Lecture 5: Traditional crop breeding Flashcards
the varieties of plants we real on are of fundamental importance for
human survival
how are seeds stored around the world?
large seed banks
was domestication of plants achieved once?
NO, it was achieved a number of times across the world independently
how do we date when domestication has occurred? & e.g.
- Archeological records
- cucurburbita pepo peduncle 14C date of 7340 +/- 60 years BP
Characteristics of wild plant populations:
- species are genetically diverse
- within a local region, genes which confer a selective advantage will be predominant
- ECOTYPE
sub-population of wild plants which share local region, genes which confer a selective advantage reulsting in predominance is known as an
ECOTYPE
Characteristics of wild plant populations: a balance is set up between:
- adaptations to the local environment which tend to REDUCE local genetic diversity
- A requirement to respond to altering conditions which INCREASES genetic diversity
the traits we want in crops are often not those that have evolved naturally so humans
Selected traits
Traits selected for by humans for domesticated plants:
- High carbohydrate (or oil) - STAPLES
- Possess traits that are useful in an agricultural environment (seed retention, size etc)
- Therefore there were multiple domestication events occurred throughout human history
- creating a more reliable food supply
seed retention allows you to
harvest your crop all at the same time
Why were crops domesticated?
- MORE RELIABLE FOOD SUPPLY
- provides for a more predictable food supply
- -location
- -uniformity
- Gives greater yields since conditions can be controlled
- -irrigation
- -fertilisation
- -protection
- Select FOR beneficial traits, AGAINST undesirable traits, FOR new traits
What were the consequences of domestication of crops?
-yield increase
-population increases
-people stop moving , they live in settlement (villages, towns, cities)
-people have more time (science, art, communication)
Higher densities = more disease
-We want what others have = WAR
what do Cauliflower, Kale, Broccoli, Brussel sprouts, Kohl rabi, Cabbage have in common?
SAME SPECIES
-we’ve selected different traits
The agricultural environment is different to the wild environment, meaning the selection pressures are
also different
selection of a wild population in an agricultural environment generates
LANDRACES
continued selection from one individual plant will give rise to an
INBRED CULTIVAR.
Breeding introduces new genes into these cultivars
cultivation of potatoes was introduced to Europe in the
mid 16th century
potatoes originated in the tropical highlands of
South America
original varieties of potato compared to European varieties
ORIGINAL VARIETIES:
-diploid
-low yield
-flower when days are short (flowers in Autumn in Europe > no tubers)
-High alkaloid content (good for pest resistance but toxic)
EUROPEAN VARIETIES:
-tetraploid
-high yield
-flower when days are long(flowers in Summer in Europe)
-Low alkaloid content
-not toxic
Wild beet is:
leafy & is thought to be Beta maritima
Wild beet was domesticated in
prehistoric times
- leafy plants= swiss chard
- Root crop = beetroot
by 18th century sugar beet had been developed with
6% sucrose content
Beet & Napoleon & Achard
- in 1799 Achard developed a process for extraction sugar from sugar beet
- in 1811 Napoleon decreed that beet should be grown as an alternative to cane sugar (in response to British naval blockade)
sucrose content in beet over time:
- sucrose content rose steadily as a result of selection
- limit eventually reached
- genetic diversity exhausted
- physical max reached
- root sizes still increased further
