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Poster: Diseases of Plants: New & Emerging Diseases


Xylella fastidiosa isolates differ in the ability to undergo genetic recombination
P. KANDEL (1), R. Almeida (2), L. De La Fuente (1) (1) Department of Entomology and Plant Pathology, Auburn University, U.S.A.; (2) Department of Environmental Science, Policy and Management, UC Berkeley, U.S.A.

Xylella fastidiosa (Xf) is a bacterium causing incurable diseases in economically important crops such as grapevines, citrus, and olives. Historically assumed to be restricted to the Americas, Xf diseases have been reported in both new locations and new crops in recent years. Inter-subspecific recombination (ISR) has been proposed to contribute to host shifts based on genetic diversity studies. Natural competence, as a mode of recombination, has been shown to occur in vitro in systems mimicking natural habitats. However, little is known about the recombination potential of Xf isolates, which are believed to be somewhat host specific. Therefore, in this study we compared the recombination frequencies of twelve Xf isolates belonging to two subspecies (fastidiosa and multiplex), using plasmids containing antibiotic markers flanked on either side by Xf homologous regions. The recombination frequency varied greatly (3.14×10-2 – 2.3×10-8) among isolates. Generally, subsp. fastidiosa isolates had higher recombination frequencies than multiplex isolates, and within a subspecies, the most virulent isolates had higher frequencies. When combinations of marker-tagged, heat-killed donor and live recipient cells from two subspecies were mixed, ISR occurred with a genomic region of ~10kb transferred from the donor to the recipient cell. This study demonstrates different recombination abilities, and therefore suggests different evolutionary potentials among Xf isolates.