The Origin of Spanish Durum Wheat and Olive Tree Landraces Based on Genetic Structure Analysis and Historical Records

Abstract

In this study, the origin of Spanish durum wheat and olive tree landrace collections (preserved in seed banks and ex situ field collections, respectively) was traced throughout different studies on genetic structure analysis of different landrace collections and historical records of plant material circulation of these two crops in the south and east of Spain (the main cultivation areas). Although there were several groups of Spanish durum wheat landraces, they did not cluster geographically and likely came from intense grain circulation within the country and abroad (due to a high seeding rate of about 100 kg/ha and an unstable production) from the 15 to 19th centuries (especially the Maghreb and Sicily). However, Spanish olive tree landraces experienced lower genetic circulation over time and space due to the longevity of the species and the large size of the reproductive material. They can be clearly divided into two groups: those from the south, of Maghrebi origin, which most likely originated during the Islamic expansion of the 8–15th centuries, and those from the east, arriving most likely during Roman times from Italy. The genetic circularity levels of the plant material of these two crops are different.