Olive Domestication

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Olive Domestication
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Olea europaea

• Family Oleaceae
• Six subspecies
• Olea europaea ssp. europaea (olives) grows in
  Mediterranean Basin at the N limit of Olea range
• Other 5 subspecies grow in Africa and Asia
• Olea fruit gathered 19,000 year BP in E.
  Mediterranean
• One of the first plants cited in early literature
  
• Can live 2000-3000 years

Kohler's Medizinal-Pflanzen in naturgetreuen
Abbildungen mit kurz erlauterndem Texte Atlas
zur Pharmacopoea germanica,  Volume 2 (1887)
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Oleaceae phylogeny
www.ruhr-uni-bochum.de/.../ Olea.europaea.ho5.jpg
Wallander, E. and V. A. Albert. 2000. Phylogeny
and classification of Oleaceae beased on rps16
and trnL-F sequences. American Journal of Botany
12 1827-1841.
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Olea europea ssp. europaea

• 2 practically indistinguishable varieties
• Olea europaea ssp. europaea var. sylvestris
  wild olive, ancestor of cultivated olive.
• Olea europaea ssp. europaea var. europea
  cultivated olive

www.classatravel.com/ gordana/Sicily/images/Ag...
www.bestofsicily.com/ mag/art160.gif
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Olea europaea ssp. europaea var. europaea
(cultivated olive)

• Wind pollinated and diploid
• Propagated by cuttings or grafting
• Self incompatible male often sterile
• Morphologically very similar to oleaster
• 90 of olives grown
• for oil production
• healing leaf

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Ancient olive DNA in pits preservation,
amplification and sequence analysis (Elbaum et
al. 2006)

• Archeological studies verify intensive
  exploitation of fruit 8000 years ago.
• Developed method to select pits with high quality
  DNA-Mediterranean climate is not favorable for
  DNA preservation
• Successfully sequences first ancient olive DNA.

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Olive Pit Collection Sites

• Kfar Samir - coast off of Haifa olive oil
  extraction site (7530-6570 BP) 3 pits analyzed
• Nahal Megadim - off Carmel coast 6 (6115 BP), 6
  pits analyzed
• Qumran hundreds of desiccated olive pits, date
  palm pits found in a Byzantine layer (1430 BP)
  10 pits analyzed

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Elbaum et al. only had 2 pits with high quality
DNA

• Amplified 109 bp segment from TrnT-TrnL in
  chloroplast genome. Only 35 bp could be read
  for these, the sequence was identical to the
  database for modern O. europaea.

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Today olives are cultivated throughout the
Mediterranean Basin, as well as in CA, Argentina
Australia.
Breton et al. 2006
flickr.com/photos/ turquoise_bleue/162944624/jpg
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Using Multiple Types of Molecular Markers to
Understand Olive Phylogeography

• Catherine Breton, Guillaume Besnard, and André A.
  Bervillé

Breton et al. used mitotypes, SSR and RAPD data
to gain better understanding of olive
domestication.
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Previous hypotheses on olive domestication and
distribution

• First believed that domesticated olive was
  introduced to the Mediterranean Basin
• More recently scientists hypothesized
• 1. The wild olive was only in E. Med.
• 2. Cultivars were derived in the East and spread
  West.
• 3. Wild olives in the West are all feral
  escapes.

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However, Breton et al. propose

• There is an obvious genetic difference between
  eastern and western oleaster populations the
  western populations are not feral.
• These disjunct populations, which have different
  mitotypes, are the result of multiple isolated
  refugia during the glaciations.
• According to SSR and RAPD data, oleaster genetic
  diversity is higher in the western Mediterranean
  than in the East.

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However, Breton et al. propose

• 4. Generally cultivars are of eastern origin.
• 5. Olive cultivars on Corsica Sicily may have
  been directly selected from ancient native
  oleasters (based on MCA).
• 6. O. europaea ssp. europaea arose and
  diversified in Morocco, where it picked up the
  MCK mitotype.
• 7. At least two simultaneous domestications
  occurred on opposite ends of the Basin.

