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 8425 B(Z8425 B)and Chinese Spring(CS),and to develop convenient molecular markers for markerassisted 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 1 B(2),2 D and 6 D and four putative QTL(2≤LOD≤2.5)were detected on chromosomes 1 A,3 A,6 B,and 7 B,explaining 3.32%–6.52%of the phenotypic variance.The positive alleles for increased RHL of QTL on chromosomes 2 D,6 B and 6 D(QRhl.cau-2 D,q Rhl.cau-6 B,and QRhl.cau-6 D)were contributed by Z8425 B,and CS contributed positive QTL alleles on chromosomes 1 A(q Rhl.cau-1 A),1 B(QRhl.cau-1 B.1 and QRhl.cau-1 B.2),3 A(q Rhl.cau-3 A)and 7 B(q Rhl.cau-7 B).STARP markers were developed for QRhl.cau-1 B.1,QRhl.cau-2 D,QRhl.cau-6 D,and q Rhl.cau-7 B.Haplotype and association analysis indicated that the positive allele of QRhl.cau-6 D 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.