Presence of endophytes YM11 (gray circles), P5 (red circles), and YCB36 (green circles) in local stem pieces at day 21 of the experiment. The treatments E−O− (mock-inoculated plants in both treatment dates), E+O− (endophyte-inoculated plants subsequently inoculated with water), and E+O+ (endophyte-inoculated plants subsequently inoculated with O. novo-ulmi) were evaluated in the elm genotypes MDV1 (DED-susceptible), MDV2.3 (DED-resistant), and VAD2 (DED-resistant). The mean value in each case is represented by circles whose dimensions are proportional to the fungal DNA quantity (ng fungal DNA ng−1 plant DNA) as indicated in the circle scale. Different letters indicate significant differences between treatments and genotypes according to Tukey’s HSD post-hoc test (p < 0.05). Independent analyses were performed for each fungal strain. The results of the ANOVA analysis are detailed in Table S3.