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Oleaster population collections
EAST
lt1/4
The above oleasters and over 100 cultivars
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Oleaster genetic diversity is higher in the
western Mediterranean than in the East and higher
in oleaster than in cultivars

• From Table 11. 3 Distribution of Molecular in
  Oleasters and Olive Cultivars

Type of Marker Oleasters Oleasters Oleasters Cultivars
Type of Marker Total Specific to East Specific to West Cultivars
Mitotypes 3 1 2 4
RAPD 57 6 12 45
SSR 167 12 33 99
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Cultivars are generally of eastern origin.
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Some cultivars possess western-specific oleaster
RAPD bands as well as western-specific mitotypes,
suggesting that these cultivars were selected
directly from oleasters in the western
Mediterranean.
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SSR-based dendrogram showed 3 main groupings
western Med, eastern Med and Corsica/Sicily
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Pairwise estimated Variance for cultivated, wild
and ancient olives
Baldoni et al. 2006

• CVcultivated Wwild ATancient
• UMUmbria, SASardinia, SISicily

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Ancestry of oleaster

• Mitotype data show 2 mitotypes (MOM and MCK) not
  found in other subspecies. The authors note that
  the MCK type is very similar to MMA found in O.
  e. maroccana. This supports the hypothesis that
  oleaster diversified in the West. Breton et al.
  suggest a southern Moroccan diversification.
• Chlorotype data also show that O. e. europaea has
  chlorotypes from two distinct lineages, implying
  that it may be a hybrid.

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Oleaster and cultivar movement

• Three refugia
• NW Africa
• W. Med.
• Near East

Breton et. al. 2006
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Genetic diversity and gene flow between the wild
olive and the olive several Plio-Pleistocene
refuge zones in the Mediterranean basin suggested
by SSR analysis. Breton, C., Tersac, and A.
Bervillé. Journal of Biogeography (2006) 33

• 166 oleaster species and 40 cultivars were used
• Chlorotype data from 12 unlinked SSR loci
• Constructed ancestral populations (RPOP)
• Found
• Diversity of oleasters, with unique populations,
  can be explained by glacial refugia.

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• Used STRUCTURE to assign each individual to one
  or several RPOP (80 probability, if less then
  possibly hybrid)
• Seven pre-defined RPOPs
• 1. Corsica 2. Turkey 3. Sicily
• 4. Tunisia 5. Libya 6. Spain 7. Israel

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Map of RPOPs

• Figure 4 Map of the Mediterranean basin showing
  the approximate locations of the seven oleaster
  populations. RPOPs are circled by continuous
  lines and numbered according to Table 4. Dotted
  circles indicated that the two RPOPs were not
  differentiated by all methods.

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Conclusions

• Distribution of oleaster diversity can be
  explained by recolonization into the
  Mediterranean Basin after the last glaciation.
• There is gene flow between some populations due
  to overlap

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Questions

• If there were at least 2 sites of olive
  domestication, why do most cultivars have a high
  percentage of ME1 mitotype?
• Given that oleaster has more genetic diversity,
  why do cultivars have an additional mitotype?
• Is it likely that the mitotype presence was
  biased by large sample size in West and small in
  the East?
• Why not use phylogenic analysis of molecular data
  instead of dendrogram?
• Only 1 to 2 samples of the other O. europaea
  subspecies were examined. Is this sufficient?

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Bibliography

• Baldoni. et al. 2006. Genetic structure of wild
  and cultivated olives in the Central
  Mediterranean Basin. Annals of Botany 98
  935-942
• Breton, C., Tersac, and A. Bervillé. 2006.
  Genetic diversity and gene flow between the wild
  olive and the olive several Plio-Pleistocene
  refuge zones in the Mediterranean basin suggested
  by SSR analysis. Journal of Biogeography 33
  1916-1928.
• Breton, C., G. Besnard, and A. A. Bervillé.
  2003. Using multiple types of molecular markers
  to understand olive phylogeography. Documenting
  Domestication.
• Elbaum, R. et al. 2006. Ancient olive DNA in
  pits preservation, amplification and sequence
  analysis, Journal of Archaeological Science 33
  77-88.
• Wallander, E. and V. A. Albert. 2000. Phylogeny
  and classification of Oleaceae based on rps16 and
  trnL-F sequences. American Journal of Botany 12
  1827-1841.
• .