BUSCADOR RECOLECTA

Mediterranean pines are large-sized, long-lived, iteroparous species. During their long life, they have to endure changing biotic and abiotic environments that favour plastic strategies in the relative investment of resources in growth, maintenance and reproduction. The variation in the biotic and abiotic conditions along the distribution range of species, together with other evolutionary forces related with the biogeographic past and demography, have favoured the intraspecific differentiation of adaptive syndromes in relation with the investment in different vital functions. But the speed of the ongoing environmental change imposes serious doubts about the capacity of adaptation of different populations to the future environment, and about the viability of individual plasticity as an adaptation strategy to change. In the current thesis, we aim to retrospecively explore, through dendrochronological tools and other procedures, the trade – offs between the investment in defences and growth in Mediterranean pines. To do so, we will use Pinus pinaster as a model species, and the density and other characteristics of resin ducts in different plant tissues as proxies of defensive investment. We will pay special attention to the influence of genetic and environmental factors, and particularly, past climatic conditions, on allocation to defences in this species. The studies comprising this thesis, will be carried out in provenance trials (common gardens) from the National Network of Forest Genetic Trials (GENFORED, from its acronym in Spanish) and in manipulative greehouse experiments, where populations coming from different provenances in the species distribution range, cohabit in the same environment or under the same experimental conditions. With this, we expect to generate knowledge about the variability in the defence investment in Iberian pines, as well as about the source of this variability, either environmental or genetic, and their relevance in the adaptation to change. The results, will be useful for designing future woodland adaptive management policies in the frame of global change., Os piñeiros mediterráneos son especies de gran talle, lonxevas e iteróparas. Durante o seu longo ciclo de vida, están sometidos a un ambiente biótico e abiótico cambiante que favorece estratexias plásticas na inversión relativa de recursos a crecemento, mantemento e reprodución. A variación nas condicións bióticas e abióticas ó longo do rango de distribución das especies, xunto con outras forzas evolutivas relacionadas co pasado bioxeográfico e a demografía, favoreceu, a súa vez, a diferenciación intraespecífica de síndromes adaptativos en relación á inversión nas distintas funcións vitais. Pero o ritmo de cambios ambientais determinados polo cambio global, impón serios interrogantes sobre a capacidade de adaptación das distintas poboacións ó ambiente futuro e sobre a viabilidade da plasticidade individual como estratexia de adaptación ó cambio. Na presente tese, preténdese avaliar, de forma retrospectiva, mediante ferramentas dendrocronolóxicas e outros procedementos, os compromisos existentes entre a inversión en defensas e o crecemento en piñeiros mediterráneos, empregando a Pinus pinaster como especie de piñeiro modelo, e empregando como proxy de inversión defensiva a densidade e propiedades das canles resiníferas presentes nos tecidos vexetais. Para elo, estudiarase a influencia dos factores xenéticos e ambientais, e en particular das condicións climáticas pasadas, na inversión en defensas nesta especie. Os estudos que conforman esta tese levaranse a cabo en ensaios de procedencias (common gardens) da Rede Nacional de Ensaios Xenéticos Forestais (GENFORED) e en experimentos manipulativos de invernadoiro, onde poboacións de diferentes procedencias do rango de distribución de cada especie conviven nun mesmo ambiente. Con este, pretendemos xerar coñecemento acerca da variabilidade existente na inversión en defensas en piñeiros ibéricos, nas fontes de dita variabilidade, ben sexa ambiental, ou xenética, e a súa relevancia na adaptación ó cambio. Os resultados de esta tese serán de gran utilidade para o deseño dos futuros plans de xestión adaptativa das masas forestais no marco do cambio global., Los pinos mediterráneos son especies de gran tamaño, longevas e iteróparas. Durante su
largo ciclo de vida están sometidos a un ambiente biótico y abiótico cambiante que favorece estrategias plásticas en la inversión relativa de recursos a crecimiento, mantenimiento y reproducción. La variación en las condiciones bióticas y abióticas a lo largo del rango de distribución de las especies, junto con otras fuerzas evolutivas relacionadas con el pasado biogeográfico y la demografía, ha favorecido, a su vez, la diferenciación intraespecífica de síndromes adaptativos en relación a la inversión en las distintas funciones vitales. Pero el ritmo de cambios ambientales determinados por el cambio global impone serios interrogantes sobre la capacidad de adaptación de las distintas poblaciones al ambiente futuro y sobre la viabilidad de la plasticidad individual como estrategia de adaptación al cambio. En la presente tesis, se pretende evaluar, de manera retrospectiva, mediante herramientas dendrocronológicas y otros procedimientos, los compromisos existentes entre la inversión en defensas y el crecimiento en pinos mediterráneos utilizando a Pinus pinaster como especie modelo, y utilizando como proxy de inversión defensiva la densidad y propiedades de canales resiníferos presentes en tejidos vegetales. Para ello, se estudiará la influencia de los factores genéticos y ambientales, y en particular de las condiciones climáticas pasadas, en la inversión defensiva en esta especie. Los estudios que comprenden esta tesis se llevarán a cabo en ensayos de procedencias (common gardens) de la Red Nacional de Ensayos Genéticos Forestales GENFORED y en estudios manipulativos de invernadero, donde poblaciones de diferentes procedencias del rango de distribución de cada especie conviven en un mismo ambiente. Con esto, pretendemos generar conocimiento acerca de la variabilidad existente en la inversión en defensas en pinos ibéricos, las fuentes de dicha variabilidad, bien sea ambiental, o genética, y su relevancia en la adaptación al cambio. Los resultados de esta tesis serán de gran utilidad para el diseño de los futuros planes de gestión adaptativa de las masas forestales en el marco del cambio global., Ministerio de Economía y Competitividad |Ref. BES-2016-076624, Ministerio de Economía y Competitividad |Ref. AGL2015-68274-C3-2-R, Ministerio de Economía y Competitividad |Ref. RTI2018-094691-B-C33

