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Solanum betaceum is a tree from the Andean region bearing edible fruits, considered an exotic export. Although there has been renewed interest in its commercialization, sustainability, and disease management have been limiting factors. Phytophthora betacei is a recently described species that causes late blight in S. betaceum. There is no general study of the response of S. betaceum, particularly, in the changes in expression of pathogenesis-related genes. In this manuscript we present a comprehensive RNA-seq time-series study of the plant response to the infection of P. betacei. Following six time points of infection, the differentially expressed genes (DEGs) involved in the defense by the plant were contextualized in a sequential manner. We documented 5,628 DEGs across all time-points. From 6 to 24 h post-inoculation, we highlighted DEGs involved in the recognition of the pathogen by the likely activation of pattern-triggered immunity (PTI) genes. We also describe the possible effect of the pathogen effectors in the host during the effector-triggered response. Finally, we reveal genes related to the susceptible outcome of the interaction caused by the onset of necrotrophy and the sharp transcriptional changes as a response to the pathogen. This is the first report of the transcriptome of the tree tomato in response to the newly described pathogen P. betacei.

The growing concerns on human and environment health are forcing the plant protection industry toward the formulation of more eco-sustainable plant protection products (PPP), both efficient and innovative in their approach to disease control. A large number of these innovative formulations now rely on a combination of pathogens antagonistic properties and stimulation of natural plant defense to pathogens. The formulation HA + Cu(II), in which copper is delivered to the plants by the drug-delivery molecule hydroxyapatite (HA), was found efficient against the grapevine pathogens Plasmopara viticola and Phaeoacremonium minimum and able to induce the host-plant defense system. We investigated the HA + Cu(II) impacts on grapevine physiology, both in uninfected and when infected by the Botryosphaeria dieback agents Diplodia seriata and Neofusicoccum parvum. This study of plant physiology and disease impact were addressed to evaluate both the HA + Cu(II) potential as a plant defense elicitor and its possible and future use as PPP in vineyard. Our results showed that HA + Cu(II) induced several key-defense genes without negatively affecting plant growth and photosynthetic activity. In addition, fungistatic effect on the two Botryosphaeriaceae at the in planta tested concentrations is reported. Altogether, our results obtained under controlled conditions fully support the potential of HA + Cu(II) as a promising PPP toward grapevine trunk diseases in vineyard.

To have a cleaner environment, good well-being, and improve the health of citizens it is necessary to expand green urban and suburban areas using productive and adapted material of tree species. The quality of urban greenery, resistance to negative climate change factors and pollution, as well as efficiency of short-rotation forestry in suburban areas, depends primarily on the selection of hybrids and clones, suitable for the local environmental conditions. We postulate that ecogenetic response, phenotypic plasticity, and genotypic variation of hybrid poplars (Populus L.) grown in plantations are affected not only by the peculiarities of hybrids and clones, but also by environmental conditions of their vegetative propagation. The aim of the present study was to estimate growth and biochemical responses, the phenotypic plasticity, genotypic variation of adaptive traits, and genetically regulated adaptability of Populus hybrids in field trials which may be predisposed by the simulated contrasting temperature conditions at their vegetative propagation phase. The research was performed with the 20 cultivars and experimental clones of one intraspecific cross and four different interspecific hybrids of poplars propagated under six contrasting temperature regimes in phytotron. The results suggest that certain environmental conditions during vegetative propagation not only have a short-term effect on tree viability and growth, but also can help to adapt to climate change conditions and grow successfully in the long-term. It was found that tree growth and biochemical traits (the chlorophyll A and B, pigments content and the chlorophyll A/B ratio) of hybrid poplar clones grown in field trials, as well as their traits’ genetic parameters, were affected by the rooting-growing conditions during vegetative propagation phase. Hybrids P. balsamifera × P. trichocarpa, and P. trichocarpa × P. trichocarpa have shown the most substantial changes of biochemical traits across vegetative propagation treatments in field trial. Rooting-growing conditions during vegetative propagation had also an impact on coefficients of genotypic variation and heritability in hybrid poplar clones when grown in field trials.

The diverse roles of non-coding RNA and DNA in cross-species communication is yet to be revealed. Once thought to only involve intra-specifically in regulating gene expression, the evidence that these genetic materials can also modulate gene expression between species that belong to different kingdoms is accumulating. Plants send small RNAs to the pathogen or parasite when they are being attacked, targeting essential mRNAs for infection or parasitism of the hosts. However, the same survival mechanism is also deployed by the pathogen or parasite to destabilize plant immune responses. In plants, it is suggested that exposure to extracellular self-DNA impedes growth, while to extracellular non-self-DNA induces the modulation of reactive oxygen species, expression of resistance related genes, epigenetic mechanism, or suppression of disease severity. Exploring the potential of secreted RNA and extracellular DNA as a green pesticide could be a promising alternative if we are to provide food for the future global population without further damaging the environment. Hence, some studies on plant secreted RNA and responses towards extracellular DNA are discussed in this review. The precise mode of action of entry and the following cascade of signaling once the plant cell is exposed to secreted RNA or extracellular DNA could be an interesting topic for future research.

[EN] Orius laevigatus is a generalist predator that is widely used in augmentative strategies against the key pest of sweet pepper, Frankliniella occidentalis. Despite being a zoophytophagous predator, the phytophagous behavior of O. laevigatus has not been previously explored in depth nor has the impact of phytophagy on plant physiology. Here, the hierarchical significance of O. laevigatus feeding on sweet pepper is compared with other behaviors. O. laevigatus spends the majority of its time (38%) feeding on apical meristems and apical fresh leaves, which were also preferred residence locations. Here, the phytophagous feeding behavior of O. laevigatus on sweet pepper is shown to trigger defensive responses in the plant. These O. laevigatus plant-induced defenses are then shown to contribute to the repellence or attraction of pests or natural enemies, respectively. Specifically, O. laevigatus-punctured sweet pepper plants induce repellency for the whitefly Bemisia tabaci and the thrips species F. occidentalis. In contrast, the whitefly parasitoid Encarsia formosa was significantly attracted to O. laevigatus-punctured plants. The plant responses to O. laevigatus punctures include the release of an altered blend of volatiles and activation of the jasmonic acid and salicylic acid signalling pathways. These results highlight an interesting facet to the biology of O. laevigatus, in which the ability of the predator to induce defensive responses in sweet pepper plants may serve to improve the biological control of both thrips and whiteflies., The research leading to these results was partially funded by the Spanish Ministry of Economy and Competitiveness (AGL2014-55616-C3) and the Conselleria d'Agricultura, Pesca i Alimentacio de la Generalitat Valenciana. The authors thank Dr. Javier Calvo (KOPPERT BS, Spain) for supplying the insects, Dr. Pablo Bielza (Universidad Politecnica de Cartagena, Spain) for thrips colonies, Dimitrios Afentoulis, Zoi Thanou and Konstantinos Birmpilis (Erasmus + from Agricultural University of Athens) for providing support in the behavior experiments and Alice Mockford (University of Worcester) and two anonymous reviewers for their constructive review of this manuscript. MP-H was the recipient of a postdoctoral fellowship from the MEC (Juan de la Cierva program-FPDI-2013-17968) and SB was the recipient of a grant from Russell IPM Ltd.

