Abstract
Assessment of genetic diversity and population structure in crops is essential for breeding and germplasm conservation. A collection of 354 bread wheat genotypes, including Mediterranean landraces and modern cultivars representative of the ones most widely grown in the Mediterranean Basin, were characterized with 11196 single nucleotide polymorphism (SNP) markers. Total genetic diversity (HT) and polymorphic information content (PIC) were 0.36 and 0.30 respectively for both landraces and modern cultivars. Linkage disequilibrium for the modern cultivars was higher than for the landraces (0.18 and 0.12, respectively). Analysis of the genetic structure showed a clear geographical pattern for the landraces, which were clustered into three subpopulations (SPs) representing the western, northern and eastern Mediterranean, whereas the modern cultivars were structured according to the breeding programmes that developed them: CIMMYT/ICARDA, France/Italy, and Balkan/eastern European countries. The modern cultivars showed higher genetic differentiation (GST) and lower gene flow (0.1673 and 2.49, respectively) than the landraces (0.1198 and 3.67, respectively), indicating a better distinction between subpopulations. The maximum gene flow was observed between landraces from the northern Mediterranean SPs and the modern cultivars released mainly by French and Italian breeding programmes.
Highlights
Wheat is one of the most widely cultivated crops in the world, covering an area of 219 million ha with a production of nearly 772 million t in 2017
8 markers with more than 25% of missing values as well as 730 markers with minor allele frequency (MAF) lower than 5% were excluded from the analysis, leaving a total of 10458 single nucleotide polymorphism (SNP) (Table 1)
In agreement with the results shown by STRUCTURE, the first two coordinates of the Principal coordinates analysis (PCoA) clearly separated the landraces from the modern cultivars, and within each group accessions were clustered matching the results of STRUCTURE (Fig 3)
Summary
Wheat is one of the most widely cultivated crops in the world, covering an area of 219 million ha with a production of nearly 772 million t in 2017 (http://www.fao.org/faostat). Of the daily intake of humans, wheat provides 19% of the calories and 21% of the protein It is generally accepted that to match the global population demand wheat production will need to increase by 1.7% per year by 2050 [1]. Population structure and genetic differentiation in Mediterranean wheats. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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