Induction of Biochemical Defence Compounds in Banana (Musa sp.) by Four Plant-based Biofungicides against Black Leaf Streak Disease (Mycosphaerella fijiensis)

Abstract

Black leaf streak disease, caused by Mycosphaerella fijiensis, is the principal foliar disease affecting banana plants in tropical regions. Given the limitations of conventional chemical control, the use of biopesticides that mobilise plants’ natural defence mechanisms is a promising approach. This study aimed to evaluate the effects of the biopesticides PRORALY 50 EC, NECO 50 EC, FERCA 50 EC, and ASTOUN 50 EC, and the synthetic elicitor ACTIGARD 50 WG, on the biochemical responses of the banana varieties Grande Naine and Big Ebanga inoculated with M. fijiensis. The inhibitory efficacy of the treated banana extracts against M. fijiensis was assessed. The total polyphenol, condensed tannin, and flavonoid contents, as well as antioxidant activity, were determined before and after inoculation. The inhibition rates of spore germination and germ-tube growth of M. fijiensis were also determined. The biopesticides and synthetic elicitor significantly increased phenolic compound accumulation and enhanced the antioxidant capacity of banana plants compared with the controls. The most pronounced responses were observed with PRORALY 50 EC and NECO 50 EC, whereas FERCA 50 EC and ASTOUN 50 EC showed intermediate efficacy, outperforming ACTIGARD 50 WG, particularly in terms of fungal inhibition. Strong positive correlations were found among phenolic metabolites and antioxidant and antifungal activities, indicating the ability of the treatments to induce defence mechanisms against black leaf streak disease. These results indicate that the biopesticides evaluated, particularly PRORALY 50 EC and NECO 50 EC, are promising candidates for enhancing banana plants’ resistance to M. fijiensis. Their incorporation into integrated disease management strategies could help reduce reliance on synthetic fungicides and promote more sustainable banana production.