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– Fusarium wilt, caused by Fusarium oxysporum f. sp. cubense (Foc), is one of the most destructive diseases affecting banana crops worldwide. Therefore, the development of resistant cultivars is a promising alternative to mitigate the effects of the disease on banana plantations. The objectives of this study were to induce somaclonal variation in banana cultivars of the Silk and Cavendish types and to select somaclones resistant to subtropical race 4, thereby enabling the production of fruit in areas where this race is present. Shoot clump apexes of the Grand Naine and Maçã (Silk) cultivars were grown in MS medium. The cultures were subcultured four times. They were then challenged with fusaric acid (FA) in an experiment consisting of four treatments with different concentrations (0.1, 0.2, 0.3, and 0.4 mM) and five repetitions, each consisting of a Petri dish containing seven multiple shoot clumps in MS culture medium supplemented with 2.5 mg/L benzylamine purine. Multiple shoot clumps without the addition of FA were also used in the experiment, and were subcultured three times and maintained in a dark room. The multiple shoot clumps that survived the treatment with FA were transferred to MS medium and maintained in the growth chamber in the presence of light. The regenerated plants were later planted in tanks containing soil infested with an isolate classified as Foc subtropical race 4 (Foc STR4), and were evaluated for resistance to the pathogen at 90 days after inoculation (d.a.i.). Pathogen structures were confirmed by root clarification and root staining technique. All somaclones of the Maçã (Silk) cultivar were susceptible to Fusarium wilt and two somaclones of the Grand Naine cultivar were selected as resistant. The addition of FA as a selective agent was effective in the selection of somaclones among plants of the Grand Naine cultivar, as shown by the selection of two somaclones resistant to Foc STR4. The next step will consist of the agronomic and market potential validation of the selected somaclones, aiming to confirm their potential use by producers.

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The instability of in vitro cultures may cause genetic and epigenetic changes in crops called somaclonal variations. Sometimes, these changes produce beneficial effects; for example, they can be used in breeding programs to generate new cultivars with desirable characteristics. In this article, we present a systematic review designed to answer the following question: How does somaclonal variation contribute to plant genetic improvement? Five electronic databases were searched for articles based on pre-established inclusion and exclusion criteria and with a standardized search string. The somaclonal variation technique has been most frequently applied to ornamental plants, with 49 species cited in 48 articles, and to the main agricultural crops, including sugarcane, rice, banana, potato and wheat, in different countries worldwide. In 69 studies, a technique was applied to evaluate the genetic diversity generated between clones, and, in 63 studies, agronomic performance characteristics were evaluated. Other studies are related to resistance to pathogens, ornamental characteristics and resistance to abiotic stresses. The application of the plant growth regulators (PGRs) benzylaminopurine (BAP) and dichlorophenoxyacetic acid (2,4-D) was the most common method for generating somaclones, and randomly amplified polymorphic DNA (RAPD) molecular markers were the most commonly used markers for identification and characterization. Somaclonal variation has been used in genetic improvement programs for the most economically important crops in the world, generating genetic diversity and supporting the launch of new genotypes resistant to diseases, pests and abiotic stresses. However, much remains to be explored, such as the genetic and epigenetic mechanisms from which somaclonal variation is derived.

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