Non-Conventional Breeding of Banana (Musa spp.)

This paper presents research in non-conventional breeding of banana, more specifically genetic transformation, protoplast culture, somatic hybridisation and EMS-induced mutation, carried out at the Key Laboratory of Gene Engineering, China. By using explants of immature flowers, embryogenic cell suspensions (ECS) were established of several banana cultivars, including 'Pisang Mas' (AA), 'Guo Shan Xiang' (AAB, Silk), 'Ba Xi Jiao' (AAA, Cavendish) and 'Dong Guan Da Jiao' (ABB, local banana cultivar resistant to Fusarium oxysporum f. sp. cubense (Foc) race 4. To introduce disease resistance from 'Dong Guan Dajiao' into 'Guo Shan Xiang' and obtain somatic hybrids, an asymmetric protoplast fusion with polyethylene glycol was developed. Six of the surviving plants were identified as hybrids by RAPD-ISSR and GISH analysis. We also studied the asymmetric somatic hybridisation of 'Ba Xi Jiao' and 'Dong Guan Da Jiao'. Cell colonies were formed from the fusion products after 45 days on a feeder layer culture, and 1236 somatic embryos were obtained. However, they all failed to germinate in further culture. We established a microcross sections cultural system combined with EMS-induced mutation of 'Ba Xi Jiao' to screen for Foc-resistant plants, and five putative Foc race 4-resistant plants were obtained by screening with the method reported by Mak et al. (2004). We cloned a novel full-length NPR1-like gene, designated MdNPR1 (accession number FJ357442) from 'Dong Guan Da Jiao'. The transcripts of MdNPR1 accumulated stronger in the resistant 'Dong Guan Da Jiao' than in 'Fen Jiao' (AAB), a local cultivar which is very susceptible to Foc race 4. MdNPR1 were also transferred into ECS of 'Ba Xi Jiao' via Agrobacterium-mediated transformation. The expression of the GUS gene could be detected in the transformed ECS after coculture and in the putative transformed somatic embryogenesis, but regeneration was not achieved.