DEVELOPMENT OF MICROSATELLITE MARKERS AND ANALYSIS OF GENETIC DIVERSITY AND POPULATION STRUCTURE OF SANDALWOOD (Osyris lanceolata Hochst. & Steud.) IN KENYA

Abstract

African sandalwood (Osyris lanceolata Hoscht and Steud) is a multipurpose and drought tolerant, African tropical hemi-parasitic tree species belonging to Santalaceae family. It is an evergreen dioecious shrub or small tree growing to a height of 1-7 meters depending on soil-type, climate and genetics of the tree. The species is valued globally for its essential oils used in perfumery and pharmaceutical industries. The increased demand for its essential oils and other products is bringing pressure to bear on the dwindling O. lanceolata populations and habitats in Kenya and East African region. due to overexploitation through anthropogenic activities that include illegal trade, overgrazing bush burning and destruction of host plant species for fuel wood, timber, charcoal burning and building materials. Consequently, the Convention on International Trades in Endangered Species (CITES) recently issued notification to review and gather information on the conservation status of O. lanceolata among other concerns. Although protected under CITES, the species continued to be heavily smuggled and overexploited. However, knowledge regarding the genetic diversity and population structure of the extant Kenyan populations, which is vital in informing conservation and sustainable management strategies of the species is still limited. Therefore, the aim of this work was to develop microsatellite (SSR) markers and use them to evaluate the genetic diversity and population structure of the species across the geographical distribution range in Kenya. A set of 12 polymorphic and five monomorphic microsatellite markers were developed and characterised using standard genome assembly, SSR identification and primer design protocols. Ten highly polymorphic microsatellite loci were used to characterise 288 individuals over ten natural populations, namely Baringo, Embu, Gachuthi, Gwasi, Kibwezi, Kitui, Makueni, Meru, Mau and Mt Elgon. The loci produced 178 alleles with a high Shannon’s Information index (I) values ranged from 0.805 to 1.6. The average observed heterozygosity across all loci varied from 0.112 to 0.815. A high level of genetic diversity was inferred from the genetic diversity parameters (He = 0.587, I = 1.302 and PPL = 97 %). The unweighted pair group method of arithmetic averages (UPGMA) and population structure analysis grouped these 288 individuals into two major groups. The AMOVA results indicated that 62% of the total genetic variation was found within populations, while only 38% was observed among populations. Evaluating genetic diversity is vital for identifying populations for conservation priority and establishing baseline data for informed conservation strategies at the local level. This study represents the first examination of the genetic diversity and population structure of O. lanceolata using SSR markers. The newly developed microsatellite markers will be valuable for future breeding programs and genetic studies aimed at formulating effective conservation plans.