The basic concept of varietal development

1
The basic concept of varietal development

• Produce or identify genetically variable
  germplasm
• Carry out selection procedure
• Stabilize and multiply these superior genotypes

2
A successful plant breeder will require knowledge
in many (if not all) of the following subjects

• Evolution (Geographic area of origin)
• Botany
• Biology mode of reproduction, types of cultivar
  and breeding systems
• Genetics
• Pathology nematology, entomology, virology
• Weed science
• Food science
• Biometry (A numbers game), Breeder are required
  to be good data manager
• Agronomy
• Molecular biology molecular markers, genetic
  engineering, tissue culture

3
Professor N.W. Simmonds defined domestication as
follow

• A plant population has been domesticated when it
  has been substantially altered from the wild
  state and certainly when it has been so altered
  to be unable to survive in the wild.

4
Modes of reproduction and types of cultivar
A cultivar (or variety) is defined as a group of
one or more genotypes which have a combination of
characters giving it distinctness, uniformity and
stability (DUS)

• Distinctness
• Morphological characters (not to be influenced
  by environment)
• Physiology
• Disease or virus reaction-insect
  resistant-chemical quality
• Molecular

Distinctness is described as follow The variety,
whatever the origin, artificial or natural, of
the initial variation from which it has resulted
shall be clearly distinguishable, by one or more
important characteristics, from any other plant
variety
5
UniformityAny variation should be predictable
and capable of being described by the breeder
Stability It must remain true to its description
when it is reproduced or propagated. The plant
variety shall continue to exhibit its essential
characteristics after successive reproductions
or, where the breeder has defined a particular
cycle of reproduction, at the end of each cycle
of reproduction (three of four way crosses).
?? ???? ???????? ?? ???????? ???? (VCU) value
for cultivation and use
6
?? 122 ???? ????? ?????

• 32 ???? ??????
• 70 ???? ??????
• 20 ???? ?????? ?? ????? ????? ???????

7
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• ???? ???? ??? ????? ????? ??? ???
• ???? ???? ??? ????? ??? ?? ?? ?????? ??????
• ???? ???? ??? ????? ???? ?????? ???
• ???? ?????? ???? ???? ??? ????
• ???? ???? ????? ???? ?? ????? ??? ????

8
Asexual reproduction
Bulb is a modified shoot consisting of a very
much shortened stem enclosed by fleshy leaves
(onion)

• Corm is a swollen stem base bearing buds in the
  axils of scale-like remains of leaves from the
  previous years growth (garlic)

A rhizome is an underground stem with buds in the
axils of reduced leaves (Mint)
A tuber is a swollen stem that grows beneath the
soil surface bearing buds (potato)
Cutting
A stolon is a horizontally growing stem that
roots at nodes (strawberry runners)
9
Apomixis

• Androgenesis sperm nucleus of a pollen grain
• Apospory somatic ovary cells
• Diplospory 2n megaspore mother cells
• Partenogenesis egg cell without fertilization
• Semigamy sperm and egg cells independently
  without fussion
• ?? ?????? ?? ???? ?? ???? ???????? ???? ??????
  ???? ???? pseudogamy ???? ?? ???

10
Type of cultivar
1- Pure line cultivars 90 or more
homozygosity ?? ???? ?????? ?????? ????? ?????
??????? ???? ?? ????? ?? ???? ???? ???? ?? ??? ?
?????? ???? ?? ???? ???? ???. ?? ???? ??? ?????
????? ??? ??? ???? ? ???? ?????? ????? ????? ???
?? ??? ????? ???? ???????? ????? ???? ????.
2- Open pollinated cultivars ?? ????? ?? ????
?????? ???? ?? ??? ???????? F1 ????? ???? ?? ????
3- Hybrid cultivars ????? ? ????????? ?????
11
Type of cultivar
4- Clonal cultivars ??????? ?? ??? ?????? ?
????????? ?????
5- Synthetic cultivars ?????? ???? ??????? ?? ??
??? ????????? ???? ?? ???? (??? ?????) ???? ??
????. ???? ????? ?????? ???? ?? ???? ? ??? ???
??? ????? syn1? ??????? ?? ??????? ?? Syn2 ?
....?? ????? ?? ???.
6- Multiline cultivars (Near isogenic lines) ??
?????? ????? 5 ???? ?? ????? ?? ???. ???? ??????
?????. ???? ???? ?? ???????? ???? ??????.
7- Composite-cross cultivars ?? ????? ??? ?? ??
?????? ???????? ?? ???? ?????? ?? ??? ?? ??? ??
?????? ?????. ??? ????? ???? ?? ?? ????? ? ??? ??
???. ???????? ???? ????????? ?????? ?????? ? ????
????????? ???????? ???? ????? ????. Breeders seed
can never be maintained as the cultivar was
originally released.
12
Breeding objectives
-what political and economic factors are likely
to be of greatest importance in future years?
-what criteria will be used to determine the
yielding ability required of a new cultivar?
-what end-use quality characters are likely to be
of greatest importance when the new releases are
at a commercial stage?
-what diseases or pests are likely to be of
greatest importance in future years?
-what type of agricultural system will the
cultivar be developed for?
13
Plant breeders can increase growers
profitability by
-Increasing the yield per planted area, assuming
input costs remain constant (biomass and
partition)
-Increasing the region of crop production
-Reducing input costs (including herbicide,
insecticide and fungicides) while maintaining
high yield per unit area
-Increasing the inherent quality component of the
end product so that growers receive a higher unit
price when the harvestable product is sold, or
such that the product is more nutritious.
For example boiled potatoes need to remain
relatively firm and not disintegrate on boiling
(lower solid content of tuber) Potato chip (high
solid content with low water content and low
reducing sugare)