Genome-wide linkage mapping of QTL for root hair length in a Chinese common wheat population

Root hairs are fast growing, ephemeral tubular extensions of the root epidermis that aid nutrient and water uptake. The aim of the present study was to identify QTL for root hair length (RHL) using 227 F₈ recombinant inbred lines (RILs) derived from a cross of Zhou 8425B (Z8425B) and Chinese Spring (CS), and to develop convenient molecular markers for marker-assisted breeding in wheat. Analysis of variance of root hair length showed significant differences (P < 0.01) among RILs. The genetic map for QTL analysis consisted of 3389 unique SNP markers. Using composite interval mapping, four major QTL (LOD > 2.5) for RHL were identified on chromosomes 1B (2), 2D and 6D and four putative QTL (2 ≤ LOD ≤ 2.5) were detected on chromosomes 1A, 3A, 6B, and 7B, explaining 3.32%–6.52% of the phenotypic variance. The positive alleles for increased RHL of QTL on chromosomes 2D, 6B and 6D (QRhl.cau-2D, qRhl.cau-6B, and QRhl.cau-6D) were contributed by Z8425B, and CS contributed positive QTL alleles on chromosomes 1A (qRhl.cau-1A), 1B (QRhl.cau-1B.1 and QRhl.cau-1B.2), 3A (qRhl.cau-3A) and 7B (qRhl.cau-7B). STARP markers were developed for QRhl.cau-1B.1, QRhl.cau-2D, QRhl.cau-6D, and qRhl.cau-7B. Haplotype and association analysis indicated that the positive allele of QRhl.cau-6D had been strongly selected in Chinese wheat breeding programs. Collectively, the identified QTL for root hair length are likely to be useful for marker-assisted selection.