The metabolic regulations of evergreen Mediterranean Quercus ilex trees growing at extra-urban and urban sites with different percentages of surrounding impervious pavements and distance to major traffic roads were investigated at the peak of the summer drought season. Plants from extra-urban site experienced lower water stress due to a fine regulation of reactive oxygen species (ROS, concomitant rise of anion superoxide and hydrogen peroxide content, +55 and +44%), abscisic acid and water soluble carbohydrates (+111 and +9%). The level of ROS was kept under the injury threshold by both enzymatic and metabolic antioxidants. Plants from the sub-urban site followed a different strategy, with a lower production of ROS and the concomitant reduction in phenols and carotenoids. Despite these differences, indications for stress-induced injury were not observed in any of the sites. Our work shows new relations between urban stress conditions and metabolic regulations of trees growing under such harsh environments.

Olive anthracnose caused by the hemibiotrophic fungal pathogen Colletotrichum acutatum is a serious threat to the olive sector. Olive oil and fruit production is severely constrained by Colletotrichum spp. infection, being C. acutatum the most distributed pathogen in Portuguese olive orchards. To understand the impact of C. acutatum on phenylpropanoids biosynthesis, the enzyme activity, phenolic compounds, ortho-diphenols, and flavonoids content were determined and correlated with the expression of gene encoding key enzymes within phenylpropanoids metabolism in susceptible and tolerant olive fruits, during maturation and when infected with C. acutatum. Differences between cultivars was observed, the tolerant olive cv. Picual presented a higher basal value and a stable phenolic content throughout the infection process, supporting its high C. acutatum tolerance, whereas in the susceptible olive cv. Galega these secondary metabolites were significantly increased only after the elicitation with C. acutatum.

Coleoptera, the largest and the most diverse Insecta order, is characterized by multiple adaptations to plant feeding. Insect-associated microorganisms can be important mediators and modulators of interactions between insects and plants. Interactions between plants and insects are highly complex and involve multiple factors. There are various defense mechanisms initiated by plants upon attack by herbivorous insects, including the development of morphological structures and the synthesis of toxic secondary metabolites and volatiles. In turn, herbivores have adapted to feeding on plants and further sophisticated adaptations to overcome plant responses may continue to evolve. Herbivorous insects may detoxify toxic phytocompounds, sequester poisonous plant factors, and alter their own overall gene expression pattern. Moreover, insects are associated with microbes, which not only considerably affect insects, but can also modify plant defense responses to the benefit of their host. Plants are also frequently associated with endophytes, which may act as bioinsecticides. Therefore, it is very important to consider the factors influencing the interaction between plants and insects. Herbivorous insects cause considerable damage to global crop production. Coleoptera is the largest and the most diverse order in the class Insecta. In this review, various aspects of the interactions among insects, microbes, and plants are described with a focus on coleopteran species, their bacterial symbionts, and their plant hosts to demonstrate that many factors contribute to the success of coleopteran herbivory.

Rising atmospheric CO2 concentration is a key driver of enhanced global greening, thought to account for up to 70% of increased global vegetation in recent decades. CO2 fertilization effects have further profound implications for ecosystems, food security and biosphere‐atmosphere feedbacks. However, it is also possible that current trends will not continue, due to ecosystem level constraints and as plants acclimate to future CO2 concentrations. Future predictions of plant response to rising [CO2] are often validated using single‐generation short‐term FACE (Free Air CO2 Enrichment) experiments but whether this accurately represents vegetation response over decades is unclear. The role of transgenerational plasticity and adaptation in the multigenerational response has yet to be elucidated. Here, we propose that naturally occurring high CO2 springs provide a proxy to quantify the multigenerational and long‐term impacts of rising [CO2] in herbaceous and woody species respectively, such that plasticity, transgenerational effects and genetic adaptation can be quantified together in these systems. In this first meta‐analysis of responses to elevated [CO2] at natural CO2 springs, we show that the magnitude and direction of change in eight of nine functional plant traits are consistent between spring and FACE experiments. We found increased photosynthesis (49.8% in spring experiments, comparable to 32.1% in FACE experiments) and leaf starch (58.6% spring, 84.3% FACE), decreased stomatal conductance (gs, 27.2% spring, 21.1% FACE), leaf nitrogen content (6.3% spring, 13.3% FACE) and Specific Leaf Area (SLA, 9.7% spring, 6.0% FACE). These findings not only validate the use of these sites for studying multigenerational plant response to elevated [CO2], but additionally suggest that long‐term positive photosynthetic response to rising [CO2] are likely to continue as predicted by single‐generation exposure FACE experiments., Plant responses to future, elevated atmospheric CO2 from single‐generation FACE experiments were compared with those observed in naturally high carbon dioxide springs, following multi‐generation exposure. Responses for a panel of traits, including enhanced photosynthesis and reduced stomatal conductance, were broadly conserved suggesting that FACE experiments are a good proxy for long‐term, multi‐generational responses to this facet of the changing climate. These findings have implications for enhanced global greening, since our data suggest that vegetation will not acclimate to elevated, CO2 growth stimulation is likely to persist. Similarly, the data are relevant for future plant breeding and conservation strategies.

© 2018 by the authors. Licensee MDPI, Basel, Switzerland. Warming surface temperatures and increasing frequency and duration of widespread droughts threaten the health of natural forests and agricultural crops. High temperatures (HT) and intense droughts can lead to the excessive plant water loss and the accumulation of reactive oxygen species (ROS) resulting in extensive physical and oxidative damage to sensitive plant components including photosynthetic membranes. ROS signaling is tightly integrated with signaling mechanisms of the potent phytohormone abscisic acid (ABA), which stimulates stomatal closure leading to a reduction in transpiration and net photosynthesis, alters hydraulic conductivities, and activates defense gene expression including antioxidant systems. While generally assumed to be produced in roots and transported to shoots following drought stress, recent evidence suggests that a large fraction of plant ABA is produced in leaves via the isoprenoid pathway. Thus, through stomatal regulation and stress signaling which alters water and carbon fluxes, we highlight the fact that ABA lies at the heart of the Carbon-Water-ROS Nexus of plant response to HT and drought stress. We discuss the current state of knowledge of ABA biosynthesis, transport, and degradation and the role of ABA and other isoprenoids in the oxidative stress response. We discuss potential variations in ABA production and stomatal sensitivity among different plant functional types including isohydric/anisohydric and pioneer/climax tree species. We describe experiments that would demonstrate the possibility of a direct energetic and carbon link between leaf ABA biosynthesis and photosynthesis, and discuss the potential for a positive feedback between leaf warming and enhanced ABA production together with reduced stomatal conductance and transpiration. Finally, we propose a new modeling framework to capture these interactions. We conclude by discussing the importance of ABA in diverse tropical ecosystems through increases in the thermotolerance of photosynthesis to drought and heat stress, and the global importance of these mechanisms to carbon and water cycling under climate change scenarios.

