Abstract

Fusarium oxysporum f. sp cubense (FOC) causes wilt disease known as Panama disease which is one of the most serious constraints on banana (Musa spp.) production worldwide. The conspicuous external symptom of Panama disease initially occurs as yellowing of the margins of older leaves, and yellowing progresses from the older to the younger leaves. Leaves gradually collapse at the petiole and finally hang down around the pseudostem. Internal symptoms are characterized by vascular discoloration beginning with yellowing at the roots and corm which progresses to continuous browning of vascular strands in the pseudostem. Management of the disease is difficult due to the speed of symptom development and lack of knowledge on the pathogen. At present, field sanitation, soil treatments with fumigant, crop rotation with non- host of FOC, and injecting fungicides into corm tissue are the only possible measures against the disease. As a new potential concept for chemical mediated control of the disease, we are applying plant activators which induce plant- resistance against pathogens. We found that foliar spray of ASM (acibenzolar-S-methyl, PBZ (probenazole), or VMA (Validamycin A) could decrease the severity of the disease. Among these plant activators, VMA gave the highest protective efficacy. Whereas, drenching of ASM could also suppress the disease. We quantified salicylic acid (SA) which is a molecule marker of systemic acquired resistance (SAR). In banana leaves treated with VMA and PBZ the concentration of SA increased. FOC in banana tissue was monitored using a pHYG-EGFP-transformant which emits green fluorescence under excitation by blue light. Plant activators seemed to prevent FOC from penetrating into banana tissues and growing in the banana tissues.