Genetic Diversity of Ethiopian Coffee (Coffea arabica L.) CollectionUsing SSR Marker

Abstract

Many studies reported wide genetic variability of Arabica coffee accessions collected from Ethiopia compared with commercial cultivars demonstrating the great potential of these accessions for future breeding purposes. However,little work has been done on the molecular genetic structure and diversity of Ethiopian Arabica coffee populations. Hence, this study was initiated with the objective of studying the genetic diversity of Coffea arabica populationscollected from different regions of Ethiopia using SSR markers. A total of 20 SSR markers were used to genotype 86 accessions and produced a total of 112 alleles, ranging from 3 to 11 with an average of 5.6 alleles per locus.All the loci across the entire populations were found to be highly polymorphic and informative with PIC values ranging from 0.45 to 0.75 with a mean of 0.6 confirming the good discriminatory power of the SSR loci used.Average observed heterozygosity andallelic richness across all populations ranged from (0.22-0.27 and 3.52-4.26), with a mean of 2.43 and 3.97, respectively. AMOVA showed 63% of the variation to be within populations, 33% among individuals within populations and 4% among population based on geographical origin.The smallerFst (0.037) observed indicates the presence of lower population geneticdifferentiation as a result of higher gene flow (Nm =2.45) between the C. arabica populations. The lowest mean genetic distance observed between C. arabica populations was 0.21. The populations from Bale and Hararge were highly distant from other populations.The unweighted pair group methods with arithmetic meanbased cluster analysis and principal coordinate analysis poorly grouped the individuals into distinct clusters confirming the presence of population admixture due to the long distance movement of C. arabica seeds and high gene flow among populations of adjacent geographical regions. The observed higher genetic variability in all populations indicates that the country has huge coffee genetic diversity which can serve coffee improvement.Comparatively, the populations from Omo, Ilubabor and Benchi Maji were more diverse than other populations. Thus, special attention on these populations may be useful in future Coffea arabica breeding program, germplasm conservation.