International audience; There is tremendous diversity of interactions between plants and other species. These relationships range from antagonism to mutualism. Interactions of plants with members of their ecological community can lead to a profound metabolic reconfiguration of the plants’ physiology. This reconfiguration can favour beneficial organisms and deter antagonists like pathogens or herbivores. Determining the cellular and molecular dialogue between plants, microbes, and insects, and its ecological and evolutionary implications is important for understanding the options for each partner to adopt an adaptive response to its biotic environment. Moving forward, understanding how such ecological interactions are shaped by environmental change and how we potentially mitigate deleterious effects will be increasingly important. The development of integrative multidisciplinary approaches may provide new solutions to the major ecological and societal issues ahead of us. The rapid evolution of technology provides valuable tools and opens up novel ways to test hypotheses that were previously unanswerable, but requires that scientists master these tools, understand potential ethical problems flowing from their implementation, and train new generations of biologists with diverse technical skills. Here, we provide brief perspectives and discuss future promise and challenges for research on insect–plant interactions building on the 16th International Symposium on Insect–Plant interactions (SIP) meeting that was held in Tours, France (2–6 July 2017). Talks, posters, and discussions are distilled into key research areas in insect–plant interactions, highlighting the current state of the field and major challenges, and future directions for both applied and basic research.

[Departement_IRSTEA]Territoires [ADD1_IRSTEA]Dynamique et fonctionnement des écosystèmes; Plant-plant interactions show differential responses to different combinations of available resources that has been underexplored. The short-term functional response of Quercus petraea seedlings and Deschampsia cespitosa tufts grown alone or in mixture was monitored in contrasting combinations of soil inorganic nitrogen x light availabilities in a greenhouse experiment. Growth, biomass allocation, functional traits and resource acquisition were quantified. Intensity and importance of interactions were calculated by organ biomass-based indices. Competition exerted by D. cespitosa on oak was primarily driven by light availability and secondly, for each light level, by nitrogen supply, leading to a strong hierarchy of resource combinations for each considered plant organ. Under high light, oak preferentially allocated biomass to the roots, underlining the indirect role of light on the belowground compartment. Unexpectedly, Deschampsia cespitosa grew better in the presence of oak seedlings under high nitrogen supply whatever the light availability. Oak short-term nitrogen storage instead of investment in growth might be a long-term strategy to survive D. cespitosa competition. Why Deschampsia had a higher biomass in the presence of oak under nitrogen fertilization is an intriguing question. The role of root exudates or change in balance between intra- nu s interspecific interactions may hold the answer. There may be an active mechanism of competition rather than only competitive resource exploitation. Forest managers sometimes practice adding nitrogen fertilizer to improve oak seedling growth in plantations or natural regeneration. Here, the higher biomass in mixture to the benefit of the competitor clearly questions this practice: oak may provide extra nitrogen to competitors during the early period of plant-plant interaction or it may influence the balance between intra- vs interspecific interactions. The identification and quantification of active competition may result in new practices for a broad diversity of plant-plant interactions such as tree regeneration, intercrop management and weed control in agriculture. (C) 2018 Gesellschaft fur Okologie. Published by Elsevier GmbH. All rights reserved.

Clonal plants producing both clumping and spreading ramets can adjust their growth forms in response to resource heterogeneity or environmental stress. They might produce clumping ramets to retain favorable patches, or produce spreading ramets to escape from stress-affected patches. This study aimed to investigate the rarely reported concurrent effects of sediment accretion and nutrient enrichment, which often occur simultaneously in lacustrine wetlands, on the vegetative propagation and clonal growth forms of Carex brevicuspis C.B. Clarke by conducting a factorial experiment of sediment burial and nutrient addition. Biomass accumulation, new ramet and rhizome numbers, and ramet length of C. brevicuspis were not affected at moderate burial, but were significantly lower after deep burial. Similarly, nutrient enrichment increased the growth and vegetative propagation of C. brevicuspis up to moderate sediment burial, but not after deep burial. Sediment accretion increased the proportion of spreading ramets produced by C. brevicuspis, whereas nutrient addition had no effect on the clonal growth forms. Our results indicated that the plasticity of clonal growth forms is an effective strategy used by plants to acclimate to moderate sediment accretion. Nutrient enrichment did not influence the clonal growth forms of C. brevicuspis and could not facilitate its acclimation to heavy sedimentation condition.

During plant-pathogen interactions, the plant cell wall forms part of active defence against invaders. In recent years, cell wall-editing enzymes, associated with growth and development, have been related to plant susceptibility or resistance. Our previous work identified a role for several tomato and Arabidopsis endo-1,4-β-glucanases (EGs) in plant-pathogen interactions. Here we studied the response of the Arabidopsis thaliana T-DNA insertion mutant lacking EG Korrigan1 (KOR1) infected with Pseudomonas syringae. KOR1 is predicted to be an EG which is thought to participate in cellulose biosynthesis. We found that kor1-1 plants were more susceptible to P. syringae, and displayed severe disease symptoms and enhanced bacterial growth if compared to Wassilewskija (Ws) wild-type plants. Hormonal and gene expression analyses revealed that the jasmonic acid (JA) pathway was activated more in kor1-1 plants with an increase in the JA-biosynthesis gene LOX3 and a greater accumulation of JA. Upon infection the accumulation of JA and JA-isoleucine (JA-Ile) was higher than in wild-type plants and increased the induction of LOX3 and the JA-responsive PDF1.2 gene. In addition, the increase of salicylic acid (SA) in healthy and infected kor1-1 may reflect the complex interaction between JA and SA, which results in the more susceptible phenotype displayed by the infected mutant plants. Callose deposition was enhanced in infected kor1-1 and an increase in pathogen-induced hydrogen peroxide took place. The susceptible phenotype displayed by KOR1-deficient plants was coronatine-independent. No significant changes were detected in the hormonal profile of the kor1-1 plants infected by coronatine-deficient P. syringae cmaA, which supports that absence of EG KOR1 alters per se the plant response to infection. We previously reported increased resistance of kor1-1 to B. cinerea, hence, the lack of this EG alters cell wall properties and plant responses in such a way that benefits P. syringae colonisation but restricts B. cinerea invasion.

