Alphonse de Candolle Origin of Cultivated Plants (1883) Charles Darwin Origin of Species (1859) The Variation of Plants and Animals under Domestication (1867) Studies of origins & domestication of crop plants images from Wikipedia

Nikolai I. Vavilov ( ) Studies on the Origin of Cultivated Plants (1926) The Origin, Variation, Immunity and Breeding of Cultivated Plants (English translation of selected works published in Chronica Botanica issued in 1951) J.R. Harlan, Economic Botany, photo by H.V. Harlan. Studies of origins & domestication of crop plants

Nikolai I. Vavilov Studies on the Origin of Cultivated Plants (1926) The Origin, Variation, Immunity and Breeding of Cultivated Plants (English translation of selected works published in Chronica Botanica issued in 1951) J.R. Harlan, Economic Botany, photo by H.V. Harlan. Trofim Lysenko Joseph Stalin Vavilov imprisoned in 1940, died of malnutrition in 1943

Vavilov’s centers of crop diversity  crop origins (one of several versions) Studies of origins & domestication of crop plants

Copyright ©2006 by the National Academy of Sciences Smith, Bruce D. (2006) Proc. Natl. Acad. Sci. USA 103, Fig. 1. Currently recognized independent centers of plant and animal domestication

Kinds of evidence about crop origins Archaeological –plant remains –artifacts Living plants –DNA, proteins, morphology, biochemistry –ecology, distributions Linguistic –names of the crop in different languages Historical –documentation in texts or illustrations Studies of origins & domestication of crop plants

Origins of domesticated crop Using DNA and other data on extant plant populations: identify the wild progenitor species determine origins of polyploidy (if applicable) pinpoint geographic area of domestication –single or multiple domestication –center or diffuse distinguish “ancestral” populations from escapes identify the genes that were the “targets of selection” during domestication Example: maize domestication… Studies of origins & domestication of crop plants

Zea mays ssp. mays = maize = corn (in USA)

Paintings of Diego Rivera

John Doebley Hugh Iltis Researchers on maize domestication

Teosinte and ‘reconstructed’ primitive maize. George Beadle created the latter by crossing teosinte with Argentine pop corn and then selecting the smallest segregants. This maize ear resembles the earliest archaeological corn recovered from the Tehuacán valley in Mexico (photo by John Doebley) Teosinte ear (Zea mays ssp mexicana) on the left, maize ear on the right, and ear of their F1 hybrid in the center (photo by John Doebley). Maize and teosinte are the same biological species: Zea mays

‘male’ flowers in tassels ‘female’ flowers in ears Where are they positioned? 2 ranks vs. many ranks 2 fertile flowers develop into grains Comparing morphology of maize and teosinte

If there was ever a grain not pre-adapted to be domesticated as a cereal, teosinte certainly would take first place. Unlike grains of all other domesticated grasses… teosinte grains are permanently imprisoned in a hard, woody shell… This structure is so hard and indestructible that human use of the grain is out of the question. (Hugh Iltis) So why was maize originally domesticated? sterile flowers

One hypothesis about maize domestication: Could maize have been originally cultivated for its sweet stems, not grain? Archaeological maize quids. figure from Mangelsdorf et al. 1967, republished in Staller (2010) Maize Cobs and Cultures: History of Zea mays L. Photo by Hugh Iltis, on cover of Economic Botany

Where did maize originate? From what wild ancestor?

Copyright ©2002 by the National Academy of Sciences Matsuoka, Yoshihiro et al. (2002) Proc. Natl. Acad. Sci. USA 99, Fig. 1. Geographic distribution of maize and teosinte used in this study Balsas river valley Where did maize originate? From what wild ancestor?

Copyright ©2002 by the National Academy of Sciences Matsuoka, Yoshihiro et al. (2002) Proc. Natl. Acad. Sci. USA 99, Balsas river valley maize in Mexico  maize in North America  maize in South America  teosinte  Where did maize originate? From what wild ancestor?

Copyright ©2002 by the National Academy of Sciences Matsuoka, Yoshihiro et al. (2002) Proc. Natl. Acad. Sci. USA 99, maize in Mexico maize in North America maize in South America teosinte Where did maize originate? From what wild ancestor?

tb1, or teosinte branched 1, the first “domestication gene” identified in maize (Research in lab of John Doebley) Identifying “domestication genes”

normal teosinte fruitsmutated fruits mutated fruits = homozygous for teosinte glume architecture 1 Could this have been the mutation that made maize kernels usable as food? (Research in lab of John Doebley) Identifying “domestication genes”

Jaenicke-Després, Viviane et al. Science 2003 unbranched stem protein starch DNA from Ancient cobs shows selection on three “domestication genes” Studying “domestication genes”

Jaenicke-Despres, et al. Science 2003

Copyright ©2002 by the National Academy of Sciences Matsuoka, Yoshihiro et al. (2002) Proc. Natl. Acad. Sci. USA 99, Fig. 1. Geographic distribution of maize and teosinte used in this study Balsas river valley