Search

2 páginas.- Resumen de la comunicación oral presentada en el Congreso celebrado en Jackson Hole, Wyoming, entre el 2 y el 4 de mayo de 2017., Because of their huge size and longevity, pines are exposed to numerous pests and pathogens, and have to cope with periods of severe abiotic stress such as water scarcity. Climate models predict an increase in mean annual temperatures and a decrease in precipitation, resulting in longer and more intense periods of drought. Associated to global change, an increase of the incidence of pests and pathogens has also been predicted. Understanding how pines are able to cope, at the same time, with both biotic and abiotic stress is, thus, necessary to know how they will finally respond to global change. Pines are isohydric species whose main mechanism to prevent water losses is the closure of stomata. Closing stomata under water deficit may imply a decrease in the carbon uptake needed for growth, reproduction and defenses. Hormonal cascading in response to both biotic and abiotic threats may also interact among each other altering the ability to tolerate each single stress. The aim of this study is to test how drought stress can constrain pine defensive responses to insect herbivory. For this purpose, 8 month-old seedlings of Maritime pine (Pinus pinaster Ait.) originating from three different populations known to differ in their tolerance to drought (San Ciprián, Coca and Oria) were submitted to three levels of water scarcity (control, moderate and severe drought stress) during four months and then subjected to herbivory (control and the pine weevil Hylobius abietis L.) for five days. Then, seedlings were harvested and biomass allocation, water potential, 13C concentration, non-structural carbohydrates and chemical defensive composition were studied. Water treatments promoted drought stress, measurable by a less discrimination to 13C, a decrease in water potential and reduced seedling dry weight in all populations. Moreover, the insect herbivore inflicted less damage on water-stressed than on well-watered plants. Pine responses to insect damage included alterations of the concentration of particular chemical defenses but these responses largely varied depending on the water treatment. Interactions between the experimental treatments and the population factor also revealed different strategies among pine populations to cope with the biotic and abiotic stressors. Overall, the results provide valuable information to understand how pines are able to tolerate at the time biotic and abiotic stressful conditions. These results will be helpful for forest management in a global change scenery.

Trabajo presentado en Estocolmo (Suecia) entre el 29 de junio y el 3 de julio de 2015., Only in Sweden 360 million conifer seedlings are planted each year but a substantial proportion of these are killed by pine weevils (Hylobius abietis) and black spruce beetles (Hylastes cunicularius). A high survival rate is essential for a high primary production of forest raw materials and biomass. There is currently no suitable non-insecticide plant protection option for a large part of these seedlings. One option may, however, be to trigger the seedlings´ own induced defense by treating them with a plant activator at the nursery so that they are prepared when they later becomes attacked by pine weevils in the field. The induced defense is under natural conditions generally expressed after damage by, e.g. a pest insect, whereas constitutive defenses are permanently present. Constitutive defenses serves to inhibit an initial attack whereas the induced defense serves to actively and vigorously stop the attack. The induced defense is powerful but the time lag after an initial attack before the induced defenses are fully expressed may be detrimental for a plant when the pest pressure is high. This weakness of the induced defense can be circumvented by applying a plant activator to trigger the induced defense of the plant before it is exposed to attacks. There is a suitable plant activator to trigger the induced defense of conifers available. That is methyl jasmonate which is a substance that also is produced naturally when a plant is attacked. It triggers the production of traumatic resin channels and different types of chemical defense substances. In this talk I will present some recent results related to the potential of this method to protect conifer seedlings against pine weevils.

Comunicación presentada en la Reunión celebrada en la ETSI Montes, Forestal y del Medio Natural de la Universidad Politécnica de Madrid, el día 8 de octubre de 2015. Pine trees are long -lived, widespread organisms that have to cope with multiple biotic stresses during their life cycle. To face against biological aggressions pine trees harbour terpenoids and phenolics as major chemical defences that may avoid or deter the attack providing resistance. Mono and sesquiterpenes, the volatile fraction of oleoresin, have been found to be adaptive resistance traits and to differ between and within species. However much less attention has been paid to sources of phenotypic variation in diterpenes, the non- volatile fraction of oleoresin that seals the stem wounds after oxidization. We examined the induced defensive responses of the diterpene fraction in two pine species, one native (Maritime pine) and one exotic (Monterey pine) to Europe, against two native insect herbivores, the bark chewing pine weevil and the pine processionary caterpillar; and explored the association between the induced chemical profile of diterpenes in each species and the subsequent damage. We found that the two pine species showed different constitutive and induced diterpene concentration in stem and needles. Whereas Pinus pinaster increased total di terpene concentration only in the stem against the two herbivores, P. radiata diterpene defences were locally induced in the damaged tissue due to herbivore feeding activity. Regarding to the chemical diterpene profile, the native P. pinaster produced a ge neral induced response increasing diterpene concentration against the two herbivores in the stem, whereas the exotic P. radiata showed a weevil -induced increase and a caterpillar -induced decrease in the most abundant diterpenes in the needles.