[EN] The ability of zoophytophagous predators to produce defensive plant responses due to their phytophagous behavior has been recently demonstrated. In the case of tomatoes, the mirids Nesidiocoris tenuis and Macrolophus pygmaeus are able to attract or repel pests and/or natural enemies in different ways. Nevertheless, the herbivore-induced plant volatiles (HIPVs) released by the phytophagy of both mirids, which are responsible for these behaviors, are unknown. In this work, the HIPVs produced by the plant feeding of N. tenuis and M. pygmaeus were characterized. In addition, the role of each HIPV in the repellence or attraction of two tomato pests, Bemisia tabaci and Tuta absoluta, and of the natural enemy Encarsia formosa was evaluated. Six green leaf volatiles (GLVs) plus methyl salicylate and octyl acetate clearly stood out as major differential peaks on the chromatogram in a directed analysis. The six GLV and methyl salicylate were repellent for B. tabaci and attractive to E. formosa, whereas they showed no effect on T. absoluta. Octyl acetate, which was significantly present only in the M. pygmaeus-punctured plants, was significantly attractive to T. absoluta, repellent to E. formosa and indifferent to B. tabaci. Unlike the remaining HIPVs, octyl acetate was emitted directly by M. pygmaeus and not by the plant. Our results showed that mirid herbivory could modulate the pest and natural plant enemy locations, since tomato plants release a blend of volatiles in response to this activity. These results could serve as a basis for future development of plant protection., The research leading to these results was funded by the Spanish Ministry of Economy and Competitiveness (AGL2014-55616-C3). The authors thank Javier Calvo (KOPPERT BS) for the supply of insects, and Sandra Fresquet and Virginia Pedroche for their technical assistance. MP-H was the recipient of a research fellowship from the INIA Spain (Subprogram DOC-INIA-CCAA). Analyses of volatile compounds were performed in the Metabolomics service facilities at IBMCP.

Abiotic stresses such as extremes of temperature and pH, high salinity and drought, comprise some of the major factors causing extensive losses to crop production worldwide. Understanding how plants respond and adapt at cellular and molecular levels to continuous environmental changes is a pre-requisite for the generation of resistant or tolerant plants to abiotic stresses. In this review we aimed to present the recent advances on mechanisms of downstream plant responses to abiotic stresses and the use of stress-related genes in the development of genetically engineered crops.

Oomycetes from the genus Phytophthora are fungus-like plant pathogens that are devastating for agriculture and natural ecosystems. Due to their particular physiological characteristics, no efficient treatments against diseases caused by these microorganisms are presently available. To develop such treatments, it appears essential to dissect the molecular mechanisms that determine the interaction between Phytophthora species and host plants. Available data are scarce, and genomic approaches were mainly developed for the two species, Phytophthora infestans and Phytophthora sojae. However, these two species are exceptions from, rather than representative species for, the genus. P. infestans is a foliar pathogen, and P. sojae infects a narrow range of host plants, while the majority of Phytophthora species are quite unselective, root-infecting pathogens. To represent this majority, Phytophthora parasitica emerges as a model for the genus, and genomic resources for analyzing its interaction with plants are developing. The aim of this review is to assemble current knowledge on cytological and molecular processes that are underlying plant-pathogen interactions involving Phytophthora species and in particular P. parasitica, and to place them into the context of a hypothetical scheme of co-evolution between the pathogen and the host.

Variation in resource input to plants triggers bottom-up effects on plant-insect herbivore interactions. However, variation in plant intrinsic traits in response to resource availability may modify the bottom-up effects. Furthermore, the consequences also may depend on the feeding strategy of insect herbivores belonging to different feeding guilds. We evaluated the performance of two insect herbivores from distinct feeding guilds, the leaf miner Tuta absoluta and the phloem feeder Bemisia tabaci. We offered the insects two tomato cultivars growing under optimal nitrogen input vs. nitrogen limitation, or under optimal water input vs. water limitation. We found that: (i) the two cultivars differed in their responses to nitrogen and water limitation by regulating primary (leaf-gas exchange related parameters, leaf nitrogen content, and leaf C/N ratio) and secondary metabolism (main defensive compounds: glycoalkaloids); (ii) for both plant cultivars, nitrogen or water limitation significantly affected T. absoluta survival and development, while B. tabaci survival was affected only by nitrogen limitation; and surprisingly (iii) plant cultivar differences did not modify the negative bottom-up effects of resource limitation on the two insect herbivores. In conclusion, the negative effects of resource limitation cascaded up to insect herbivores even though plant cultivars exhibited various adaptive traits to resource limitation.

Due to post-harvest losses more than 30% of harvested fruits will not reach the consumers' plate. Fungal pathogens play a key role in those losses, as they cause most of the fruit rots and the customer complaints. Many of the fungal pathogens are already present in the unripe fruit but remain quiescent during fruit growth until a particular phase of fruit ripening and senescence. The pathogens sense the developmental change and switch into the devastating necrotrophic life style that causes fruit rotting. Colonization of unripe fruit by the fungus initiates defensive responses that limit fungal growth and development. However, during fruit ripening several physiological processes occur that correlate with increased fruit susceptibility. In contrast to plant defenses in unripe fruit, the defense posture of ripe fruit entails a different subset of defense responses that will end with fruit rotting and losses. This review will focus on several aspects of molecular and metabolic events associated with fleshy fruit responses induced by post-harvest fungal pathogens during fruit ripening.

Resumen El conocimiento de las prácticas culturales que permiten obtener el mayor beneficio del potencial de las fuentes forrajeras es necesario para el éxito en la producción animal. El objetivo de este estudio fue explorar la respuesta bromatológica del Tripsacum laxum a la fertilización con diferentes niveles de nitrógeno, fósforo y potasio aplicado al suelo. La investigación se realizó en la Estación Experimental de Ganado Lechero “Alfredo Volio Mata” de la Universidad de Costa Rica, localizada en Ochomogo, Cartago, Costa Rica. Se utilizó un diseño de bloques al azar con cuatro repeticiones y los tratamientos dispuestos en un arreglo factorial de compuesto central y rotable 53. La materia seca (MS), proteína cruda (PC), fibra neutro detergente (FND) y el extracto etéreo (EE) fueron determinados. Dependiendo de los niveles de fertilización con N, P y K se obtuvieron las dosis apropiadas para lograr contenidos de nutrientes máximos en cada uno de los parámetros bromatológicos evaluados en este estudio, y fue posible optimizar la composición de la mezcla fertilizante según el componente nutricional que se quiera privilegiar en particular ya sea en la hoja, en el tallo o en la planta entera. No existe una dosis de fertilizante única para mejorar todos los componentes nutricionales de la planta. Abstract Getting to know the knowledge that cultural practices have allows researchers to obtain the greatest benefit from the potential of fodder sources, this knowledge is necessary for animal production success. The aim of this study was to explore the bromatological response of Tripsacum laxum to fertilization with different levels of nitrogen, phosphorus, and potassium that were applied to the ground. The investigation was conducted at the “Alfredo Volio Mata” Experimental Dairy Farm a Dairy farm that is part of the University of Costa Rica and that is located in Ochomogo, Cartago, Costa Rica. In the investigation a randomized block design with four replications and treatments arranged in a factorial central composite and on a rotatable 53 was used. Dry matter, crude protein, neutral detergent fiber, and ether extract were determined. Depending on the levels of fertilization with N, P, and K, the appropriate doses were obtained in order to reach the maximum nutrient contents in each of the bromatological parameters evaluated in this study, it was possible to optimize the composition of the fertilizer mixture based on the nutritional component to be particularly favored, either on the leaf, on the stem, or on the whole plant. No single fertilizer dose was able to improve all nutritional components of the plant.