Summary: Many ecologically important forest trees from dry areas have been insufficiently investigated for their ability to adapt to the challenges posed by climate change, which hampers the implementation of mitigation policies. We analyzed 14 common‐garden experiments across the Mediterranean which studied the widespread thermophilic conifer Pinus halepensis and involved 157 populations categorized into five ecotypes. Ecotype‐specific tree height responses to climate were applied to projected climate change (2071-2100 ad), to project potential growth patterns both locally and across the species' range. We found contrasting ecotypic sensitivities to annual precipitation but comparatively uniform responses to mean temperature, while evidence of local adaptation for tree height was limited to mesic ecotypes. We projected intriguing patterns of response range‐wide, implying either height inhibition or stimulation of up to 75%, and deduced that the ecotype currently experiencing more favorable (wetter) conditions will show the largest inhibition. Extensive height reductions can be expected for coastal areas of France, Greece, Spain and northern Africa. Our findings underline the fact that intraspecific variations in sensitivity to precipitation must be considered when projecting tree height responses of dry forests to future climate. The ecotype‐specific projected performances call for management activities to ensure forest resilience in the Mediterranean through, for example, tailored deployment strategies., This study was funded by the Spanish Government (MCIU/AEI/ coordinated grants AGL2015‐68274‐C3‐3‐R and RTI2018‐094691‐B).

Remote sensing is increasingly used in forest inventories. However, its application to
assess genetic variation in forest trees is still rare, particularly in conifers. Here we evaluate the
potential of LiDAR and RGB imagery obtained through unmanned aerial vehicles (UAVs) as highthroughput
phenotyping tools for the characterization of tree growth and crown structure in two
representative Mediterranean pine species. To this end, we investigated the suitability of these
tools to evaluate intraspecific differentiation in a wide array of morphometric traits for Pinus nigra
(European black pine) and Pinus halepensis (Aleppo pine). Morphometric traits related to crown
architecture and volume, primary growth, and biomass were retrieved at the tree level in two
genetic trials located in Central Spain and compared with ground-truth data. Both UAV-based
methods were then tested for their accuracy to detect genotypic differentiation among black pine
and Aleppo pine populations and their subspecies (black pine) or ecotypes (Aleppo pine). The
possible relation between intraspecific variation of morphometric traits and life-history strategies of
populations was also tested by correlating traits to climate factors at origin of populations. Finally, we
investigated which traits distinguished better among black pine subspecies or Aleppo pine ecotypes.
Overall, the results demonstrate the usefulness of UAV-based LiDAR and RGB records to disclose tree
architectural intraspecific differences in pine species potentially related to adaptive divergence among
populations. In particular, three LiDAR-derived traits related to crown volume, crown architecture,
and main trunk—or, alternatively, the latter (RGB-derived) two traits—discriminated the most among
black pine subspecies. In turn, Aleppo pine ecotypes were partly distinguishable by using two
LiDAR-derived traits related to crown architecture and crown volume, or three RGB-derived traits
related to tree biomass and main trunk. Remote-sensing-derived-traits related to main trunk, tree
biomass, crown architecture, and crown volume were associated with environmental characteristics
at the origin of populations of black pine and Aleppo pine, thus hinting at divergent environmental
stress-induced local adaptation to drought, wildfire, and snowfall in both species., This work was partly supported by the Spanish Government, grant numbers RTI2018-094691-B-C31 and RTI2018-094691-B-C33 (MCIU/AEI/FEDER, EU). E. Lombardi was supported by a AGAUR FI-2021 pre-doctoral fellowship (with the support from the Secretariat for Universities and Research of the Ministry of Business and Knowledge of the Government of Catalonia and the European Social Fund).