Póster presentado en Estocolmo (Suecia) entre el 29 de junio y el 3 de julio de 2015. Following an herbivore attack plants can reduce damage by inducing a wide variety of highly specific chemical and physical defences. Plants are able to recognize, integrate and respond accordingly in a specific manner to the biotic stimuli provoked by different herbivore species. This specificity of induced defences is particularly important for long-lived plants (e.g. pines) which have to face against multiple biological aggressions during their life cycle. In this sense, it has been recently documented that induction of mono- and sesquiterpenes (the volatile fraction of oleoresin) in pine trees is specific to plant species, herbivore identity and plant tissue. However, much less attention has been paid to understand the sources of phenotypic variation of diterpenes, the non-volatile fraction of oleoresin that seals the wounds after oxidization.

1 página.- Resumen de la conferencia presentada en la Reunión celebrada en la ETSI Montes, Forestal y del Medio Natural de la Universidad Politécnica de Madrid, los días 7 y 8 de octubre de 2015., The pine wilt disease (PWD) is caused by the pine wood nematode (PWN) Bursaphelenchus xylophilus, a microscopic worm that feeds off the host´s xylem cells and, under favourable edaphic-climatic conditions, is able to kill an adult tree in less than four months. It has become a devastating pest for pine forests leading to the yearly loss of thousands of pine trees worldwide, including P. pinaster plantations in Portugal. In the Iberian Peninsula it has, however, not yet significantly affected other Pinus species in the field, namely P. pinea, leading to the hypothesis that Pinus spp. have differential mechanisms that determine host susceptibility to the nematode. In the current presentation I will highlight some of the concerted Iberian efforts that have been undertaken at “Universidade Católica”, with collaboration with “Universidad de Extremadura” and “Misión Biológica de Galicia” (CSIC) in order to understand some of the anatomical, physiological, biochemical, and molecular aspects that underlie host susceptibility within different Pinus species. Controlled inoculations and an integrated analysis of several host traits allowed us to conclude that aspects related to disease resistance may be linked to stem anatomical traits, to the differential expression of specific genes, to the release of particular volatile organic compounds (VOCs), and to the constitutive and induced expression of defence molecules.

Póster presentado en Estocolmo (Suecia) entre el 3 y el 6 de febrero de 2014, en la Reunión organizada por la Nordic Society Oikos., Plants have evolved plastic responses to face the multiple stressors they have to cope with, such as light availability and insect herbivory. The former may impact the ability of producing induced defenses in response to herbivory due to conflicts in the allocation of C resources in absence of photosynthesis, and also because light may directly modulate the plant immune system. Here we hypothesized that pine tree induced responses to herbivory may depend on light availability during herbivore attack. Using a time course design we studied pine defensive responses to herbivory by the large pine weevil in 3 pine tree species under light deprivation. Plants in dark of the 3 species were significantly more consumed than control plants, and all them increased their resin concentration proportionally to the damage received by the weevil along time. Contrarily to our expectations, light deprivation did not decrease the inducibility of chemical defences in young pine trees.

Trabajo presentado en la 5th International Conference on Mediterranean Pines (Medpine5), celebrada en Solsona (España) del 22 al 26 de septiembre de 2014., Maritime pine can respond to antagonistic interactions with herbivores and pathogens by producing a modified phenotype with increased resistance. That involves quantitative and qualitative changes in chemical defences in target pine tissues. It is known that both genotype and environmental factors such as resource availability may modulate those induced responses. Maritime pine harbour a large intraspecific variation in life history traits, however little is still known about across population variation in constitutive and induced allocation to chemical defences. Here we studied the constitutive allocation to chemical defences in young pine trees and the inducibility of those defensive traits in response to real herbivory and to simulated damage signalling in ten population of this model Mediterranean pine species. We performed a greenhouse experiment growing Maritime pine juveniles belonging to the CLONAPIN® clonal collection (Serida, Asturias, Spain), consisting of 25 genotypes from each of 10 provenances covering the whole range of the species distribution, with 4 clonal copies per genotype. Clones were treated either with methyl jasmonate (MeJa), a phytohormone analogue involved in the damage signalling and production of defensive responses against chewing herbivores and necrotroph pathogens, or with the large pine weevil (Hylobius abietis, Coleoptera: Curculionidae – a conifer specialist chewing insect) in herbivory assays. We quantified pine defences (non-volatile resin and total polyphenolics) in stem and needles and the damage by the pine weevil. There were significant differences among populations for both non-volatile resin and total phenolics, suggesting a genetic diversity background for defence production. Both MeJa and real herbivory significantly increased the concentration of non-volatile resin in stem and needles (15.1% and 22% for both tissues for MeJa, 14.7% and 6.8% for both tissues for real herbivory). Total phenolics content decreased significantly after MeJa application in stem and needles (19.2% and 9.1% respectively) and no effect was detected for herbivory in stem but a significant increase for needles was observed (7.7%). We found a large variation in defence production and in defensive capability against the herbivore among pine populations, and also in quantitative responses to MeJa application. This study contributes to the understanding the role of chemical defences in herbivore-pine interactions and to the understanding of the structure of co-variation of plant defensive investment with other life history traits in local adaptation in the Mediterranean range. Further analysis should address possible geographical or climatic patterns in the divergences observed in the defensive capabilities and plasticity across populations.

