| 1. |
- Oliva Palau, Jonàs, et al.
(författare)
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Drought and Phytophthora Are Associated With the Decline of Oak Species in Southern Italy
- 2018
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Ingår i: Frontiers in Plant Science. - : Frontiers Media SA. - 1664-462X. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Forest decline induced by climate change is a global phenomenon that affects many tree species, mainly in drought-prone areas as the Mediterranean region. In southern Italy, several oak species have shown decline symptoms and elevated mortality since the 2000s due to drought stress. However, it remains to be answered whether decline occurred alone or whether a pathogen was also involved. To this aim, we compared two coexisting oak species in a forest located in southern Italy which are assumed to be less (Quercus cerris) and more tolerant to drought (Quercus pubescens). We sampled fifteen couples of neighboring declining (D) and non-declining (ND) trees of both species. Wood cores were taken from all trees to perform dendrochronological analyses to detect the decline onset and link it to potential climatic drivers. Carbon isotope ratios (d(13)C) were analyzed in wood of the two vigor classes to compare their water-use efficiency. Phytophthora presence was also assessed in soil samples from ten D-ND couples of trees per species. The oak species most affected by drought-induced decline in terms of leaf shedding and mortality was Q. cerris, i.e., the least tolerant to drought. In both species, the D trees showed a reduced growth rate compared with ND trees from 2000 onward when drought and warming intensified. Q. pubescens showed higher growth sensitivity to precipitation, temperature and drought than Q. cerris. This sensitivity to climate was magnified in D trees whose growth decreased in response to warm and dry conditions during the prior winter and the late summer. The Q. pubescens D trees were more efficient in their water use than ND trees before the growth divergence between D and ND trees amplified. In the studied area, Phytophthora quercina was isolated from 40% of the sampled trees, and tended to be more frequent amongst ND than amongst D trees. Our data suggests that droughts and warm summer conditions triggered oak decline. The high prevalence of P. quercina in the studied area warrants further study as a potential predisposing factor.
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| 2. |
- Oliva Palau, Jonàs, et al.
(författare)
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Drought Decreases Growth and Increases Mortality of Coexisting Native and Introduced Tree Species in a Temperate Floodplain Forest
- 2018
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Ingår i: Forests. - : MDPI AG. - 1999-4907. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Forest dieback and mortality events induced by drought stress are widely reported. However, few studies have jointly examined the role played by drought on growth and mortality in tree species inhabiting floodplain forests. Here, we focused on mortality events occurring since the early 2000s on large areas in a floodplain forest located within the Ticino regional park in Northwest Italy, where affected native (pedunculate oak, Quercus robur L.) and introduced tree species (black locust, Robinia pseudoacacia L.) coexist. We related growth with climate data and drought severity to discern if these species were similarly affected by drought. Then, we: (i) evaluated the presence of pathogens of the genus Phytophthora in recently dead oak trees since this was the most affected species and pathogens are often associated with oak decline cases; and (ii) compared xylem vessel diameter and tree-ring C isotope discrimination (delta C-13) to highlight differences in water-use strategies between living and dead trees in both species. The radial growth of living and dead trees started diverging in the 1970s, although only after warm-drought periods occurred during 1990s did this divergence become significant. Growth of trees that died responded more negatively to drought than in the case of living trees. Moreover, trees that died formed smaller xylem vessels in the past than living trees and also showed more negative delta C-13 values in both tree species, indicating a higher intrinsic water-use efficiency in living than in dead trees. The pathogen Phytophthora cinnamomi Rands was only detected in one recently dead tree, suggesting that it is unlikely that dead oaks were predisposed to drought damage by the pathogen. We conclude that a climate shift from wet to warm-dry summer conditions in the early 1990s triggered forest dieback and induced mortality in both tree species. Temperate floodplain forests are susceptible to drought-induced dieback. The drought-sensitivity of both species could lead to successional shifts driven by a reduction of N inputs through N-fixing by black locust and the replacement of oak by drought-tolerant species.
