Isolation, Cultivation, and Pathogenicity ofXylella fastidiosa,the Causal Bacterium of Pear Leaf Scorch Disease in Taiwan

Abstract

Leaf scorch symptoms occurred in 12-20.6% of the pear trees (Pyrus pyrifolia) in the low-altitude areas of central Taiwan in 1990. Symptoms appeared on leaves in early July and stayed until the leaves dropped in winter. If unchecked, dieback of twigs and branches, and finally death of the infected trees occurred within a few years. The disease was closely associated with a xylem-limited bacterium. An electron micrograph showed that the bacterium was rod-shaped with rippled cell walls, and measured from 0.23 1to 0.5 × 1.1 to 3.4 μm (.)