International audience; Plant growth and survival depends critically on photo assimilates. Pathogen infection leads to changes in carbohydrate metabolism of plants. In this study, we monitored changes in the carbohydrate metabolism in the grapevine inflorescence and leaves using Botrytis cinerea and Botrytis pseudo cinerea. Fluctuations in gas exchange were correlated with variations in chlorophyll a fluorescence. During infection, the inflorescences showed an increase in net photosynthesis (Pn) with a stomatal limitation. In leaves, photosynthesis decreased, with a non-stomatal limitation. A decrease in the effective photosystem II (PSII) quantum yield (ΦPSII) was accompanied by an increase in photochemical quenching (qP) and non-photochemical quenching (qN). The enhancement of qP and ΦPSII could explain the observed increase in Pn. In leaves, the significant decline in ΦPSII and qP, and increase in qN suggest that energy was mostly oriented toward heat dissipation instead of CO2 fixation. The accumulation of glucose and sucrose in inflorescences and glucose and fructose in the leaves during infection indicate that the plant’s carbon metabolism is differently regulated in these two organs. While a strong accumulation of starch was observed at 24 and 48 hours post-inoculation (hpi) with both species of Botrytis in the inflorescences, a significant decrease with B. cinerea at 24 hpi and a significant increase with B. pseudo cinerea at 48 hpi were observed in the leaves. On the basis of these results, it can be said that during pathogen attack, the metabolism of grapevine inflorescence and leaf is modified suggesting distinct mechanisms modifying gas exchange, PSII activity and sugar contents in these two organs

O genótipo da planta é fator preponderante na resposta à micorriza. Avaliou-se, neste trabalho, a resposta a fósforo e o grau de dependência micorrízica de variedades de mamoeiro (Carica papaya L.). O experimento foi realizado em casa de vegetação da Embrapa-Centro Nacional de Pesquisa de Mandioca e Fruticultura, com quatro variedades, testando-se seis doses de P: 0, 20, 40, 80, 140, 280 mg dm-3 e três tratamentos fúngicos (um controle não-micorrizado e a inoculação de Glomus clarum ou Gigaspora margarita). Foram estimados os seguintes parâmetros: dose de P para máxima eficiência micorrízica; valor T'; benefício da aplicação do P; benefício micorrízico; eficiência simbiótica, e dependência micorrízica. Plantas não-micorrizadas apresentaram resposta quadrática ao P aplicado e as inoculadas seguiram modelo raiz-quadrático, com grande incremento de matéria seca da parte aérea nas doses baixas; o benefício de P foi maior nas variedades Sunrise Solo e Improved Sunrise Solo - Line 72/12, enquanto as variedades Baixinho de Santa Amália e Tainung nº 1 apresentaram benefício micorrízico proporcionalmente maior, resultando em maior eficiência simbiótica. As variedades de mamoeiro apresentaram a seguinte classificação quanto à dependência micorrízica: Baixinho de Santa Amália = Tainung nº 1 > Sunrise Solo = Improved Sunrise Solo - Line 72/12. A maior ou menor dependência relacionou-se com a capacidade da variedade em produzir raízes. Plant genome is an important factor in plant response to arbuscular fungi. This work was designed to evaluate the degree of response to P application and mycorrhizal dependence of different varieties of papaya (Carica papaya L.). The experiment was performed under greenhouse conditions at Embrapa-Centro Nacional de Pesquisa de Mandioca e Fruticultura, Cruz das Almas, BA, Brazil, using seedlings of four varieties, six rates of P: 0, 20, 40, 80, 140 and 280 mg dm-3, and three fungi treatments (one control uninoculated and inoculation with Glomus clarum or Gigaspora margarita). The following parameters were estimated: rate of P for maximum mycorrhizal efficiency; T' value; P benefit, mycorrhizal benefit, symbiotic efficiency, and mycorrhizal dependence. Control plants had a quadratic response to applied P, while those inoculated had a root-quadratic response with a great increment in growth at lower rates; phosphorus benefit was higher in Sunrise Solo and Improved Sunrise Solo - Line 72/12 varieties, while the other two varieties showed a higher mycorrhizal benefit, resulting in a higher symbiotic efficiency. Papaya varieties showed the following classification of mycorrhizal dependency: Baixinho de Santa Amália = Tainung nº 1 > Sunrise Solo = Improved Sunrise Solo - Line 72/12. Mycorrhizal dependence related with the capability of the variety to produce roots.

International audience; In tomato, the stolbur disease caused by ‘Candidatus Phytoplasma solani’ alters developmental processes resulting in malformations of both vegetative and reproductive organs, two stolbur phytoplasma strains PO and C induce mutually distinct symptoms. The aim of the present study was to determine the effect of stolbur phytoplasma-infection on the Salicylic (SA) and Jasmonic (JA) acids hormone signalling pathways and to assess whether pre-activation of these defence pathways could protect tomato against the stolbur disease development. Expression of SA- and JA-dependent marker genes was studied in tomato by qRT-PCR. Results indicated that the SA-mediated defence response was activated by the stolbur phytoplasma strains PO and C in contrast to the JA-dependent defence pathway which was repressed by strain PO but activated by strain C. The two stolbur strains, PO and C, generated different responses, suggesting that the two strains might have distinct virulence factors, in agreement with the fact that they induce distinctive symptoms. In stolbur PO-infected tomato, pre-activation of the JA-dependent defence pathway by methyl jasmonate (MeJA) before infection had no effect on the disease development whereas pre-activation of the SA-dependent defence pathway by treatment with benzothiadiazole (BTH) prior to graft-inoculation of the phytoplasma resulted in a minor delay in phytoplasma multiplication and symptom production. As grafting implicates a high inoculum as compared to insect inoculation, it would be of interest to test BTH treatment in natural conditions.

Crenate broomrape (Orobanche crenata) is considered to be the major constraint for legume crops in Mediterranean countries. Strategies of control have been developed, but only marginal successes have been achieved. For the efficient control of the parasite, a better understanding of its interaction and associated resistance mechanisms at the molecular level is required. The pea response to this parasitic plant and the molecular basis of the resistance was studied using a proteomic approach based on 2D DIGE and MALDI-MSMS analysis. For this purpose, two genotypes showing different levels of resistance to O. crenata, as well as three time points (21, 25, and 30 d after inoculation) have been compared. Multivariate statistical analysis identified 43 differential protein spots under the experimental conditions (genotypes/treatments), 22 of which were identified using a combination of peptide mass fingerprinting (PMF) and MSMS fragmentation. Most of the proteins identified were metabolic and stress-related proteins and a high percentage of them (86%) matched with specific proteins of legume species. The behaviour pattern of the identified proteins suggests the existence of defence mechanisms operating during the early stages of infection that differed in both genotypes. Among these, several proteins were identified with protease activity which could play an important role in preventing the penetration and connection to the vascular system of the parasite. Our data are discussed and compared with those previously obtained in pea and Medicago truncatula. © 2011 The Author(s)., This research was supported by projects AGL2008-01239 and AGR-2883.

