Genetic Diversity and Population Structure Analysis of Noug (Guizotia Abyssinica) Accessions Collected from Ethiopia Using Microsatellite Markers

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Addis Ababa University


Abstract Noug (Guizotia abyssinica) is an Ethiopian indigenous oilseed crop cultivated primarily for its oil and various economic importances. Its production and productivity is very low due to different constraints. The crop has receiveda littleattention in implementing improvement programs and until very recently remained as underutilized oilseed crop. Crop improvement requires the availability and understanding of the genetic resource in terms of genetic variation and population structure.However, estimationofgenetic diversity of Noug with a wider representation of Ethiopia’s Noug growing regions using reliable molecular marker such as, microsatellite markers are rare. Thus, this study was aimed to uncover the extent of genetic diversity and population structure of 161 Noug genotypes collected from Ethiopia using 13 microsatellite markers. The analysis revealed a total of 158 alleles generated with a mean of 12.15 per locus. All the 13 microsatellite markers were polymorphic and highly informative with a mean polymorphic information content (PIC) value of 0.82. The genetic diversity indices across the 14 collection regionsindicated the presence of higher genetic variability among genotypes; including the Shannon’s information index (I) which ranged from 0.89 to 1.26 with a mean value of 1.57. Observed heterozygosity (Ho), expected heterozygosity or gene diversity (He), unbiased expected heterozygosity (uHe) was0.17, 0.74, and 0.79, respectively. Genotypes from Shewa, Wollo, Gojjam, Tigray and Benishangul Gumuz (B/G), shared the highest in both expected hetrozygosity or gene diversity and unbiased expected heterozygosity. Individuals in the populations had a fixation index (F) ranging from 0.67 to 0.80, with a mean of 0.77. The percentage of polymorphic loci (%Pl) in all the populations showed the highest (100%) and lowest (94.33%) with a mean of 99.19%.The pairwise Nei’s genetic distance showed the highest between Eritrea and Bale (0.892) followed by Eritreaand Illubabor (0.875).AMOVA revealed that 96.06% of the total genetic variation was attributed to within populations while only 3.94% was attributed to among populations, indicatingthat the highest variation was between genotypes rather than variation due to geographic distances. The NJ or UPGMA cluster and PCOA poorly grouped the genotypes based on their origin indicating high gene flow or seed exchange across geographic regions.Furthermore, the model-based population structureanalysis weakly inferred the predefinedpopulations into K=2 withconsiderable genetic admixture among tested populations.In conclusion,the microsatellites used in the present study are highly informative and could be used in future marker assisted breeding. Genotypes from Shewa, Wollo, Gojjam, Tigray and B/G are identified as hotspot areas for their high genetic diversity. They also showed the highest number of private alleles in which special focus should be given in these areas to implement breeding and future improvement programs. Key words/Phrases; Cluster analysis, Gene flow, Heterozygosity, hotspots, SSR Markers



Cluster analysis,, Gene flow,, Heterozygosity,, Hotspots,, SSR Markers