Fusarium wilt caused by Fusarium oxysporum f. sp. cubense (Foc) is one of the most destructive diseases in banana farming worldwide. Knowledge of the factors of genetic diversity and virulence of the pathogen contributes to the development of resistant cultivars and in management strategies based on exclusion. In this study, phenotypic traits such as virulence and aggressiveness in a sample of 52 Foc isolates, were analyzed and their relationship to the presence of putative effectors of gene SIX (Secreted in Xylem) pathogenicity homologues, verified. According to the dissimilarity matrix, there were three isolates closest to the standard Foc race 1 strain. Isolates 229A and 218A, were selected according to their aggressiveness profile in 'Grand Naine' and 'Prata-Anã', respectively, I order to replace the standard isolate of race 1 in the resistance screening process carried out by the breeding program. Two homologues of the SIX8 gene, SIX8a and SIX8b, are present in isolates of Foc from Brazil and the SIX8b gene correlates with avirulence in the cultivar ‘Grand Naine’ (Cavendish). These results are important to support the banana genetic breeding program by identification of sources of resistance to Foc and contribute in the establishment of the function of SIX effector proteins.

Bananas, a staple food globally and a key agricultural commodity, face a severe threat from the fungus Fusarium oxysporum form specialis cubense (Foc), significantly impacting production. Genetic improvement to develop resistant cultivars stands out as a crucial strategy to mitigate this disease. This study focused on assessing and recommending enhanced diploid banana varieties for resistance against Foc subtropical race 4 (ST4) and Foc race 1 (R1). Twenty-five improved diploids developed by Embrapa, Brazil, underwent evaluation. Utilizing a scale for internal symptoms at 90 days post-inoculation, genotypes were categorized from highly resistant to highly susceptible based on the internal symptom index. The diploid M53 exhibited high resistance to R1 and resistance to Foc ST4, while only the diploid CNPMF 0534 demonstrated complete resistance to both R1 and ST4, with resistance to the latter likely associated with penetration. These findings provide valuable insights for banana and plantain breeding programs, offering selected diploids for crossbreeding with commercial cultivars to develop new, resistant genotypes against Foc.