Abstract
Genetic divergence for nitrogen utilization in germplasms is important in wheat breeding programs, especially for low nitrogen input management. In this study, a nested association mapping (NAM) population, derived from “Yanzhan 1” (a Chinese domesticated cultivar) crossed with “Hussar” (a British domesticated cultivar) and another three semi-wild wheat varieties, namely, “Cayazheda 29” (Triticum aestivum ssp. tibetanum Shao), “Yunnan” (T. aestivum ssp. yunnanense King), and “Yutian” (T. aestivum petropavloski Udats et Migusch), was used to detect quantitative trait loci (QTLs) for nitrogen utilization at the seedling stage. An integrated genetic map was constructed using 2,059 single nucleotide polymorphism (SNP) markers from a 90 K SNP chip, with a total coverage of 2,355.75 cM and an average marker spacing of 1.13 cM. A total of 67 QTLs for RDW (root dry weight), SDW (shoot dry weight), TDW (total dry weight), and RSDW (root to shoot ratio) were identified under normal nitrogen conditions (N+) and nitrogen deficient conditions (N−). Twenty-three of these QTLs were only detected under N− conditions. Moreover, 23 favorable QTLs were identified in the domesticated cultivar Yanzhan 1, 15 of which were detected under N+ conditions, while only four were detected under N− conditions. In contrast, the semi-wild cultivars contributed more favorable N−−specific QTLs (eight from Cayazheda 29; nine from Yunnan), which could be further explored for breeding cultivars adapted to nitrogen-deficient conditions. In particular, QRSDW-5A.1 from YN should be further evaluated using high-resolution mapping.
Highlights
Nitrogen (N), an essential plant nutrient, is vital for various aspects of crop growth and development, including seed germination, root architecture regulation, shoot development, flowering, and grain production (Lea and Morot-Gaudry, 2001; Alboresi et al, 2005; Kiba and Krapp, 2016; Yuan et al, 2016)
We considered a Quantitative trait loci (QTL) to be present if the limit of detection (LOD) was >2.5 in the nested association mapping (NAM) population, and >2.0 in at least one recombinant inbred lines (RILs) population
Under N− conditions, both the RDW and SDW of the common parent YZ were reduced, but RDW increased in YT and SDW increased in YN, suggesting that these parental species possessed different levels of N-deficiency tolerance (Figures 1A–D and Supplementary Table S2)
Summary
Nitrogen (N), an essential plant nutrient, is vital for various aspects of crop growth and development, including seed germination, root architecture regulation, shoot development, flowering, and grain production (Lea and Morot-Gaudry, 2001; Alboresi et al, 2005; Kiba and Krapp, 2016; Yuan et al, 2016). In 2015, the total global N consumption was 223 million tons, and the average N application to wheat was 71–370 kg/hm (FAOSTAT, 2015), which is far higher than the safety threshold of 260 kg/hm (Liu, 2017) in many areas. This excessive N input raises the cost of production, but it causes various soil and environmental issues (Peng et al, 2009). Wheat varieties are typically developed for maximum production with high N fertilizer input, which results in a decrease in N use efficiency (Dong et al, 2014). In order to increase production without further damage to the environment, highyield crop varieties tolerant of N deficient conditions, or those that can efficiently utilize limited N, are desirable
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