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What mysteries does the Azorean Bittercress hide? ERGA may provide the answer very soon

Guilherme Roxo, CIBIO-Azores, Universidade dos Açores

The Azores archipelago is one of Portugal's best kept secrets. The volcanic soil of the islands allows various types of food to be cultivated, from your grandma's favorite tea to the pineapple devoured by children. However, it is not just agriculture that characterizes the archipelago, in fact, one of its best kept secrets is its native flora. Among the green pastures and cities with unique architecture are forests that have existed here long before human settlement. It is exactly in these forests where unique and extremely beautiful plants occur. One of these plants is the Azorean Bittercress (Cardamine caldeirarum).

Landscapes acoss the Azores.

This cress species, endemic to the Azores, belongs to the Brassicaceae family, a group that includes species of extreme importance as a food source, including cabbage, turnips, broccoli, among others. What differentiates this cress from others is that this species only grows in this archipelago, with the exception of Graciosa Island. One of the main characteristics of this cress is that it only grows in places that are permanently humid (Schäefer, 2021).

In 1838, the Swiss scientist Heinrich J. Guthnick collected a sample of the species during his visit to the archipelago, and it was described for the first time by the German botanist Moritz August Seubert in 1844 (Seubert, 1844). In 1897, the American botanist William Trelease described the species he found on the island of São Miguel, which differs from the others due to its larger flowers (Trelease, 1897). Genetic studies on this species, carried out by the DIVERGE team from the University of the Azores and led by Professor Mónica Moura, have already indicated the possibility of the existence of several cryptic species throughout the archipelago. Cryptic species are two or more species that, despite their similar (external) appearance, are considerably different at a genetic level.

Azorean bittercress in its natural habitat (right) and detail of its flowers with a potential pollinator (left).

ERGA (European Reference Genome Atlas) is a pan-European initiative that aims to sequence quality reference genomes for all European species. The genome is the set of all the genetic information of an individual or a species. Sequencing it means determining the order of the nucleotides (the building blocks of DNA) of a DNA molecule.

Sequencing species requires extremely expensive machines that do not exist in the Azores. In order to build high-quality reference genomes, it is necessary to keep the plant as healthy as possible until the moment of DNA extraction. And why is it important to sequence a species? Since the genome is all of  the genetic information of a given individual, sequencing a representative of a species can bring several discoveries that can be applied to conservation, human health, economic development, food sources, biosecurity, among many others. An example could be the transfer of genes from this cress species to, for example, watercress, making it more resistant to certain stresses, increasing its production or even increasing its nutritional value. The Azorean bittercress was one of the species chosen for sequencing as part of the ERGA pilot project.

The habitats where the Azores Bittercress occurs are degraded and the presence of this species is increasingly rare. Therefore, I traveled to the Lombadas valley in São Miguel in order to collect the necessary samples. It was a rainy day and to get to the place I had to drive through an old and skiddy stone road. When you arrive at the place, you need to enter the river and walk for about 40 minutes, galoshes are recommended and even then I couldn’t help getting wet.

The Lombadas Valley and the hydrothermal deposits found along the way.

It is a place of extreme beauty, along the river we find spots where the water is warm and the soil is orange, these are hydrothermal deposits. This orange color is acquired because beneath our feet there is magma that heats the water, this water is extremely rich in minerals and when it rises to the surface the water cools and the minerals precipitate returning to their solid state and painting the rocks orange. Upon arriving at the spot where this Bittercress occurs, I started sampling. To do this, I took a small shovel that allowed me to remove the plant with its roots intact and place it in a vase, then this vase is placed inside a jar with water from the river and closed to keep it protected.

The next step was to bring the plants to our partner laboratory in Norwich, England, where the sequencing would happen. I carried the plants in my backpack and they arrived safely at the laboratory. Upon arrival, some leaves were collected and frozen in liquid nitrogen - an efficient method for preserving them. The results of this effort are still being generated, but I can't wait to discover the mysteries that this species hides and how they can help us to create a more sustainable future in which the Azorean Bittercress can still exist.

Azorean Bittercress harvested and placed in containers for transport to England (left). The samples were then transported to the Earlham Institute in Norwich, where they are being sequenced.


Schäefer, H.  (2021) Flora of the Azores—A Field Guide. Margraf Verlag, Weikersheim

Seubert, M. (1844): Flora Azorica. Adolph Marcus, Bonn. 50 pp.

Trelease, W. (1897) Botanical observations on the Azores. Missouri Botanical Garden Annual Report 1897, 177.


For more information about other projects being developed by the DIVERGE research group or if you want to join us, contact Professor Mónica Moura via email.

🇵🇹 Would you like to interact with other scientists interested in generating reference genomes for Portuguese biodiversity? Contact ERGA representatives in Portugal! 

Images: Guilherme Roxo


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