KENNEDY NG’ANG’A WANGUI

Boswellia sacra is a frankincense-producing tree found in the Arabian Peninsula that includes Oman and southern Somaliland (Northern Somalia). In Somaliland, it is mainly distributed in the Sanaag region including Cel Afweyn where many families depend on its value chain for a living. There is a high global demand for frankincense gums and resin products due to its medicinal, cultural and cosmetic importance leading to overexploitation of existing stands, leading to failure of trees to regenerate attributed to excessive tapping on tree barks causing damage that increases pest and disease infestation. The establishment of the species is hindered by the poor seed germination rate as well as grazing of young seedlings by both wildlife and livestock. This study sought to address the decrease in B. sacra numbers through regeneration via tissue culture and avail information on genetic diversity of two B. sacra populations in Af yare Dawl-dawl and Exdad in Somaliland for conservation and germplasm enhancement. Seed viability was determined by germination rate and tetrazolium tests, which revealed 4.15 % germination rate and 3.3% viability. These values were low but comparable to previously reported percentages of less than 10%, due to lack of viable embryos attributed to self-incompatibility within the species and high tapping frequency. Clonal propagation using tissue culture applied leaf and axillary bud explants for direct and indirect in-vitro regeneration using plant growth regulators, such as TDZ, BAP, NAA, in efforts to develop a micropropagation protocol for mass propagation. Direct in-vitro regeneration did not produce any regenerants while indirect regeneration produced callus on MS media containing 5 µm TDZ. Somatic embryogenesis was initiated in MS media containing 1 µm BAP+ 0.25 µm IAA, where shoot regenerants were produced. Genetic diversity determined using morphological and molecular markers to establish diversity within and between germplasm to enhance breeding programs. Morphological characterization of B. sacra genotypes from Exdad and Af Yare Dawl-dawl had no significant (p>0.05) differences in height, height to branching, number of stems and tree bottom swelling, however, stem type was strongly correlated to height. Hierarchical cluster analysis of principle components extracted from morphological data revealed two main clusters each with two sub-clusters with genotypes from both regions distributed within these clusters, thereby showing high similarity. Molecular characterization was done on Af Yare Dawl-dawl genotypes using SRAP markers and they revealed very low heterozygosity, He=0.053, indicative of very low genetic diversity. PCoA analysis of pairwise genetic distance matrix led to formation of three major clusters with 35.14%, 11.42% and 9.08% variation, indicating existence of three major groups of genotypes with different parentage. This variation indicates that genotypes from the different clusters can be used as progenitors for hybridization and domestication purposes. Low genetic diversity observed calls for urgent conservation measures of the tree species as well as introductions from other areas to enhance the germplasm found in Af Yare Dawl-dawl. Breeding programs for enriching genetic diversity in the study area should be initiated since the current population is faced with the threat of extinction should a sudden environmental change occur. Sustainable frankincense harvesting practices should be enforced to ensure sustainable exploitation of this important resource.

kennnganga@students.uonbi.ac.ke