Vacciplant and Calliete Cotreatment Synergically Induces Phenolic Compounds Production in Plantain (Musa x paradisiaca L.) and Trigger the Natural Defense Activation for Protection to Black Leaf Streak Disease

Aims: To evaluate the synergistic action of two elicitors or stimulators of natural plant defense, vacciplant and calliete, on the synthesis of defense metabolites and their impact on tolerance to Mycosphaerella fijiensis, causal agent of the black leaf streak disease (BLSD) in plantain (Musa x paradisiaca L.).

Place and Duration of Study: The study was conducted in Abidjan (southern Côte d'Ivoire) in 2019.

Methodology: The ability of plants co-treated with vacciplant+calliete to product phenolic compounds was compared to vacciplant and the control. Subsequently, the treated plants were inoculated with the pathogenic filtrate of Mycosphaerella fijiensis in order to induce the black leaf streak disease. Afterwards, the content of phenolic compounds was determined and then their analysis by ultra-high performance liquid chromatography was performed (U-HPLC). Finally, foliar pigments were quantified to have an indication of the sanitary state of elicited and infected plants.

Results: plants treated with vacciplant and inoculated, as well as plants co-treated with vacciplant+calliete and inoculated, accumulated more phenolic compounds than the control plants. However, the phenol content of the co-treated plants (191.10 mg/g FL) was higher than that of the plants treated with vacciplant alone (142 mg/g FL). In addition, qualitative analysis by U-HPLC revealed that treated plants synthesized de novo two compounds including trans-resveratrol, a stilbene with significant antifungal activity, in plants co-treated with vacciplant+calliete. In addition, it allowed the plants to acquire a higher leaf greening state than those treated with vacciplant alone, indicating a more intense photosynthetic activity and thus a good sanitary state

Conclusion: Vacciplant+calliete has a synergistic effect on the activation of the plantain's defense reactions and thus on the good tolerance to M. fijiensis, an agent of plantain BLSD.