Efficient regeneration and genetic transformation platform applicable to five Musa varieties

Background: Banana ( Musa spp.) is an important staple food, economic crop, and nutritional fruit worldwide. Conventional breeding has been seriously hampered by their long generation time, polyploidy, and sterility of most cultivated varieties. Establishment of an efficient regeneration and transformation system for banana is critical to its genetic improvement and functional genomics. Results: In this study, a vigorous and repeatable transformation systemfor banana using direct organogenesiswas developed. The greatest number of shoots per explant for all five Musa varieties was obtained using Murashige and Skoog medium supplemented with 8.9 \u3bcM benzylaminopurine and 9.1 \u3bcM thidiazuron. One immature male flower could regenerate 380\u2013456, 310\u2013372, 200\u2013240, 130\u2013156, and 100\u2013130 well-developed shoots in only 240\u2013270 d for Gongjiao, Red banana, Rose banana, Baxi, and Xinglongnaijiao, respectively. Longitudinal sections of buds were transformed through particle bombardment combined with Agrobacterium -mediated transformation using a promoterless \u3b2-glucuronidase (GUS) reporter gene; the highest transformation efficiency was 9.81% in regenerated Gongjiao plantlets in an optimized selection medium. Transgenic plants were confirmed by a histochemical assay of GUS, polymerase chain reaction, and Southern blot. Conclusions: Our robust transformation platform successfully generated hundreds of transgenic plants. Such a platform will facilitate molecular breeding and functional genomics of banana