QTL mapping for root traits in wheat under different phosphorus levels in hydroponic culture

Identification of genes for tolerance against phosphorus (P) deficiency is important for wheat production in P-deficient soils. Nine root system architecture (RSA) and root biomass-related traits (RBT) in 198 double haploid lines derived from cross between Yangmai 16/Zhongmai 895 were characterized under zero (control), low, and high P treatments (KH2PO4 contents: 0, 0.005, 0.25 mmol/L, respectively) in hydroponic culture, and the DH lines and parents were genotyped using Wheat 660K SNP array. All traits showed significant variations among the DH lines with high heritabilities (0.76 to 0.91) and high correlations (r =0.59 to 0.98) with each other. Inclusive composite interval mapping using 10,242 markers identified 34 QTLs for all traits in the three P treatments. Of these, 11 QTLs under low P condition on chromosomes 2BL, 4BS (2 QTLs), 4DS (2), 6BL (2), 7AL (2), and 7BL (2) for root length (RL), root tip number (RTN) and ratio of root to shoot dry weight (RRS) explained 4.6 - 20.4% of the phenotypic variances. QRRS.caas-4DS (16.64 - 30.66 Mb) was detected in all three P treatments and accounted for 8.4 to 20.4% of the phenotypic variances. Seven QTLs clusters (C1 to C7) were mapped on chromosomes 3DL, 4BS, 4DS, 6BL, 7AS, 7AL and 7BL, of which five (C3 to C7) were detected under low P condition. Cluster C5 on chromosome 7AS (AX-109955164 - AX-109445593) played the key role in modulating RL, RTN and ROSA, with the favorable allele coming from Zhongmai 895. SNPs closely linked to QTLs and clusters could be used for improving root nutrient-use efficiency traits in future breeding.