Molecular and histochemical characterization of Grand Naine somaclones resistant to Fusarium oxysporum f. sp. cubense subtropical race 4Wanderley Diaciso dos

Banana farming is essential for the food and occupational security of numerous families who rely on subsistence agriculture. However, banana production has been severely affected by Fusarium wilt, caused by the pathogen Fusarium oxysporum f. sp. cubense (Foc), particularly the tropical race 4 (Foc TR4) and subtropical race 4 (Foc STR4). So far, the only reliable, effective way to manage the disease is by using resistant plant varieties, as no complete control methods are currently available. However, developing these through conventional breeding remains challenging, particularly in combating TR4. Given this scenario, alternative approaches, such as somaclonal variation induction have shown promise in offering farmers resistant cultivars. This study aimed to characterize Grand Naine somalclones cultivars resistant to Foc STR4, at both molecular and histochemical levels. Fourteen somaclones were genetically analyzed using Inter-Retrotransposon Amplified Polymorphism (IRAP) markers, qPCR, and histochemical assays. The IRAP markers revealed higher genetic stability than the control plant (non-mutagenized Grand Naine). After inoculation with Foc STR4, somaclones E10, E13, E14, E15, and E16 showed complete resistance. The genotypes E10, E13, and E15 stand out due to their higher activation of defense genes, such as LOX, PIP2-3, PI206, and PTI6. Histochemical analyses revealed that somaclone E13 showed increased callose and phenolic compound deposition in the roots, with no fungal structures present. Overall, all somaclones showed superior resistance compared to the control, and their future commercial validation will be crucial for developing more productive and Fusarium wilt-resistant banana cultivars, significantly contributing to the sustainability of global banana production.