly, thermostable extracellular DNase and protease were detected in the supernatant of the culture of Serratia sp. FS14 while this strain was a mesophile microorganism. This is the first time to report thermostable extracellular enzymes from Serratias, so it deserved to be further study. |
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