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| 3. |
- Redondo, Miguel Angel, et al.
(författare)
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Climate acts as an environmental filter to plant pathogens
- 2024
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Ingår i: ISME Journal. - 1751-7362 .- 1751-7370. ; 18
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Tidskriftsartikel (refereegranskat)abstract
- Climate shapes the distribution of plant-associated microbes such as mycorrhizal and endophytic fungi. However, the role of climate in plant pathogen community assembly is less understood. Here, we explored the role of climate in the assembly of Phytophthora communities at >250 sites along a latitudinal gradient from Spain to northern Sweden and an altitudinal gradient from the Spanish Pyrenees to lowland areas. Communities were detected by ITS sequencing of river filtrates. Mediation analysis supported the role of climate in the biogeography of Phytophthora and ruled out other environmental factors such as geography or tree diversity. Comparisons of functional and species diversity showed that environmental filtering dominated over competitive exclusion in Europe. Temperature and precipitation acted as environmental filters at different extremes of the gradients. In northern regions, winter temperatures acted as an environmental filter on Phytophthora community assembly, selecting species adapted to survive low minimum temperatures. In southern latitudes, a hot dry climate was the main environmental filter, resulting in communities dominated by drought-tolerant Phytophthora species with thick oospore walls, a high optimum temperature for growth, and a high maximum temperature limit for growth. By taking a community ecology approach, we show that the establishment of Phytophthora plant pathogens in Europe is mainly restricted by cold temperatures.
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| 4. |
- Redondo, Miguel Angel
(författare)
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Competitive exclusion amongst endophytes determines shoot blight severity on pine
- 2020
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Ingår i: Functional Ecology. - : Wiley. - 0269-8463 .- 1365-2435. ; 35, s. 239-254
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Tidskriftsartikel (refereegranskat)abstract
- The role of competitive interactions among endophytes and latent pathogens that determine disease on stressed plants is largely unknown. Shoot blight caused byDiplodia sapineais an emerging disease affecting pine forests in Europe.D. sapineais an endophyte that becomes pathogenic following drought or hail. Disease expression depends on the availability of nutrient-rich metabolites produced by trees to alleviate stress. We studied whether competition for these compounds with other endophytes could modulate symptom expression. We compared the shoot-inhabiting fungal community of trees that developed blight symptoms or remained asymptomatic following a hailstorm that affected four pine species. Communities were characterised by isolation and metabarcoding of the ITS2 region. Endophytes were functionally annotated in their response to C, N and proline. Hail promotedD. sapineaand other endophytes with a rapid colonisation strategy of N-rich substrates. Asymptomatic trees had a community of endophytes showing a strong negative association withD. sapinea. These antagonistic endophytes were functionally similar toD. sapineain their response traits to hail, but they were more specialised to proline. The association was conserved across pine species. Our data suggest that after a stress-inducing event, rapid niche occupation is critical forD. sapineato cause disease. However, competition with other endophytes for key metabolites can supress the pathogen and prevent trees from developing symptoms. Our findings can pave the way to a better understanding of the contribution of latent pathogens on widespread tree mortality events involving abiotic stressors, such as drought, heat or hail. A freePlain Language Summarycan be found within the Supporting Information of this article.
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| 5. |
- Redondo, Miguel Angel, et al.
