news January 2023

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IFISC News - Modeling the spread of Pierce's disease of grapevines

by ifisc＠ifisc.uib-csic.es

Modeling the spread of Pierce's disease of grapevines Wine production is being decimated in some places by Pierce's disease, caused by the bacterium Xylella fastidiosa. Researchers propose a model that takes into account the effect of ambient temperature to see how climate change will affect its spread. A new study led by IFISC (CSIC-UIB) scientists and with the participation of researchers from the public company Tragsa, the Department of Geography of the UIB and ICA-CSIC, predicts the risk that the disease caused by Xylella fastidiosa in the vineyard will spread and become established worldwide. In the study, published in the journal Communications Biology, the authors propose a model that reproduces where the pathogen can establish as a function of ambient temperature while estimating its future evolution. By integrating high-resolution spatio-temporal climate data and different infectivity scenarios into the model, the study shows how, although areas of high epidemic risk are currently marginal outside the USA, a global expansion of risk areas is expected by 2050. Pierce's disease (abbreviated PD) is caused by the bacterium Xylella fastidiosa and is transmitted between plants by insect vectors, namely Philaenus spumarius in Europe. PD originated in the American continent and is a disease that affects vines and causes great economic losses, in addition to causing water stress in plants due to occlusions caused by the bacterium in the xylem. This disease can even cause the death of the plant. International plant trade is expanding the geographic range of the pathogen, posing a new threat to global viticulture. To assess the potential incidence of PD, researchers have constructed a dynamic epidemiological model based on the response of 36 grapevine varieties to the pathogen in inoculation trials and vector distribution. Key temperature-driven epidemiological processes such as symptom development and winter recovery by cold accumulation have been modeled by integrating high-resolution spatio-temporal climate data from 1981 to the present. The results show that the main wine-growing regions are mainly located in low-risk, transitional or epidemic-risk areas with potentially low growth rates of PD incidence. Currently, in Europe, epidemic risk areas with moderate to high rates are marginal and are mainly concentrated in the Mediterranean islands and coasts. These areas are characterized by mild winters, such as the island of Mallorca. However, the model estimates that by 2050 the risk zones will expand globally due to small increases in the rate of disease growth as a consequence of climate change. Hotter summers and milder winters are expected in western Europe, which will increase the risk of epidemics in areas that are currently safe, such as some regions of southern France or northern Portugal. This study analyzes the risk of PD establishment and highlights the importance of considering climate variability, vector distribution and invasion criteria as key factors to obtain more accurate risk maps to help reduce the effects of the pathogen. The same Xylella fastidiosa bacterium is the cause of diseases of great economic relevance in other crops, such as almond trees (e.g. Mallorca) or olive trees (with great affectation in Apulia, Italy), so it is expected that the model can be applied to predict the risk of establishment of these other diseases. Giménez-Romero, A., Galván, J., Montesinos, M. et al. Global predictions for the risk of establishment of Pierce’s disease of grapevines. Commun Biol 5, 1389 (2022). https://doi.org/10.1038/s42003-022-04358-w http://ifisc.uib-csic.es/en/news/modeling-spread-pierces-disease-grapevines/

8 months

IFISC News - Traveling patterns in seagrass meadows

by ifisc＠ifisc.uib-csic.es

Traveling patterns in seagrass meadows A new study led by scientists from IFISC (CSIC-UIB) and IMEDEA (CSIC-UIB), published in the prestigious journal Proceedings of the National Academy of Sciences (PNAS), has found that strips of vegetation that form in seagrass meadows such as Posidonia oceanica move at a constant speed and can collide with each other in a process of annihilation. The authors propose a model that reproduces these dynamics and at the same time allows to check the state of the meadows. Posidonia meadows are an important source of ecosystem services and act as carbon sinks in coastal regions around the world. However, these seagrass meadows are known to be under threat due to multiple anthropogenic pressures, leading to increased seagrass mortality. In general, when reproduction and mortality rates are close to equilibrium, scale-dependent feedbacks are the dynamics that govern the spatio-temporal evolution of seagrass meadows. These interactions between plants can generate regular patterns such as those observed in the fairy circles in Namibia or the labyrinths of the Negev desert, so studying these patterns and their evolution is key to diagnosing the health of vegetation expanses. The international team of researchers has discovered that this situation of high mortality leads in some cases to the formation of traveling pulses of vegetation, strips of Posidonia in the specific case of Mediterranean meadows, approximately 1.5 m wide that advance without changing shape at a speed of a few centimeters per year, and that generate complex spatio-temporal patterns in the form of rings, spirals or arcs (Fig. 1). These structures arise due to high plant mortality caused by the absorption of sulfur by the roots. This sulfide comes from the decomposition of organic matter by bacteria in the absence of oxygen. The resulting spatiotemporal patterns resemble those formed in other excitable media, such as cardiac tissue or the Belousov-Zhabotinsky reaction, but on a much larger scale. The researchers have developed a mathematical model that reproduces the observed seascapes and predicts the annihilation of these circular structures when they collide with each other, a hallmark of excitable pulses. They have also shown that field images and radial profiles of vegetation, as well as the concentration of sulfide in the sediment, are consistent with the predictions of the theoretical model. The simulations reproduce remarkably well the evolution of the rings from 1973 to the present, including the self-destruction of two vegetation strips upon collision. The authors conclude that, in addition to explaining the patterns and their dynamics, the results of the study have diagnostic value, and allow the identification of these ring-shaped structures as terminal states of the meadows before their collapse. New monitoring technologies based on artificial intelligence can automatically detect these ring structures in aerial or satellite images and thus warn of the risk of collapse of key ecosystems in coastal areas.Ruiz-Reynés, D. et al. (2023) “Self-organized sulfide-driven traveling pulses shape seagrass meadows,” Proceedings of the National Academy of Sciences, 120(3). https://doi.org/10.1073/pnas.2216024120. Yahoo!EFECOPE http://ifisc.uib-csic.es/en/news/traveling-patterns-seagrass-meadows/

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2023

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