FIG 4.

Pathogenicity and HR assays. (A and B) Symptoms caused by the WT strain, the relA, spoT, dksA, relA/spoT (ppGpp⁰), and relA/dksA mutants (A), and their complementation strains (B) on immature pear fruits. Immature pears (cv. ‘Bartlett’) were surface sterilized, pricked with a sterile needle, and inoculated with 2 μl of bacterial suspension. Symptoms were recorded and photos were taken at 4 and 8 dpi. (C and D) HR assay on tobacco leaves. The E. amylovora WT strain, the relA, spoT, dksA, relA/dksA, and ppGpp⁰ mutants (C), and their complementation strains (D) were allowed to infiltrate into 8-week-old tobacco leaves at a concentration of 10⁸ CFU ml⁻¹. PBS was used as a negative control. Photographs were taken at 24 h postinfiltration.