(författare)
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Contrasting distribution patterns between aquatic and terrestrial Phytophthora species along a climatic gradient are linked to functional traits
- 2018
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Ingår i: ISME Journal. - : Springer Science and Business Media LLC. - 1751-7362 .- 1751-7370. ; 12, s. 2967-2980
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Tidskriftsartikel (refereegranskat)abstract
- Diversity of microbial organisms is linked to global climatic gradients. The genus Phytophthora includes both aquatic and terrestrial plant pathogenic species that display a large variation of functional traits. The extent to which the physical environment (water or soil) modulates the interaction of microorganisms with climate is unknown. Here, we explored the main environmental drivers of diversity and functional trait composition of Phytophthora communities. Communities were obtained by a novel metabarcoding setup based on PacBio sequencing of river filtrates in 96 river sites along a geographical gradient. Species were classified as terrestrial or aquatic based on their phylogenetic Glade. Overall, terrestrial and aquatic species showed contrasting patterns of diversity. For terrestrial species, precipitation was a stronger driver than temperature, and diversity and functional diversity decreased with decreasing temperature and precipitation. In cold and dry areas, the dominant species formed resistant structures and had a low optimum temperature. By contrast, for aquatic species, temperature and water chemistry were the strongest drivers, and diversity increased with decreasing temperature and precipitation. Within the same area, environmental filtering affected terrestrial species more strongly than aquatic species (20% versus 3% of the studied communities, respectively). Our results highlight the importance of functional traits and the physical environment in which microorganisms develop their life cycle when predicting their distribution under changing climatic conditions. Temperature and rainfall may be buffered differently by water and soil, and thus pose contrasting constrains to microbial assemblies.
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| 6. |
- Redondo, Miguel Angel
(författare)
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Extensive morphological and behavioural diversity among fourteen new and seven described species in Phytophthora Clade 10 and its evolutionary implications
- 2022
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Ingår i: Persoonia. - : Naturalis Biodiversity Center. - 0031-5850 .- 1878-9080. ; 49, s. 1-57
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Tidskriftsartikel (refereegranskat)abstract
- During extensive surveys of global Phytophthora diversity 14 new species detected in natural ecosystems in Chile, Indonesia, USA (Louisiana), Sweden, Ukraine and Vietnam were assigned to Phytophthora major Clade 10 based on a multigene phylogeny of nine nuclear and three mitochondrial gene regions. Clade 10 now comprises three subclades. Subclades 10a and 10b contain species with nonpapillate sporangia, a range of breeding systems and a mainly soil- and waterborne lifestyle. These include the previously described P. afrocarpa, P. gallica and P. intercalaris and eight of the new species: P. ludoviciana, P. procera, P. pseudogallica, P. scandinavica, P. subarctica, P. tenuimura, P. tonkinensis and P. ukrainensis. In contrast, all species in Subclade 10c have papillate sporangia and are self-fertile (or homothallic) with an aerial lifestyle including the known P. boehmeriae, P. gondwanensis, P. kernoviae and P. morindae and the new species P. celebensis, P. chilensis, P. javanensis, P. multiglobulosa, P. pseudochilensis and P. pseudokernoviae. All new Phytophthora species differed from each other and from related species by their unique combinations of morphological characters, breeding systems, cardinal temperatures and growth rates. The biogeography and evolutionary history of Clade 10 are discussed. We propose that the three subclades originated via the early divergence of pre-Gondwanan ancestors > 175 Mya into water- and soilborne and aerially dispersed lineages and subsequently underwent multiple allopatric and sympatric radiations during their global spread.
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| 10. |
- Redondo, Miguel Angel, et al.
(författare)
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Functional Ecology of Forest Disease
- 2020
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Ingår i: Annual Review of Phytopathology. - : Annual Reviews. - 0066-4286 .- 1545-2107. ; 58, s. 343-361
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Forskningsöversikt (refereegranskat)abstract
- Global change is pressing forest pathologists to solve increasingly complex problems. We argue that understanding interactive effects between forest pathogens and global warming, globalization, and land-use changes may benefit from a functional ecology mindset. Traits can be more informative about ecological functions than species inventories and may deliver a more mechanistic description of forest disease. Myriad microbes with pathogenic potential interact with forest ecosystems at different organizational levels. Elucidation of functional traits may enable the microbial complexity to be reduced into manageable categories with predictive power. In this review, we propose guidelines that allow the research community to develop a functional forest pathology approach. We suggest new angles by which functional questions can be used to resolve burning issues on tree disease. Building up functional databases for pathogenicity is key to implementing these approaches.
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