A simple procedure for slow growth maintenance of banana (Musa spp.) embryogenic cell suspension cultures at low temperature

Although earlier banana cell suspensions have been cryopreserved for the purpose of germplasm conservation, for routine work it is desirable to develop a simple method of maintaining the cell suspensions under slow/suspended growth, from which actively growing cultures can be retrieved quickly. Experiments were hence conducted to develop a method for slow growth maintenance of embryogenic cell suspension cultures without losing their regeneration potential. The embryogenic cell suspensions of banana cultivars Rajeli and Rasthali were maintained at different temperatures (37 degrees C, 25 degrees C, 15 degrees C and 8 degrees C) for studying the growth parameters. The suspensions of both the varieties maintained at 37 degrees C showed necrosis and turned brown, whereas at 25 degrees C, 39-fold (cv. Rajeli) and 18-fold (cv. Rasthali) increase in the cell mass was noticed within 49 days. Substantially slow cell growth of 4.5-fold (cv. Rajeli) and 4.6-fold (cv. Rasthali) could be attained at 15 degrees C. A temperature of 8 degrees C suspended the growth of the cells and a constant settled cell volume was maintained for over 49 days corresponding to seven subcultures. Morphologically, normal plants were regenerated from the cells maintained at 25 degrees C, 15 degrees C as well as 8 degrees C and were hardened in the greenhouse. It has been revealed that the banana cell suspensions can be maintained without subculturing at 8 degrees C for over 4 months.