The quantitative response of wheat vernalization to environmental variables indicates that vernalization is not a response to cold temperature

Abstract

The initiation of flowering is a crucial trait that allows temperate plants to flower in the favourable conditions of spring. The timing of flowering initiation is governed by two main mechanisms: vernalization that defines a plant's requirement for a prolonged exposure to cold temperatures; and photoperiod sensitivity defining the need for long days to initiate floral transition. Genetic variability in both vernalization and photoperiod sensitivity largely explains the adaptability of cultivated crop plants such as bread wheat (Triticum aestivum L.) to a wide range of climatic conditions. The major genes controlling wheat vernalization (VRN1, VRN2, and VRN3) and photoperiod sensitivity (PPD1) have been identified, and knowledge of their interactions at the molecular level is growing. However, the quantitative effects of temperature and photoperiod on these genes remain poorly understood. Here it is shown that the distinction between the temperature effects on organ appearance rate and on vernalization sensu stricto is crucial for understanding the quantitative effects of the environmental signal on wheat flowering. By submitting near isogenic lines of wheat differing in their allelic composition at the VRN1 locus to various temperature and photoperiod treatments, it is shown that, at the whole-plant level, the vernalization process has a positive response to temperature with complex interactions with photoperiod. In addition, the phenotypic variation associated with the presence of different spring homoeoalleles of VRN1 is not induced by a residual vernalization requirement. The results demonstrate that a precise definition of vernalization is necessary to understand and model temperature and photoperiod effects on wheat flowering. It is suggested that this definition should be used as the basis for gene expression studies and assessment of functioning of the wheat flowering gene network, including an explicit account of the quantitative effect of environmental variables.

Quantification of the effects of VRN1 and Ppd-D1 to predict spring wheat (Triticum aestivum) heading time across diverse environments

“…3). Vrn-A1 has been suggested elsewhere to have the strongest effects on wheat development (Trevaskis et al , 2003; Loukoianov et al , 2005; Allard et al , 2012). While some researchers indicated stronger winter allele effects of Vrn-B1 than that of Vrn-D1 , others found the weaker effects for the winter allele of Vrn-B1 (Loukoianov et al , 2005; Allard et al , 2012).…”

“…Previous studies have found different effects among VRN1 and Ppd-D1 genes (González et al , 2005; Loukoianov et al , 2005; Eagles et al , 2010; Allard et al , 2012), so the different effects were allowed to vary in magnitude via a weighting function. A multiplicative model was used to simulate the interaction between VRN1 and Ppd-D1 genes on PPD sensitivity.…”

GWAS for Fusarium Head Blight Related Traits in Winter Wheat (Triticum Aestivum L.) in an Artificially Warmed Treatment

“…A prerequisite for winter wheat is the accumulation of cold temperature which may be affected by climate change in that warm winters will be more frequent. Vernalization requirements are controlled by Vrn genes and specific environmental conditions are needed for the activation of these genes [52,53]. Zheng et al [54] studied the rates of climate change in Australia; they suggested an earlier sowing to escape frost and heat stresses.…”

The role of seasonal flowering responses in adaptation of grasses to temperate climates

“…For example, in experiments performed by Allard et al (2012) wheat plants exposed to prolonged low-temperatures (5°C for 30 days) flowered with 8 leaves (primary tiller). Typically there are four to five leaf primordia present at the time of germination and these develop into leaves irrespective of conditions during subsequent growth, so a final leaf number of 8 is indicative of a rapid progression toward flowering.…”