Evidence of Correlation between Pathogenicity, Avirulence Genes, and Aggressiveness of Fusarium oxysporum f. sp. cubense in Banana “Cavendish” and “Prata” Subgroups

Abstract

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 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 homologs was verified. The similarity matrix revealed three isolates that were 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, to replace the standard isolate of race 1 in the resistance screening process carried out by the breeding program. Two homologs 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 identifying sources of resistance to Foc and contributing to the establishment of the function of SIX effector proteins.