Abstract
Plant roots are critical for water and nutrient acquisition, environmental adaptation, and yield formation. Herein, 196 wheat accessions from the Huang-Huai Wheat Region of China were collected to investigate six root traits at seedling stage under three growing environments [indoor hydroponic culture (IHC), outdoor hydroponic culture (OHC), and outdoor pot culture (OPC)] and the root dry weight (RDW) under OPC at four growth stages and four yield traits in four environments. Additionally, a genome-wide association study was performed with a Wheat 660K SNP Array. The results showed that the root traits varied most under OPC, followed by those under both OHC and IHC, and root elongation under hydroponic culture was faster than that under pot culture. Root traits under OHC might help predict those under OPC. Moreover, root traits were significantly negatively correlated with grain yield (GY) and grains per spike (GPS), positively correlated with thousand-kernel weight (TKW), and weakly correlated with number of spikes per area (SPA). Twelve stable chromosomal regions associated with the root traits were detected on chromosomes 1D, 2A, 4A, 4B, 5B, 6D, and unmapped markers. Among them, a stable chromosomal interval from 737.85 to 742.00 Mb on chromosome 4A, which regulated total root length (TRL), was identified under three growing environments. Linkage disequilibrium (LD) blocks were used to identify 27 genes related to root development. Three genes TraesCS4A02G484200, TraesCS4A02G484800, TraesCS4A02G493800, and TraesCS4A02G493900, are involved in cell elongation and differentiation and expressed at high levels in root tissues. Another vital co-localization interval on chromosome 5B (397.72–410.88 Mb) was associated with not only RDW under OHC and OPC but also TKW.
Highlights
As the population increases, the demand for wheat doubles approximately every 20 years; a continuous yield improvement in wheat production is an urgent issue. Xie et al (2017) found that grain number per unit area, grain per spike, and plant biomass were lower for wheat lines with shorter root lengths, while lines with longer roots had the highest biomass and grain yield
Previous reports indicated that the 196 accessions could be divided into two subpopulations, which are largely consistent with the K-values, principal component analysis (PCA)-matrix and quantile (Q)-matrix in the present study (Jakobsson and Rosenberg, 2007; Earl and Vonholdt, 2012)
Root dry weight (RDW) between Outdoor Hydroponic culture (OHC) and Outdoor Pot culture (OPC) was closely correlated at earlier stages
Summary
The demand for wheat doubles approximately every 20 years; a continuous yield improvement in wheat production is an urgent issue. Xie et al (2017) found that grain number per unit area, grain per spike, and plant biomass were lower for wheat lines with shorter root lengths, while lines with longer roots had the highest biomass and grain yield. Root system facilitates aerial growth and is very critical for yield (Fang et al, 2017), and its morphological characteristics include root length, surface area, volume, diameter, and number of root tips. Surface area, and volume affect the spatial arrangement of roots underground, while root diameter is associated with the ability to penetrate strong soil and drought tolerance, and the root tip is the most active part of the root system (Kabir et al, 2015; Maccaferri et al, 2016; Bai et al, 2019). A few genes regulating wheat root morphology have been identified using reverse genetics methods, including TaZFP34 (Chang et al, 2016), lateral organ boundaries (LOB) family member TaMOR (Li et al, 2016), and zinc finger protein OsCYP2 (Cui et al, 2017)
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