Assessment of genetic divergence in eucalyptus tereticornis, sm using physiological parameters

Eucalyptus tereticornis is a fast-growing, hardwood species commercially planted as a source of paper pulp and timber. The species has been introduced in India to meet the ever increasing demand for paper pulp and the species shows excellent adaptability in the Indian soils. There is large amount of variability exists in the species but only a few efforts have been made to assess the genetic divergence of this species using physiological parameters. The present study was undertaken to assess the genetic divergence, heritability and genotype clustering of thirty eight clones of Eucalyptus tereticornisin order to cluster elite clones for future hybridization programmes and to sort out inferior clones which need further genetic improvement. The results showed that significant differences in net photosynthetic rate (Pn), stomatal conductance (gs), internal CO2 concentration (Ci), transpiration rate (E), intrinsic wue, instantaneous wue, intrinsic carboxylation efficiency and intrinsic mesophyll efficiency. All the selected parameters showed good heritability values. PCA showed that intrinsic carboxylation efficiency contributed maximum to the genetic divergence followed by intrinsic mesophyll efficiency. D2 analysis revealed seven clusters of which cluster II and III had elite clones while inferior clones in other clusters. The cluster analysis would definitely help the tree breeders for the selection of genetically divergent parents in order to achieve heterosis in hybrids.