Genetic Diversity of Avocado (Persea americana Mill) From Southern Ethiopia Using SSR Markers

Abstract

Background: Avocados are a cash crop in Ethiopia. However, its genetic diversity has not been investigated. This study explored the genetic diversity of avocados in southern Ethiopia using SSR markers. Method and Result: One hundred nine avocado trees were sampled in sixteen districts. One hundred forty alleles were detected across the 12 loci. The average number of alleles per locus was 11.7. The average expected and observed heterozygosity was 0.63 ± 0.12 and 0.48 ±0.19, respectively. All loci showed a significant deviation from HWE. The analysis of molecular variance showed that about 5% of the variation was among the sixteen populations. Pairwise comparisons of population FST values revealed a lack of genetic differentiation for seven out of 48 paired comparisons. UPGMA based on Nie and Li similarity index, classified the genotypes into three major classes with 100 and 53 bootstrap values. Genetic distance analyses showed a mixing of avocado trees from different districts. DAPC divided the tree samples into three groups, while the model-based STRUCTURE subdivided the tree samples into two major genetic clusters. Conclusion: Moderate diversity was detected in the analyzed avocado germplasm. These imply, the germplasms are a valuable source of alleles for genetic improvement in Ethiopia. The mixing of avocado trees from different districts observed in UPGMA tree, DAPC, and STRUCTURE analysis. This indicated strong gene flow among the avocado populations. There is, however, significant variation among the tree populations from different districts to be used in the avocado breeding program.