International audience; Plant hormones, in addition to regulating growth and development, are involved in biotic and abiotic stress responses. To investigate whether a hormone signalling pathway plays a role in the plant response to the heavy metal cadmium (Cd), gene expression data in response to eight hormone treatments were retrieved from the Genevestigator Arabidopsis thaliana database and compared with published microarray analysis performed on plants challenged with Cd. Across more than 3000 Cd-regulated genes, statistical approaches and cluster analyses highlighted that gene expression in response to Cd and brassinosteroids (BR) showed a significant similarity. Of note, over 75% of the genes showing consistent (e.g. opposite) regulation upon BR and Brz (BR biosynthesis inhibitor) exposure exhibited a BR-like response upon Cd exposure. This phenomenon was confirmed by qPCR analysis of the expression level of 10 BR-regulated genes in roots of Cd-treated wild-type (WT) plants. Although no change in BR content was observed in response to Cd in our experimental conditions, adding epibrassinolide (eBL, a synthetic brassinosteroid) to WT plants significantly enhanced Cd-induced root growth inhibition, highlighting a synergistic response between eBL and the metal. This effect was specific to this hormone treatment. On the other hand, dwarf1 seedlings, showing a reduced BR level, exhibited decreased root growth inhibition in response to Cd compared with WT, reversed by the addition of eBL. Similar results were obtained on Brz-treated WT plants. These results argue in favour of an interaction between Cd and BR signalling that modulates plant sensitivity, and opens new perspectives to understand the plant response to Cd.

With the evolution of high-throughput techniques, performing organism-wide analyses of gene expression, protein content and metabolite profile is becoming easier. This new era of biology opens the way for incredibly promising advances but also extremely challenging difficulties in the aim of integrating these datasets into biologically relevant models. To address questions and unravel networks occurring in cadmium stressed plants, researchers have already taken advantage of such tools. We provide here an overview of the discoveries that have been made regarding plant−cadmium interaction using “omics” methods, and show how their use is relevant to compare species and stresses at the whole plant level. At the end, we propose future breakthroughs to be addressed using these techniques, and discuss the up-coming challenges of data mining and model drawing.

15 pages; International audience; Derelict contaminated sites are often colonized spontaneously by plant species leading to a vegetal cover thought to limit particle dispersal and polluted water infiltration. Those plants must cope with soil pollutants through tolerance mechanisms that are not yet fully understood. Here, we focused our attention on a particular Asteraceae plant, Solidago canadensis, considered as invasive in Europe. S. canadensis spontaneously growing on either polluted (NM soil) or control soils dumped on experimental plots were studied for their physiological status, oxidative stress and 2D-DIGE of leaf extracts. S. canadensis tolerance to soil pollutants was demonstrated since growth rates, allocation to reproduction ratios and Fv/Fm ratios were similar in plants from control and NM soil. At the cell level, the catalase activity level was increased in plants collected on NM soil while lipoperoxidation was unaffected. Also, the leaf proteomic study revealed thirty down-regulated and sixty-six up-regulated proteins. Abundances of proteins related to oxidative stress, carbohydrate metabolism, ion transport were mainly up-regulated while those of proteins involved in cell cycle and transcription/translation were mostly down-regulated. Proteins associated to protein metabolism were either down- or up-regulated. Considered altogether, we highlighted that S. canadensis exhibited a complex proteome response when experiencing a multicontaminated soil.

Viroids are small circular RNA molecules, 246 to 400 nt long, which infect several crop plants and can cause diseases of economic importance. Citrus spp. are the hosts in which the highest number of viroids has been recovered. Citrus exocortis viroid (CEVd), causal agent of citrus exocortis disease, is responsible for several losses in citrus crops. Little is known about the molecular and cellular mechanisms by which viroids infect plants and produce symptoms. To deepen this knowledge, changes in the gene-expression profile during the early (pre–symptomatic) and the last (post-symptomatic) stage of Etrog citron infection by Citrus exocortis viroid (CEVd) were investigated using a citrus cDNA microarray. MaSigPro analysis was performed, and based on their expression profile along time, genes were divided into five clusters. These results will allow us to have a clearer idea about the changes in the plant transcriptome that are associated with symptom expression and/or with specific plant defense mechanisms.

Freezing temperatures are one of the environmental stresses with more impact in plant development in temperate regions. By means of cold acclimation, many plant species are able to increase their freezing tolerance in response to low-nonfreezing temperatures. In the last years, an important effort has been made to characterize the molecular mechanisms that control this adaptive process. Transcriptome analyses indicate that cold acclimation is mainly regulated by low temperatures through changes in gene expression. In this regard, it has been reported that 3.4% of Arabidopsis genes are regulated by low temperature, including 95 genes annotated as transcription factors. The control of coldinducible gene expression is very complex and involves many different signaling pathways that, in some cases, seem to share common intermediates. Interestingly, recent reports have shown that RNA processing and export, as well as post-translational modifications, including ubiquitylation and SUMOylation, also play important roles in regulating cold acclimation. Furthermore, histone modifications seem to be relevant in this regulation. In fact, histone acetylation and deacetylation are needed for correct activation of gene expression in response to low temperatures. All these data reveal that post-transcriptional mechanisms should be taken into consideration when analyzing the control of cold acclimation. Following, is a brief overview of the current understanding on the regulatory mechanisms that ensures the accurate development of this adaptive response. Las temperaturas de congelación son uno de los estreses ambientales con mayor impacto en el desarrollo de las plantas en las regiones templadas. Por medio de la respuesta de aclimatación, muchas especies son capaces de incrementar su tolerancia a la congelación en respuesta a temperaturas bajas propiamente dichas. En los últimos años, se ha realizado un gran esfuerzo en la caracterización de los mecanismos moleculares que controlan este proceso adaptativo. Análisis transcriptómicos indican que la aclimatación al frío es regulada principalmente por cambios en la expresión génica. En este sentido, se ha descrito que la expresión de un 3,4% de los genes de Arabidopsis está regulada por las temperaturas bajas, incluyendo 95 genes anotados como factores de transcripción. El control de la expresión génica inducible por frío es muy complejo e implica diferentes rutas de señalización de la señal que, en algunos casos, parecen compartir intermediarios comunes. Trabajos recientes han mostrado que el procesamiento y movilización de RNA, y algunas modificaciones post-traduccionales de proteínas como la ubiquitinación y la SUMOilización también juegan un papel importante en la regulación del proceso de aclimatación a las temperaturas bajas. Más aún, la modificación de histonas parece ser también relevante en esta regulación. De hecho, la acetilación y deacetilación de histonas es necesaria para una correcta activación de la expresión génica en respuesta a las temperaturas bajas. Todos estos datos ponen de manifiesto que a la hora de estudiar el control de proceso de aclimatación se han de tener en cuenta los mecanismos de regulación post-transcripcional. A continuación, repasaremos los conocimientos actuales sobre los mecanismos que aseguran el correcto desarrollo de esta respuesta adaptativa.

