A banana susceptibility gene underlying fusarium wilt: validation as a target for disease resistance

Fusarium wilt, caused by the soil-borne fungus Fusarium oxysporum f. sp. cubense, remains the principal constraint on banana production, particularly for the widely cultivated cultivar 'Prata-Ana' (AAB) in Brazil. Given the limited efficacy of conventional control strategies, susceptibility (S) genes have emerged as promising targets for developing resistant cultivars. This study investigated the expression of the banana DMR6 gene during the interaction with Foc. DMR6 was selected because it is a conserved plant susceptibility gene that negatively regulates salicylic acid-mediated immunity, making it a promising target for genome editing.

Banana plantlets were inoculated with Foc Subtropical Race 4 under controlled conditions. Temporal expression of the banana DMR6 gene was analyzed by RT-qPCR, and host defense responses were assessed by histochemical and microscopic analyses. DMR6 expression initially decreased and subsequently increased, reaching a 6.5-fold induction at 72 h post-inoculation relative to non-inoculated controls. This expression peak coincided with spore formation and advanced vascular colonization. Although infected roots exhibited callose deposition and phenolic compound accumulation, these defense responses were insufficient to restrict pathogen progression, resulting in severe disease symptoms and a disease severity index of 80% at 90 days after inoculation.

The findings indicate that banana DMR6 functions as a negative regulator of plant immunity and is closely associated with susceptibility to Fusarium wilt. These results provide a molecular basis for future functional validation and support DMR6 as a potential target for precise genome editing to develop resistant banana cultivars.