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Title: Geography of genetic differentiation in the barley wild relative Hordeum vulgare subsp. spontaneum in Jordan

Author
item THORMANN, IMKE - Bioversity International
item Reeves, Patrick
item Reilley, Ann
item ENGELS, JAN - Bioversity International
item LOHWASSER, ULRIKE - Leibniz Institute Of Plant Genetics And Crop Plant Research
item BOERNER, ANDREAS - Leibniz Institute Of Plant Genetics And Crop Plant Research
item PILLEN, KLAUS - Martin Luther University
item Richards, Christopher

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/25/2016
Publication Date: 7/11/2016
Citation: Thormann, I., Reeves, P.A., Reilley, A.A., Engels, J.M., Lohwasser, U., Boerner, A., Pillen, K., Richards, C.M. 2016. Geography of genetic differentiation in the barley wild relative Hordeum vulgare subsp. spontaneum in Jordan. PLoS One. DOI:10.1371/journal.pone.0160745.

Interpretive Summary: To make efficient genetic resource collections, plant collectors must add novel diversity without duplicating materials already in the collection. Hence, they need guidelines to determine what is and isn’t novel, especially when collecting from the wild. It is often assumed that diversity among wild plant populations increases with geographic distance or with environmental gradients, such as rainfall or minimum winter temperature. In other words distant populations are assumed to represent novel diversity. Several genebanking approaches use this assumption and layers of geographic data to infer gaps in collections. This study carefully examines the assumption in natural populations of wild barley in Jordan. Our results indicate that genetic diversity of wild barley populations do not correlate with environmental distance or environments gradients. This result suggests a limited role for the use of ecogeographic features as a proxy for genetic diversity in some plant genetic resources collections. Populations of wild barley were highly influenced by anthropogenic disturbance, which introduces the question of whether poor correlations between diversity and geographic distance occurs in other crop wild relatives and among species with no history of domestication.

Technical Abstract: Informed collecting, conservation, monitoring and utilization of genetic diversity require knowledge of the distribution and structure of genetic variation occurring in a species. Hordeum vulgare subsp. spontaneum (K. Koch) Thell., a primary wild relative of barley, is an important source of genetic variation for barley improvement and co-occurs with domesticated barley within the center of origin. We studied the current geography of genetic diversity and magnitude of genetic differentiation in H. vulgare subsp. spontaneum in Jordan and investigated whether genetic differentiation is correlated with either spatial or environmental variation. The genetic structure of 32 populations collected in 2012 was analyzed using 37 SSRs. Three genetic clusters were identified, including a small southern cluster and two clusters distributed longitudinally in the northern part of the study area. Populations were characterized by admixture and high allelic richness and genetic diversity was concentrated in the northern part of the study area. Correlation analyses between geographical, environmental and genetic distances did not reveal significant correspondence between environmental variation and genetic structure. H. vulgare subsp. spontaneum thrives predominantly in ruderal habitats and field edges. We suggest that genetic diversity in this species in Jordan is shaped not only by natural diffusion but by other mechanisms such as anthropogenic disturbance and dispersal that can act to decouple genetic variation from environmental or geographic variation. This result suggests a limited role for the use of ecogeographic features as a proxy for genetic diversity in some plant genetic resources collections.