Use of Genetic Markers in the Management of Micropropagated Eucalyptus Germplasm

Clonal propagation through rooted cuttings and micropropagation is widely used for large-scale Eucalyptus plantation program because of its ability to fix the desirable traits of mature plus trees. However, when a large number of clones are handled, variations and mixings are commonly confronted which may go undetected in the absence of prominent morphological descriptors. Material from germplasm resources are also used in breeding program. The economic implications of such inadvertent variations could be serious as considerable time and money is spent before the mistakes are detected. This paper reports the identification of mislabeling in Eucalyptus clones maintained through tissue culture, and the reestablishment of the identity of the mislabeled clones using genetic markers viz., RAPDs/AFLPs. The in vitro propagated Eucalyptus plants from two groups, group 1 derived directly from SMD7 (a candidate plus tree), and group 2 derived from coppice shoots of trees of group 1, were assessed for their genetic uniformity using RAPD markers. The small intra-group genetic variations of 0.02 in the second group were attributed to somaclonal variations induced during long culture periods. However, the genetic distances of 0.20 and 0.31 between SMD7 and the two micropropagated groups were too high to be attributed to somaclonal variations as axillary bud culture was used for micropropagation. To test the possibility of inadvertent mixing, RAPD profiles of the micropropagated groups were compared with that of other clones in the tissue-cultured Eucalyptus germplasm. The RAPD profiles of group 2 plantlets matched with that of another unrelated clone in the germplasm. The authenticity of this donor was further re-established using AFLP markers.