Natural and culture-induced genetic variation in plantains (Musa spp. AAB group)

Random amplified polymorphic DNA (RAPD) analysis of 15, mostly African, pla ntain land races revealed a very low proportion of polymorphic bands (13 of 276). However, further examination of these 13 marker bands demonstrated t hat they varied within land races and could not be used to distinguish betw een land races. In many cases, this could be directly associated with tissu e culture treatment of the material. In order to investigate tissue culture effects in more detail, a single meristem of the West African plantain Agb agba was introduced into axenic culture and subjected to three cycles of mi cropropagation. A total of 48 regenerated plants were established under fie ld conditions and subjected to RAPD analysis. By using 40 arbitrarily selec ted primers, about 400 bands were scored across this population of in vitro -derived plants. Sixteen of the bands were polymorphic within the populatio n of Agabgba plants, distinguishing 13 genotypes. The pattern of relationsh ips of these genotypes was established by cluster analysis; field character isation of the plants supported the relationships revealed by RAPD data. Th e high level of RAPD polymorphism (4% of bands polymorphic), along with a c lear correlation between the genotypic classification of individual plants and their tissue culture pedigree, suggests that a substantial amount of ge netic variation existed within the original cultured meristem. On this basi s, a putative Agbagba meristem representing an apparent sectoral chimera ha s been constructed. A model is presented that takes account of the persiste nce and high rate of somaclonal variation and proposes that the mother Agba gba plant comprised a periclinal chimera.