Allelic variation at the vernalization and photoperiod sensitivity loci in Chinese winter wheat cultivars (Triticum aestivum L.).

Xiangfen Zhang,Manxia Gao,Shasha Wang,Dangqun Cui,Feng Chen

doi:10.3389/fpls.2015.00470

Abstract

A total of 205 wheat cultivars from the Yellow and Huai valley of China were used to identify allelic variations of vernalization and photoperiod response genes, as well as the copy number variations (CNVs) of Ppd-B1 and Vrn-A1 genes. A novel Vrn-D1 allele with 174-bp insertion in the promoter region of the recessive allele vrn-D1 was discovered in three Chinese wheat cultivars and designated as Vrn-D1c. Quantitative real-time polymerase chain reaction showed that cultivars with the Vrn-D1c allele exhibited significantly higher expression of the Vrn-D1 gene than that in cultivars with the recessive allele vrn-D1, indicating that the 174-bp insertion of Vrn-D1c contributed to the increase in Vrn-D1 gene expression and caused early heading and flowering. The five new cis-elements (Box II-like, 3-AF1 binding site, TC-rich repeats, Box-W1 and CAT-box) in the 174-bp insertion possibly promoted the basal activity level of Vrn-D1 gene. Two new polymorphism combinations of photoperiod genes were identified and designated as Ppd-D1_Hapl-IX and Ppd-D1_Hapl-X. Association of the CNV of Ppd-B1 gene with the heading and flowering days showed that the cultivars with Ppd-B1_Hapl-VI demonstrated the earliest heading and flowering times, and those with Ppd-B1_Hapl-IV presented the latest heading and flowering times in three cropping seasons. Distribution of the vernalization and photoperiod response genes indicated that all recessive alleles at the four vernalization response loci, Ppd-B1_Hapl-I at Ppd-B1 locus, and Ppd-D1_Hapl-I at the Ppd-D1 locus were predominant in Chinese winter wheat cultivars. This study can provide useful information for wheat breeding programs to screen wheat cultivars with relatively superior adaptability and maturity.

Highlights

Heading and flowering times of bread wheat, mainly modulated by vernalization and photoperiod genes, are important factors that determine the adaptation of wheat plants to different environmental conditions and influence the growth and productivity of wheat (Law and Worland, 1997)
We further identified the molecular characterization of the vernalization and photoperiod response genes in backbone parents in the wheat breeding program of this wheat region and found a new Vrn-D1 allele, a Vrn-D1 null allele, two new polymorphism combinations of photoperiod genes, and several copy number variations (CNVs)
Discovery of a Novel Dominant Vrn-D1 Allele in Chinese Winter Wheat Identification of the 205 Chinese winter wheat cultivars by four primer sets (Vrn-P8F/R, Vrn-P9F/R, Vrn-P10F/R, and Vrn-P11F/R; Supplemental Table 1) indicated that 119 cultivars (58.0%) contained the recessive allele vrn-D1, and 59 (28.8%) and 24 (11.7%) cultivars contained the dominant alleles VrnD1a and Vrn-D1b, respectively

Summary

Introduction

Heading and flowering times of bread wheat, mainly modulated by vernalization and photoperiod genes, are important factors that determine the adaptation of wheat plants to different environmental conditions and influence the growth and productivity of wheat (Law and Worland, 1997). Vrn-1 genes, encompassing Vrn-A1, VrnB1, and Vrn-D1 genes on the long arms of chromosome 5 (Law et al, 1975; Galiba et al, 1995; Dubcovsky et al, 1998; Barrett et al, 2002; Iwaki et al, 2002), are upregulated by vernalization treatment, and their overexpression can accelerate flowering and maturity of wheat (Yan et al, 2003). Loss of functional mutation of Vrn resulted in the spring growth of bread wheat to head and flower under non-vernalization treatment. The Vrn-B3a allele is a 5300-bp insertion in the promoter region, and Vrn-B3b and Vrn-B3c alleles were recently discovered in bread wheat (Yan et al, 2006; Chen et al, 2013a). The predominant result is a C/T double peak in sequence trace files in exon 4 on Vrn-A1, and plants with an increased CNV showed an increased requirement for vernalization, thereby requiring longer cold treatment to potentiate flowering (Diaz et al, 2012)

Methods

Results

Conclusion