Disease Severity In 'Nicola And Spunta'

3. Results and discussions

3.1. Disease Severity

Results presented in Table 2 showed the disease severity (PDS) after 15 d of inoculation. A significant difference in the PDS was noticed between ‘Nicola’ and ‘Spunta’. The resistant cultivar (Nicola) showed lower incidence of infection compared to the susceptible cultivar (Spunta). Inducers’ treatments individually or in combination with difenoconazole (fungicide) showed significant protective effects against A. solani. The 2,4-D was the most effective in inducing response against the Early Blight. These effects were more pronounced in the resistant cultivar (Nicola). After 15 d of inoculation, PDS values were 42.6, 19, 9.2, 14, 6, 6.2, and 2.3% for Nicola and 61, 32, 16, 20, 8.5, 9, and
Enzyme activity of PAL was greater in Nicola compared to Spunta. Folds of increase of PAL of Spunta were more than 2 for 2,4-D and 2,4-D with the fungicide treatments compared to A. solani-infected plants. Moreover, the enzymatic activity of PAL of Nicola potato was more than 5-folds compared to control plants. The chemical inducers treatments increased the activity of PAL significantly for longer than 15 d after inoculation greater compared to
The percentages of disease severity of all inducers’ treatments varied from 2 to 19% for Nicola and 5 to 32% for Spunta compared with 43 and 61% for both cultivars challenged with A. solani, respectively. The 2,4-D was the most effective treatment followed by H2O2 and ABA. Data also indicated that the spray with the fungicide (difenoconazole as a single application) with elicitors slightly decreased the disease severity compared with the elicitors alone. PAL gene expression was significantly and rapidly up-regulated after treating potato plants with 2,4-D followed by H2O2 with or without the fungicide compared to ABA treatment, very obvious effects in the heat map (Figure 4). Application of the fungicide along with inducers significantly increased both enzymatic activity and gene expression of POD, PAL, and PPO. Induced resistance reported herein highlighted the promising role of repetitive treatments of 2,4-D and H2O2 against A. solani on potato plants. Also, it’s the first study (to the best of our knowledge) to report about the use of H2O2 as chemical inducer against potato fungal diseases. Additionally, incorporation of such treatments in a management program with synthetic fungicides might have significant reduction in the amount of fungicides required. The Early Blight disease is very