Single seed descent (SSD) is a method of rapidly inbreeding plant populations by advancing generations through growing individual seeds from each plant in isolation. It separates the inbreeding and selection phases of plant breeding to speed up the process. With SSD, a single seed is harvested from each F2 plant and bulked, then the bulk is planted to produce the F3 generation. This continues for several generations until homozygosity is achieved, at which point lines can be tested. SSD allows for faster generation advancement than pedigree breeding methods while maintaining genetic diversity from the original cross. Some disadvantages are the inability to track superior early generation plants and reduced ability to select through progeny performance.

1. Single seed descent
method
SUBMITTED BY:
ANKITA PANDA
ADM.NO.-42 HO/16
SUBMITTED TO:
DR. KOUSHIK KU.
PANIGRAHI
DR. BHIMSEN NAIK

2. SSD
 Single seed descent can be used in
self or cross pollinated crops. It is a
method of inbreeding a segregating
population that is quite conducive
to environments that are not typical
: good news for off-season
nurseries!!

3. Goulden (1941)
proposed a similar
system (without
calling it SSD) and it
resulted from the
interest of plant
breeders
to rapidly inbreed
populations before
evaluating individual
lines.

4. His alternative was to separate the
inbreeding and selecting generations in order
to speed the process along.
He noted that a wheat breeding program could be
divided into the development of pure lines from a
segregating populations and selection among the best of
those lines. He emphasized that with the pedigree
method, plants had to be grown in an environment in
which genetic differences would be expressed for the
characters under selection; and thus probably limited to
one generation per year.

5. By doing this, the number of progeny grown
from a plant in each generation should be one
or two only, and two generations can be grown
in the greenhouse and one in the field. He
proposed the model with spring-sown cereals.
In this manner, he could attain the F6
generation in 2 years, as opposed to 5 years as
with the pedigree method. After the desired
level of homozygosity was achieved, the lines
could then be tested for desired characteristics.

6. Single Seed Procedure
This is the classic
of having a single seed
each plant, bulking the
individual seeds, and
planting out the next
generation.

8. Season 1: F2 plants grown. One
F3 seed per plant is harvested
and all seeds are bulked. Collect
a reserve sample of 1
Brim suggested harvesting the
3 seeded soybean pod and
1 seed for planting and 1-2 for
reserve.

9. Season 2: Bulk of F3 seed is
planted. One F4 seed per plant
is harvested and all seeds are
bulked. Collect a reserve
sample of 1 seed/plant.
Season 3: Repeat.

10. Season 4: Grow bulk of F5 seed
and harvest individual plants
separately.
Season 5: Grow F5:6 lines in
rows; select among rows and
harvest selected rows in bulk.
Season 6: Begin extensive
testing of F5 derived lines.

12. In reality, the population size will decrease
with each generation (due to lack of
germination, lack of seed set, etc.). So if
you want 200 F4 plants and 70% of the
seeds in each generation will produce
plants with at least one seed. Then, by
working back to the F2 generation, you
need to plant 584 F2 plants. Be sure to
take this into account when selecting the
number of F2 seeds.

13. Each single seed traces back to
a single F2 plant.
Theoretically, if you start with
a large enough F2 sample,
then by the F5 generation you
will still have a broad
representation of variability
from the cross.

14. SSD’s Bonus Points:
Rapid generation advance,
maintenance of an unbiased
broad germplasm base, labor
and time efficient, able to
large number of samples, and
easily modified!

15. Genetic Considerations
1) Additive genetic variation among
individuals increased at a rate of
(1+F)2
A where F=0 in F2.
2) There is little natural selection,
except for seed germination potential
or where the environment prevents
some genotypes from setting seed.

16. 3) In multiple seed procedure, there
may be a variation associated with
sampling of seed from a bulk samples to
plant the next generation.
4) This sampling results in exclusion of
progeny from some plants, and multiple
representation of progeny from others.

17. ADVANTAGES
 Easy way to maintain pops during inbreeding
 Natural selection does not influence pops
 Well suited to GH and off season nurseries
 Large number of crosses can be evaluated.
 It is convenient, less expensive and time saving
method.
 There is no need of keeping much records.

18. DISADVANTAGES
 Selection based on individual phenotype rather than
progeny performance
 Natural selection cannot influence pop in a positive
manner.
 The frequency of getting desirable genotypes in the
advanced generation is reduced in this method.
 The identity of superior F2 plants can’t be
maintained.

19. Thank you