Abstract:
Genus Eucalyptus belongs to the family Myrtaceae and consists of more than 900 species,
various hybrids and varieties. The major species that are grown in Kenya are Eucalyptus grandis,
E. globulus, E. saligna and E. camaldulensis. Most Eucalyptus species are highly dependent on rainfall
and this is challenged by climatic changes owing to global warming making it difficult to effectively
match the availability of mature trees and the market demand especially for use as power transmission
poles. With the widespread availability of other naturally occurring Eucalyptus species such as
E. camaldulensis and E. globulus, it becomes important to determine the genetic diversity and to
analyze the phenotypic traits of these species for suitability as power transmission poles in order to
counter the overdependence on E. grandis. Phenotypic traits investigated included measuring total
tree height and diameter at breast height (DBH), while molecular data were obtained from sequencing
MatK, rbcL and TrnL-F genes from selected species and evolutionary analyses such as nucleotide
substitution rates, base composition disparity indices, evolutionary divergence, nucleotide diversity
indices and phylogeny construction were conducted in MEGA 11. Significant differences in DBH
and height among Eucalyptus species were observed when the phenotypic data were subjected to
ANOVA. In this study, E. robusta, E. paniculata, E. maculata, E. dunnii, E. camaldulensis and E. citriodora
are fit to be used as power transmission poles but they are limited by their short height. However,
E. tereticornis and E. glaucina have the desired DBH and height and hence can be used as substitutes
for E.grandis. Generally, the molecular phylogeny study has shown that the studied Eucalyptus
species are closely related and form various monophyletic clades which can be attributed to the short
genetic distances, low substitution rates, low nucleotide bias disparity indices and low diversity
scores. Further phylogenetic and gene expression studies involving more Eucalyptus species are
needed to better understand Eucalyptus phylogeny, and diversity and identify species with similar
genetic make-up to that of E. grandis which has been used extensively for the provision of electricity
transmission poles.