1. Plant plastic responses to herbivore damage may include rapid, active reallocation of plant resources to reduce the impact of herbivory on future plant fitness. However, whether these inducible tolerance responses can be extended to pine trees and how these responses could be modulated by genetic and environmental factors remains unclear., 2. Biomass allocation and phosphorus (P) and nitrogen (N) concentrations in above- and belowground tissues were measured in Pinus pinaster juveniles belonging to 33 open-pollinated families grown under two P availabilities (P-deficient and complete fertilization). Measurements were taken 15 days after half of the plants received a foliar spray treatment of 22 mmol L)1 methyl jasmonate (MJ) to simulate above-ground herbivore attack., 3. Simulated above-ground herbivory promoted a strong preferential allocation of biomass below ground in the form of fine roots, leading to an almost two-fold increase in fine root biomass in MJ-treated plants and a significant reduction in above-ground tissues and coarse roots. In addition, MJ signalling increased P andN concentrations in the shoots while reducing (P) or maintaining (N) concentrations in the roots. These results suggest that induced resource sequestration is not a generalized strategy in this pine species. Fine root biomass and concentration of N and P in plant tissues showed additive genetic variation, but responses to MJ signalling did not vary among families. Allocation of biomass to fine roots was not affected by P availability, whereas allocation of P to the shoot was more intense under complete fertilization., 4. Synthesis: Two new putative tolerance mechanisms inducible by MJ signalling may help to minimize the impact of above-ground herbivore damage on the future fitness of young pine trees by (i) allocation of carbon to fine roots, this appeared to be a generalized strategy with weak environmental modulation and (ii) reallocation of P and N from roots to shoots, which was largely affected by P availability, and thus susceptible to greater phenotypic variation in heterogeneous environments. We provide evidence that changes in tolerance-related traits are rapidly inducible by herbivory cues in this pine species. These results should be integrated with induced resistance responses to fully understand the costs and benefits associated with induced responses to herbivory., This research was supported by the grants AGL2010-18724, RTA07-100, PSE310000. LS and XM received financial support from DOC-INIA and PREDOC-INIA grant programs respectively., INIA

1. The natural enemy hypothesis (NEH) predicts that alien plant species might receive less pres- sure from natural enemies than do related coexisting native plants. However, most studies to date are based on pairs of native and alien species, and the results remain inconclusive. The level of attack by native generalist herbivores can vary considerably between plant species, depending on defensive traits and strategies. Plant defences include preformed constitutive and induced defences that are activated as plastic responses to herbivore attack. However, the efficacy of induced defences could be altered when alien species entering an area are exposed to native enemies. 2. We tested the NEH for several closely related alien and native pines to Europe by examining early anti-herbivore resistance to damage by two generalist native insect herbivores (Hylobius abietis and Thaumetopoea pityocampa); the differences in constitutive and inducible chemical defences (i.e. non-volatile resin and total phenolics in the stem and needles); and whether con- sumption preferences shift after induced defences have been triggered by real herbivory. 3. We did not find alien pines to be less damaged by two generalist herbivores than native pines were. The constitutive concentration of chemical defences significantly differed among pine spe- cies. The concentration of constitutive total phenolics in the stem was greater in native than in alien pines. The opposite trend was found for constitutive total phenolics in the needles. The con- centration of chemical defences (non-volatile resin and total phenolics) in the stem significantly increased after herbivory by H. abietis. Moreover, the induction of total phenolics by H. abietis damage was significantly greater in native pine species than in alien pines. On the other hand, only concentrations of non-volatile resin in needles significantly increased after herbivory by T. pityocampa, but without significant differences in inducibility between alien and native pines. In cafeteria bioassays, H. abietis consumed the twigs from alien more than those from native species irrespective of prior exposure to the insect. Meanwhile, no differences among range ori- gin were found in the T. pityocampa cafeteria bioassays. 4. Overall, we found no support for the NEH in alien pines to Europe. This suggests that alien pines, in regions where they coexist with native congeners, may be controlled by native generalist herbivores, this being one reason that invasion by alien pines is not frequent in Europe.

