Catharanthus roseus, an experimental host plant for the citrus strain of Xylella fastidiosa

We verified by pathogenicity tests that the herbaceous plant Catharanthus r oseus (Madagascar periwinkle) can be used as an experimental host for the s train of Xylella fastidiosa that causes citrus variegated chlorosis (CVC). Plants were mechanically inoculated with CVC strain 9a5c, the genome of whi ch was recently sequenced. Plants were inoculated with the virulent 8th pas sage (9a5c-8) and the 51st passage (9a5c-51). Leaf deformation and stunting were seen 2 months after inoculation on 18 of 21 plants with 9a5c-8 and 8 of 21 plants with 9a5c-51. The plants were infected with X. fastidiosa as s hown by polymerase chain reaction. The bacterium could be reisolated from a ll plants tested, showing that CVC-X. fastidiosa multiplied and moved syste mically in C. roseus plants causing dysfunction in plant growth. The diseas e symptoms evolved within 4 months post-inoculation to a severe leaf chloro sis in all inoculated plants. The localization of X. fastidiosa in the xyle m was verified by immunofluorescence. Genes coding for proteins with homolo gies to plant sterol-C-methyltransferase, a transketolase-like protein, sub unit III of photosystem I, and a desiccation protectant protein were found to be differentially expressed in symptomatic C. roseus plants as a respons e to infection with X. fastidiosa in comparison to healthy plants. A tentat ive correlation between the pattern of expression of these C. roseus genes with the mechanism of pathogenicity of X. fastidiosa is discussed.