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 leaf temperature and diffusive resistance were free from epistatic interaction. For the characters PAR, non-allelic interaction was obserrved. Leaf temperature was shown to be under the influence of predominantly dominant gene action. Predominance of additive gene action was evident in respect of diffusive resistance and transpiration rate. The gene distribution among the parents was observed to be unequal with greater frequencies of dominant allels for PAR and diffusive resistance. The number of genes that control the characters was one for leaf temperature, PAR and transpiration rate and two for diffusive resistance. Narrow sense heritability was low for all the attributes.
diallel mating, Eucalyptus, genetic analysis, gene action, physiological traits, tree breeding
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