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The Domestication of Phaseolus vulgaris L

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					The Domestication of
Phaseolus vulgaris L.
        Taxonomic Overview
 Family: Fabaceae/
  Leguminosae
 Subfamily:
  Papilionoideae
 Tribe: Phaseolae
 Phaseolus is a
  monophyletic genus
 Diploid: 2n = 22 x=11
 Predominantly self-
  pollinating due to
  papilionaceous,
  cleistogamous flower
  structure (some bees)
•The genus Phaseolus is strictly
New World in tropical and
subtropical locales.
•Documenting Domestication reports
range as from Mexico to Argentina
•However, two species P. sinuatus
Nuttall ex T & G and P. polystachios
(L.) BSP are found throughout the
Southeastern U.S.A. (Radford,
1964)
     Importance to Humans
 Fabaceae is one of the most important
  plant families; has been for millenia
 Includes other domesticates such as:
  Cicer arietinum L. “Chick pea”
  Arachis hypogaea L. “Peanut”
  Lathyrus odoratus L. “Sweet pea”
 Phaseolae also includes:
  Glycine max (L.) Merr “soybean”
  Vigna unguiculata (L.) Walp.
   --> 4 ssps “Cowpea, Black-eyed pea,
  Yardlong bean, Catjang”
Phaseolus includes 5 domesticated species: P.
vulgaris L., P. lunatis L. (“lima bean”), P.
acutifolius A. Gray (“tepary bean”), P. coccineus
L. (“runner bean”), P. polyanthus Greenman.
Of these, Phaseolus vulgaris L. is the most
important vegetable protein source for humans!
Diversity!
              History
 Native to Central/South Americas
 Arrived in Spain & Portugal from
  Central America in 1506 after the
  “discovery” of the “New World.”
 Accessions from the Andes started
  arriving in Europe after 1532.
 Reached Germany by at least 1543, as
  evidenced by a description in a
  German herbal.
   Mystery of Domestication!
 Role of introgressive hybridization of P.
  vulgaris and P. coccineus in Mexico
  (bumblebees!)?
 Domesticated twice?!
 How many species are we dealing with
  here??
       Role of Hybridization
 Discussed in article at some length;
  hybridization b/t P. coccineus and P. vulgaris
  resulting in P. polyanthus?
 Also, proposed by Freytag in 1955 that gene
  flow from P. coccineus could be responsible
  for the larger seed size in Mesoamerican
  varieties as opposed to Andean varieties.
  (Gepts and Khairallah both report the
  Andean varieties to have larger seeds.)
     Domesticated Twice?!
 Archaeological Evidence
 Molecular Evidence
    Archaeological Evidence
 Supports two events of domestication
   because:
   1. Domesticates appear before evidence for
   cultural contact b/t Meso- & Andean-America
   (occurred ~2000-1000 yrs BPE) (Gepts et
   al., 1986)
   2. Distinct varieties matching varieties today
   found in sites.
   3. Wild P. vulgaris grows in both regions.
(Kaplan, 1980)
•Earliest evidence in
Mesoamerica found
in Coxcatlan Cave
of Tehuacan Valley,
dating to 5,500-
7,000 yrs BPE
•Earliest evidence in
Andes dates to
8,000 yrs BPE,
found in Guitarrero
•Wild remains were
found in
Mesoamerica, but
not in Andes (all
sites located outside
of natural growth of
wild P. vulgaris.)
       Molecular Evidence
 Wealth of evidence!
 Focus mainly on:
  1. Phaseolin types (protein markers)
  2. RFLP diversity
  3. mtDNA analysis (for you, Phil!)
 Following table is from Gepts, 1996
         Phaseolin Types
 Authoritative article on this subject is
  Gepts et al., 1986
 Analyzes phaseolin variations b/t
  Andean & Mesoamerican wild plants as
  well as landraces using 1-D SDS-
  PAGE and 2-D IEF-SDS/PAGE on 106
  wild forms and 99 landraces
 Condensed Results from Gepts,
 1986 on Phaseolin Distribution
 Wild forms:                  Domesticated:
Mexico: M, S (nearly all M)   Mexico: S (2 T)
Guatemala: same as            Colombia, Guatemala,
   Mexico                        Costa Rica: S (1 T)
Peru: S, T (mainly T)         Ecuador: S, T, C (1 C)
Brazil, Argentina: T          Peru: few S, lots T, 2 C, 2
                                 H, 1 A
                              Bolivia, Chile, Argentina:
                                 T, C, few S, 2 H.
           RFLP Diversity
 Looked at Velasquez & Gepts, 1994
 Digested genomic DNA four ways: one
  time each with three different restriction
  enzymes, EcoRI, EcoRV, and HindIII,
  and one time with all three.
 Generated diagrams based on Nei’s
  distances.
Nei’s Distance Diagrams, Velasquez
           & Gepts, 1994
Mitochondrial DNA Analysis
 Khairallah et al., 1990.
 Examined 23 Malawian landraces
 Digested mtDNA with 8 restriction
  endonucleases, HaeIII, BamHI, DraI, EcoRI,
  HindIII, PstI, SalI, XhoI.
 2 distinct mtDNA groups were discovered,
  corresponding to the two nuclear DNA
  groups.
 However, a high level of mt genome
  homogeneity
 •Demonstrates divergence before
 domestication!
  How Many Species Are We
    Dealing with Here??
 Evidence supports that P. vulgaris is at least
   in the process of speciation
Two divergent gene pools repeatedly
identified
Gepts & Bliss, 1985 demonstrated F1 hybrid
lethality b/t Meso- and Andean-American
varieties
 •3 gene pools? Islam et al., 2002
Map of Type
Distribution of Wild
Phaseolus vulgaris




Gepts, 1996
 Condensed Results from Gepts,
 1986 on Phaseolin Distribution
 Wild forms:                  Domesticated:
Mexico: M, S (nearly all M)   Mexico: S (2 T)
Guatemala: same as            Colombia, Guatemala,
   Mexico                        Costa Rica: S (1 T)
                              Ecuador: S, T, C (1 C)
Peru: S, T (mainly T)
                              Peru: few S, lots T, 2 C, 2
Brazil, Argentina: T             H, 1 A
                              Bolivia, Chile, Argentina:
                                 T, C, few S, 2 H.
Nei’s Distance Diagrams, Velasquez
           & Gepts, 1994
                                Sources
•Freytag, G. F. (1955) Variation of the common bean in Central America.
        Unpublished thesis, Henry Shaw School of Botany, Washington Univ.,
        St. Louis, MO.
•Gepts, Paul. (1996) Origin and evolution of cultivated Phaseolus species. In:
        B. Pickersgill and J.M. Lock (eds). Advances in Legume Systematics 8:
        Legumes of Econoic Importance, pp. 65-74. Royal Botanic Gardens,
        Kew.
•Islam, F.M.A., et al. (2002) Genetic variability in cultivated common bean
         beyond the two major gene pools. Gen. Res. Crop Evol. 49: 271-283.
•Kaplan, Lawrence. (1981) What is the Origin of the Common Bean?
•Khairallah, M.M. et al. (1990) Mitochondrial DNA polymorphisms of Malawian
         bean lines: further evidence for two major gene pools. Theor. Appl.
         Genet., 80: 753-761.
•Velasquez, Viviana L. Becerra and Paul Gepts (1994) RFLP diversity of
       common bean (Phaseolus vulgaris) in its centres of origin. Genome,
       37: 256-263.

				
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