Genetic Diversity and Population Structure of Ethiopian Chickpea (Cicer arietinum L.) Germplasm Accessions from Different Geographical Origins as Revealed by Microsatellite Markers

Genetic diversity and population structure were studied in 155 chickpea (Cicer arietinum L.) entries using 33 polymorphic microsatellite (SSR) markers. Molecular analysis of variance showed variations of 73% within and 27% among populations. Introduced genotypes exhibited highest polymorphism (70.27%) than the landraces (36-57%). Collections from Shewa, Harerge, W. Gojam and S. Gonder regions also showed higher polymorphism (50-57%) than the rest of the local accessions (36-45%). Analyses of pairwise population Nei genetic distance and PhiPT coefficients, expected heterozygosity (He) and unbiased expected heterozygosity (UHe), Shannon's information index (I) and percent polymorphism (% P) showed existence of high genetic variation between geographical regions. Accessions from adjoining geographical regions mostly showed more genetic similarities than those from origins far isolated apart. This could be associated with the ease and likelihood of inter-regional gene flow and seed movement particularly during times of drought. The 155 entries were grouped into five clusters following analysis of population structure. The first cluster (C-1) constituted accessions from Arsi; the second (C-2) from Gojam and Gonder; the third (C-3) from Harerge and E. and N. Shewa; and the fourth (C-4) from W. Shewa, Tigray, and Wello regions. The fifth cluster (C-5) was entirely consisted of improved genotypes. Improved genotypes of both Kabuli and Desi types distinctly fell into cluster five (C-5) regardless of their difference in seed types. The result has firmly established that introduction of genetic materials from exotic sources has broadened the genetic base of the national chickpea breeding program. Further implications of the findings as regards to chickpea germplasm management and its utilization in breeding program are also discussed.