Stability in plant and bunch traits of a 'French-type' dwarf plantain micropropagated from the floral axis tip and five lateral corm tips of a singlemother plant: Good news on the tissue culture and bad news on banana streak virus

Field evaluation of plants produced in vitro initiated from a phenotypicall y distinct, apparently healthy dwarf 'French-type' plantain clone 'Dwarf Su perplatano' (Musa 'AAB') was carried out at three sites in Puerto Rico. The use of the floral axis tip from a 'mother plant' versus vegetative apices from lateral buds of the same plant as a source of the primary explant was compared and contrasted. Material from floral axis tip consistently showed high phenotypic uniformity whereas materials from vegetative apices of 'swo rd' suckers were less so. 'Virus-like symptoms' that became apparent in muc h of the material just before flowering (shooting stage) were determined to be due to the badnavirus banana streak virus (BSV), a dsDNA pararetrovirus . The 'good news' is that a primary explant taken from the floral axis tip was quicker in its initial response to yield a multiplication system in vit ro, and produced significantly fewer virus-infected plants, ca. 5%. By cont rast, primary explants obtained from the vegetative sucker-derived apices w ere later in their production of initial buds, and produced many mon virus- infected plants, an average of 32%. Comparison of vegetative-apex-derived p lants and floral axis tip-derived plants disclosed no evidence that apices from vegetative suckers or floral stem tips gave rise to genetic off-types due to mutations were brought about by the in vitro process per se. Phenoty pic differences were due to virus infestation. The 'bad news' is that this dwarf plantain clone of considerable interest and potential in Puerto Rico can show very severe BSV symptoms. The occurrence of BSV infection in tissu e culture-derived plants may be related to the presence of viral sequences integrated into the host genome, in which case there is no apparent strateg y to rid the clone of this 'virus'. (C) 1999 Elsevier Science B.V. All righ ts reserved.