Genetic diversity of selected kenyan eucalyptus species and their suitability as power transmission poles

Abstract

Eucalyptus is a genus in the Myrtaceae family that has many varieties of species. Among these species, Eucalyptus grandis, E. globulus, E. saligna and E. camaldulensis are majorly found in Kenya. E. grandis is the only species that is preferred for use as a source of power transmission poles. This species is known to mostly depend on high rainfall but due to global warming, there is insufficient rainfall making E. grandis to be unavailable hence the demand for this particular species is not met in electrification. There are other Eucalyptus species that occur naturally such as E. camaldulensis and E. globulus, and therefore it was important to carry out molecular phylogenetics and analyze the phenotypic traits of these other species to inform their use as power transmission poles in order to avoid the over exploitation of E. grandis. In this study, the phenotypic traits investigated included measuring tree height and diameter at breast height (DBH), while molecular data was obtained from sequences of MatK, RbcL and TrnL-F genes from the selected species. Evolutionary analyses such as nucleotide substitution rates, base composition disparity index, evolutionary divergence, nucleotide diversity indices and phylogeny construction were conducted in MEGA 11. Significant differences in DBH and height among Eucalyptus species were noted when the phenotypic data was analyzed using ANOVA (p≤0.05). The results obtained suggested that E.robusta, E.paniculata, E.maculata, E.dunnii, E. camaldulensis and E.citriodora might be used as power transmission poles but they are limited due to their shorter height (<30 meters). However, E. tereticornis and E. glaucina have the prefered DBH (18.3–28.3 cm) and height (>30 meters) and hence can be used as substitutes for E.grandis. Generally, the molecular phylogeny study suggested that most of the studied Eucalyptus species have a common ancestor because of the short genetic distances between them, low substitution rates and low nucleotide bias disparity index. The resulting phylogenetic trees will enhance knowledge on genetic relatedness of Kenyan Eucalyptus species as well as enhancing the efforts towards improvement and identification of known species with standard DBH and height for use as power transmission poles. Further studies involving more Eucalyptus species from various regions are needed to better understand the genetic diversity of the genus Eucalyptus and identify more species for use as alternative power transmission poles.