The Domestication of Phaseolus vulgaris L.Taxonomic OverviewPowerPoint PresentationImportance to HumansSlide 5Slide 6HistoryMystery of Domestication!Role of HybridizationDomesticated Twice?!Archaeological EvidenceSlide 12Molecular EvidenceSlide 14Phaseolin TypesCondensed Results from Gepts, 1986 on Phaseolin DistributionRFLP DiversityNei’s Distance Diagrams, Velasquez & Gepts, 1994Mitochondrial DNA AnalysisHow Many Species Are We Dealing with Here??Slide 21Slide 22Slide 23Slide 24The Domestication of Phaseolus vulgaris L.Taxonomic OverviewFamily: Fabaceae/ LeguminosaeSubfamily: PapilionoideaeTribe: PhaseolaePhaseolus is a monophyletic genusDiploid: 2n = 22 x=11Predominantly 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 HumansFabaceae is one of the most important plant families; has been for milleniaIncludes 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 !HistoryNative to Central/South AmericasArrived 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 HybridizationDiscussed 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 EvidenceMolecular EvidenceArchaeological EvidenceSupports 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 EvidenceWealth of evidence!Focus mainly on: 1. Phaseolin types (protein markers) 2. RFLP diversity 3. mtDNA analysis (for you, Phil!)Following table is from Gepts, 1996Phaseolin TypesAuthoritative article on this subject is Gepts et al., 1986Analyzes 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 landracesCondensed Results from Gepts, 1986 on Phaseolin DistributionWild forms:Mexico: M, S (nearly all M)Guatemala: same as MexicoPeru: S, T (mainly T)Brazil, Argentina: TDomesticated:Mexico: S (2 T)Colombia, Guatemala, Costa Rica: S (1 T)Ecuador: S, T, C (1 C)Peru: few S, lots T, 2 C, 2 H, 1 ABolivia, Chile, Argentina: T, C, few S, 2 H.RFLP DiversityLooked at Velasquez & Gepts, 1994Digested 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, 1994Mitochondrial DNA AnalysisKhairallah et al., 1990.Examined 23 Malawian landracesDigested 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 identifiedGepts & Bliss, 1985 demonstrated F1 hybrid lethality b/t Meso- and Andean-American varieties•3 gene pools? Islam et al., 2002Map of Type Distribution of Wild Phaseolus vulgarisGepts, 1996Condensed Results from Gepts, 1986 on Phaseolin DistributionWild forms:Mexico: M, S (nearly all M)Guatemala: same as MexicoPeru: S, T (mainly T)Brazil, Argentina: TDomesticated:Mexico: S (2 T)Colombia, Guatemala, Costa Rica: S (1 T)Ecuador: S, T, C (1 C)Peru: few S, lots T, 2 C, 2 H, 1 ABolivia, Chile, Argentina: T, C, few S, 2 H.Nei’s Distance Diagrams, Velasquez & Gepts, 1994Sources•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:
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