Advancements in genetic diversity assessment and tissue culture protocol optimisation for the conservation and improvement of local banana germplasm: A systematic review

Banana (Musa spp.) is a key food security crop increasingly constrained by biotic and abiotic stresses, necessitating urgent germplasm conservation and improvement. Despite growing research interest, limited systematic reviews have comprehensively integrated evidence across molecular diversity assessment and tissue culture optimisation for local banana germplasm. This review, conducted following PRISMA 2020 guidelines, synthesised 70 peer-reviewed studies published between 2011 and 2026, sourced from six academic databases, to address five research questions covering molecular techniques, tissue culture protocols, combinations of plant growth regulators, key challenges, and the influence of genetic diversity on propagation success. Simple Sequence Repeat (SSR) markers were the most widely employed molecular tool, appearing in 28 studies, with a discernible shift toward high-throughput genomic platforms, including SNP markers, next-generation sequencing, and genotyping-by-sequencing in recent literature. Shoot-tip culture using Murashige and Skoog (MS) medium supplemented with BAP (2–5 mg/L) for multiplication and IBA (0.5–2 mg/L) for rooting represented the most consistently optimised protocol across genotypes. Genetic fidelity, confirmed at 90–100% true-to-type rates through SSR and ISSR markers under direct organogenesis pathways, was substantially compromised by callus-mediated regeneration and prolonged subculturing. Genotype dependency emerged as the dominant determinant of tissue culture success, with triploid AAA and AAB cultivars outperforming diploid local landraces, which exhibited greater recalcitrance, phenolic browning, and acclimatisation difficulties. Major challenges identified include microbial contamination (38 studies), phenolic oxidation (35 studies), and limited laboratory capacity in developing country contexts. The evidence base remains heavily concentrated in Asia, with Africa critically underrepresented despite its reliance on bananas for food security. This review concludes that integrating molecular characterisation with genotype-specific tissue culture optimisation is essential for effective conservation and scalable propagation of local banana germplasm, and calls for targeted investment in capacity building, standardised open-access protocols, and expanded research on recalcitrant African landraces.