The development of techniques for tissue culture of mango (Mangifera indica L.) var. Carabao and successful transfer of ex vitro-grafted plants to soil and the field

The mango, a virtually neglected fruit before the advent of nitrate-induced flowering, is now the third leading export fruit in the Philippines, with the 'Carabao' mango being the only variety exported. Delay or control of ripening, as well as the ability to program market availability, would further increase the value of mango. Prolonging its shelf life and improving other characteristics can be achieved through biotechnology, requiring a reliable tissue culture regeneration protocol, and a successful transfer-to-soil system. Between 2004 and 2008, immature fruits were collected and cultured in vitro. Primary somatic embryo (SE) induction ranged from 16-100% depending on the strain, collection time, and tree source. A single SE was required to initiate SE proliferation. When subcultured, the SEs proliferated, germinated, and produced plantlets. Initial shoot formation was 8-64%, while succeeding true leaf formation was reduced to 0-36%. In some cultures, abscission and browning were observed, but gas chromatography assays ruled out ethylene as the cause. Regenerated plants survived transfer to soil, but at low percentages. While it took 1 y to develop the tissue culture protocol, it took 3 y to develop the technique for successful transfer of plantlets to soil, and to the field. This is the first report, of a polyembryonic mango, variety Carabao, for which successful tissue culture and field transplantation systems were developed. The technology is equally important as a way to rapidly propagate uniform rootstocks of superior 'Carabao' strains or other varieties, for generation of variability, genetic transformation, and for germplasm conservation and exchange.