Genetic diversity of populus ilicifolia populations in Kenya using amplified fragment length polymorphism (AFLP) markers.

Many species in the genus Populus and their hybrids are economically valuable, fast growing, short rotation woody trees for producing wood, fiber, and biofuels, as well as sequestering atmospheric carbon in large plantations and agroforestry settings. Industrial facilities to produce liquid transportation fuels from Poplar feedstock are currently being built in the USA. Populus ilicifolia locally known as Tana River Poplar is the only species in the Populus genus that falls within the tropics. It occurs in river valleys of Tana, Athi and Ewaso Nyiro in Kenya. P. ilicifolia is an endangered species threatened by massive felling by humans, floods and destruction by large herbivores. As such the species populations have become decimated to IUCN vulnerable status. Unlike its relatives in Americas, Europe and Asia, P. ilicifolia has received very little attention for utilization and conservation. Incorporating this species into on-going tree improvement and genomics research on temperate Populus species is expected to have tremendous economic and scientific benefits to Kenya. Genetic diversity studies using DNA markers have become very crucial in the conservation of tree species that are endangered. The objective of this study was to assess the genetic variation and heterozygosity of four Populus populations from Kenya and show the genetic relatedness between Kenyan P. ilicifolia and Poplar reference samples from USA by employing Amplified Fragment Length Polymorphism (AFLP) with the aim of providing important information for improvement and in situ/ex situ conservation of this species. Leaf samples were collected from three locations along the species natural ranges (i.e. Athi, Ewaso Nyiro and Tana Rivers), Muguga KEFRI (planted) and 10 reference samples from the USA were provided. Six AFLP primer combinations that provided clear and polymorphic bands were used for the analysis. Fragments were resolved using capillary electrophoresis (ABI 3730 DNA analyzer). A sum total 521 bands in the range of 100500 base pairs were produced. GenALEx 6.5 was used to reveal the partitioning of variation within and among the populations. Genetic diversity estimates were computed using TFPGA software. The percentage polymorphic loci results were lowest in Ewaso Nyiro population recording 23.80% and Athi population 65.26% which was the highest among the three natural populations. The average Heterozygosity across the populations was between 0.09 and 0.4. According to AMOVA results, there was more genetic variation partitioning within population 60% (P<0.001) than among populations 40% (P<0.001) thus there was a significant variation between populations genetically. UPGMA clustering in form of a dendogram showed two clusters in accordance with their geographical origin where Tana, Athi and Ewaso Nyiro populations clustered together as opposed to the reference samples and KEFRI population. The study showed that Athi population is more diverse than any other Kenyan population and can be used for improvement studies, domestication and conservation of P. ilicifolia.