61 Genetic Transformation of Banana Embryogenic Cells Through Particle Bombardment using a Herbicide Resistance Gene as Selectable Marker K. Matsumoto and L.S. Morais G.R. Vianna, F.J.L. Aragªo and E.L. Rech Laboratory of Plant Tissue Culture Laboratory of Gene Transfer Embrapa Genetic Resources and Biotechnology Embrapa Genetic Resources and Biotechnology PqEB Final Av. W3 Norte PqEB Final Av. W3 Norte 70770-900 Braslia-DF, Brazil 70770-900 Braslia-DF, Brazil Email: kazumoto@cenargen.embrapa.br Keywords: Imazapyr, Musa, biolistic, transgenic plants Abstract Bananas and plantains (Musa spp.) are among the most important horticultural crops in tropical and subtropical regions of the world. However, various diseases caused by fungi and viruses have seriously endangered the production of this species. Through genetic transformation technologies, disease resistant varieties may be produced. However, an effective selection process is needed to increase the efficiency of transformant recovery. For banana transformation, antibiotic resistance genes are widely used to enable this selection. The purpose of this study was to develop a simple and routine particle- bombardment system to generate transgenic bananas using a herbicide resistance gene as selectable marker. Preliminary experiments were conducted to evaluate the effects of the herbicide Imazapyr on the development of embryogenic cells of “Maçã” banana (Musa sp. AAB group, Silk). A dose of 1 μM of Imazapyr was chosen for the transformation experiments. Embryogenic cells were bombarded with a plasmid vector compiling the ahas gene, under control of the ahas promoter from Arabidopsis thaliana. The bombarded cells were cultured with the herbicide- containing medium for 30 days, and putative transformed plants were regenerated. PCR analyses showed that the regenerated plants contained bombarded ahas gene. Southern hybridization confirmed the integration of the transgene into the banana genome. These results will provide a new selectable marker for banana transformation, in addition to antibiotic resistance genes, and should form the foundation for the introduction of economically important traits in banana. INTRODUCTION Bananas and plantains (Musa spp.) are among the most important horticultural crops in tropical and subtropical regions of the world, being cultivated in areas of about 9 million hectares spread throughout more than 100 countries. They are the fourth most important monocot crops in the world after rice, maize and wheat (FAO 1990-1998), and the main food source for millions of people. Although global Musa production has almost doubled in the last 30 years, the productivity has risen only 18%. The production increase resulted from an expansion in the plantation area, mainly in Asia (INIBAP, 1999). One of the most serious problems of Musa plants is the lack of varieties that are both highly productive and resistant to major diseases such as the Black Sigatoka and Panama diseases. Breeding to obtain disease resistant plants is of fundamental importance. However, to this date only a few new cultivars have been obtained by conventional crossbreeding. Application of the crossbreeding method in this species is still very difficult, since most of the cultivated varieties are triploids and show low fertility. Genetic transformation promises to bypass the difficulties of conventional breeding by enabling the direct use of the widely-cultivated sterile varieties. In bananas and plantains (Musa sp.), some reports about embryogenesis from suspension cells (Dheda et al., 1991; Cte et al., 1996) and protoplasts (Media et al., 1993; Panis et al., 1993; Matsumoto and Oka, 1998) already exist. Genetic transformation Proc. IS on Trop. & Subtrop. Fruits Ed. R. Drew Acta Hort. 575, ISHS 2002