Investigating the impact of spring (Vrn-A1) and winter (vrn-A1) vernalization alleles on frost tolerance induced by light spectrum and low temperatures in different wheat backgrounds

Abstract

The need for exposure to low, but non-freezing temperatures is a common aspect of both cold acclimation and vernalization, suggesting a possible link between these two processes. Cold hardiness levels are regulated by the C-repeat binding factor (CBF) regulon, whereas vernalization requirements are influenced by vernalization genes (VRNs). The VRN1 gene has an epistatic effect on the CBF regulon, reducing frost tolerance during post-vernalization. It is widely acknowledged that, apart from low temperature, light also serves as an external signal influencing the expression of CBF genes indicating that photoperiod and light quality play important roles in regulating cold acclimation processes. For instance, frost-tolerant winter wheat illuminated by white light with additional far-red light increases frost resistance due to low red:far-red (R:FR) ratio. However, information regarding the regulation or influence of VRN1 gene on the light quality induced frost tolerance is currently lacking. In the present study, reciprocal near-isogenic lines (NILs) produced from crossing the non-hardy spring-habit (Vrn-A1) cultivar ‘Manitou’ with the very cold-hardy winter-habit (vrn-A1) cultivar ‘Norstar’ were used. Our objective was to investigate how winter/spring VRN1 alleles (vrn-A1/Vrn-A1), inserted in the same genetic background, affect wheat frost tolerance under different spectral illuminations at temperatures of 15 °C and 5 °C. Based on freezing tests and the cold-related gene expressions patterns, it appears that the light-induced frost tolerance does not completely depend on VRN1 gene expression but is strongly dependent on the background. Additionally, the presence of the spring allele is capable of sensitizing an otherwise frost-tolerant genotype to frost.