Scientists harvest a bumper crop of data as they inch closer to mapping the date palm genome
▶ Researchers at New York University Abu Dhabi have studied the desert plant for years, writes Anna Zacharias
Date palm cultivation is a story as old as civilisation. The Ancient Egyptians embossed them on amulets, the Romans incorporated them in mosaics and people in Mesopotamia painted them on vases.
Yet the genetic make-up of the species has never been mapped as extensively as it is now, a success largely attributable to geneticists at New York University Abu Dhabi.
For nearly eight years, an international team of scientists have been hard at work meticulously recording its significant genetic variations.
Seed and plant samples were collected from Pakistan to Libya, all in an effort to accurately map its genome and ensure that enough is known about the plant for it to be protected from pests, secured against a changing climate and even improved in taste.
“For the past few years, what we’ve been interested in doing is to try to map genes in date palms that might be important, for key traits in fruit especially,” said Michael Purugganan, the geneticist who leads NYUAD’s Centre for Genomics and Systems Biology.
“The climate is changing and we don’t know what’s going to happen in terms of date palm agriculture. The land that’s being used for date palms is rapidly deteriorating.
“How do we deal with deteriorating land issues? How do we face different diseases and pathogens and pests?”
The groundbreaking UAE study of the slow-growing, hardy desert plant presented a unique set of challenges to researchers.
Most crop species, such as corn or wheat, have an international seed repository, but dates do not.
There are at least 3,000 named varieties of date palms and NYUAD first had to build its own collection, approaching colleagues from across the world. But word soon spread and their database grew. One geneticist even couriered dates from Damascus to the UAE at the beginning of the Syrian civil war.
North African and Middle Eastern date palms are the same species but are genetically different. One theory is that the tree evolved twice, once in North Africa and once in the Middle East.
The oldest archaeological date palm records in the Gulf are two date stones from Abu Dhabi’s Delma Island, which are between 6,600 and 7,100 years old. Nothing shows up in North African records for another 4,000 years.
Given the time gap, they had another theory: maybe dates were like apples.
Dr Purugganan explained: “The original apple came from Kazakhstan but when it got to Europe it hybridised with the European crab apple and that gave us the modern apple.”
Support for this theory came out of the blue from scientists working in Oman in 2017.
There, French geneticist Muriel Gros-Balthazard was on her own search for the wild date palm. But dates were so widely cultivated for millennia, it was difficult to find palms that had not descended from farmed populations.
“You can find uncultivated palms everywhere, in the Sahara, in the Sinai, in the Dead Sea region, in the Zagros Mountains,” Dr Gros-Balthazard said.
“The issue is you don’t know if they are truly wild populations or feral.”
Dr Gros-Balthazard got a break when colleagues in
Oman presented her with small, round date seeds from the Hajar mountain range.
The shape of the seeds was promising. Older species of olives and grapes also have rounder seeds.
When the DNA was analysed, they proved to be wild and offered evidence that the palm probably originated in the Arabian Peninsula.
“Right now we are really interested in trying to understand what the wild relatives of the date palms are doing,” Dr Purugganan said.
“We’re in the process of looking really carefully at those other wild species that are closely related because in the future if we wanted to improve date palms, we can get genes from these other species and help them adapt to different environments.
“The population of the world is going to hit 9.7 billion by 2050. In every food species, we’ve got to be able to increase productivity.”
By early 2019, researchers had established that the North African date palm had originated from a palm found mainly on Crete, in the eastern Mediterranean.
Last week, the team announced another significant breakthrough: they had identified the date palm genes for colour and sugar production.
The traits were found in a new genome sequence of 772 million base pairs, the basic building blocks of DNA. It is the longest piece of the date palm genome sequence that has yet been read.
The research, carried out in partnership with UAE University and the University of Arizona, was published in the peer-reviewed journal Nature Communications.
The technique used in this research, called genome-wide association study, is already being used on other date varieties, including the famed black Ajwa dates of Madinah, a favourite snack of the Prophet Mohammed.
“You really learn about the history of life by understanding these genomes,” said Rod Wing, director of the Centre for Desert Agriculture at King Abdullah University of Science and Technology in Saudi Arabia, and one of the researchers on the project.
“It’s in there, you’ve simply got to know how to look for it. We’re in a place now where we can do this and the Middle East is opening up to more investigations and there are lots of opportunities.”
It seems that major advances in both the accuracy and affordability of genome mapping, increased Gulf funding and a heightened global demand for crops that can withstand drought, have combined to enhance the study of the date palm.
As Khaled Al Amiri, director of the Khalifa Centre for Genetic Engineering and Biotechnology at UAE University, said, the date palm – to date – has been overlooked. But this is changing.
“We are living in the desert and climate change is coming up on us so we need to develop plants that are able to live in harsh conditions,” he said.
“The date palm is considered an orphan plant because there’s not much research on it. We want to make those resources.
“We want to make this plant’s fruit as prominent as apples, or peaches.”
The world population is going to hit 9.7 billion by 2050. We’ve got to be able to increase food productivity MICHAEL PURUGGANAN Geneticist