Flowering in wheat is genetically controlled by three main genes: 1) Vernalization genes (Vrn) which determine winter or spring growth habit and require cold temperature exposure for transition to flowering. 2) Photoperiod sensitivity genes (Ppd) which determine response to day length with dominant alleles being insensitive. 3) 'Earliness per se' (Eps) genes which affect flowering time regardless of environment. The interaction between these genes, particularly Vrn1, Vrn3, and Ppd1, help regulate the flowering mechanism through protein interactions and feedback loops in response to environmental signals like photoperiod and vernalization.

1. Genetics of
Flowering in
Wheat.

2. Contents • Introduction
• Genetic Control of Flowering in Wheat
• Mechanism of Regulation of Flowering in
Wheat
• References

3. Introduction
• Domestication of crops begins in the fertile crescent.
• Over 11,000 years of trial and error, humans have
carefully selected desirable traits (Eaton, 2021).
• Two main wheat species : Tetraploid durum/pasta
(Triticum durum) and the hexaploid bread (Triticum
aestivum) wheat (Nesbitt, 2001).

4. Introduction
• Produced more than 6 million tons world wide.
• Used as food by more than 40% of the world's
population
• Increasing yield remains the most important goal of
wheat breeding programs.
• Necessary to conduct research on the control of wheat
flowering time to increase productivity.

5. Introduction
• Flowering induction: Plays a pivotal role in the plant life
cycle, affecting reproductive success and yield depending
on the prevailing climatic conditions of the target
environment.
• Flowering Time: Critical stages in crop development as
they play an important role in adaptation, yield potential
and grain quality (Gupta et. al, 2020).

6. Genetic Control of
Flowering in Wheat.
Flowering is controlled by 3 genes.
Presentation title 20XX 6
2. Photoperiod
sensitivity genes
(Ppd)
1. Vernalization
genes (Vrn)
3. ‘narrow-sense
earliness’ or ‘earliness per
se’ (Eps) genes

7. 1.Vernalization
genes (Vrn)
• Two types of wheat (Based on Vernal requirement reaction): Winter and Spring
• Vernalization for transition from vegetative growth to reproductive growth phase.
• Degree of temperature and the duration of exposure plays role for the reaction
(Iqbal et al. 2006).
• In spring wheat one or more dominant alleles are found in the Vrn-1, Vrn-3, and
Vrn-4 genes, and these genetic mutations do not respond to vernal treatment.
• On the other hand, winter wheat has the Vrn-2 gene of the dominant allele and the
Vrn-1, Vrn-3, and Vrn-4 genes of the recessive allele, so spring treatment is
essential for flowering.
• The Vrn-1 genes have three orthologous genes, Vrn-A1, Vrn-B1, and Vrn-D1, on
chromosomes 5A, 5B, and 5D, respectively (Lee, 2019).

8. 1.Vernalization
genes (Vrn)
• The Vrn-2 genes: regulating winter growth habits have been characterized by
Vrn-A2 and Vrn-B2 in biploid and quadruploid wheat, and Vrn-A2 is located
on chromosome 5A of T. monococcum (Yan et al. 2004)
• The Vrn-3 genes, Vrn-A3, Vrn-B3 (formerly known as Vrn-5 or Vrn-D4), and
Vrn-D3, are located on chromosomes 7A, 7B, and 5D, respectively, in
hexaploid mills.
• Vrn-D4 is known to be located on chromosome 5D, but the function of this
gene has not yet been elucidated (Lee, 2019).
• Vrn-D4 gene may be associated with a feedback regulatory loop involving the
higher levels of the Vrn-1, Vrn-2, and Vrn-3 genes, or the Vrn-1, Vrn-2, and
Vrn-3 genes (Kippes et al. 2014).

9. 2. Photoperiod
sensitivity
genes (Ppd)
• Second most important genetic system in determining the flowering of wheat.
• Photoperiodic insensitive varieties switch from vegetative to reproductive
growth as soon as the temperature rises in spring, while photoperiodic-
sensitive varieties bloom only when the daylight length is long and the
photocycle requirements are satisfied. Chromosomes might have carried
flower inhibitors(Law and Worland, 1997).
• The genes that determine the response to the photoperiod are the Ppd gene,
which is known to be located on chromosome 2 of wheat.
• So far, the Ppd-A1, Ppd-B1, and Ppd-D1 have been identified, and they are
located on chromosomes 2A, 2B, and 2D, respectively (Law et al. 1978, Lee,
2019, Gupta et al. 2020)
• The dominant allele Ppd gene is insensitive to daylight length, and the
recessive allele Ppd gene is sensitive to daylight length.

10. 2. Photoperiod
sensitivity
genes (Ppd)
• Genetic analysis has shown that the Ppd-D1 gene is the most effective
photoperiodic desensitization gene compared to the Ppd-B1 and Ppd-A1
genes.
• Variation in alleles of the Ppd-D1 and Ppd-A1 genes is important in
determining the flowering time of wheat according to the photoperiod
response (Whittal et al. 2018).
• In addition to the Ppd-A1, Ppd-B1, and Ppd-D1 genes there are photoperiod
response genes on other chromosomes that affect the flowering time of wheat.
• For example, chromosome 1 has a genome that delays flowering in response
to both the vernal process and the photoperiod, and chromosome 3D has a
photoperiod insensitive gene ( Law et al. 1998).

