Speed Breeding; An innovative approach to shorten crop life span and increase rate of breeding programs under controlled conditions

1. Speed breeding: a powerful tool
to accelerate crop research and
breeding
Dr. Sammyia Jannat
Department of Biotechnology
University of Kotli Azad Jammu and Kashmir
Pakistan

2. Speed breeding
• ‘Speed breeding’ (SB) shortens the breeding cycle and accelerates
crop research through rapid generation advancement.
• SB can be carried out in numerous ways, one of which involves
extending the duration of plants’ daily exposure to light, combined
with early seed harvest, to cycle quickly from seed to seed, thereby
reducing the generation times for some long-day (LD) or day-neutral
crops.

3. • By adopting a 22-h photoperiod and a controlled temperature regime,
generation times were substantially reduced for spring bread wheat
(Triticum aestivum), durum wheat (T. durum), barley (Hordeum
vulgare), chickpea (Cicer arietinum), pea (Pisum sativum), canola
(Brassica napus), the model grass, B. distachyon, and the model
legume, Medicago truncatula, in comparison to those of plants grown
in a field or a glasshouse with no supplementary light.

4. • Under the rapid growth conditions, plant development is normal,
plants could be easily crossed (wheat and barley), and seed
germination rates are high.
• Speed breeding can be used to accelerate gene transformation
pipelines and that adult plant phenotyping for traits such as flowering
time, plant height and disease resistance in wheat; leaf sheath
glaucousness in barley; and pod shattering in canola could be
performed under SB conditions

5. • Glasshouse and Growth chamber–based SB approaches with
supporting data from experimentation can be done on several crops.
• The conditions that promote the rapid growth of bread wheat, durum
wheat, barley, oat, various Brassica species, chickpea, pea, grass pea,
quinoa and Brachypodium distachyon.

6. • Plant density can be increased to efficiently scale up plant numbers
for single-seed descent (SSD).
• Performing Speed Breeding on a small scale in a bench top growth
cabinet, enabling optimization of parameters at a low cost.

7. Green House

8. Growth Chamber

10. Single seed descent (SSD)
• Single seed descent (SSD) is commonly used in breeding programs
and research to facilitate development of homozygous lines following
a cross.
• This process only requires one seed per plant to advance each
generation.

11. Light spectrum

13. Photoperiodism
• Photoperiodism is the physiological reaction of organisms to the
length of night or a dark period. It occurs in plants and animals.
• Plant photoperiodism can also be defined as the developmental
responses of plants to the relative lengths of light and dark periods.
• They are classified under three groups according to the photoperiods:
short-day plants, long-day plants, and day-neutral plants.

14. • Many flowering plants (angiosperms) use a photoreceptor protein,
such as phytochrome or cryptochrome, to sense seasonal changes in
night length, or photoperiod, which they take as signals to flower.
• In a further subdivision, obligate photoperiodic plants absolutely
require a long or short enough night before flowering,
whereas facultative photoperiodic plants are more likely to flower
under one condition.

15. Visible light wavelengths important for plant
growth/photosynthesis
• Red Light: 400-700nm; absorbed by plants extensively
• Far red Light: 700-750nm; cannot observed by human vision bu
important for plants
• Blue Light: 400-500nm; absorbed by plants
• Green Light: 500-600nm slightly absorbed and help to excite the
photon flux

16. Photoreceptors/ Photoreceptor protein
• Phytochrome
 Phytochrome comes in two forms: Pr and Pfr. Red light
(which is present during the day) converts phytochrome to its active
form (Pfr) which then stimulates various processes such as
germination, flowering or branching.
 Phy A, Phy B, Phy C…. Red and far red light
• Cryptochrome
 Cryptochromes entrain the circadian clock to light
 Blue and UV-A

17. Protocol of speed breeding
• To evaluate speed breeding as a method to accelerate applied and basic research
on cereal species, standard genotypes of spring bread wheat (T. aestivum), durum
wheat (T. durum), barley (H. vulgare) and the model grass Brachypodium
distachyon were grown in a controlled environment room with extended
photoperiod (22 hours light/2 hours dark)
• A light/dark period was chosen over a continuous photoperiod to support
functional expression of circadian clock genes.
• Growth was compared with that of plants in glasshouses with no supplementary
light or heating during the spring and early summer of 2016.
• Plants grown under speed breeding progressed to anthesis (flowering) in
approximately half the time of those from glasshouse conditions.
• Depending on the cultivar or accession, anthesis was reached in 37 to 39 days
(wheat - with the exception of Chinese Spring), and 37 to 38 days (barley), while it
took 26 days to reach heading in B. distachyon (Concurrently, the corresponding
glasshouse plants reached the early stem-elongation growth stage or 3-leaf stage
respectively.

