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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.

Three pleiotropic QTL regions associated with spikelet number and heading date were identified, with FT-A1 considered the candidate gene for QTspn/Hd.cau-7A. Spikelet number traits and heading date (HD) play key roles in yield improvement of wheat and its wide adaptation to different environments. Here, we used a Recombinant Inbred Lines population derived from a cross between Yi5029 (5029) and Nongda4332 (4332) to construct a high-density genetic linkage map and identify quantitative trait loci (QTL) associated with total spikelet number per spike (TSPN), fertile spikelet number per spike (FSPN), sterile spikelet number per spike (SSPN) and HD. A total of 22 environmentally stable QTL for TSPN, FSPN, SSPN and HD were identified. Notably, three pleiotropic QTL regions for TSPN and HD were detected on chromosomes 2A, 7A and 7D. The QTL associated with TSPN and HD on chromosome 7AS was designated QTspn/Hd.cau-7A. Furthermore, the candidate gene FT-A1 located in the region of QTspn/Hd.cau-7A had a single-nucleotide polymorphism (T-G) within the third exon, which might be the cause of diversity in spikelet number and HD between the two parents. Additionally, we developed a semi-thermal asymmetric reverse PCR (STARP) marker to analyze the geographical distribution and evolution of FT-A1 (T or G) alleles. This study contributes to our understanding of the molecular mechanisms of the four traits (TSPN, FSPN, SSPN and HD) and provides further insights into the genetic relationship between spikelet number traits and HD in wheat.

Hexaploid triticale (×Triticosecale, AABBRR) is an important forage crop and a promising energy plant. Transferring D-genome chromosomes or segments from common wheat (Triticum aestivum) into hexaploid triticale is attractive in improving its economically important traits. Here, a hexaploid triticale 6D(6A) substitution line Lin 456 derived from the cross between the octoploid triticale line H400 and the hexaploid wheat Lin 56 was identified and analyzed by genomic in situ hybridization (GISH), fluorescence in situ hybridization (FISH), and molecular markers. The GISH analysis showed that Lin 456 is a hexaploid triticale with 14 rye (Secale cereale) chromosomes and 28 wheat chromosomes, whereas non-denaturing fluorescence in situ hybridization (ND-FISH) and molecular marker analysis revealed that it is a 6D(6A) substitution line. In contrast to previous studies, the signal of Oligo-pSc119.2 was observed at the distal end of 6DL in Lin 456. The wheat chromosome 6D was associated with increased grain weight and decreased spikelet number using the genotypic data combined with the phenotypes of the F2 population in the three environments. The thousand-grain weight and grain width in the substitution individuals were significantly higher than those in the non-substitution individuals in the F2 population across the three environments. We propose that the hexaploid triticale 6D(6A) substitution line Lin 456 can be a valuable and promising donor stock for genetic improvement during triticale breeding. Keywords: In situ hybridization, Spikelet number, Substitution line, Thousand-grain weight, Triticale

Grain yield in bread wheat (Triticum aestivum L.) is largely determined by inflorescence architecture. Zang734 is an endemic Tibetan wheat variety that exhibits a rare triple spikelet (TRS) phenotype with significantly increased spikelet/floret number per spike. However, the molecular basis underlying this specific spike morphology is completely unknown. Through map-based cloning, the causal genes for TRS trait in Zang734 were isolated. Furthermore, using CRISPR/Cas9-based gene mutation, transcriptome sequencing and protein-protein interaction, the downstream signalling networks related to spikelet formation and awn elongation were defined. Results showed that the null mutation in WFZP-A together with deletion of WFZP-D led to the TRS trait in Zang734. More interestingly, WFZP plays a dual role in simultaneously repressing spikelet formation gene TaBA1 and activating awn development genes, basically through the recruitments of chromatin remodelling elements and the Mediator complex. Our findings provide insights into the molecular bases by which WFZP suppresses spikelet formation but promotes awn elongation and, more importantly, define WFZP-D as a favourable gene for high-yield crop breeding.