Apple (Malus domestica Borkh.) a.k.a. Malus pumila P. Mill.

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Apple (Malus domestica Borkh.) a.k.a. Malus
pumila P. Mill.
Jake Fleming Department of Geography, UW
Madison jefleming_at_wisc.edu
Image from bestapples.com
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Taxonomy

• Family Rosaceae
• Subfamily Maloideae (with pears)
• Genus Malus (40 sp.)
• Section Malus
• Series Malus
• Species domestica

www.billnymanart.com
A note on nomenclature In his 2006 book The
Story of the Apple, BE Juniper refers to both the
domestic apple and the wild Central Asian apple
as Malus pumila. The USDA has also adopted this
convention. For clarity, and as Coart et al.
2006 calls into question the hypothesis upon
which this is based, I use the older names Malus
sieversii for the wild Central Asian apple and
Malus domestica for the orchard apple.
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Importance

• Worlds most important temperate fruit crop 63
  million tons/yr.
• Leading producers in 2004 China 18.7 Mtons (4
  Mtons in 1990), United States 6 Mtons, Russia,
  Germany, Japan

Food and Agriculture Organization of the United
Nations. http//faostat.fao.org
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Malus domestica - the specifics

• Woody, long-lived tree
• Unlike congeners, extreme heterozygosity, does
  not breed true. Single parental event yields
  massive variation in fruit color, size, taste,
  flower color, thorns, tree habit, so
• Cultivars must be vegetatively propagated
  instant domestication
• Perfect, self-incompatible flowers. n 17.
  Most congeners and cultivars 2n, some 3n, 4n.

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3 Stories of Domestication

• Compilospecies conventional wisdom until c.
  1990. Eurasian origin, somewhere/everywhere
• Malus sieversii Roem. Vavilov 1930. Harris,
  Robinson, Juniper 2002. Central Asian origin
• BREAKING!! Malus sylvestris Mill. Coart et al.
  2006. European origin?

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Compilospecies hypothesis
Hypothesis Malus domestica arose from some
combination of crabapples in Eurasia, with
possible recent introgression in North America
(Watkins 1995)

• In Maloideae, hybridization between genera not
  rare (e.g. Malus x Pyrus)
• In Malus, species boundaries fuzzy, some hybrids
  occur
• M. domestica may (or may not) readily hybridize
  with sympatric congeners

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M. sieversii hypothesis
Hypothesis Malus sieversii of Central Asia is
the wild ancestor of domesticated apples. Other
species contributed little or nothing. (Vavilov
1930)

• As the Tien Shan Mountains rose and the Gobi and
  Taklamakan Deserts grew, ancestral Malus
  populations were isolated
• Among a very diverse population making up as much
  as 80 of the forest,
• Some wild fruits are indistinguishable from
  cultivars
• Selection by bears?
• Human-mediated dispersal along Silk Road
• trade routes (but not by current residents)
• (Juniper and Mabberley 2006)

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M. sieversii hypothesis
Hypothesis Malus sieversii of Central Asia is
the wild ancestor of domesticated apples. Other
species contributed little or nothing. (Vavilov
1930)

• As the Tien Shan Mountains rose and the Gobi and
  Taklamakan Deserts grew, ancestral Malus
  populations were isolated
• Among a very diverse population making up as much
  as 80 of the forest,
• Some wild fruits are indistinguishable from
  cultivars
• Selection by bears?
• Human-mediated dispersal along Silk Road
• trade routes (but not by current residents)
• (Juniper and Mabberley 2006)

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M. sieversii hypothesis
Hypothesis Malus sieversii of Central Asia is
the wild ancestor of domesticated apples. Other
species contributed little or nothing. (Vavilov
1930)

• As the Tien Shan Mountains rose and the Gobi and
  Taklamakan Deserts grew, ancestral Malus
  populations were isolated
• Among a very diverse population making up as much
  as 80 of the forest,
• Some wild fruits are indistinguishable from
  cultivars
• Selection by bears?
• Human-mediated dispersal along Silk Road
• trade routes (but not by current residents)
• (Juniper and Mabberley 2006)

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M. sieversii hypothesis
Hypothesis Malus sieversii of Central Asia is
the wild ancestor of domesticated apples. Other
species contributed little or nothing. (Vavilov
1930)

• As the Tien Shan Mountains rose and the Gobi and
  Taklamakan Deserts grew, ancestral Malus
  populations were isolated
• Among a very diverse population making up as much
  as 80 of the forest,
• Some wild fruits are indistinguishable from
  cultivars
• Selection by bears?
• Human-mediated dispersal along Silk Road
• trade routes (but not by current residents)
• (Juniper and Mabberley 2006)

Bearington Bears catalog. 10.95
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M. sieversii hypothesis
Hypothesis Malus sieversii of Central Asia is
the wild ancestor of domesticated apples. Other
species contributed little or nothing. (Vavilov
1930)