Mycorrhizal fungi can help plants to cope with drought, but research on the fungal communities that are more resistant to drought or alleviate drought stress of trees is still scarce. In this study, we investigated effects of drought on soil fungal communities and explored potential fungal traits related to drought resistance under greenhouse conditions. We manipulated water availability in pine seedlings belonging to three Spanish Pinus pinaster populations from geographical areas subjected to contrasting summer drought. A set of plant ecophys-iological traits were quantified and soil fungi was quantified and profiled using ergosterol and Pacific Biosciences sequencing. Abundance of ectomycorrhizal (ECM) fungi in plants subjected to drought was lower than in well-watered plants. Most ECM taxa in plants surviving drought had long exploration types and were taxa typically forming rhizomorphs and hydrophobic mycelia. By contrast, ECM taxa in well-watered plants had wider range of distinct exploration types. No differences in fungal communities were found among P. pinaster populations. No associations between ECM fungi and plant ecophysiological traits were found, but significant interactions be-tween drought treatments and belowground plant biomass were found for the relative abundances of ECM fungi, particularly ECM with long exploration types. Plants subjected to drought may benefit by associating to ECM taxa previously shown to transport water efficiently., L.S. and R.Z. acknowledge support from Ministerio de Economía y Competitividad/FEDER Grants FUTURPIN AGL2015-68274-C3-2-R, RESILPIN RTI2018-094691-B-C33 and Xunta de Galicia-GAIN grant IN607/2021/03. J.O. was supported by a Ramón y Cajal fellowship (RYC-2015-17459) and J.A.B. was supported by the Serra-Hunter Program-Generalitat de Catalunya.

Insect outbreaks of increasing frequency and severity in forests are predicted due to climate change. Insect herbivory is known to promote physiological changes in forest trees. However, little is known about whether these plant phenotypic adjustments have cascading effects on tree microbial symbionts such as fungi in roots and foliage. We studied the impact of defoliation by the pine processionary moth in two infested Pinus nigra forests through a multilevel sampling of defoliated and non-defoliated trees. We measured tree growth, nutritional status and carbon allocation to chemical defenses. Simultaneously, we analyzed the putative impact of defoliation on the needle endophytes and on the soil fungal communities. Higher concentrations of chemical defenses were found in defoliated trees, likely as a response to defoliation; however, no differences in non-structural carbohydrate reserves were found. In parallel to the reductions in tree growth and changes in chemical defenses, we observed shifts in the composition of needle endophytic and soil fungal communities in defoliated trees. Defoliated trees consistently corresponded with a lower biomass of ectomycorrhizal fungi in both sites, and a higher alpha diversity and greater relative abundance of belowground saprotrophs and pathogens. However, ectomycorrhizal alpha diversity was similar between non-defoliated and defoliated trees. Specific needle endophytes in old needles were strongly associated with non-defoliated trees. The potential role of these endophytic fungi in pine resistance should be further investigated. Our study suggests that lower biomass of ectomycorrhizal fungi in defoliated trees might slow down tree recovery since fungal shifts might affect tree-mycorrhizal feedbacks and can potentially influence carbon and nitrogen cycling in forest soils., J.J.C. acknowledges the support of the CGL2015-69186-C2-1-R and RTI2018-096884-B-C31 projects (Spanish Ministry of Science), and L.S. and R.Z. acknowledge support from MCIU/AEI/FEDER/UE grants FUTURPIN AGL2015-68274-C3-2-R and RESILPINE RTI2018-094691-B-C33 and from Xunta de Galicia‐GAIN grant IN607A2016/013. J.O. and J.G.A. were supported by a Ramón y Cajal fellowship (RYC-2015-17459; RYC-2016-20528, respectively) and J.A.B. was supported by the Serra-Hunter Program-Generalitat de Catalunya.

