Phenotypic plasticity of maritime pine to insect herbivory

PósterPeer Reviewe

Genetic variation and phenotypic plasticity of nutrient re-allocation and increased fine root production as putative tolerance mechanisms inducible by methyl jasmonate in pine trees

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.INIAPeer Reviewe

Nutritional status and genetic variation in the response to nutrient availability in Pinus pinaster. A multisite field study in NW Spain

The low nutrient availability of the acidic and sandy soils of Galicia (Northwest Spain) is probably the main environmental factor limiting forest primary productivity in the area. These particular edaphic conditions could have imposed selective pressures on maritime pine populations leading to specific local adaptations. We first assessed the nutritional status of 22 young contemporary Pinus pinaster plantations in Northwest Spain, and then analysed the response to fertilization in three family × fertilization trials, and how this response varied across sites and genotypes. Growth of P. pinaster in Northwest Spain appeared to be largely limited by nutrient availability, where most of the plantations showed severe nutrient deficiencies, especially in P and Mg. According to these deficiencies, a strong positive response to nutrient additions was observed in the three trials, with height increments of up to 30% compared with the unfertilized control. However, the response to fertilizers was very variable from site to site, and in some cases did not agree with the foliar nutritional diagnosis. The response to fertilization was also significantly affected by pine genotype, suggesting that the plastic response to nutrient additions within each environment was under genetic control. However, the family response to nutrient availability was not consistent across sites, and no significant differences among families were observed for the RDPI plasticity index – a single index that summarizes the phenotypic change in multiple environments – when analysed across environments. The strong environmental component modulating phenotypic responses to fertilization could impose an important obstacle to evolve specific adaptations to the local edaphic conditions, as well as to artificially select genotypes adapted to different environments and silviculture regimes.This research was funded by the INIA projects RTA05-173 and RTA07-100.Peer reviewe

Genetics, phosphorus availability, and herbivore-derived induction as sources of phenotypic variation of leaf volatile terpenes in a pine species

Oleoresin produced and stored in pine tree leaves provides direct resistance to herbivores, while leaf volatile terpenes (LVT) in the resin are also powerful airborne infochemicals. Resin concentration and profile show considerable spatial and temporal phenotypic variation within and among pine populations. LVT biochemistry is known to be under genetic control, and although LVT should be plastic to diverse abiotic and biotic environmental factors such as nutrient availability and herbivore attack, little is known about their relative contributions and interactive effects. The aim of this paper was to clarify whether reduced phosphorus availability could increase the LVT concentration and affect the expression of herbivore-derived induced defences, and how plasticity would contribute to the phenotypic variation of LVT. The constitutive and methyl-jasmonate (MeJa) induced LVT concentration and profile were analysed in 17 half-sib Pinus pinaster families growing under two levels of P-availability (complete and P-limited fertilization). Individual terpene concentrations showed large additive genetic variation, which was more pronounced in the control than in MeJa-induced pines. MeJa application did not affect the LVT concentration, but significantly modified the LVT profile by depleting the α-pinene content and reducing the sesquiterpene fraction. Low P-availability strongly reduced plant growth and foliar nutrient concentrations, but did not affect LVT concentration and profile, and did not interact with MeJa-induction. Results indicate a strong homeostasis of LVT concentration to P-availability, and minor changes in the LVT profile due to MeJa-induction. Genetic variation appears to be the main source of phenotypic variation affecting the LVT concentration in this pine species.This work was supported by the Spanish Instituto Nacional de Investigación y Tecnología Agraria y Agroalimentaria (grant number INIA-RTA07-100; and DOC-INIA and PREDOC-INIA fellows for LS and XM, respectively); the Spanish Agency of Science and Technology (grant numbers CGL2006-04025/BOS, CGL2010-17172, and CSD2008- 00040 for JP and JL; and AGL2010-18724 and PSE310000 for RZ and LS); and the Catalonian Government (grant number SGR 2009-1458).Peer reviewe

Densidad y área de los canales resiníferos de "Pinus pinaster" ante tratamientos de fertilización, y su relación con la defensa ante "Hylobius abietis"