Aphids are economically important insect pests of agriculture and forest crops. They feed on phloem sap by extremely efficient mouthparts modified into long and flexible stylets. Adaptation to phytophagy is completed by an extremely ductile reproduction system that can alternate biparental and parthenogenetic generations. In order to reach plant phloem, aphids must overcome plant defences, either physically and/or chemically. However, plants respond to aphid attack by activating defence genes that lead to the production of physical barriers and/or chemical toxic compounds (direct resistance). In addition, attacked plants can attract the natural enemies of aphids by releasing specific volatile compounds (indirect resistance). We can take advantage of these different types of resistance in order to enhance the sustainable control of these phytophagous insects. In this review we summarize the main aspects of plant-aphid interactions, focusing on those issues that can have an economic application.

This paper discusses the influence of form of nitrogen (N) used as fertilizer, such as N2, NH4+, NO3-, (NH4+ + NO3-) and -NH2, on the development and yield and the protein content and yield of low-alkaloid cultivars of Lupinus albus L. from Poland, Spain, and Chile. The experiments were carried out in a greenhouse and plants were grown in perlite. The different forms of N used significantly influenced lupin development and yield. Plants only developed normally in treatments where N was delivered in the molecular form N2 or as (NH4+ + NO3-). For the other forms of N anomalies like necrosis, chlorosis, and small leaves were present. In contrast to cv. Butan, the N used as NH4+ disturbed flowering in cvs. Multolupa and Marta, which produced no seed. Moreover, N form also influenced protein seed protein content and yield. El objetivo de este trabajo fue estudiar la influencia de diferentes formas de nitrógeno (N2, NH4+, NO3-, (NH4+ + NO3-) y -NH2), utilizadas como fertilizante, sobre el desarrollo, el rendimiento vegetativo y el contenido y rendimiento proteico de diferentes variedades dulces de Lupinus albus L. originarias de Polonia, España y Chile. Los experimentos se llevaron a cabo en invernadero, utilizando perlita como sustrato. Las plantas se desarrollaron adecuadamente sólo cuando el aporte de nitrógeno fue en forma de N2 o como (NH4+ + NO3-). Cuando se utilizaron las otras formas de nitrógeno se observaron anomalías como necrosis, clorosis u hojas de tamaño reducido. En contraste con el cultivar Butan, cuando se utilizó NH4+, los cultivares Multolupa y Marta presentaron alteraciones en la floración, que dieron lugar a una carencia de semillas. Además, la forma del nitrógeno utilizada tuvo una importancia crucial en el contenido proteico de las semillas, así como en el rendimiento proteico.

Height control is often required in order to obtain bulb plants that are proportional to their pot size and to reduce post-harvest stem elongation. Plant growth regulators afford an effective means of controlling plant height. In this study, paclobutrazol (Pbz) was studied for use in the chemical dwarfing of potted Lilium plants -the hybrids "Ercolano" and "Royal Respect"- for marketing. Their bulbs were dipped in the growth regulator (0, 50, 100, and 150 ppm) for 10 min before planting. Plant height (measured at 7 day intervals), the duration of the different stages of the growth cycle, the number of flower buds formed, and the number of open and aborted flowers were recorded. The average day and night air temperatures were 25 and 13 deg C, respectively. Increasing Pbz dose progressively reduced the height of the "Ercolano" hybrid by between 29% (46.2 cm; 50 ppm) and 45% (35.3 cm; 150 ppm) compared to control plants (64.4 cm), however, neither the duration of flowering nor the number of flowers was modified. The "Royal Respect" hybrid responded with a marked shortening - by 45% (20.8 cm; 50 ppm) to 59% (28.2 cm; 150 ppm) in comparison with the average control height (51.1 cm), but in this case both the duration of flowering and the number of open flowers was reduced at the highest concentration. The feasibility of cultivating these Lilium hybrids for marketing in pots is demonstrated. However, the concentration of paclobutrazol should be adjusted according to the hybrid grown. En la producción de bulbosas en maceta, a menudo se requiere el control de la altura para obtener plantas proporcionales al tamaño del contenedor y para reducir el elongamiento del tallo en post-cosecha. Un medio efectivo de controlar la altura de las plantas es el uso de reguladores de crecimiento. Para proporcionar información sobre el enanizamiento químico en producción de plantas de Lilium en maceta, se estudió la efectividad del regulador de crecimiento paclobutrazol (0, 50, 100 y 150 ppm) en dos híbridos de Lilium L.A., "Ercolano" y "Royal Respect", aplicado por inmersión de bulbos durante 10 minutos. Se registró la altura a intervalos de 7 días, la duración de los diferentes estadios del ciclo y el número de flores formadas, abiertas y abortadas. Las temperaturas medias del aire (día/noche) fueron 25/13 grados C. El incremento de las dosis de paclobutrazol produjo un incremento en el control de la altura en el híbrido "Ercolano" de 29% (46,2 cm) a 45% (35,3 cm) con respecto al testigo (64,4 cm), sin modificación en la duración de la floración ni en el número de flores. El híbrido "Royal Respect" respondió al paclobutrazol con una marcada reducción de la altura, de 45% (20,8 cm) a 59% (28,2 cm), en comparación con el testigo (51,1 cm), pero en este caso, tanto la duración de la floración como el número de flores abiertas disminuyeron con la concentración más alta. Se demostró la viabilidad de cultivar los híbridos Lilium "Ercolano" y "Royal Respect" en macetas para su comercialización, y se confirmó que la concentración de paclobutrazol debe ajustarse para cada híbrido.

Among plant pathogens, sedentary endoparasitic nematodes are one of the most damaging pests in global agriculture. These obligate parasites interact with their hosts in a quite unique and intriguing way. They induce the redifferentiation of root cells into specialized feeding cells essential for nematode growth and reproduction; thus, nematodes have evolved the ability to exploit plant genes and hijack host functions for their own requirements. Various approaches to engineer plants with resistance to parasitic nematodes have been pursued, most focusing on the introduction of resistance genes. An alternative strategy to achieve resistance is to exploit the susceptibility of plant disease. Better knowledge of the plant response during the compatible interaction should allow the identification of targets to engineer resistance to parasitic nematodes in crop species.