Premise: Persistence of tree populations in the face of global change relies on their capacity to respond to biotic and abiotic stressors through plastic or adaptive changes. Genetic adaptation will depend on the additive genetic variation within populations and the heritability of traits related to stress tolerance. Because traits can be genetically linked, selective pressure acting on one trait may lead to correlated responses in other traits. Methods: To test direct and correlated responses to selection for growth and drought tolerance in Pinus halepensis, we selected trees in a parental population for higher growth and greater water-use efficiency (WUE) and compared their offspring with the offspring of random trees from the parental population in two contrasting common gardens. We estimated direct responses to selection for growth and WUE and correlated responses for growth and tolerance to abiotic and biotic stressors. Results: We found a strong response to selection and high realized heritability for WUE, but no response to selection for growth. Correlated responses to selection in other life-history traits were not significant, except for concentration of some chemical defenses, which was greater in the offspring of mother trees selected for growth than in the offspring of unselected control trees. Conclusions: The empirical evidence of direct responses to selection for high WUE suggests that P. halepensis has the potential to evolve in response to increasing drought stress. Contrary to expectations, the results are not conclusive of a potential negative impact of WUE and growth selection on other key life-history traits., This research was supported by grants AGL2015-68274-C03 (“Futurpine”, MINECO / FEDER / UE, subprojects 01R, 02R and 03R) and RTI2018-094691-B-C33 (“Resilpine”, MCIU / AEI / UE, subprojects C31, C32 and C33). E.S.V. received financial assistance from the FPU grant program (Ministerio de Educación, Cultura y Deporte, Gobierno de España).

Centro de Investigación Forestal (CIFOR), Persistence of tree populations in the face of global change relies on their capacity to respond to biotic and abiotic stressors through plastic or adaptive changes. Genetic adaptation will depend on the additive genetic variation within populations and the heritability of traits related to stress tolerance. Because traits can be genetically linked, selective pressure acting on one trait may lead to correlated responses in other traits., This research was supported by grants AGL2015-68274-C03 (“Futurpine”, MINECO / FEDER / UE, subprojects 01R, 02R and 03R) and RTI2018-094691-B-C33 (“Resilpine”, MCIU / AEI / UE, subprojects C31, C32 and C33). E.S.V. received financial assistance from the FPU grant program (Ministerio de Educación, Cultura y Deporte, Gobierno de España), Peer reviewed, 11 Pág.

Phenotypic plasticity is a main mechanism for organisms to cope with changing environments and broaden their ecological range. Plasticity is genetically based and can evolve under natural selection, such that populations within a species show distinct phenotypic responses to the environment if evolved under different conditions. Understanding how intraspecific variation in phenotypic plasticity arises is critical to assess potential adaptation to ongoing climate change. Theory predicts that plasticity is favored in more favorable but variable environments. Yet, many theoretical predictions about benefits, costs, and selection on plasticity remain untested. To test these predictions, we took advantage of three genetic trials in the northern Rocky Mountains, USA, which assessed 23 closely located Pinus ponderosa populations over 27 years. Mean environmental conditions and their spatial patterns of variation at the seed source populations were characterized based on six basic climate parameters. Despite the small area of origin, there was significant genetic variation in phenotypic plasticity for tree growth among populations. We found a significant negative correlation between phenotypic plasticity and the patch size of environmental heterogeneity at the seed source populations, but not with total environmental spatial variance. These results show that populations exposed to high microhabitat heterogeneity have evolved higher phenotypic plasticity and that the trigger was the grain rather than the total magnitude of spatial heterogeneity. Contrary to theoretical predictions, we also found a positive relationship between population plasticity and summer drought at the seed source, indicating that drought can act as a trigger of plasticity. Finally, we found a negative correlation between the quantitative genetic variance within populations and their phenotypic plasticity, suggesting compensatory adaptive mechanisms for the lack of genetic diversity. These results improve our understanding of the microevolutionary drivers of phenotypic plasticity, a critical process for resilience of long-lived species under climate change, and support decision-making in tree genetic improvement programs and seed transfer strategies., This project was partially funded by a McIntire-Stennis Cooperative Forestry Research Grant MONZ-1206 from the College of Forestry and Conservation of the University of Montana to A.S.
R.Z. and L.S. were supported by the RESILPINE grant funded by the Spanish Government (RTI2018-094691-B-C33, MCIU/AEI/FEDER-UE) and a GAIN grant funded by the regional Government of Galicia (IN607/2021/583535)., Peer reviewed

