Six species of Eucalyptus viz., E. alba, E. camaldulensis, E. microtheca, E. tereticornis, E. polycarpa and E. torelliana, were subjected to full diallel mating. The cross between E. polycarpa and E. torelliana was characterised by post-fertilization abortion. An evaluation of the remaining four parents and 12 hybrids revealed that characters like height, DBH, leaf number and leaf breadth were free from epistatic interaction. For characters like internode length and leaf length, non-allelic interaction was manifest. The magnitude of dominant genes was high for most characters indicating the promise of heterosis breeding for these traits. Symmetrical distribution of positive and negative genes was inferred. The number of genes that control the characters was one for collar diameter and leaf length, two for height and internode length and three for leaf breadth. Narrow sense heritability was high for all the attributes, barring internode length.
Eucalyptus, GCA, genetic interactions, SCA, diallele mating, heritability
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