11. 3. narrow-
sense earliness
or earliness per
se (Eps)
• Called "earliness per se" and affects the flowering time regardless of
environmental change. The EPS gene affects flowering time only when there is
no effect of vernal treatment and photoperiod genes, and is known to be a
quantitative trait in which some genes are involved.
• The eps gene and related quantitative traits have been reported to be located on
all chromosomes of wheat, but mainly in chromosomes 5A, 2B, 3A, 5B, 7B,
and 4D (Gupta et al. 2020).

12. Mechanism
of
regulation
of
flowering
in wheat.
• Wheat with a deletion mutation of the VRN1 gene is known to play an
important role in flowering because it does not bloom. Recent studies have
shown that the expression of the VRN1 gene is associated with the gene
encoding carbohydrate-binding proteins,
• PPD1 gene promotes flowering by increasing the expression of the VRN3 gene
under long-day conditions.
• The VRN3 gene incorporates environmental signals mediated by the
photoperiod genes PPD1-CO module and the VRN1-VRN2 module of the
physiological genes (Lee, 2019).

13. • In this process, the CO protein and VRN2 protein with the CCT domain
interact with the CCT domain of HAP2/3/5, which is a trimeric complex, to
regulate the flowering signal coming to the PPD1-CO module and VRN1-
VRN2 module under long-term conditions.
• Binding between VRN3 protein and FDL2 protein increases the expression of
the VRN1 gene. Vernal treatment inhibits the expression of VRN2 gene by
increasing the expression of the VRN1 gene under long and single conditions.
• The VER2 protein migrates to the nucleus and binds to the TaGRP2 protein,
thereby unraveling the inhibition of the expression of the VRN1 gene by the
TaGRP2 protein (Xiao et al. 2014).
• The interaction between VRN3 constitutes a feedback regulatory loop,
through which flowering begins.
Mechanism
of
regulation
of
flowering
in wheat.

14. Mechanism
of
regulation
of
flowering
in wheat.
(Lee, 2019)

15. References.
1. C. N. Law and a. J. Worland. 1997 John Innes Centre, Norwich NR4 7UH, UK
2. Eaton, W. M., 2021. UNDERSTANDING THE REGULATION OF FLOWERING TIME THROUGH
PHOTOPERIOD-1 (Ppd-1) and FLOWERING LOCUS T (FT) GENES IN BREAD WHEAT, The University of
Leeds, School of Biology, Centre for Plant Science.
3. Gupta, P.; Kabbaj, H.; El Hassouni, K.; Maccaferri, M.; Sanchez-Garcia, M.; Tuberosa, R.; Bassi, F.M. Genomic
Regions Associated with the Control of Flowering Time in Durum Wheat. Plants 2020, 9, 1628.
4. Iqbal, M., Navabi, A., Salmon, D. F., Yang, R.-C. And Spaner, D. 2006. A genetic examination of early flowering
and maturity In Canadian spring wheat. Can. J. Plant Sci. 86: 995–1004.
5. Jeong Hwan Lee, 2019. Flowering-time Genes and Flowering-time Pathways in Wheat (Triticum aestivum L.),
Division of Life Sciences, Chonbuk National University, 567 Baekje-daero, Deokjin-gu, Jeonju, Jeollabuk-do
54896, Republic of Korea
6. Kippes N, Zhu J, Chen A, Vanzetti L, Lukaszewski A, Nishida H, Kato K, Dvorak J, Dubcovsky J. 2014. Fine
mapping and epistatic interactions of the vernalization gene VRN-D4 in hexaploid wheat. Mol Genet Genomics
289: 47-62.

16. References.
7. Law CN, Suarez E, Miller TE, Worland AJ. 1998. The influence of the group 1 chromosomes of wheat on ear-
emergence times and their involvement with vernalization and day length. Heredity 41: 185-191.
8. Law CN, Sutka J, Worland AJ. 1978. A genetic study of day length response in wheat. Heredity 41: 575-585.
9. Nesbitt, M., 2001. Wheat Evolution: integrating archaelogical and biological evidence. Wheat Taxonomy: The
legacy of John Percival, Issue 3, pp. 37-59.
10. Whittal A, Kaviani M, Graf R, Humphreys G, Navabi A. 2018. Allelic variation of vernalization and photoperiod
response genes in a diverse set of North American high latitude winter wheat genotypes. Plos One 13: e0203068.
11. Xiao J, Xu S, Li C, Xu Y, Xing L, Niu Y, Huan Q, Tang Y, Zhao C, Wagner D, Gao C, Chong K. 2014. O-glcnac-
mediated interaction between VER2 and tagrp2 elicits tavrn1 mrna accumulation during vernalization in winter
wheat. Nat Commun 5: 4572.
12. Yan L, Loukoianov A, Blechl A, Tranquilli G, Ramakrishna W, sanmiguel P, Bennetzen JL, Echenique V,
Dubcovsky J. 2004. The wheat VRN2 gene is a flowering repressor down-regulated by vernalization. Science 303:
1640-1644.

17. Thank you