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Instituto de Ciencias Forestales (ICIFOR), The potential of pine resin as a renewable non-timber product is furthering the socioeconomic relevance of the resin industry in Europe, where maritime pine (Pinus pinaster Ait.) is the main tapped species. Characterizing maritime pine genetic resources in terms of resin yield potential and its covariation with tree growth is crucial to implement efficient tree breeding programs aiming to maximize resin yield without negatively impact tree growth. We explored genetic variation in resin yield and tree growth among provenance regions, populations within regions, and families of maritime pine. We used a progeny trial located at Central Spain to estimate additive genetic variation and heritability of resin yield, and a common garden located at Northwest Spain to explore variation among provenance regions and populations within regions. Resin yield was assessed in both trials with and without sulphuric-based stimulant paste. Association between growth and resin yield at different levels (phenotypes, families, populations and provenance regions) was also explored. Growth and resin yield were highly variable within populations, with narrow-sense heritability estimates being particularly high for resin yield (hi2 = 0.49). Growth varied significantly across provenance regions and populations within regions, while resin yield was only variable among provenance regions. Genetic variation in resin yield was similar in trees with and without stimulant paste. We did not find evidence of genetic correlations between growth and resin yield. However, at the phenotype level resin yield and growth were significantly correlated, although the sign of such association switched between trials. Across provenance regions, growth and resin yield where negatively correlated. Altogether, the high narrow-sense heritability estimate, the highly consistent genetic variation and the lack of negative genetic correlation with growth evidence the opportunity for implementing breeding programs to increase resin yield in maritime pine forests., This study was supported by the Regional Government of Galicia (“RESDRON” grant, Feader2018/066B, Xunta de Galicia/FEADER) and by the Spanish Government (“RESILPINE” grant, RTI2018-094691-B-C33, MCIU/AEI/FEDER-UE and “GENMAC” grant, 2018ES06RDEI12479V1, MAPA/AEI-Agri/FEADER, UE). C.V.G. and X.L.G. received financial support from the FPI grant programme (MINECO-Spain BES-2016-076624 and BES-2013-062663). Authors thank ‘Consellería do Medio Rural, Xunta de Galicia’ who supported the establishment of the Saviñao provenance trial, and CIFOR INIA and UPM who established and maintained the Carbonero provenance trial. Help in field assessments by Jacobo Roselló, Santiago Gil, Fernando Peña, María Bragados, and the Asociación Nacional Resinera are also acknowledged. We also thank Silvana Poceiro and María Lores for their help in the lab., Peer reviewed

Mycorrhizal fungi can help plants to cope with drought, but research on the fungal communities that are more resistant to drought or alleviate drought stress of trees is still scarce. In this study, we investigated effects of drought on soil fungal communities and explored potential fungal traits related to drought resistance under greenhouse conditions. We manipulated water availability in pine seedlings belonging to three Spanish Pinus pinaster populations from geographical areas subjected to contrasting summer drought. A set of plant ecophysiological traits were quantified and soil fungi was quantified and profiled using ergosterol and Pacific Biosciences sequencing. Abundance of ectomycorrhizal (ECM) fungi in plants subjected to drought was lower than in well-watered plants. Most ECM taxa in plants surviving drought had long exploration types and were taxa typically forming rhizomorphs and hydrophobic mycelia. By contrast, ECM taxa in well-watered plants had wider range of distinct exploration types. No differences in fungal communities were found among P. pinaster populations. No associations between ECM fungi and plant ecophysiological traits were found, but significant interactions between drought treatments and belowground plant biomass were found for the relative abundances of ECM fungi, particularly ECM with long exploration types. Plants subjected to drought may benefit by associating to ECM taxa previously shown to transport water efficiently., L.S. and R.Z. acknowledge support from Ministerio de Economía y
Competitividad/FEDER Grants FUTURPIN AGL2015-68274-C3-2-R,
RESILPIN RTI2018-094691-B-C33 and Xunta de Galicia-GAIN grant
IN607/2021/03. J.O. was supported by a Ramon ´ y Cajal fellowship
(RYC-2015-17459) and J.A.B. was supported by the Serra-Hunter Pro gram-Generalitat de Catalunya, Peer reviewed

4 páginas, 1 figura, Plant plastic responses to environmental variation, at scales smaller than the individual plant size, promote phenotypic and epigenetic diversity among repeated structures within genotypes. Different epigenetic marks in the somatic line can translate to the germline and seeds, generating a fitness patchwork in the progeny with unexplored effects on plant evolutionary dynamics., M.S. was a beneficiary of grant I2CB, Xunta de Galicia.
L.S. was partially supported by the grant RESILPINE
(RTI2018-094691-B-C33, MCIU/AEI/FEDER-UE), Peer reviewed

