Objectives The objective of this study was to detect quantitative trait locus (QTL) for N use efficiency related traits at the seedling stage of wheat under different levels of phosphorus (P) and potassium (K) treatments. The results will deepen our understanding of the relationship between N and P/K, and this knowledge could be applied for map-based cloning and marker assisted selection (MAS) in wheat breeding.
Methods Population employed for QTL analysis was a set of 131 RILs derived from a Chuan 35050 × Shannong 483 cross. The 131 RILs and their parental lines were grown under hydroponic culture in greenhouse. Nine treatments were designed. The concentrations of the applied P and K treatments were as follows: moderate P and K (MPMK), high P (HP), low P1 (LP1), low P2 (LP2), low P3 (LP3), high K (HK), low K1 (LK1), low K2 (LK2) and low K3 (LK3). Combined with an enriched genetic map, we conducted research on the N use efficiency traits under different P and K treatments in order to map the QTLs (quantitative trait loci) related to N use efficiency of 10 traits at the wheat seedling stage and to conduct genetic analysis at the whole genome level.
Results A total of 137 QTLs for the 10 seedling traits were detected on 20 chromosomes, with the exception of 3D. Of these QTLs, 122 (89.05%) were detected in only one treatment. Three relatively high-frequency QTLs (QRnue-1A.2, QSnue-1A.1 and QTnue-1A.1) were detected in four treatments at least. Five QTLs (QRnue-1A.1, QTnue-1A.1, QSnc-4A, QRnc-6A.3 and QSnue-6B) were detected in both the low P and low K treatments. Seventeen important QTL clusters (C1-C17) containing at least three or more traits which involved 66 out of 137 QTLs (48.18%) were mapped on chromosomes 1A, 1B, 2B, 2D, 3A, 3B, 4A, 4B, 5D, 6A, 6B, 6D and 7A. Most QTL clusters were detected in both P and K treatments, while five QTL clusters only associated with specific phosphorus or potassium treatments. Many QTL cluster sites in this study were also related to the biomass, yield and other nutrients in the predecessors' investigation.
Conclusions The supply of P and K significantly affects N efficiency of wheat at the seedling stage and the expression of related QTLs. Most N efficiency related QTLs were only detected in certain treatments, but many QTLs were located at the same hot sites and composed clusters (hot sites). Many of these sites were also co-located QTLs for biomass, yield and other nutrient traits in the previous study. The detection of these QTL/gene hot sites is valuable for further understanding about the genetic control of N efficiency related traits of wheat and their relationship with P and K environment.
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