Competence of scalps for somatic embryogenesis in Musa

During the past 5 years, much progress has been made in the establishment of embryogenic cell cultures in Musa. Explants such as seeds and male flowers have limited value because only wild bananas produce seeds and male flowers cannot be derived from Horn and False Horn plantains. Scalps, somatic explants derived from in vitro proliferating meristem cultures, can however be generated from any given, banana or plantain landrace (Musa spp.). At the Laboratory of Tropical Crop Improvement a widely applicable methodology has been developed for the initiation of embryogenic cell suspensions using such explants. A preculture of meristems on a medium with 100 mu M N6-benzylaminopurine was found to enhance significantly the competence for somatic embryogenesis. Out of 21 landraces covering all diploid and triploid genome groups and the most important banana types, 18 cultivars showed an embryogenic response. From 15 accessions an embryogenic cell suspension could be established. Embryogenic frequencies of responding accessions varied between 15 and 80 %. For some of the cultivars the induction period was reduced by 8-10 weeks as compared with the protocol without preculture. Less than 2 % off-types were observed at the vegetative level but complete evaluation is proceeding in the field. Many of the cell suspensions were cryopreserved and used in genetic transformation programs.