Identification and Validation of a New Source of Low Grain Cadmium Accumulation in Durum Wheat (Triticum Turgidum L. Subsp. Durum (Defs.))
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Abstract
Cadmium (Cd) is a toxic heavy metal with no known biological function. The maximum level of Cd concentration allowed in the international market for wheat grain is 0.2 mg kg-1. Higher Cd levels in durum wheat (Triticum turgidum L. var. durum Desf) may threaten its export. To develop new durum wheat cultivars low in Cd uptake and speed up the selection process in breeding programs, this study attempted to identify SNP(s) associated with a low Cd uptake in the durum experimental line D041735. D041735 was developed from a cross between hexaploid (Sumai 3) and durum wheat by NDSU breeding program and has consistently shown low grain Cd levels. Therefore, this study sought 1) to identify SNP marker(s) tightly linked to Cd uptake and genetic dissection of the grain Cd content in a recombinant inbred line mapping population derived from D041735 and Divide (a high Cd accumulator cultivar) using wheat 90k SNP chips and 2) to test for alleles from detected Cd-linked markers among three sources of low Cd accumulators, including Strongfield, Haurani, and D041735. The QTL analysis performed in this study identified only a single major QTL for Cd uptake on chromosome arm 5BL. The QTL was detected in a 0.3 cM interval flanked by SNP markers RAC875_c20785_1219 and Kukri_c66357_357. Validation results using these flanking markers initially suggested the existence of a different gene or allele for low Cd uptake in the D041735 line as a new source for the durum breeding program at NDSU. The BLAST analysis of these flanking markers suggested the Aluminum Induced Protein Like Protein and heavy metal transporter ATPase 3 as candidate genes for the major QTL. Allelism testing revealed that the identified QTL in this study is novel and not the previously mapped QTL Cdu1on 5BL. This study therefore confirmed that the D041735 experimental line is a novel source of low Cd uptake in durum wheat germplasms, where the major QTL is most likely introduced from hexaploid wheat.