Selection and Characterization of Somaclonal Variants of Prata Banana (AAB) Resistant to Fusarium Wilt

Abstract

Fusarium wilt, caused by the fungus Fusarium oxysporum f. sp. cubense (Foc), is one of the most devastating diseases affecting banana cultivation worldwide. Although Foc tropical race 4 (TR4) has not yet been identified in Brazilian production areas, the damage caused by races 1 and subtropical 4 is the main cause of production losses, especially affecting cultivars of the Prata subgroup. Thus, the induction of somaclonal variation is a promising strategy in biotechnology to generate genetic variability and develop resistant varieties. This study aimed to induce somaclonal variation in the Prata Catarina cultivar (AAB genome) using successive subcultures in Murashige and Skoog (MS) medium enriched with the plant regulator Thiadizuron (TDZ) at two concentrations: 1 and 2 mg/L. After evaluating the symptoms, we selected 13 resistant somaclones that were not infected by the fungus. Histochemical and histological analyses of the somaclones indicated possible defense mechanisms that prevented colonization and/or infection by Foc, such as intense production of phenolic compounds and the presence of cellulose and callose in the roots. Some somaclones showed no pathogen structures in the xylem-conducting vessels, indicating possible pre-penetration resistance. Furthermore, molecular studies indicated that the genetic alterations in the somaclones may have induced resistance to Foc without compromising the agronomic characteristics of the commercial genotype.