19. LEDs (Light Emitting Diode)
• A low cost speed breeding growth room design, lit exclusively by LEDs
(light emitting diode) to reduce the operational cost of lighting and
cooling, which permits 4-5 generations a year, depending on
genotype and crossing plans (Supplementary Fig. 2).

20. • Besides exploring the various ways in which speed breeding can be
used to accelerate generation time, it helps to evaluate the ability to
phenotype some key adult plant phenotypes of wheat and barley.

21. Information about setting up Speed Breeding in an
existing plant growth chamber or CER.
The core ‘recipe’ for programming an existing growth room to set up SB conditions.
● Lights.
Any light that produces a spectrum that reasonably covers the PAR region (400–700 nm), with particular focus
on the blue, red and far-red ranges, is suitable to use for SB.
The referenced study has several examples of these spectra, and similar examples of possible SB spectra are
provided here. An appropriate spectral range can be achieved through LEDs, or a combination of LEDs and other
lighting sources (e.g., halogen lamps), or in the case of a glasshouse, by simply supplementing the ambient
lighting with LEDs or SVLs.
Measurements of the light spectrum be taken before commencement of the SB experiment. In addition to
controlling the light quality, PPFD of ~450–500 μmol/m2/s at plant canopy height is recommended. Slightly lower
or higher PPFD levels are also suitable.
Crops species vary in their response to high irradiance. However, the suggested level of 450–500 μmol/m2/s has
been demonstrated to be effective for a range of crop species.

22. Photoperiod
Photoperiodism of 22 h with 2 h of darkness in a 24-h diurnal cycle is
recommended.
Continuous light is another option, but experience has shown that the
dark period slightly improves plant health. Gradually increasing light
intensity to mimic dawn and dusk states should be done, if possible,
but is not vital.
In previous studies, 18-h photoperiod was sufficient to achieve faster
generation times for wheat, barley, oat and triticale.

23. Temperature
The optimal temperature regime (maximum and minimum temperatures) should be
applied for each crop. A higher temperature should be maintained during the photoperiod,
whereas a fall in temperature during the dark period can aid in stress recovery.
A 12-h 22 °C/17 °C temperature cycling regime with 2h of darkness occurring within 12 h of
17 °C has proven successful.
By contrast, a temperature cycling regime of 22 °C/17 °C for 22 h of light and 2 h of dark,
respectively, was used.
In both scenarios, the generation times of all crops were successfully accelerated and
comparable. In the controlled-environment chamber in which this was demonstrated, the
temperature was ramped up and down similarly to the lights, but this was subsequently
found to not be of particular importance.

24. Humidity
Most controlled-environment chambers have limited control over
humidity, but a reasonable range of 60–70% is ideal. For crops that are
more adapted to drier conditions, a lower humidity level may be
advisable.
Speed breeding is normally done in growth chambers and glasshouses
for crop breeding and model plant research.

25. Photmorphogenic responses of peanut
genotypes in short day and long day light
conditions
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Experiment

26. )
Plant Material
Peanut varieties
Stem elongation and number of leaflets were
observed after emergence with five days interval
Chlorophyll concentration (µMol/m2 )
Apogee chlorophyll meter (MC-100)
Chlorophyll florescence Fv/Fm
Hensatech pocket pea chlorophyll fluorimeter
Leaf area (cm2)
Chlorophyll content (μg/mL)
Microplate Reader (FluoStar Omega, BMG Labtech)
and Software (Omega).
Methods
Morphological
data
Physiological
data
• Short day light conditions
10 h light, 14 h dark
• Long day light conditions
14 h light, 10 h dark
Materials and Methods

27. Light spectrum within light chambers measured
using PG100N handheld spectral PAR meter

28. Red and Blue light experiments
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29. Chlorophyll concentration measurement using apogee
chlorophyll meter
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30. Fluorimeter used to measure the leaf fluorescence
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31. Conclusion
Speed Breeding with the inclusion of high-throughput
phenotyping, genotyping, genome editing, and genomic
selection, accelerating the rate of crop improvement.
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32. Thanks
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