Colony morphology of Xylella fastidiosa almond leaf scorch strains and its research applications

• Author(s): Chen, Jianchi; Civerolo, Ed; Freeman, M.; Groves, Russell; Viveros, Mario; Zheng, Y.;
• Abstract: Xylella fastidiosa is the causal agent of almond leaf scorch disease (ALSD) which is currently re-emerging in California as a potential threat to almond production. We previously reported the presence of different colony morphotypes of X. fastidiosa ALSD strains on PW (periwinkle wilt) medium solidified with Gel-Rite and their association with genotypes/pathotypes after a low number of serial transfers. In this study, we evaluated the colony morphology variations up through 14 subculture passages. The smooth colony morphotype was consistently associated with G-genotype strains and the rough colony morphotype was associated with A-genotype strains. Colony morphology was successfully used to discern genotypes of an ALSD survey with >95% accuracy. Variations of colony morphology did, however, occur during sub-culturing at a low frequency (<5%). Of a particular interest is the smooth variant of the rough A-genotype strains, described as phase variation. The phenotypic traits described in this study are also of value for further biological and molecular characterization of X. fastidiosa.
• Publication Date: Nov 2006
• Journal: Canadian Journal Of Plant Pathology