6 páginas, 3 tablas -- Actas de la I Reunión sobre Sanidad Forestal celebrada en Palencia el 24 y 25 de septiembre de 2007.Las coníferas poseen una estructura de canales resiníferos que actúa como defensa contra el ataque de insectos y patógenos. Varios autores han observado que un aumento en la disponibilidad de nutrientes puede alterar el reparto de energía en las plantas, en detrimento de los sistemas defensivos. El presente estudio tiene como objetivo determinar el efecto de la fertilización de establecimiento sobre el desarrollo del sistema de canales resiníferos en Pinus pinaster. Mediante histología en brinzales de 3 savias sometidos a dos ensayos familia x fertilización se cuantificó la densidad y el área de los canales resiníferos del floema y del xilema tanto en el tallo principal como en ramas laterales en dos ensayos familia x fertilización. Se observó un efecto significativo de la fertilización en el desarrollo de los canales resiníferos del floema (p<0,05), con valores de 0,45 y 0,36 canales.mm-2 para brinzales no fertilizados y sí fertilizados, respectivamente. Este efecto no se observó en las variables del xilema. La densidad de canales resiníferos en el xilema fue significativamente diferente entre las dos parcelas estudiadas, siendo mayor en la atacada por el curculiónido Hylobius abietis. Por último, la relación tallo-rama de las variables cuantificadas no fue lo suficientemente consistente como para utilizar los canales en ramas de P. pinaster como indicadores de los canales en el tronco principal.Este trabajo se ha realizado bajo financiación del proyecto INIA-RTA05-173.Peer reviewe

Micro‑climatic efects on plant phenolics at the community level in a Mediterranean savanna

5 páginas.- 2 figuras.- 1 tabla.- 27 referenciasResearch has shown that warming and drought change plant phenolics. However, much of this work has centered on the effects of individual abiotic stressors on single plant species rather than the concurrent effects of multiple stressors at the plant community level. To address this gap, we manipulated rainfall and air temperature to test for their individual and interactive effects on the expression of leaf phenolics at the community level for annual plant species occurring in two habitat types (under oak tree canopies or in open grasslands) in a Mediterranean savanna. We found that augmented temperature had a significant positive effect on the community-weighted mean of total phenolics whereas reduced rainfall had no effect. In addition, we found no evidence of interactive effects between climatic stressors and these patterns remained consistent across habitat types. Overall, this study points at increasing efforts to investigate the linkages between climate change and community-level shifts in plant secondary chemistry.Tis study was funded by a Spanish National Research Project to IMPR (CGL2015-70123-R)Peer reviewe

Alterations of the resin canal system of Pinus pinaster seedlings after fertilization of a healthy and of a Hylobius abietis attacked stand

Abstract Changes in resource availability and biotic and abiotic stress may alter the defensive mechanisms of pine trees. The effect of fertilisation on the resin canal structure of Pinus pinaster seedlings established in two trials in NW Spain, one attacked by Hylobius abietis and the other nonattacked, was studied. The leaders of 50 plants were destructively sampled and the resin canal density, the canal area and its relative conductive area in the phloem and xylem were assessed. Experimentally increased nutrient availability significantly decreased resin canal density in the phloem of the seedlings in the two analysed trials, where unfertilised seedlings presented up to 30% more resin canal density than the fertilised seedlings (mean value ± SEM = 0.32 ± 0.02 resin canals mm -2 in the fertilised plants versus 0.45 ± 0.04 resin canals mm -2 in the control plants). Fertilisation had no effect on the resin canal system in the xylem, but significantly increased tracheid size. Significant differences of resin canals among sites were observed mainly in the xylem; the resin canal density was 1.7-fold greater in the attacked site than in the non-attacked site. The similar structure of phloem resin canals in both sites supports that phloem resin canals are constitutive mechanisms of defence in P. pinaster, whereas xylem resin canals would be constitutive mechanisms but also inducible mechanisms of resistance following the attack of pine weevils or bark beetles

Sexual and genotypic variation in terpene quantitative and qualitative profiles in the dioecious shrub Baccharis salicifolia.

