Crop Evolution Flashcards
Timeline of domestication
1200 - open field system
1650 - private land, fallowing, enclosures
1700 - seed drills
1850 - 4 year rotation (wheat, turnips, barley and clover)
1920 - fertilisers, plant breeding
1950 - more fertilisers, herbicides, pesticides
1980 - more fertilisers, fungicides, short straw cultivars
Definitions
Cultivation - grow plants out of natural range
Domestication - choosing ideal characteristics
Breeding - crossing of plants to get desired characteristics in 1 plant
Genetic modification - manipulate genes for characteristics
Ancient vs modern crop traits
Loss of dispersal mechanism:
Don’t want seed dispersal as seeds fall off
Good for seed collection
e.g. maize and wheat
Loss of dormancy:
Less time between sowing and germination
Germinates quicker
e.g. wheat and rice
Perennial to annual:
One big reproductive event instead of several
All energy into 1 event to maximise yields
e.g. rice and rye
Loss of fruit production:
Energy into tuber/roots
e.g. yam
Loss of seed production:
Eat fruit without seeds
e.g. banana and citrus
Increase size of:
Seeds (e.g. legumes)
Fruit (e.g. squash)
Storage organ (e.g. carrot)
Loss of bitterness:
Now higher in starch and sugar
e.g. cucurbits
Cereal crops
Ear: single group of seeds w grains attached to rachis; grain covered in husk which has bred out
Shattering: grain falling off rachis for dispersal; loss of this as was hard to collect grains
Tillering: branching of stem; reduce this for more energy into seeds
Maize
Evolved from teosinte
Changes: larger ears, reduced tillering and seed shattering
Slow change in DNA over time - stepwise transition through mutations and changes in gene expression
Loss of husk thorugh amino acid substitution (Lys –> Asp)
Hybridisation between teosinte and maize
Wheat
Accidental evolutionary events
Complex genetics
Einkorn - diploid; unhospitable areas
Durum - tetraploid; free threshing; hard grain
Emmer - tetraploid; heavy milling in mountainous regions
Bread - hexaploid; free threshing; easy to mill; large leaves and grains
Dwarf - reduced lodging and large grains
