Coffee leaf scorch caused by a strain of Xylella fastidiosa from citrus

Citrus variegated chlorosis (CVC) and coffee leaf scorch (CLS) are two econ omically important diseases in Brazil caused by the bacterium Xylella fasti diosa. Strains of the bacterium isolated from the two plant hosts are very closely related, and the two diseases share sharpshooter insect vectors. In order to determine if citrus strains of X. fastidiosa could infect coffee and induce CLS disease, plant inoculations were performed. Plants of coffee , Coffea arabica 'Mundo Novo', grafted on Coffea canephora var, robusta 'Ap uatao 2258' were mechanically inoculated with triply cloned strains of X. f astidiosa isolated from diseased coffee and citrus. Three months postinocul ation, 5 of the 10 plants inoculated with CLS-X. fastidiosa and 1 of the 10 plants inoculated with CVC-X. fastidiosa gave positive enzyme-linked immun osorbent assay (ELISA) and/or polymerase chain reaction (PCR). Eight months postinoculation, another six plants inoculated with CVC-X. fastidiosa gave positive PCR results. The two X. fastidiosa strains were isolated from the inoculated plants and showed the same characteristics as the original clon es by microscopy, ELISA, and PCR. None of the plants inoculated with steril e periwinkle wilt (PW) medium as controls gave positive reactions in diagno stic tests, and none developed disease symptoms. Six months postinoculation , seven plants inoculated with CLS-X. fastidiosn and eight inoculated with CVC-X. fastidiosa began to develop characteristic CLS symptoms, including a pical and marginal leaf scorch, defoliation, and reductions of internode le ngth, leaf size, and plant height, terminal clusters of small chlorotic and deformed leaves, and lateral shoot dieback. We have demonstrated that X, f astidiosa from citrus plants is pathogenic for coffee plants. This has impo rtant consequences for the management of CLS disease and has implications f or the origin of citrus variegated chlorosis disease.