Morphological analysis to identify the pollen parent of an ornamental interspecific hybrid eucalyptus

Abstract

Eucalyptus ‘Urrbrae Gem’ is an attractive amenity tree which is believed to be a spontaneous F1 hybrid with Eucalyptus erythronema var. erythronema the known female parent. Previous observations based on adult morphology led to suggestions that either E. gomphocephala or E. stricklandii could be the male parent. Multivariate analysis of 54 adult morphological characters placed E. ‘Urrbrae Gem’ between E. erythronema var. erythronema and E. stricklandii, with minimum spanning tree values of 0.21 and 0.27, respectively. Controlled hybridisation between E. erythronema var. erythronema and both E. stricklandii and E. gomphocephala were undertaken, and the resulting seedlings were compared to each other, and to open pollinated seedlings of the putative parent species and of the F1 and second generation E. ‘Urrbrae Gem’ trees. Based on 14 morphological characters, seedlings clustered into eight groups, with E. erythronema var. erythronema × E. stricklandii seedlings most similar to open pollinated seedlings of the F1 and second generation E. ‘Urrbrae Gem’ trees. In contrast, E. erythronema var. erythronema × E. gomphocephala seedlings clustered into a number of groups, with the majority close to E. gomphocephala open pollinated seedlings. The results indicated that E. stricklandii is the male parent of E. ‘Urrbrae Gem’.