Major Co-localized QTL for Plant Height, Branch Initiation Height, Stem Diameter, and Flowering Time in an Alien Introgression Derived Brassica napus DH Population.

Yusen Shen,Xianhong Ge,Zaiyun Li,Yang Xiang,Ensheng Xu

doi:10.3389/fpls.2018.00390

Abstract

Plant height (PH), branch initiation height (BIH), and stem diameter (SD) are three stem-related traits that play crucial roles in plant architecture and lodging resistance. Herein, we show one doubled haploid (DH) population obtained from a cross between Y689 (one Capsella bursa-pastoris derived Brassica napus intertribal introgression) and Westar (B. napus cultivar) that these traits were significantly positively correlated with one another and with flowering time (FT). Based on a high-density SNP map, a total of 102 additive quantitative trait loci (QTL) were identified across six environments. Seventy-two consensus QTL and 49 unique QTL were identified using a two-round strategy of QTL meta-analysis. Notably, a total of 19 major QTL, including 11 novel ones, were detected for these traits, which comprised two QTL clusters on chromosomes A02 and A07. Conditional QTL mapping was performed to preliminarily evaluate the genetic basis (pleiotropy or tight linkage) of the co-localized QTL. In addition, QTL by environment interactions (QEI) mapping was performed to verify the additive QTL and estimate the QEI effect. In the genomic regions of all major QTL, orthologs of the genes involved in phytohormone biosynthesis, phytohormone signaling, flower development, and cell differentiation in Arabidopsis were proposed as candidate genes. Of these, BnaA02g02560, an ortholog of Arabidopsis GASA4, was suggested as a candidate gene for PH, SD, and FT; and BnaA02g08490, an ortholog of Arabidopsis GNL, was associated with PH, BIH and FT. These results provide useful information for further genetic studies on stem-related traits and plant growth adaptation.

Highlights

Rapeseed (Brassica napus L., AACC, 2n = 38) is the second largest oil crop in the world after soybean, with an annual production of ∼70 million metric tons in recent years (2015–2017)
In the spring-type rapeseed area 17WN, Plant height (PH) was determined to be significantly positively correlated with branch initiation height (BIH) (r = 0.67, P < 0.001), stem diameter (SD) (r = 0.76, P < 0.001), and flowering time (FT) (r = 0.61, P < 0.001); BIH was significantly positively correlated with both SD (r = 0.53)and FT (r = 0.68); and significant positive correlations were observed between SD and FT (r = 0.54, P < 0.001) (Table 2)
We previously developed one doubled haploid (DH) population from a cross between an alien introgression line Y689 and B. napus cv

Summary

Introduction

Together with flowering time (FT), these traits constitute selection targets in the breeding of varieties with preferred morphologies and adaptations. Both PH and FT are complex traits that are controlled by endogenous and environmental factors (Zhang et al, 2015). Genes associated with phytohormone biosynthesis and signaling determine plant height (Fujioka and Yokota, 2003; Sakamoto, 2004; Muhr et al, 2016; Zhao et al, 2017; Li et al, 2018). FT and TSF encode a long- range signal (florigen) that carries information about the inducement of flowering from the leaf to the shoot apical meristem (SAM) (You et al, 2017)

Methods

Results

Conclusion