Fungicide sensitivity and fitness traits of Brazilian Colletotrichum musae isolates exposed to flutriafol and tebuconazole

Abstract This study evaluated the sensitivity of Colletotrichum musae isolates to demethylation inhibitor (DMI) fungicides flutriafol and tebuconazole, as well as fitness and competitive ability of isolates with reduced sensitivity. A positive correlation was observed between the sensitivity of C. musae isolates to different concentrations of both fungicides; however, the isolates were generally more susceptible to tebuconazole. The effective concentration required to inhibit mycelial growth by 50% (EC₅₀) was determined and used to select four isolates with the lowest and highest EC₅₀ values for each fungicide, classified as sensitive (S) and less sensitive (LS), respectively. Isolates sensitivity profile remained stable after ten successive transfers on fungicide-free medium. Both fungicides effectively controlled anthracnose caused by S and LS isolates on banana fruit when applied at recommended doses. Fitness analyses included mycelial growth, sporulation, conidial germination, and disease severity. No significant differences were detected between the fitness parameters of the S and LS isolates those classified by their sensitivity to flutriafol and tebuconazole; however, the occurrence of adaptive cost for LS isolates to these fungicides could be observed through competition tests. These results provide new insights into the sensitivity and fitness of C. musae isolates from Brazil and underscore the importance of continuous monitoring of LS isolates to guide more effective chemical management strategies for banana anthracnose.