1. Current hypotheses predict contrasting roles for natural enemies in determining the success or failure of plant invasions. Differences in plant-induced resistance and tolerance to native herbivores between native and exotic species might contribute to resolve this controversy., 2. We examined the differences between the native Pinus pinaster and the exotic P. radiata in constitutive resistance, inducibility of chemical defences, realized resistance and tolerance to the large pine weevil Hylobius abietis in NW Spain. In this region, both pine species closely coexist and are threatened by the weevil, a harmful phloem feeder that causes extensive mortality and growth reduction in young pine stands., 3. We performed two in vitro cafeteria bioassays, two induction experiments with direct exposure to the weevil and spraying methyl jasmonate and an exhaustive field study of the genetic variation in tolerance and resistance in forestry genetic trials., 4. The weevil significantly preferred the native to the exotic pine when twigs were offered as cut material in Petri dishes. However, the pattern in the field was the opposite, with greater damage on the exotic. Inducibility of stem oleoresin did not differ between species when elicited by the application of methyl jasmonate. However, after a 72-h experimental exposure to the weevil, stem resin content in the native pine was double that in the exotic pine, suggesting a lower capability of the exotic pine to respond to the insect damage. In the field, family relationships between early damage and several pine fitness correlates revealed a significantly greater tolerance of the native pine to the insect damage. Furthermore, only the native pine showed genetic variation in tolerance to the damage., 5. Synthesis. The preference of the herbivore for the native species was counterbalanced by a lower capability for expressing induced resistance to the weevil and reduced tolerance in the exotic species, resulting in no apparent fitness advantage of the exotic P. radiata over the native P. pinaster. Differences in inducibility by and tolerance to native enemies between exotic and native host congeners emerge as key traits for understanding how native enemies might contribute to preventing an introduced species from becoming invasive., Research was supported by the grants RTA2007-100 and AGL2010-18724.

Póster y resumen, The use of organic fertilizers such as vermicompost has shown to enhance germination and growth of several plant species. Nevertheless effects might vary depending on plant genotype. Here we investigated how the incorporation of vermicompost can affect seed germination in six progenies of pine trees., Cristina Lazcano is financially supported by a grant from “Fundación la Caixa”

Póster y resumen, We investigated the effect of vermicompost on pine seedling growth independently of nutrient mediated effects, and the influence of plant genotype on the response to the addition to this kind of organic amendment. Vermicompost was incorporated, either solid or liquid, at several doses into the potting media of five selected pine progenies. Growth and maturation of the seedlings were evaluated 20 weeks after sowing., Cristina Lazcano is financially supported by a fellowship from “Fundación la Caixa”

[EN] Damage by the pine weevil Hylobius abietis L. (Coleoptera: Curculionidae) on Pinus pinaster Ait. was evaluated in a fertilization × progeny test in Galicia (NW Spain) to determine the genetic variation among families and the possibility to include the resistance to this insect as a selection criteria in the Galician maritime pine breeding program. Several damage and symptoms traits were evaluated. All these traits showed highly significant family effects and were strongly correlated among each other. Individual and family heritability estimates of the wound evaluations in the seedling stems were around 0.2 and 0.8, respectively. Strong genetic correlations among wounds and the average seedling color indicated that this last simple and subjective trait can be used for screening for pine weevil susceptibility. A positive genetic correlation was also observed between diameter growth and pine weevil damage. Faster growing families were more attacked hindering the possibility to include the susceptibility to the insect in the breeding program., [FR] Les dommages provoqués par Hylobius abietis L. (Coleoptera : Curculionidae) au pin maritime (Pinus pinaster Ait.) ont été évalués sur un test génétique de descendances maternelles soumis à différents traitements de fertilisation en Galice (NO Espagne). Le but était d'étudier la variation entre familles du niveau d'attaque de l'insecte et la possibilité d'inclure ce caractère dans le programme d'amélioration du pin maritime en Galice. Différents dégâts et symptômes ont été mesurés ainsi que la hauteur et le diamètre. Tous les traits évalués ont montré un effet famille très significatif et ils ont souvent corrélés entre eux. Les blessures évaluées au niveau de la tige du jeune plant montrent une héritabilité individuelle et familiale d'environ 0,2 et 0,8 respectivement. Le nombre de blessures sur la tige et la couleur des jeunes plants sont corrélés génétiquement. Il semble donc possible d'utiliser cette mesure de coloration, simple et subjective, pour évaluer la sensibilité du pin à l'hylobe. Nous avons aussi observé une corrélation génétique positive entre la croissance en diamètre et les dommages dus à H. abietis. Les familles les plus vigoureuses ont été les plus attaquées, ce qui limite les possibilités d'inclure la sensibilité à l'insecte dans le programme d'amélioration du pin maritime., This study was supported by the INIA project RTA2-109.