Terpenoids are secondary metabolites produced in most plant tissues and are often considered toxic or repellent to plant enemies. Previous work has typically reported on intra-specific variation in terpene profiles, but the effects of plant sex, an important axis of genetic variation, have been less studied for chemical defences in general, and terpenes in particular. In a prior study, we found strong genetic variation (but not sexual dimorphism) in terpene amounts in leaves of the dioecious shrub Baccharis salicifolia. Here we build on these findings and provide a more in-depth analysis of terpene chemistry on these same plants from an experiment consisting of a common garden with male (N = 19) and female (N = 20) genotypes sourced from a single population. Our goal in the present study was to investigate quantitative and qualitative differences in terpene profiles associated with plant sex and genotypic variation. For this, we quantified leaf mono- and sesquiterpene amount, richness, and diversity (quantitative profile), as well as the composition of compounds (qualitative profile). We found no evidence of sexual dimorphism in monoterpene or sesquiterpene profiles. We did, however, find significant genotypic variation in amount, diversity, and composition of monoterpenes, but no effects on sesquiterpenes. These findings indicated that genotypic variation in terpene profiles largely surpassed variation due to sexual dimorphism for the studied&nbsp;population of this species

Effects of insularity on insect leaf herbivory and chemical defences in a Mediterranean oak species

Aim Research on plant–herbivore interactions has shown that islands typically have low abundances and diversity of herbivores because of barriers to dispersal, isolation and reduced land area. Islands commonly have lower levels of herbivory relative to mainland regions, and, as a consequence, insular plants should exhibit lower levels of defences than their mainland counterparts. Despite these predictions, there are significant gaps in our understanding of insularity effects on plant–herbivore interactions. For instance, most work addressing the effects of insularity on plant–herbivore interactions have compared one or a few islands with a single mainland site. In addition, studies have measured herbivory or plant defences but not both, and the influence of abiotic factors has been neglected. Location Mediterranean Basin (from Spain to Greece). Taxon Quercus ilex L. Methods We conducted a large‐scale study to investigate whether insect leaf herbivory and plant chemical defences in holm oak (Quercus ilex L.) differ between insular versus mainland populations. We further investigated mechanisms by which insularity effects on herbivory may take place by assessing the influence of defences and climatic variables on herbivory. Results We found that insular populations exhibited lower herbivory and higher defences (condensed tannins) than their mainland counterparts. Our analyses, however, suggest that these concomitant patterns of insect herbivory and plant defences were seemingly unrelated as island versus mainland differences in defences did not account for the observed pattern in herbivory. Furthermore, climatic factors did not explain insularity effects on either herbivory or plant defences. Main conclusions Overall, this study provides one of the most robust assessments to date on insularity effects on herbivory and builds towards a better understanding of the ecology and evolution of plant–insect interactions in insular ecosystems.info:eu-repo/semantics/acceptedVersio

Effects of insularity on insect leaf herbivory and chemical defences in a Mediterranean oak species

Aim Research on plant–herbivore interactions has shown that islands typically have low abundances and diversity of herbivores because of barriers to dispersal, isolation and reduced land area. Islands commonly have lower levels of herbivory relative to mainland regions, and, as a consequence, insular plants should exhibit lower levels of defences than their mainland counterparts. Despite these predictions, there are significant gaps in our understanding of insularity effects on plant–herbivore interactions. For instance, most work addressing the effects of insularity on plant–herbivore interactions have compared one or a few islands with a single mainland site. In addition, studies have measured herbivory or plant defences but not both, and the influence of abiotic factors has been neglected. Location Mediterranean Basin (from Spain to Greece). Taxon Quercus ilex L. Methods We conducted a large‐scale study to investigate whether insect leaf herbivory and plant chemical defences in holm oak (Quercus ilex L.) differ between insular versus mainland populations. We further investigated mechanisms by which insularity effects on herbivory may take place by assessing the influence of defences and climatic variables on herbivory. Results We found that insular populations exhibited lower herbivory and higher defences (condensed tannins) than their mainland counterparts. Our analyses, however, suggest that these concomitant patterns of insect herbivory and plant defences were seemingly unrelated as island versus mainland differences in defences did not account for the observed pattern in herbivory. Furthermore, climatic factors did not explain insularity effects on either herbivory or plant defences. Main conclusions Overall, this study provides one of the most robust assessments to date on insularity effects on herbivory and builds towards a better understanding of the ecology and evolution of plant–insect interactions in insular ecosystems.info:eu-repo/semantics/acceptedVersio