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Poster: Biology & Disease Mgmt: Bacteriology


Modification of chemically defined medium XF-26 for in-vitro cultivation of Xylella fastidiosa and Xylella taiwanensis isolated in Taiwan
W. DENG (1), N. Sharma (1), S. Hsu (1), C. Su (2), C. Chang (3), Y. Tseng (1), F. Jan (1) (1) National Chung Hsing University, Taiwan; (2) Taiwan Agricultural Chemicals and Toxic Substances Research Institute, Taiwan; (3) University of Georgia, U.S.A.

Strains of Xylella fastidiosa (PD) and X. taiwanensis (PLS) are plant pathogenic bacteria that were respectively isolated from grapevine and pear tree in Taiwan. The bacteria are nutritionally fastidious and require a complex nutrient for ex-planta growth. The Taiwan Xylella PD and PLS strains can grow on PD2 but not on the chemically defined XF-26 medium that was developed for in-vitro cultivation of X. fastidiosa strains isolated in North America. To develop a defined medium that supports growth of the Taiwan Xylella strains, different medium formulations modified from the original XF-26 were tested. A XF basal medium containing 20 amino acids resulted in good growth of Taiwan PD and PLS strains. By omitting amino acids one by one or in combination from the basal medium, tyrosine was found to be an essential amino acid for cultivating Taiwan PD and PLS strains, and the bacteria can grow in the XF-26 medium supplemented with tyrosine (XF-Tyr). Moreover, replacing asparagine with aspartic acid in the XF-Tyr medium also supported bacterial growth of purified PD and PLS strains or the ones isolated from diseased tissues during primary cultivation. To simplify the preparation of the chemically defined medium, the 17 amino acids in the XF-26 medium were substituted by 0.4% (w/v) casamino acids containing tyrosine, aspartic acid, and 16 other amino acids, and the modified XF-26 (mXF-26) was demonstrated to support good growth of the Taiwan-isolated Xylella strains.