observed a correlation between the expression of PR2
and lesion reduction. Gene expression responses suggest that Hx
activates both the AOS and PR responses, but AOS induction was
significant only at 20 dpi after the first inoculation in soil drench.
Similar results were obtained by Fu et al. (2011) using transgenic
sweet orange plants overexpressing spermidine synthase, which
induced high constitutive levels of PR gene expression and resistance
to Xcc.