Effects of photo and thermo cycles on flowering time in barley: a genetical phenomics approach

Abstract

The effects of synchronous photo (16 h daylength) and thermo (2 °C daily fluctuation) cycles on flowering time were compared with constant light and temperature treatments using two barley mapping populations derived from the facultative cultivar ‘Dicktoo’. The ‘Dicktoo’בMorex’ (spring) population (DM) segregates for functional differences in alleles of candidate genes for VRN-H1, VRN-H3, PPD-H1, and PPD-H2. The first two loci are associated with the vernalization response and the latter two with photoperiod sensitivity. The ‘Dicktoo’בKompolti korai’ (winter) population (DK) has a known functional polymorphism only at VRN-H2, a locus associated with vernalization sensitivity. Flowering time in both populations was accelerated when there was no fluctuating factor in the environment and was delayed to the greatest extent with the application of synchronous photo and thermo cycles. Alleles at VRN-H1, VRN-H2, PPD-H1, and PPD-H2—and their interactions—were found to be significant determinants of the increase/decrease in days to flower. Under synchronous photo and thermo cycles, plants with the Dicktoo (recessive) VRN-H1 allele flowered significantly later than those with the Kompolti korai (recessive) or Morex (dominant) VRN-H1 alleles. The Dicktoo VRN-H1 allele, together with the late-flowering allele at PPD-H1 and PPD-H2, led to the greatest delay. The application of synchronous photo and thermo cycles changed the epistatic interaction between VRN-H2 and VRN-H1: plants with Dicktoo type VRN-H1 flowered late, regardless of the allele phase at VRN-H2. Our results are novel in demonstrating the large effects of minor variations in environmental signals on flowering time: for example, a 2 °C thermo cycle caused a delay in flowering time of 70 d as compared to a constant temperature.

Expression analysis of vernalization and day-length response genes in barley (Hordeum vulgare L.) indicates that VRNH2 is a repressor of PPDH2 (HvFT3) under long days

“…Under conditions with a short photoperiod, HvFT3 was expressed in all the genotypes that carried the active allele. There are numerous reports that describe the effect of this gene under conditions of short days (Laurie et al 1995; Faure et al , 2007; Karsai et al , 2008; Kikuchi et al , 2009). HvFT3 was also expressed weakly under conditions of a long photoperiod in ‘Alexis’.…”

Diversity in the Response to Low Temperature in Representative Barley Genotypes Cultivated in Europe

“…These two factors were identifi ed as the main environmental cues regulating the expression level of low temperature up-regulated genes. The mode of their complex interaction in diff erent genetic materials is still under investigation (Karsai et al, 2008).…”

Cool night‐time temperatures induce the expression ofCONSTANSandFLOWERING LOCUS Tto regulate flowering in Arabidopsis

“…In nature, plants experience temperature fluctuations coinciding with day and night, and daily temperature fluctuations affect plant development (Myster & Moe, 1995). When exposed to day/night temperature cycles, flowering of rice and barley can be accelerated or delayed relative to constant-temperature conditions (Yin & Kropff, 1996;Karsai et al, 2008). Time-of-day information is important for a range of physiological responses as sensitivity to temperature is modulated by the circadian clock throughout the day (McClung, 2006).…”