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

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

2. 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.

3. Importance • World’s 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

4. 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.

5. 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?

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

7. 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)

8. 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)

10. 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)

13. 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

14. 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

15. Geography of M. sieversii Note: What’s up with this map? Harris et al. 2002

16. 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

17. 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

18. = Nuclear ribosomal ITS • No M. sylvestris Robinson et al 2001

19. USDA collections, M. sieversii Forsline et al. 2003

20. Harris et al 2002’s matK duplication 8 of 10 M. sieversii accessions from Uzbekistan and Tajikistan (Robinson et al 2001) Forsline et al. 2003

21. 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 don’t 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) 538:51-56

22. Morphological evidence for M. sieversii • Floral morphology • Fruit morphology Juniper and Mabberley 2006

23. 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

24. 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

25. Coart et al. 2006

26. Coart et al. 2006

27. Coart et al. 2006

28. matK dupII Coart et al. 2006

29. 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

30. Coart et al. 2006

31. 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.