What is causing the cork oak decline?

By TPN/Lusa, in News, Algarve, Renewable · 19-02-2021 01:00:00 · 2 Comments

A study coordinated by a researcher from the University of Algarve (UAlg) has linked the appearance of a protein in the foliage with a pathogen that affects the roots and causes the decline of the cork oak.

The study coordinated by Ana Cristina Coelho, from the Centre for Electronics, Optoelectronics and Telecommunications (CEOT) of UAlg, was published in the online magazine PLoS ONE and “is framed in a phenomenon that already has taken place for many years” in Portugal, and in particular in the Algarve, but also in Spain and Italy.

It was based on work that brought plants into contact with the micro-organism responsible for infecting roots and which “seems to be responsible for slowly undermining the vitality of trees”.

“We have a sharp decline in cork and holm oak forests and in the montado, and that decline has been associated with a number of factors. One of the factors has been associated with the interaction with a pathogenic organism [the oomycete Phytophthora cinnamomi],” Ana Cristina Coelho told Lusa news agency.

The researcher explained that the “pathogenic organism infects the roots” of adult trees, in the field, and this “makes it difficult to eradicate and treat and also to study the process” that leads to the loss of vitality and, ultimately, the death of these species.

“It is difficult to detect, to isolate, and it will be difficult to do any kind of treatment at root level. But above all it is necessary to prove that there really is a relationship between the vitality of the tree and what happens at root level related to this infection”, she argued.

The UAlg researcher clarified that, “among the multiple factors” that cause the decline of the cork oak, she has “worked on the interaction of the cork oak and this pathogen”.

The study tried to understand if there were alterations in other parts of the tree, other than the roots, that could establish a relationship with the organism responsible for the infection.

“And we left the plants for eight months, with watering and all the conditions for them to be able to vegetate well, and then we went to see, after the eight months, if it was really possible to identify any alteration in the leaves. What we observed was that there were alterations in the leaves at the level of proteins, and there may be a relationship between the proteins that were identified in the leaves and the infection”, he added.

Today, she stressed, it is only known that a tree is in decline through the observation of visual factors - the loss of leaves, dripping of liquid in the trunk or the appearance of dry branches at the extremities. Decline “is very slow, it can take 10 or 15 years” before it can be detected.

The complex detection is motivated by the fact that there are also several other factors that can influence the appearance of the problem, such as climatic ones, and makes it difficult to confirm if the tree is growing well, or if it is infected, “because one will never be able to know the level of infection of a tree’s rhizosphere - the set of roots or root system”.

Although there are no figures available to measure this problem, the UAlg researcher said that “visually, the most affected area is the Algarve”, where there is “a percentage of trees with very, very strong symptoms”, and “areas where there is already a great disappearance of trees”, but the problem has also been registered in Spain and Italy.

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In relation to the disease causing oak decline, we have been working with endophytes to be able grow certain plants in diseased soil caused by Fusarium oxysporum subsp.
Microorganisms such as Bacillus amyloliquefaciens, Tricoderma harzianum and a couple of Bacillus types enable us to grow plants in diseased soils so maybe by injecting a combination of the above it may be a way to control the Phytophora cinnamoni.

I am not a microbiologist but we have seen the results and it may be worth a try.

By John Walker from UK on 19-02-2021 04:55

I read with interest your article on Cork Oak. Perhaps you can help me trace a Mr Antnio Cappas de Sousa. This gentleman travelled with his Mother aboard my ship TSS REINA DEL MAR which left Lisbon on a cruise approximately 1970. We became friends. I was a Purser on board. He mentioned that his family farmed "Cork Oak" and I would like to get in touch again after all these years. I am currently staying in Lagos with my Son. Many thanks for your help, Alan Charlesworth ex Purser Reina del Mar.

By Alan Charlesworth from Algarve on 19-02-2021 04:29
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