Pathogen Identification of Kiwi Bacterial Wilt in Fujian.

To identify the pathogenic agent of a newly bacterial wilt disease in kiwifruit, which found in Shihou village, Jiaocheng district, Ningde city, Fujian province in recent years, the bacterial strains were isolated and purified by the dilution separation method. The pathogenicity of the isolated strains was tested by inoculating on stems and roots of kiwifruit seedlings, and its taxonomic status were identified by Koch's postulates, bacteria biological and biochemical characteristics, biolog test, PCR verification with the specific primer, evolutionary type was determined by multiplex PCR, analysis of 16S rDNA and endoglucanase gene (egl) sequences. The results showed that 9 strains were isolated and purified from the vascular tissues of the infected stems. Followed Kock's postulates, the 9 strains could produce the similar symptoms on the inoculated kiwifruit seedlings, and the similar bacterial strains were also re-isolated. The colony morphology of the isolates was irregular, flat, spreading around, and could not produce viscous substances in NA medium, the colony color was dark red, producing reddish-brown pigment diffused into the medium and poor fluidity in TTC medium, while the colony was milky whitish in YDC medium. According to all kinds of analysis, the 9 isolates were identified as Ralstonia pseudosolanacearum, belonging to biovar III, phylotype I (Asia group), sequevar 14. This was the first report of a disease caused by R. pseudosolanacearum on kiwifruit (Actinidia chinensis Planch). Above results provided a theoretical basis for the accurate and effective prevention and control of kiwifruit bacterial wilt. [ABSTRACT FROM AUTHOR]