Genomic Variation in Micropropagated Robinia ambigua `idahoensis' Revealed by RAPD Markers

Abstract

The authors have previously reported an efficient in vitro system for mass micropropagation of Robinia ambigua `idahoensis' (Idaho locust). Their method used enhanced branching of axillary buds from a single donor plant along with detection of somaclonal variation by the intersimple sequence repeat (ISSR) markers. Because ISSRs tend to be clustered to specific chromosomal regions in plant genomes, the extent and scope of the genomic variations and the sequences underlying the variation warranted further investigations. In this study, the authors analyzed the same set of 40 randomly selected micropropagated R. ambigua plants by a more general molecular marker—random amplified polymorphic DNA (RAPD) using 34 selected primers. In addition, they sequenced some of the variable bands. Of the 260 reproducible RAPD bands scored, 70 were polymorphic among the 41 plants (40 micropropagated and one donor), corresponding to a polymorphism level of 26%. Cluster analysis revealed a genetic similarity ranging from 0.61 to 0.97. Of the 20 sequenced bands underlying the variations, eight showed significant homology to known or predicted functional cellular genes or retroelements. These results clearly indicated that micropropagation of R. ambigua, even by enhanced branching of axillary buds, can be accompanied by extensive genomic variations, which should be taken into account for commercial propagation of this plant by in vitro means.