Crop wild relatives use in durum wheat breeding: Drift or thrift?
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Crop wild relatives (CWRs) are an important source of genetic diversity for crop improvement. The aim of this study was to assess the usefulness of deploying CWRs in durum wheat [Triticum turgidum L. subsp. durum (Desf.) van Slageren] breeding. A set of 60 accessions was selected to include cultivars from nine countries, top lines obtained via elite-by-elite crossing, and CWR-derived lines. These accessions were screened for resistance against four major fungal diseases to reveal that CWR-derived lines are a good source of resistance against Septoria leaf blotch (Zymoseptoria tritici), while they were highly susceptible to tan spot (Pyrenophora tritici-repentis). Drought tolerance was assessed at eight environments with contrasting nitrogen levels and tillage practices to reveal a clear superiority of CWR-derived lines for grain size as well as higher grain yield (GY) under low nitrogen and normal tillage (NT). Temperature-stress tolerance was assessed at four heat-stressed environments along the Senegal River to confirm CWR-derived had up to 42% yield advantage and a higher grain number per spike (GNspk). Combined testing under plastic heat tunnels imposed at the time of flowering also revealed good performance of CWR-derived lines. However, the CWR-derived lines had low gluten sedimentation index and poor yellow color compared with cultivars and elite germplasm. High genetic diversity was found in CWR-derived lines with 75% of individuals having minor allele frequency (MAF) of 40-44% for frequent alleles but low genetic diversity for alleles with low frequency. In addition, 8-13% of the CWR parent genome was retained in the derived progenies, which contributed to improve several phenotypic traits.
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