Adaptation and diversity along an altitudinal gradient in Ethiopian barley (Hordeum vulgare L.) landraces revealed by molecular analysis

<p>Abstract</p> <p>Background</p> <p>Among the cereal crops, barley is the species with the greatest adaptability to a wide range of environments. To determine the level and structure of genetic diversity in barley (<it>Hordeum vulgare </it>L.) landraces from the central highlands of Ethiopia, we have examined the molecular variation at seven nuclear microsatellite loci.</p> <p>Results</p> <p>A total of 106 landrace populations were sampled in the two growing seasons (<it>Meher </it>and <it>Belg</it>; the long and short rainy seasons, respectively), across three districts (Ankober, Mojanawadera and Tarmaber), and within each district along an altitudinal gradient (from 1,798 to 3,324 m a.s.l). Overall, although significant, the divergence (e.g. F_ST) is very low between seasons and geographical districts, while it is high between different classes of altitude. Selection for adaptation to different altitudes appears to be the main factor that has determined the observed clinal variation, along with population-size effects.</p> <p>Conclusions</p> <p>Our data show that barley landraces from Ethiopia are constituted by highly variable local populations (farmer's fields) that have large within-population diversity. These landraces are also shown to be locally adapted, with the major driving force that has shaped their population structure being consistent with selection for adaptation along an altitudinal gradient. Overall, our study highlights the potential of such landraces as a source of useful alleles. Furthermore, these landraces also represent an ideal system to study the processes of adaptation and for the identification of genes and genomic regions that have adaptive roles in crop species.</p

Adaptation and diversity along an altitudinal gradient in Ethiopian barley (<i>Hordeum vulgare</i> L.) landraces revealed by molecular analysis

Background. Among the cereal crops, barley is the species with the greatest adaptability to a wide range of environments. To determine the level and structure of genetic diversity in barley (Hordeum vulgare L.) landraces from the central highlands of Ethiopia, we have examined the molecular variation at seven nuclear microsatellite loci. Results. A total of 106 landrace populations were sampled in the two growing seasons (Meher and Belg; the long and short rainy seasons, respectively), across three districts (Ankober, Mojanawadera and Tarmaber), and within each district along an altitudinal gradient (from 1,798 to 3,324 m a.s.l). Overall, although significant, the divergence (e.g. FST) is very low between seasons and geographical districts, while it is high between different classes of altitude. Selection for adaptation to different altitudes appears to be the main factor that has determined the observed clinal variation, along with population-size effects. Conclusions. Our data show that barley landraces from Ethiopia are constituted by highly variable local populations (farmer's fields) that have large within-population diversity. These landraces are also shown to be locally adapted, with the major driving force that has shaped their population structure being consistent with selection for adaptation along an altitudinal gradient. Overall, our study highlights the potential of such landraces as a source of useful alleles. Furthermore, these landraces also represent an ideal system to study the processes of adaptation and for the identification of genes and genomic regions that have adaptive roles in crop species

Molecular variation along an altitude gradient in Ethiopian barley landraces

To determine the level and pattern of genetic variation in barley (Hordem vulgare L.) landraces from North Shewa zone, in the central highlands of Ethiopia, the genetic variability at seven nuclear microsatellite loci was examined. Analysis was carried out on a total of 106 landrace populations sampled in two growing seasons (Meher and Belg, the long and short rainy season, respectively), across three districts (Ankober, Mojanawadera and Tarmaber), and, within each district, all along an altitudinal gradient (from 1798 to 3324 m a.s.l). Genetic variation has been ascribed to differences between altitudinal classes (FST = 0.10) more than between seasons or among districts (FST = 0.02). The most relevant outcome of the experiment is that altitude level largely overrides geographical distance as main cause of divergence among individual plants. Moreover, results also suggest that the patterns of clinal variation among districts and seasons are inconsistent with a simple model drift and dispersal (seed exchange). They suggested instead a role for historical patterns of colonization, or, alternatively, present-day selective forces acting on some of the SSR analysed

Genetic diversity and cline of variation in barley landraces from the central highlands of Ethiopia

Ethiopia is a secondary centre of diversity for barley (Hordeum vulgare L.), where barley is the third most important cereal crop. In several regions of Ethiopia, barley is often grown in two different planting seasons per year: during the long rainy season (Meher), and during the short rainy season (Belg). To determine for the first time the role of this ‘two-season-system’ on the structure of the genetic diversity of barley landraces, we performed an analysis of a hierarchical collection of barley (seasons, districts within seasons, altitude classes within districts) from North Shewa, in the central Highlands of Ethiopia. Overall, 106 landrace populations were analysed, using both morphological (8 traits, 3,170 genotypes) and molecular (7 SSR, 212 genotypes) markers. The divergence between the populations collected in the Meher and Belg seasons was very limited. The genetic variation was ascribed to differences between altitude classes rather than between seasons or among districts. The altitude largely overrides geographical distance as the main cause of divergence among individual genotypes. These results are discussed particularly in the context of the exploitation of these landraces for plant breeding and genetic analysis