13 páginas, 4 figuras
Los datos a los que hace referencia este artículo han sido depositados en el repositorio DIGITAL.CSIC (doi:10.20350/digitalCSIC/15430), Phenotypic plasticity is a main mechanism for sessile organisms to cope with changing environments. Plasticity is genetically based and can evolve under natural selection so that populations within a species show distinct phenotypic responses to environment. An important question that remains elusive is whether the intraspecific variation in plasticity at different spatial scales is independent from each other. To test whether variation in plasticity to macro- and micro-environmental variation is related among each other, we used growth data of 25 Pinus pinaster populations established in seven field common gardens in NW Spain. Phenotypic plasticity to macro-environmental variation was estimated across test sites while plasticity to micro-environmental variation was estimated by using semivariography and kriging for modeling within-site heterogeneity. We provide empirical evidence of among-population variation in the magnitude of plastic responses to both micro- and macro-environmental variation. Importantly, we found that such responses were positively correlated across spatial scales. Selection for plasticity at one scale of environmental variation may impact the expression of plasticity at other scales, having important consequences on the ability of populations to buffer climate change. These results improve our understanding of the ecological drivers underlying the expression of phenotypic plasticity., This project was funded by the Spanish Government (‘RESILPINE’ grant, RTI2018-094691-B-C33) to RZ. RdlM was supported by a grant funded by the Regional Government of Andalucıa (P18-FR-3307) to Xavier Pico’s laboratory.
We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI)., Peer reviewed

15 Páginas, 8 figuras, The data of this study are available upon request to the first author., 24 February 2025A Correction to this paper has been published: https://doi.org/10.1007/s00468-025-02613-1, Key message: The effects of MJ on pine trees are species-specific and trigger a resistant phenotype to the PWN. A more dynamic response of hormones and gene expression in Pinus pinea explains the high resistance to Bursaphelenchus xylophilus of this species. Abstract: Knowledge on hormonal and genetic mechanisms of pine trees in response to the pinewood nematode (PWN; Bursaphelenchus xylophilus) is limited. To describe tree defence strategies against B. xylophilus, this study used the plant stress hormone methyl jasmonate (MJ) on four pine species with different susceptibility (Pinus pinaster < P. radiata ≈ P. sylvestris < P. pinea). Three-year-old trees were sprayed with MJ at 0, 25, and 50 mM, and 2 months later challenged with the PWN. Multiple samples were taken to assess nematode content, oxidative stress, secondary metabolites, phytohormone levels, and stress-related gene expression. Nematode infestation in trees correlated negatively with the water content of needles and phenolics of stems, and positively with the concentration of indole-3-carboxylic acid in stems. MJ spray reduced in a dose-dependent manner the nematode content in P. pinaster and P. sylvestris. The effects of MJ were species-specific, although a more pronounced impact was observed in the susceptible P. pinaster species, leading to a decrease of chlorophyll and water loss and to the upregulation of the gene involved in the biosynthesis of terpenoids (AFS). After MJ spray, increased levels of JA-Ile were observed in P. pinea only. Hormone profiling, predisposition to activate antioxidant response, and gene expression in P. pinea trees provide evidence of why this species is highly resistant to B. xylophilus. On the contrary, the lack of effective hormonal changes in P. pinaster explained the lack of defence responses to B. xylophilus of this susceptible species. This study is a first approach to explore biochemical, molecular, and hormonal interactions between Pinus species and the PWN, and presents unprecedented insights into alterations induced by exogenous MJ in regulating defence mechanisms in pine trees., Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. The study was performed within the \u2018Characterization of the pinewood nematode/Pinus system: a phytochemical and histopathological approach\u2019 project (PTDC/AGR-CFL/120184/2010), funded by Funda\u00E7\u00E3o para a Ci\u00EAncia e a Tecnologia (FCT). Additional financial support to AS, LS and RZ came from the Spanish National Research Agency MCIU/AEI/FEDER RESILPINE (RTI2018-094691-B-C33) and PLASTICPINE (PID2022-140521OB-C31) grants; OTR07700, IN607A2021/03, 2022.01903 from Intramural CSIC ref-201640I030 and Xunta de Galicia-GAIN IN607/2023 grant. Also supported by the FCT\u2019s bilateral action Spain-Portugal PRIAIBPT-2011-1152 (NEMARES) and UIDB/50016/2020 R&D Unit., Peer reviewed