Читать книгу Biotechnology of Fruit and Nut Crops - Группа авторов - Страница 104

There are related palm genera found on the plains, plateaus and highlands of continental South America, but the coconut appears to have evolved on the beaches of atolls and islands of the Indian Ocean and Western Pacific (Harries, 1978). Its seagoing fruit possesses an ability to disperse and colonize coastal strands far removed from any of its ancestral species (Harries, 1978). Ethnological indicators place the centre of diversity for coconut in South-east Asia and Melanesia (Harries, 1978; De Taffin, 1998; Harries and Clement, 2014). The wild coconut was most probably present on the coastal strands of the Indian Ocean for some millions of years before the earliest humans migrated from Africa to Asia and from Asia to Australasia and Melanesia around 50,000 years ago and later to Micronesia and Polynesia. Human colonizers would have thrived on the coconut water and food already present in these newly discovered lands.

Between 8000 and 14,000 years ago, an extensive land area now known as Malesia was gradually inundated by rising sea level. As the shallow continental shelf between the present-day Malay Peninsula, Sumatra, Borneo and Mindanao was progressively submerged, settlements and palm groves must have been moved further inland, ahead of the encroaching ocean. During that era, it appears that human selection for increased water and kernel content, early germination and other fruit characteristics took place (Harries, 1978).

The people who first sailed to islands in the Indian and Pacific oceans took supplies of large fruit in their canoes for food and drink and others for planting on arrival with no foreknowledge of the islands where they might land, e.g. Madagascar or Samoa, and that would be colonized. People, now known as Polynesians, reached Samoa around 4000 years ago with a quantity of large coconut fruits that were planted alongside the wild palm groves already present. Inevitably intermediate forms of fruit arose through introgression, but the subpopulations producing large fruit have been maintained as well as transferred to many other Polynesian islands.

From 1499, Portuguese navigators returning from the Indian Ocean introduced the coconut to the Cape Verde Islands off the West African coast. Just 50 years later, fruit from those islands were taken to Brazil and Puerto Rico, later to the West African mainland, the Atlantic coast of the Americas and the Caribbean coast and islands (Harries, 1978). Phenotypic differences between coconut populations from the Caribbean coast (introduced) and the Pacific coast of Panama (provenance uncertain) have been recognized, and in 1966 the Polynesian names for these two contrasting palm types – Niu kafa and Niu vai – were first used to identify these as wild-type and domestic-type forms of the modern cultivated coconut (Whitehead, 1966; Harries, 1978).

Investigation of the distribution of coconut varieties using DNA-based techniques has supported the concept of wild-domestic-introgressed coconut types and has identified two major gene pools representing sources of predominantly ‘wild-type’ and ‘domestic-type’ populations from which all modern cultivars are derived (Harries, 1995; Batugal et al., 2009; Baudouin and Lebrun, 2009).