North African date palms are a hybrid between cultivated date palms from the Middle East and a different, wild species of palm, a recent study revealed. The source of our North African date palms belong to other species that grow on the island of Crete and in small areas of Southern Turkey, according to genome analysis.
Researchers from the New York University-Abu Dhabi’s Centre for Genomics and Systems Biology (NYUAD CGSB), revealed in a research published in the journal Proceedings of the National Academy of Sciences, the US, the evolutionary history of one of the earliest domesticated tree crops in the world, which remains a major fruit crop in North Africa and the Middle East.
Using genome analysis, the researchers have found that hybridisation between date palms and P theophrasti, a species known as the Cretan wild palm which was found in the Eastern Mediterranean, is the source of the mixed ancestry and genetic distinction of North African date palms.
When the researchers say ‘Middle East’ they exclude the Egypt, Libya, and other Arab African countries that were mentioned as ‘North African’ countries.
For years, it was similar to a mystery regarding the origin of the date palms in the Middle East and North Africa. It was believed in previous scientific works that the date palms from the Middle East and North Africa are genetically different, despite their one origin, as they belong to one species ‘Phoenix dactylifera’.
Due to its differentiated characteristics, which include such popular date varieties as Medjool and Deglet Noor, the nature of North African dates, has led to questions as to how they originated. There have been suggestions, for example, that North African date palms may have been domesticated independently from date palms in the Middle East.
Researchers from NYUAD, collaborating with other scientists from NYU in New York and researchers in Greece, France, Switzerland, and the UK, gathered to solve the mystery of the origin of North African date palms. They have sequenced the genomes of a large sample of date palms from the Middle East, North Africa and South Asia, as well as palms from related but distinct wild species.
Findings of the study revealed that about 5-18% of the North African date palm genome is derived from the Cretan wild palm.
Compared to date palms from the Middle East, the hybridisation of Middle East varieties with wild Phoenix theophrasti has led to increased genetic diversity in the North African date palms.
The results also showed the possibility of hybridisation with P theophrasti to create new genes being introduced to cultivated date palms that could help provide better date palm varieties, for disease resistance and yield.
The P theophrasti is currently found in 10 populations on the island of Crete, with a population near the popular beach resort of Vai, which is considered to be the largest palm forest in Europe. Small populations of P theophrasti can also be found in various islands in the Aegean Sea, in mainland Greece, and Southern Turkey.
Although this species looks similar to the cultivated date palm, the fruit of P theophrasti are thin and fibrous and are generally inedible. The International Union for Conservation of Nature (IUCN) classifies P theophrasti are ‘near-threatened’ in status, which indicates that this species, while not an immediate cause for concern, may find itself threatened with extinction in the near future, according to the paper.
The researchers suggested, based on the findings of the analysis, that date palms were initially domesticated in the Middle East, possibly in the Gulf region.
The oldest archaeological evidence for Phoenix dactylifera is found in the Dalma island in the UAE, and in Kuwait, during the Arabian Neolithic period about 7,000 years ago.
In its movement of the domesticated date palms from its origin in the Arab peninsula, the P dactylifera encountered populations of Phoenix theophrasti when they reached the eastern Mediterranean.
The two hybrid species led to the origin of the date palms which currently grow in North Africa since approximately 3,000 years ago, according to archaeological evidence that was mentioned in the paper.
This study is part of the New York University Abu Dhabi Date Palm Genome Project, which was started in 2012. “We are interested in using genomics to study the diversity of date palms, so we can understand their genetic variability, their origin, and spread across the Middle East and North Africa. We are also interested in mapping genes that may be important for improving date palm agriculture,” said Michael Purugganan, silver professor of Biology at the Centre for Genomics and Systems Biology, New York University, and leader of the project.
He informed Daily News Egypt that the results of the study continue a trend of the researchers’ ideas that the movement of many fruit tree crops are accompanied by hybridisation with local wild species. Furthermore, he said that he and his team believe that hybridisation helps domesticated crops adapt to new environments by getting new alleles from wild species. So one impact of the study is to continue to highlight the importance that between-species hybridisation has on crop adaptation.
“Another impact is it provides date palm breeders with a new source of genes to help improve date palms as a crop. Breeders need not limit themselves to other date palms, but can use the related species Phoenix theophrasti as a source of genes,” Purugganan added.
Moreover, he explained further that one thing he and his team did not highlight in their paper is that the timing of the appearance of the North African date coincides with the Minoan and Phoenician activity in the Mediterranean, so it is interesting to speculate on how these old civilisations may have had a role in the origin and spread of this important North African crop species.
According to Purugganan the Date Palm Genome Project is 7 years old now, and the current study on the origin of North African dates is just one of many projects they are conducting. “This study helps us understand where the genetic differences of the North African dates like Medjool and Deglet Noor come from-part of it comes from this other species from Crete,” he said.
Purugganan told DNE that he and his team are still working on the issue of the origin of dates. They will continue to try to expand their knowledge of the genetic diversity of date palms using genomics.
