Positional relationships between photoperiod response QTL and photoreceptor and vernalization genes in barley

Abstract

Winterhardiness has three primary components: photoperiod (day length) sensitivity, vernalization response, and low temperature tolerance. Photoperiod and vernalization regulate the vegetative to reproductive phase transition, and photoperiod regulates expression of key vernalization genes. Using two barley mapping populations, we mapped six individual photoperiod response QTL and determined their positional relationship to the phytochrome and cryptochrome photoreceptor gene families and the vernalization regulatory genes HvBM5A, ZCCT-H, and HvVRT-2. Of the six photoreceptors mapped in the current study (HvPhyA and HvPhyB to 4HS, HvPhyC to 5HL, HvCry1a and HvCry2 to 6HS, and HvCry1b to 2HL), only HvPhyC coincided with a photoperiod response QTL. We recently mapped the candidate genes for the 5HL VRN-H1 (HvBM5A) and 4HL VRN-H2 (ZCCT-H) loci, and in this study, we mapped HvVRT-2, the barley TaVRT-2 ortholog (a wheat flowering repressor regulated by vernalization and photoperiod) to 7HS. Each of these three vernalization genes is located in chromosome regions determining small photoperiod response QTL effects. HvBM5A and HvPhyC are closely linked on 5HL and therefore are currently both positional candidates for the same photoperiod effect. The coincidence of photoperiod-responsive vernalization genes with photoperiod QTL suggests vernalization genes should also be considered candidates for photoperiod effects.

Detection of photoperiod responsive and non-responsive flowering time QTL in barley

“…Extremely early flowering winter-type cultivars can be damaged by late frost, whereas in the Far East region, late flowering ones typically yield poorly and produce poor quality grain due to seasonal rainfall patterns. Photoperiod also plays an important role in determining winter hardiness (Hayes et al 1997, Szucs et al 2006, Takahashi and Yasuda 1970. The photoperiod response gene Ppd-H1, located on chromosome arm 2HS, regulates flowering time under long days, while Ppd-H2 on chromosome arm 1HL functions only under short days (Laurie et al 1995).…”

“…None of the genes responsible for this phenotype has yet been isolated, although some candidates have been suggested . Barley germplasm can be broadly divided into winter, facultative, and spring types (Mahfoozi et al 2001, Szucs et al 2006. Three epistatic genes Vrn-H1 (Sgh2), Vrn-H2 (sgh1), and Vrn-H3 (Sgh3), located on chromosomes 5H, 4H and 7H, respectively, are responsible for the spring growth habit Komatsuda 2004, Takahashi andYasuda 1956).…”

Structural and functional characterization of a winter malting barley

“…As in the case of malting quality, the capacity to survive the winter (winter hardiness) also constitutes a complex phenotype that consists of three principal components: low-temperature (LT) tolerance, vernalization (VRN) response and photoperiod (PPD) sensitivity (Szűcs et al 2006). Two major QTL on chromosome 5H are associated with LT tolerance in barley, Frost resistance-H1 and Fr-H2 (Francia et al 2004).…”

PHYTOCHROME C plays a major role in the acceleration of wheat flowering under long-day photoperiod

“…In wheat and barley, the chromosome region encompassing PHYC has been associated with differences in flowering time under inductive LD photoperiods, but genetically linked loci have not been ruled out as candidate flowering time genes (15)(16)(17)(18). In both species, PHYC is tightly linked to the VERNALIZATION 1 (VRN1) gene, a MADS-box meristem identity gene similar to Arabidopsis APETALA1, which promotes the vegetative-toreproductive transition of the shoot apical meristem (19)(20)(21).…”