Abstract
Kernel size and shape are important parameters determining the wheat profitability, being main determinants of yield and its technological quality. In this study, a segregating population of 118 recombinant inbred lines, derived from a cross between the Iranian durum landrace accession “Iran_249” and the Iranian durum cultivar “Zardak”, was used to investigate durum wheat kernel morphology factors and their relationships with kernel weight, and to map the corresponding QTLs. A high density genetic map, based on wheat 90k iSelect Infinium SNP assay, comprising 6,195 markers, was developed and used to perform the QTL analysis for kernel length and width, traits related to kernel shape and weight, and heading date, using phenotypic data from three environments. Overall, a total of 31 different QTLs and 9 QTL interactions for kernel size, and 21 different QTLs and 5 QTL interactions for kernel shape were identified. The landrace Iran_249 contributed the allele with positive effect for most of the QTLs related to kernel length and kernel weight suggesting that the landrace might have considerable potential toward enhancing the existing gene pool for grain shape and size traits and for further yield improvement in wheat. The correlation among traits and co-localization of corresponding QTLs permitted to define 11 clusters suggesting causal relationships between simplest kernel size trait, like kernel length and width, and more complex secondary trait, like kernel shape and weight related traits. Lastly, the recent release of the T. durum reference genome sequence allowed to define the physical interval of our QTL/clusters and to hypothesize novel candidate genes inspecting the gene content of the genomic regions associated to target traits.
Highlights
Durum wheat (T. turgidum L. var. durum) is a major crop in Mediterranean regions with a total of about 14 million hectares cultivated worldwide
Durum wheat breeding has constantly pursued the improvement of Thousand Kernel Weight (TKW) and test weight (TW)
While some works investigated the genetic bases of grain shape and size traits and their relationship with TKW and TW in bread wheat (Sun et al, 2008; Gegas et al, 2010; Ramya et al, 2010; Tsilo et al, 2010; Prashant et al, 2012; Maphosa et al, 2014; Rasheed et al, 2014; Williams and Sorrells, 2014; Wu et al, 2015; Kumar et al, 2016; Cheng et al, 2017; Würschum et al, 2018), very few were dedicated to durum wheat (Russo et al, 2014; Golan et al, 2015)
Summary
Durum wheat (T. turgidum L. var. durum) is a major crop in Mediterranean regions with a total of about 14 million hectares cultivated worldwide. Especially for durum wheat, kernel size and shape influence the test weight (TW), which, in turn, has an effect on semolina yield (Gegas et al, 2010). For these reasons, increasing TKW and TW are main targets in wheat breeding, in addition to total yield. Larger kernels impact on grain yield and have favorable effects on seedling vigor and early growth (Peng et al, 2003) These traits are quantitative and complex, highly influenced by the environment (E) and display high Genotype × Environment interactions (GxE). Durum wheat landraces show a much greater variability for kernel size and shape (Moore, 2015; Liu et al, 2017)
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