Marques Isabel, Shiposha Valeriia, López-Alvarez Diana, Manzaneda Antonio J, Hernandez Pilar, Olonova Marina, Catalán Pilar
Departamento de Ciencias Agrarias y del Medio Natural, Escuela Politécnica Superior de Huesca, Universidad de Zaragoza, Ctra. Cuarte km 1, 22071, Huesca, Spain.
Department of Botany, Institute of Biology, Tomsk State University, Lenin Av. 36, Tomsk, 634050, Russia.
BMC Evol Biol. 2017 Jun 15;17(1):139. doi: 10.1186/s12862-017-0996-x.
Brachypodium distachyon (Poaceae), an annual Mediterranean Aluminum (Al)-sensitive grass, is currently being used as a model species to provide new information on cereals and biofuel crops. The plant has a short life cycle and one of the smallest genomes in the grasses being well suited to experimental manipulation. Its genome has been fully sequenced and several genomic resources are being developed to elucidate key traits and gene functions. A reliable germplasm collection that reflects the natural diversity of this species is therefore needed for all these genomic resources. However, despite being a model plant, we still know very little about its genetic diversity. As a first step to overcome this gap, we used nuclear Simple Sequence Repeats (nSSR) to study the patterns of genetic diversity and population structure of B. distachyon in 14 populations sampled across the Iberian Peninsula (Spain), one of its best known areas.
We found very low levels of genetic diversity, allelic number and heterozygosity in B. distachyon, congruent with a highly selfing system. Our results indicate the existence of at least three genetic clusters providing additional evidence for the existence of a significant genetic structure in the Iberian Peninsula and supporting this geographical area as an important genetic reservoir. Several hotspots of genetic diversity were detected and populations growing on basic soils were significantly more diverse than those growing in acidic soils. A partial Mantel test confirmed a statistically significant Isolation-By-Distance (IBD) among all studied populations, as well as a statistically significant Isolation-By-Environment (IBE) revealing the presence of environmental-driven isolation as one explanation for the genetic patterns found in the Iberian Peninsula.
The finding of higher genetic diversity in eastern Iberian populations occurring in basic soils suggests that these populations can be better adapted than those occurring in western areas of the Iberian Peninsula where the soils are more acidic and accumulate toxic Al ions. This suggests that the western Iberian acidic soils might prevent the establishment of Al-sensitive B. distachyon populations, potentially causing the existence of more genetically depauperated individuals.
短柄草（禾本科）是一种一年生对铝敏感的地中海草本植物，目前被用作模式物种，以提供有关谷类作物和生物燃料作物的新信息。该植物生命周期短，是禾本科中基因组最小的物种之一，非常适合进行实验操作。其基因组已被完全测序，并且正在开发多种基因组资源以阐明关键性状和基因功能。因此，所有这些基因组资源都需要一个能反映该物种自然多样性的可靠种质库。然而，尽管它是一种模式植物，我们对其遗传多样性仍然知之甚少。作为克服这一差距的第一步，我们使用核简单序列重复（nSSR）来研究在伊比利亚半岛（西班牙）其最著名的地区之一采集的14个短柄草种群的遗传多样性模式和种群结构。
我们发现短柄草的遗传多样性、等位基因数量和杂合度水平非常低，这与高度自交的系统一致。我们的结果表明至少存在三个遗传簇，为伊比利亚半岛存在显著的遗传结构提供了额外证据，并支持该地理区域作为一个重要的遗传库。检测到几个遗传多样性热点，生长在碱性土壤上的种群比生长在酸性土壤上的种群明显更加多样化。部分Mantel检验证实，在所有研究种群中存在统计学上显著的距离隔离（IBD），以及统计学上显著的环境隔离（IBE），揭示了环境驱动的隔离是伊比利亚半岛发现的遗传模式的一种解释。
在伊比利亚半岛东部碱性土壤中出现的种群具有更高遗传多样性这一发现表明，与伊比利亚半岛西部地区那些土壤酸性更强且积累有毒铝离子的种群相比，这些种群可能具有更好的适应性。这表明伊比利亚半岛西部的酸性土壤可能会阻止对铝敏感的短柄草种群的建立，可能导致存在更多遗传上贫乏的个体。
