Spatial and Temporal Genetic Variation in Ethiopian Barley (Hordeum
vulgare L.) Landraces as Revealed by Simple Sequence Repeat (SSR)
Markers
Abstract
Ethiopia is a center of diversity for barley (Hordeum vulgare L.) and it
is grown across different agro-ecologies of the country. Unraveling
population structure and gene flow status on temporal scales assists an
evaluation of the consequences of physical, demographic as well as
overall environmental changes on the stability and persistence of
populations. Here, we examine spatial and temporal genetic variation
within and among barley landrace samples collected over a period of four
decades (1976-2017), using simple sequence repeat (SSR) markers. Our
objective was to evaluate spatial and temporal changes in barley
population connectivity associated with the closure of geographic origin
and time periods. Low to strong genetic diversity was observed among the
landraces and STRUCTURE, Neighbour joining tree and Discriminant
Analysis of Principal Component analysis revealed three clusters. The
cluster analysis revealed a close relationship between landraces along
geographic proximity with genetic distance increases along with
geographic distance. The grouping of landraces based on altitudinal
classes was influenced by geographic proximity. From AMOVA year
categories, it was observed that within population genetic diversity
much higher than between population genetic diversity and that the
temporal differentiation is considerably smaller. The low to strong
genetic differentiation between landraces from various geographic
origins could be attributed to gene flow across the region as a
consequence of seed exchange among farmers. Nevertheless, we found some
connectivity between changes in population dynamics as well as
contemporary gene flow. The results demonstrate that this set of SSRs
was highly informative and was useful in generating a meaningful
classification of barley germplasms. Furthermore, our data also suggest
that landraces are a source of valuable germplasm for sustainable
agriculture in the context of future climate change, and that in-situ
conservation strategies based on farmers use can conserve the genetic
identity of landraces while allowing adaptation to local-environments.