Establishment of cell suspension cultures and induction of somatic embryogenesis on local banana cultivars
2007
Aspuria, E. T. | De Juras, R. J. C., Philippines Univ. Los Banos, College, Laguna (Philippines). Crop Science Cluster
Explant size of 1 cu cm and air drying of field-grown suckers prior to preparation and isolation of explants were found to reduce contamination of initial explants. Frequent transfer of initial explants (3 days intervals) onto freshly prepared culture medium reduced browning of tissue up to 82% compared with continuous inoculation for 21 days. Sterile shoot tip cultures of 3 local banana cultivars previously inoculated onto MC + 22.2 micro M BA were induced to form meristemic buds (scalps) on MS + 1 micro M IAA supplemented with either BA at various concentrations (10, 20, 50 and 100 micro M) or TDI (1 micro M). 'Lakatan' and 'latundan' showed highest number of meristemic buds formed in MS + 1 micro M IAA + 50 micro M BA in less than 3 weeks of incubation, where as 'Saba' required higher concentration of Ba (100 micro M). On the other hand, higher number of scalps was obtained in the TDZ supplemented culture medium in all the banana cultivars compared to BA supplementation. Hence, TDZ is more effective cytokinin supplement than BA at all concentrations tested for induction of scalp formation. Globule formation was induced in modified liquid medium consisting of 1/2 MS macro and Fe-EDTA with 5 micro M 2,4-D and 1 micro M zeatin to induce globule formation. Refreshing the culture medium every two days for the first two weeks of culture also effectively reduced browning of scalps. Globules formation was observed 5-7 weeks after inoculation regardless of explant source (i.e. sterile cultures or field grown suckers). About 50-55 globules from each of the 3 banana cultivars were collected and transferred into fresh medium (as for globule formation) for establishment of embryogenic cell suspension cultures. Among the 3 banana cultivars 'Latundan' produced the least number of embryogenic cells in the trials, hence, insufficient for induction of somatic embryogenesis. Thus, only mature cells of 'Lakatan' and 'Saba' were induced to undergo somatic embryogenesis in MS medium supplemented with BA singly or in combination with ABA alone or with ABA plus malt extract. Four weeks of incubation in these culture media induced early embryogenesis but did not develop into mature somatic embryos. In a zeatin enriched liquid medium (MS + 9.1 micro M zeatin), embryo development was already evident in 'Saba' after 2 weeks of incubation, however, 'Lakatan' did not respond even after extended incubation period. Transfer of mature somatic embryos of 'Saba' cultivar onto semi-solid MS + 9.1 micro M zeatin induced germination. Germinated somatic embryos passed through 4 sub cultures onto MS + 1 micro M IAA + 22.2 micro M BA and further increased rate of shoot multiplication in MS + 15% coconut water + 22.2 micro M BA.
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