ORIGIN AND DOMESTICATION OF CULTIVATED PLANTS

ORIGIN OF AGRICULTURE Possibly 10,000 yrs ago Ties to end of Ice Age Many differing opinions: Vavilov – Russian plant geneticist eight independent centers (1951) Sauer – cradle in Southeast Asia woody areas vs. river valleys vegetative methods

Opinions (cont) Harlan – opposed Vavilov’s eight centers wide geographic areas called non-centers three large independent systems: - Near East and Africa - China and Southeast Asia - Mexico and South America Bender – transition from hunter/gatherer to producer - profoundly changed human culture Harlan;Hawkes – climatic/cultural factors - motivated man to “invent agriculture”

What Do We Know For Certain? Definite evidence from archeological sites: - agricultural villages 8000-9000 B.C. - Fertile Crescent - diversity of crops: wheat, barley, lentil, oats, vetch, dates, grapes, olives, almonds, figs, pomegranates

Chinese Center of Agriculture - About 4000 B.C. Crops domesticated: millet, chestnuts, hazelnuts, peaches, apricots, mulberries, soybeans, and rice

Southeast Asia/Indonesia - Domesticated Rice around 6000 B.C. other crops followed: sugar cane, coconut, banana, mango, citrus

New World Southern Mexico and Central America 5000 – 7000 B.C. maize (corn), sweet potato, tomato, cotton, pumpkin, peppers, squash, avocado, pineapple

South America Broad “non-center” stretches from Chile northward to Atlantic Ocean and eastward into Brazil - snap beans and lima beans 6000 B.C. - other crops: potato, peanut, pineapple, cashew, Brazil nut, peppers, tobacco, tomato

Australia Only one crop: macadamia or Queensland nut

United States No major cultivated crop origins - relies on introduced crops - many minor fruit and nut crops: American grapes and plums, pecan, chestnut, hickory nut, hazelnut, black walnut, persimmon, blueberry, raspberry, blackberry, and cranberry

United States (cont) Additional crops: - sunflower (important oil crop) - hops - Jerusalem artichoke - some grasses - many ornamentals - timber tree species

Methods of Plant Domestication Vegetative (Asexual) Propagation - observation/experience revealed - some of the oldest woody plants: grape, fig, olive, mulberry, pomegranate, quince - many tree fruit species native to near east: almond, apple, pear, cherry, walnut

Vegetative (Asexual) Propagation (cont) Many ancient plants: - potato (tuber) - sweet potato (an enlarged root) - banana (rhizome) - bamboo (rhizome) - ginger (rhizome) - filbert (layering) - pineapple and date (suckering)

Methods of Plant Domestication Seed (Sexual) Propagation - harvesting wild grass seeds led to two population types: 1) shattering - reseeded itself 2) nonshattering - harvested and resown - nonshattering thus improved as it was more easily harvested

Seed (Sexual) Propagation (cont) Close planting of harvested seeds led to better competition against weeds - selects stronger, vigorous plants - larger seeds increase germination - harvested crop from superior seed - unknowingly developed superior

Seed (Sexual) Propagation (cont) Other desirable characteristics: - loss of seed dormancy - increased flower numbers - larger inflorescences - trend toward determinate growth Sometimes change is slow/complex Sometimes rapid with few genes