Abstract
BackgroundDurum wheat (Triticum turgidum L. ssp. durum Desf. Husn) is the main staple crop used to make pasta products worldwide. Under the current climate change scenarios, genetic variability within a crop plays a crucial role in the successful release of new varieties with high yields and wide crop adaptation. In this study we evaluated a durum wheat collection consisting of 197 genotypes that mainly comprised a historical set of Argentinian germplasm but also included worldwide accessions.ResultsWe assessed the genetic diversity, population structure and linkage disequilibrium (LD) patterns in this collection using a 35 K SNP array. The level of polymorphism was considered, taking account of the frequent and rare allelic variants. A total of 1547 polymorphic SNPs was located within annotated genes. Genetic diversity in the germplasm collection increased slightly from 1915 to 2010. However, a reduction in genetic diversity using SNPs with rare allelic variants was observed after 1979. However, larger numbers of rare private alleles were observed in the 2000–2009 period, indicating that a high reservoir of rare alleles is still present among the recent germplasm in a very low frequency. The percentage of pairwise loci in LD in the durum genome was low (13.4%) in our collection. Overall LD and the high (r2 > 0.7) or complete (r2 = 1) LD presented different patterns in the chromosomes. The LD increased over three main breeding periods (1915–1979, 1980–1999 and 2000–2020).ConclusionsOur results suggest that breeding and selection have impacted differently on the A and B genomes, particularly on chromosome 6A and 2A. The collection was structured in five sub-populations and modern Argentinian accessions (cluster Q4) which were clearly differentiated. Our study contributes to the understanding of the complexity of Argentinian durum wheat germplasm and to derive future breeding strategies enhancing the use of genetic diversity in a more efficient and targeted way.
Highlights
Larger numbers of rare private alleles were observed in the 2000–2009 period, indicating that a high reservoir of rare alleles is still present among the recent germplasm in a very low frequency
Our study contributes to the understanding of the complexity of Argentinian durum wheat germplasm and to derive future breeding strategies enhancing the use of genetic diversity in a more efficient and targeted way
The results showed other annotated genes carrying polymorphic Single Nucleotide Polymorphisms (SNPs) aligned as the Gli-B1 locus encoding for gamma-gliadin in 1BS chromosome ([low frequency (LF)], AX-94659353), the HYD-B1 locus encoding the carotenoid β-hydroxylase 1 gene ([high frequency (HF)], AX-94475906) in the 2B chromosome, a soluble starch synthase gene located in 1A and a lipoxygenase gene putatively encoding the Lpx-A2 locus in chromosome 5A ([HF], AX-94964352), all important genes associated with relevant quality traits in durum wheat breeding programs [49,50,51,52]
Summary
Durum wheat (Triticum turgidum L. ssp. durum Desf. Husn) is the main staple crop used to make pasta products worldwide. The main producing areas of durum wheat are in the Mediterranean Basin, North America and India, Canada and Turkey being the main producer countries of this cereal, followed by Argelia, Italy and India [4] It has been used as the main source for making different products, mainly flat and leavened bread, couscous, burghul and frekeh in the West Asia, and the North and East Africa region and to elaborate pasta in Western Europe, as well as in North America and worldwide [5]. The older cultivars, typically conformed by high and less productive plants, were progressively replaced before the beginning of the 80’s and all the durum wheat varieties cultivated in Argentina today are semi-dwarf [7]. Durum wheat grains are mainly used for dry pasta production, one of the main staple foods in Argentina, with a consumption of 8.54 kg per capita p.a. and occupying the 7th worldwide position of production and consumption [8]
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