Approaches to in vitro conservation of Philippine sugarcane (Saccharum officinarum) genetic resources

The Philippines has approximately 1,285 sugarcane varieties developed locally or introduced from other countries which are maintained in the field genebanks of Sugar Regulatory Administration (2016) excluding the variety collection from other research institutions or in small and big sugarcane plantations through the country. In vitro conservation of sugarcane offers a means of maintaining valuable genotypes in a small space, free from pests and diseases, with high multiplication potential. For the last two years, a total of 317 sugarcane accessions were successfully introduced in vitro and currently maintained in MS medium with 1 mg/L BAP or MS + 0.2 mg/L BAP + 0.1 mg/L Kinetin (SRA medium) and sub-cultured onto fresh medium every 1-2 months. To prolong culture storage duration, studies on the use of different culture vessel covers to minimize media losses and slow growth medium by addition mannitol were conducted. In vitro parameters such as number of shoots, length of longest shoot, number of roots, length of longest roots, shoot vigor and degree of culture media browning were recorded 60 days after inoculation. Five types of culture vessel cover (rubbers stopper, cotton plug, aluminum foil, polypropylene plastic cap and aluminum foil + cotton plug) were used to determine the optimum culture vessel cover for sugarcane in vitro cultures. Cultures covered with cotton plug showed the lowest shoot growth and proliferation and highest culture media loss. On the other hand, the lowest shoot vigor and relatively high culture media browning, and highest culture contamination were observed on cultures covered with foil + cotton plugs. The lowest media reduction, highest vigor, least culture contamination, and relatively low culture media browning were observed in cultures covered with polypropylene plastic cap. The effects of mannitol (0, 1 and 2%) on shoot growth and vigor were determined using two culture media (MS basal medium and SRA medium. Culture media supplemented with 1 and 2% mannitol showed no significant differences on all in vitro parameters. SRA medium supplemented with 1% mannitol showed the lowest shoot growth and proliferation and highest shoot vigor. On the other hand, cultures with 2% mannitol showed highest culture media browning. The response of different sugarcane accessions to SRA medium + 1% mannitol will be conducted.