International audience; 1. Optimal foraging models ultimately predict that female parasitoids should exploit rich host patches for longer than poorer ones. At the proximate level, mechanistic models and experimental studies show that parasitoids use both chemicals produced by their hosts and direct encounters with their hosts to estimate patch quality. Although it has been extensively studied in the context of host location, the use of herbivore-induced plant response by insect parasitoids has never been considered in the context of patch time allocation. 2. In this study, the respective roles of herbivore-induced plant response and direct contact with hosts on the foraging behaviour of Lisiphlebus testaceipes females on an aphid patch were quantified. For this, the level of herbivore-induced plant response and the number of aphids on the leaf bearing the patch were manipulated independently. Different levels of plant response were obtained by varying the duration of infestation on another leaf. 3. Parasitoid residence time and number of attacks increased with both the level of plant response and the number of aphids. 4. These results suggest that L. testaceipes females use the combination of herbivore-induced response of plants and direct encounters with hosts to assess patch quality and adjust their patch use behaviour

The aim of this work was to determine the influence of early inoculation of semi-woody olive cuttings (cv. Cornicabra), cultivated under mist propagation conditions, with arbuscular mycorrhizal fungi. A strongly positive response was seen to root inoculation with the three fungal species tested —Glomus mosseae, G. intraradices and G. claroideum— both in nursery phase plantlets, and in older plants grown in 5 L pots. El objetivo de este trabajo ha sido valorar la influencia de la inoculación temprana con micorrizas arbusculares en el desarrollo de olivos cv. Cornicabra obtenidos por propagación bajo nebulización de estaquillas semileñosas. Los resultados muestran la respuesta altamente positiva que en el desarrollo de las jóvenes plantas de olivo tiene la colonización de sus raíces por tres hongos micorrícicos distintos (Glomus mosseae, G. intraradices y G. claroideum), tanto en la primera fase de vivero como en plantas de más edad cultivadas en macetas de 5 L de capacidad.

The present field study was conducted to analyse the physiological response of a pepper (Capsicum annuum L.) cropto different trickle irrigation rates, by means of periodical measurements of leaf water potential (leaf) and stomatal resistance(Rs) at predawn during the plant growth cycle and at different times of the day during the fruit-growing stage,from predawn to nightfall. The internal water status of the plants was related to their growth rate (measured as aerialdry matter and leaf area index) and yield (marketable and total). The different irrigation rates tested were determinedaccording to the crop irrigation requirements (IR) calculated on the basis of crop evapotranspiration (ETc). Four treatmentswere established: 1.25 IR, 1.00 IR, 0.75 IR and 0.50 IR. Irrigation water amounts between 75 and 125% IR didnot cause important variations in growth and yield parameters, although a severe water deficit did induce a continuousadaptation of the plants by reducing their size (reflected by less dry matter accumulation and leaf area) and consequentlytheir yield. However, there were small differences between treatments in the measurements of leaf and Rs, which indicatesthat crop growth was more affected by severe water deficits than these two parameters in pepper crops with dailytrickle irrigation. leaf did not justify the mechanisms of stomatal regulation, even on hot and dry middays. Se estudió la respuesta fisiológica de un cultivo de pimiento (Capsicum annuum L.) a distintas dosis de riego por goteo, mediante medidas periódicas al alba y a lo largo del día, durante el período de engorde de los frutos, del potencial hídrico y de la resistencia estomática (Re) de la hoja. El estado hídrico de las plantas se relacionó con su nivel de crecimiento (materia seca área total, índice de área foliar) y rendimiento (comercial y total). Las dosis de riego se determinaron en función de las necesidades de riego calculadas (NRc) a partir de la evapotransporación del cultivo, ensayándose cuatro tratamientos correspondientes a 1.25 NRc, 1.00 NRc, 0.75 NRc y 0.50 NRc. La aplicación de dosis de riego comprendidas entre el 75 y el 125% de NRC no produjo variaciones importantes en los parámetros de crecimiento y producción, si bien la restricción severa de agua provocó una adaptación continua de las plantas (...)

A mutation in the ilvC gene of Sinorhizobium meliloti 1021 determines a symbiotically defective phenotype, ilvC mutants obtained from different S. meliloti wild-type strains are able to induce root hair deformation on alfalfa roots and show variable activation of the common nodulation genes nodABC. All of these mutants are noninfective. The presence of extra copies of nodD3-syrM in an IlvC‒ background does not promote nod expression but allows the detection of low levels of Nod factor production. The sulphation of the Nod factor metabolites, however, is not affected. Furthermore, IlvC‒ strains induce a specific pattern of starch accumulation on alfalfa roots as well as of early nodulin expression. Hence, the pleiotropic action of the ilvC gene in S. meliloti may reveal novel complexities involved in the symbiotic interaction., Instituto de Biotecnologia y Biologia Molecular, Facultad de Ciencias Exactas

Regulated deficit irrigation (RDI) during stage 2 of fruit development and summer pruning (watersprout removal, WSR) can be used to control excessive vegetative growth in high-density peach orchards. The dynamics of tree-light interception after the application of RDI (no irrigation during stage 2) and WSR in summer were evaluated during two consecutive years. RDI and WSR treatments produced similar reductions in the percentage of light intercepted by the tree at the end of the 2-year experiment. However, it was not possible to produce the same seasonal dynamics in the percentage of light intercepted by the tree using the RDI and the WSR techniques; RDI trees showed a gradual reduction in the amount of light intercepted as the productive cycle progressed, while WSR trees showed an immediate reduction in the amount of light intercepted. Moreover, the mechanisms responsible for vegetative growth reduction were different in the RDI and the WSR techniques. The RDI technique was associated with reductions in tree water status and decreases in gravimetric soil water (theta g) and fruit growth capacity. RDI may have reduced theta g below the threshold required for optimum fruit growth, whereas WSR reduced water consumption, improved water status and therefore could have benefited fruit growth. Therefore, RDI and WSR greatly differ when the mechanisms responsible for vegetative growth reduction are taken into consideration. El riego deficitario controlado (RDI) durante la fase 2 de crecimiento del fruto y la poda de chupones en verano (WSR) podrían usarse para controlar el exceso de crecimiento vegetativo en plantaciones de melocotonero de alta densidad. Se estudió el papel de la reducción en la radiación interceptada por el árbol tras la aplicación de un RDI durante la fase 2 (supresión total de riego) y la WSR durante dos años consecutivos. Ambas técnicas produjeron una reducción similar en la radiación interceptada por el árbol al final del experimento. Sin embargo, la dinámica estacional de la radiación interceptada por el árbol fue diferente entre WSR y RDI. La WSR produjo una disminución inmediata en el porcentaje de radiación interceptada por el árbol, mientras que el RDI produjo una disminución paulatina a medida que avanzó la campaña. Además, los mecanismos promotores de la reducción del crecimiento vegetativo fueron diferentes. El RDI afectó negativamente al estado hídrico del árbol, a la cantidad gravimétrica de agua en el suelo (teta g) y al crecimiento del fruto. Mientras que el RDI parece reducir el teta g por debajo del umbral necesario para obtener un crecimiento de fruto óptimo, una disminución en el consumo de agua tras la WSR habría mejorado el estado hídrico del árbol para finalmente beneficiar el crecimiento del fruto. Aunque el RDI y la WSR produjeron una reducción similar en el porcentaje de radiación interceptada por el árbol, ambas técnicas muestran claras diferencias cuando se analizan los factores relacionados con la reducción en el crecimiento vegetativo.