Diversity of Fusarium associated with banana wilt in eastern Democratic Republic of Congo

Fusarium wilt of banana (FWB) is a major agricultural threat worldwide, historically attributed to several races of Fusarium oxysporum f. sp. cubense (Foc). The updated taxonomic scheme tends to group these races of Foc into distinct species. In addition to the F. oxysporum species complex (FOSC), a few species within the Fusarium fujikuroi species complex (FFSC) have occasionally been reported on bananas. In eastern Democratic Republic of Congo, FWB has been reported across North and South Kivu. This study aims to assess the diversity of Fusarium locally associated with FWB through morphological, phylogenetic, and pathogenic characterization. Seventy Fusarium strains were isolated from pseudostems showing infection of vascular tissues. Morphological characterization was performed on synthetic low-nutrient agar, potato dextrose agar, and carnation leaf agar. Pathogenicity was assessed on Cavendish and Gros-Michel in greenhouse conditions. Molecular phylogenetic relationships were inferred based on DNA sequence data from partial translation elongation factor 1-alpha and the second-largest subunit of RNA polymerase. To confirm species identity, partial calmodulin and beta-tubulin gene regions were also sequenced for some strains. Of the 70 Fusarium strains analyzed, 31 belonged to the FOSC, including 28 strains identified as F. tardichlamydosporum and one strain (F141) identified as F. duoseptatum , both previously recognized as Foc Race 1. Two additional FOSC strains (F93 and F146) formed a distinct clade, separate from the newly defined Foc species. No isolate was identified as F . odoratissimum (Foc TR4). Thirty-five strains were classified as F. joanfreemaniae , a member of the F. fujikuroi species complex. In addition, F. solani , F. andiyazi , and F. incarnatum have been reported. Fusarium tardichlamydosporum and F. duoseptatum strains induced symptoms under all tested conditions. Inversely, F. joanfreemaniae caused symptoms on Gros Michel and Cavendish only under stressed, injured roots, indicating a weak or opportunistic role. This highlights a multi-species disease complex with implications for resistance-based management.