• As the Tien Shan Mountains rose and the Gobi and
  Taklamakan Deserts grew, ancestral Malus
  populations were isolated
• Among a very diverse population making up as much
  as 80 of the forest (adaptive?),
• Some wild fruits are indistinguishable from
  cultivars
• Selection by bears?
• Human-mediated dispersal along Silk Road trade
  routes (but not by current residents)
• (Juniper and Mabberley 2006)

Bearington Bears catalog. 10.95
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Geography of M. sieversii
Note Whats up with this map?
Harris et al. 2002
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Dispersal into Europe

• Silk Road was operational by 2100 ybp. In summer,
  went straight through Tien Shan
• One big apple found in Ireland, 3000 ybp. What is
  it?
• Alexander the Great, 2300 ybp, fought mock
  battles with apple projectiles. Must have been
  bigger than crabs.
• 2400 ybp, Celt-Persian contact?
• 1300 ybp, Muslim empire, Central Asia-Spain

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Molecular evidence

• cDNA gene matK
• Only 16 of 1341
• characters informative
• 18-bp duplication in
• M. domestica and 1 M.
• sieversii accession
• Other M. sieversii accessions tested only for
  duplication, did not have it

Wild apple Malus sieversii Domesticated apple
Malus domestica
Harris et al 2002
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• Nuclear ribosomal ITS

• No M. sylvestris

Robinson et al 2001
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USDA collections, M. sieversii
Forsline et al. 2003
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Harris et al 2002s matK duplication
Forsline et al. 2003
8 of 10 M. sieversii accessions from Uzbekistan
and Tajikistan (Robinson et al 2001)
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Other genetic support for M. sieversii

• Morphological RAPD sequence data (ITS1, 5.8S
  rRNA, ITS2, matK) Forte et al. 2002
• Isozymes DIA-2, AAT-2, PGM-1 and PGM-5 Wagner
  and Weeden 1999
• Sampling? Strength of support? I dont know
• Forte, A.V. et al. 2002. Phylogeny of the Malus
  (apple tree) species, inferred from the
  morphological traits and molecular DNA analysis.
  Russian Journal of Genetics 38 1150-1160.
• Wagner, I. and Weeden, N.F. 2000. ISOZYMES IN
  MALUS SYLVESTRIS, MALUS DOMESTICA AND IN RELATED
  MALUS SPECIES. Acta Hort. (ISHS) 53851-56

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Morphological evidence for M. sieversii

• Floral morphology
• Fruit morphology

Juniper and Mabberley 2006
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Molecular evidence against M. sylvestris

• Hybridization b/w cultivars and sympatric
  European crab apple, M. sylvestris, almost
  absent

3 of 76 wild specimens
STRUCTURE
Coart et al. 2003
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BUT WAIT. M. sylvestris

• Hypothesis Actually, M. sylvestris, the European
  crab apple, is in some way ancestral to
  domesticated apples
• Unlike M. sieversii, M. sylvestris is solitary,
  not notably heterogeneous, rare, and produces
  bitter, inedible fruit.
• Contrary to their own earlier work, Coart et
  al.s JULY 2006 article shows M. sylvestris to be
  much closer to M. domestica than previous, using
  cDNA PCR-RFLP
• 16 different chloroplast haplotypes based on
  matK duplication, 1 point mutation, 2 restriction
  endonucleases (EcoRI, MseI)

www.wikipedia.com
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Coart et al. 2006
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Coart et al. 2006
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Coart et al. 2006
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matK dupII
Coart et al. 2006
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Also,

• Greater chloroplast diversity of cultivars
  suggests some kind of hybridization
• Geographic distribution of rare haplotypes
  suggests sylvestris x domestica hybridization

Coart et al 2006
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Coart et al. 2006
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Selected Sources

• Coart, E.L.S., et al. 2003. Genetic variation in
  the endangered wild apple (Malus sylvestris (L.)
  Mill.) in Belgium as revealed by amplified
  fragment length polymorphism and microsatellite
  markers. Molecular Ecology 12 845-857.
• Coart, E.L.S., et al. 2006. Chloroplast
  diversity in the genus Malus new insights into
  the relationship between the European wild apple
  (Malus sylvestris (L.) Mill.) and the
  domesticated apple (Malus domestica Borkh.).
  Molecular Ecology 15 2171-2182.
• Forsline, P.L. et al. 2003. Collection,
  maintenance, characterization, and utilization of
  wild apples of Central Asia. Horticultural
  Reviews 29 1-62.
• Harris, S.A., J.P. Robinson, and B.E. Juniper.
  2002. Genetic clues to the origin of the apple.
  TRENDS in Genetics 18(8) 426-430.
• Juniper, B.E. and D.J. Mabberley. 2006. The
  Story of the Apple. Portland Timber Press, Inc.
• Vavilov, N.I. 1930. Wild progenitors of the fruit
  trees of Turkestan and the Caucasus and the
  problem of the origin of fruit trees. Proceedings
  of the 9th International Horticultural Congress,
  London, pp. 271-286.
• Watkins, R. 1995. Apple and pear. In Evolution
  of Crop Plants (Smartt, J. and Simmonds N.W.
  eds.). Longman. 418-422.

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