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lec03 (dragged) 5 - ber accompanied by an increase in seed...

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6 Lecture 3 Changes from Wild Species to Domesticated Crops (Source: Franz Schwanitz 1906) Gathered plants are the fi rst form of wild plants. Present-day examples of species that are still gathered in various parts of the world include: Blueberry ( Vaccinium spp.) Brazil nut ( Bertholletia excelsa ) Chickle ( Achras zapota ) Indian rice ( Zizania aquatica ) Rubber ( Hevea basiliensis ) Sugar maple ( Acer saccharum) However, wild plants become distinctly different from cultivated plants. The change from wild to cultivated crops is characterized by a number of gross genetic changes. These involve: 1. Gigas characteristics Cultivated plants appear larger, more robust, larger thicker leaves, fl eshier roots, larger fl owers, fruits, and seeds. Due to a number of factors. a. Polyploidy. (Examples: strawberry is an octoploid, bread wheat is a hexaploid.) b. Possibility of internal changes in the chromosomes which are often larger and thicker in cultivated plants c. Mutation 2. Reduction in fertility a. Decrease in fertility through reduction in seed num-
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Unformatted text preview: ber, accompanied by an increase in seed size. b. Loss of fertility, particularly true for crops in which economic portion is not the seed. Many cultivated sweet potatoes no longer F ower. Many cultivated crops are seedless, such as banana, orange. Thus, crops are often dependent on humans for sur-vival. 3. Loss of survival characters Shattering ability in grains Potatoes- tubers borne close to plant in domestic types, spread in wild types Thin vs. thick shells in nuts Fig. 3-6. Wild and domesticated forms of einkorn wheat. Wild forms needs to disperse seeds effectively and has thus evolved easily shattered ears with brittle rachises and thin, arrow-shaped spikelets designed to penetrate surface litter and em-bed themselves in cracks in the ground. In domesticated form, plumper spikelets have lost some of the key structures necessary for self-implantation, seed dispersal, and suc-cess in the soil. Source: Smith 1994, p. 73....
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