Figure 2. Expression of fungal genes in infected elm wood tissues.

(a,b) induction kinetics of fungal On-Actin and On-Cerato ulmin genes in American elm wood tissues infected with O. novo-ulmi fungus. Four-year-old saplings of ‘Valley Forge’ (VF) and the susceptible clone (S) were infected with the fungus and 2 cm² of tissues surrounding the infection zone were collected at 0–144 hpi. The expression of each gene was normalized to that of three reference genes (EIF 5a, vacuolar ATP synthase and splicing factor 3B) and was calculated relative to the control sample (0 hpi) in the susceptible clone. Values represent the mean ( ± SE) of three biological replicates. Values marked with an asterisk (*) are significantly greater (≥2 times) than the corresponding time point in the other genotype (P < 0.05).