What are the characteristics of the so-called Judean date palms that gave fruit to the people of the southern Levant in antiquity? The genome sequencing of seven “resurrected” specimens has now provided insights into this question. They germinated from seeds that are over 2000 years old and come from various ancient sites and times. According to genetic comparisons, the Judean date palms were already similar to today’s versions. Interestingly, however, increasing intersections of certain date lines become apparent over time, which could have been connected with cultural influences from the West.
The date palm (Phoenix dactylifera) one of the most important crops in the southern Mediterranean and Middle East. It is believed that their cultivation began around 7,000 years ago in the Persian Gulf area and then spread to the west. This is how important cultivation areas arose in ancient times in today’s Israel around the city of Jericho and along the Dead Sea. The so-called Judean dates from there were described as particularly large and sweet. But the knowledge about the local cultivation and the palm trees was lost, because as part of the upheavals in the region, the date plantations disappeared in late antiquity.
Awakened from the deep sleep
The ancient Judean date palms were initially thought to be extinct – but that changed in 2005: A research team succeeded in germinating a date seed that was over 2,000 years old and which had been found in the famous Masada rock fortress. As they explain, this was made possible by the amazing vitality of date seeds as well as the favorable preservation conditions. In the meantime, the little plant has developed into a male palm called “Methuselah”. The team can also point to further successes in “awakening” ancient date seeds: They succeeded in germinating six more specimens from a collection of date seeds found in Masada, Qumran and Wadi Makukh. The resulting plants were given the biblical names Hannah, Adam, Judith, Boaz, Jonah and Uriel and have now been planted outdoors.
By radiocarbon dating the seeds, the researchers were also able to narrow down when their mother plants lived. They therefore come from different periods in the time window from the 4th century BC. BC to the 2nd century AD As part of the current study, the researchers led by Michael Purugganan from New York University have now sequenced the genomes of all seven Judean date palms. They refer to their approach as “Resurrection genomics”: They compared the data obtained with each other and with genetic information from today’s date palms in order to uncover peculiarities.
“Resurrection genomics” with potential
As they report, the genetic studies initially showed that surprisingly few mutations had resulted from the long slumber of the seeds. When comparing the genomes, it was found that the oldest specimens from the 4th to 1st centuries BC BC resembled today’s West Asian date varieties. The palm trees from the second century BC In contrast, the researchers wrote that there was an increasing genetic relationship with today’s North African date palms up to the second century AD. According to the researchers, the seven Judean date palms do not really form a common identity due to their genetic differences. “In this regard, the name Judean date palm may not represent a specific genetic population, but more a designation of origin,” write Purugganan and his colleagues.
As they explain, the decisive aspect of the genetic shift from the eastern to the North African / western character in the Judean date palms is characterized by the genetic trace of a cross: modern North African palms bear the characteristics of a hybridization between the date palm Phoenix dactylifera and the wild Cretan palm Phoenix theophrasti . The results now indicate that the genome of the Cretan date palm found its way into the genome of the Judean date palms from around 2200 years ago. They suspect that the increase in genes from P. theophrasti is due to the increasing cultural influence of the West and especially the Romans in the eastern Mediterranean.
“We are fortunate that date palm seeds can survive for so long in the region’s arid environment – in this case more than 2000 years – and then germinate with minimal DNA damage,” says Purugganan. “Our approach has proven to be an effective way to study the genetics and development of past and possibly extinct plant lines such as the Judean date palm,” the researcher sums up. He also sees more far-reaching potential in the Resurrection genomics process: “By reviving biological material such as germinating old seeds from archaeological, paleontological sites or historical collections, we can not only examine the genomes of lost populations, but in some cases we may also rediscover genes that are lost in modern varieties, ”says Purugganan.
Source: New York University, professional article: PNAS, doi: 10.1073 / pnas.2025337118