GC-MS metabolite profiling of Pseudocercospora fijiensis isolates resistant to thiabendazole.

Abstract

Black Sigatoka is the most widespread banana disease worldwide. It is caused by Pseudocercospora fijiensis, a fungal pathogen known for developing resistance to fungicides such as thiabendazole. Despite the increasing costs associated with the use of chemicals to control this disease, the pathogen's mechanisms for fungicide resistance are not fully understood. The metabolite profiles of P. fijiensis isolates with different levels of resistance to thiabendazole were characterized by GC-MS. A total of 33 isolates were obtained from symptomatic banana plants and the sensitivity of each isolate to thiabendazole was assessed at 0, 1, 10, 100, 1000, and 10000 μg.mL-1. Then, the metabolite profile of each isolate was assessed using GC-MS. Metabolites such as hexadecanoic acid, tetradecanoic acid, octadecadienoic acid and octadecanoic acid were significantly over-accumulated in the presence of thiabendazole at 10 μg.mL-1. Phosphoric acid, L-proline, and D-allose increased in concentration with time in the presence of 100 μg.mL-1 of thiabendazole, and mannonic acid, 1-hexadecanol, D-sorbitol and tetracosanoic acid were only detected in the presence of the fungicide. Metabolic pathways including that of fructose, mannose metabolism, the biosynthesis of unsaturated fatty acids, and ABC transporters were upregulated in resistant isolates. Our findings show an increment of tetracosanoic (myristic) acid suggesting a possible β-tubulin-compensation mechanism in resistant isolates. The presence of myristic acid promoted the generation of diacylglycerol kinase δ which facilitated the production of β-tubulin in other studies. Additionally, important changes in the metabolite profiles were observed as soon as six hours after exposure to the fungicide showing an early response of the pathogen. To the best of our knowledge, this is the first report that describes the changes in the metabolite profile of P. fijiensis resistant to thiabendazole when exposed to the fungicide.