The potential for hybridization among three species of Eucalyptus L'Hér in the Series Macrocarpae, E. macrocarpa Hook (Mottlecah), E. pyriformis Turcz. (pear-fruited mallee), and E. youngiana F. Muell. (large-fruited mallee), was investigated using molecular data generated by randomly amplified polymorphic DNA (RAPD)-polymerase chain reaction (PCR) analysis. Samples of DNA from seedlings derived from controlled pollinations, and from different individuals from each species, were amplified with six different 10-mer primers. The presence or absence of RAPD fragments was used to generate a dendrogram based on genetic similarity, an ordination derived by multidimensional scaling (MDS), and a minimum spanning tree (MST) to show the relative links and dissimilarities between the individuals tested. Two clusters were identified on the unweighted pair-group method arithmetric average dendrogram. The first included all of the E. macrocarpa genotypes and all but one of the E. macrocarpa hybrids. The second included all of the E. youngiana and E. pyriformis genotypes and their hybrids. The MDS ordinations placed the hybrid seedlings between the parent species. From the 30 progeny investigated, 28 were assessed from the molecular data to be hybrids from controlled pollinations. The remaining two seedlings appeared to be derived from self-pollination. The parentage of two mature trees, thought to be natural hybrids involving the three species, was also investigated. One was confirmed as a cross between E. youngiana and E. pyriformis, but the second was less certain because of its low genetic similarity to all other individuals, and may be a hybrid involving species not included in this study.
Kirsty Neaylon, Kate L. Delaporte, Margaret Sedgley, Graham G. Collins and John G. Conran
Jenny R. Guerin, Susan M. Sweeney, Graham G. Collins and Margaret Sedgley
The National Olive Variety Assessment (NOVA) collection, established at the Roseworthy Campus of the University of Adelaide, contains six replicate trees of 100 olive (Olea europaea L.) accessions grown in the same environment. The DNA fingerprints of these accessions were compared, using randomly amplified polymorphic DNA (RAPD), to those of a number of cultivars obtained from international collections. A total of 86 uniquely named accessions in the NOVA collection resulted in 58 different genotypes. Different names were synonyms for the same genotype, and homonyms were also found where accessions with the same name had different DNA fingerprints. A rapid and efficient protocol was developed to identify unknown olive genotypes using a two-stage process. Data from DNA fingerprints were added to a matrix already containing binary data from recognized standard cultivars. The estimated probability of any given RAPD profile randomly occurring at this stage ranged between 6 × 10-4 and 2 × 10-8. In the second stage, the approximate identity of the unknown genotype, revealed by the resulting dendrogram, was confirmed by comparing it with appropriate standards under identical conditions of DNA amplification and band separation. The data collected in this report form the basis of a genetic database that can be used for the identification of olive samples.