Indução, seleção e caracterização de variantessomaclonais de bananeira do subgrupo Cavendish resistentes a Fusarium oxysporum f. sp. cubense.

Abstract

Banana cultivation plays a crucial role in ensuring food security for millions of families worldwide, yet it is severely threatened by Fusarium wilt, caused by the fungus Fusarium oxysporum f. sp. cubense (Foc), particularly by the Tropical Race 4 (TR4) of the pathogen. Currently, no fully effective control methods exist, and the use of resistant cultivars remains the most effective strategy. However, conventional breeding presents limitations, which has encouraged the adoption of alternative approaches such as the induction of somaclonal variation. In this study, we explored the induction of somaclonal variation mediated by Thidiazuron (TDZ) as a biotechnological strategy to obtain Foc-resistant somaclones. In Chapter 1, we evaluated the potential of TDZ (1 mg/L – T1 and 2 mg/L – T2) as an inductive agent in susceptible cultivars, ‘Grande Naine’ and ‘Valery’, targeting resistance to Foc subtropical race 4 (putative isolate). The T2 treatment proved most effective, resulting in seven ‘Grande Naine’ somaclones exhibiting complete resistance. Genetic stability, assessed through molecular markers (IRAP, REMAP, and ISSR), was predominantly monomorphic, although notable polymorphisms were detected in some T2 somaclones of ‘Grande Naine’. Histological analysis validated the resistance, revealing the absence of fungal hyphae in most resistant somaclones. In Chapter 2, we focused on the molecular and histochemical characterization of 14 ‘Grande Naine’ somaclones resistant to Foc STR4. IRAP analyses confirmed high genetic stability in these somaclones compared to the control plant. Following inoculation with Foc STR4, five somaclones (E10, E13, E14, E15, E16) exhibited complete resistance. Genotypes E10, E13, and E15 showed significant activation of defense-related genes(LOX, PIP2-3, PI206, and PTI6). Notably, somaclone E13 displayed enhanced deposition of callose and phenolic compounds in roots, effectively inhibiting fungal colonization. In summary, the induction of somaclonal variation using TDZ proved to be an effective approach for generating new banana variants with complete resistance to Foc. The genetic-molecular characterization and validation of defense responses in these somaclones confirm their immediate potential for integration into breeding programs aimed at ensuring the sustainability and stability of global banana production.