Plant Defence Research Papers - Academia.edu (original) (raw)

New insights into the phenomenon of systemic acquired resistance have been gained in recent years, by the use of techniques in molecular genetics and biology that have replaced the largely descriptive approach of earlier work. The... more

New insights into the phenomenon of systemic acquired resistance have been gained in recent years, by the use of techniques in molecular genetics and biology that have replaced the largely descriptive approach of earlier work. The isolation of mutants in the signal transduction pathway from induction to expression of resistance as well as the use of transgenic plants over-expressing or suppressing the expression of putative candidate genes involved in systemic acquired resistance and its signalling have identified several steps in the establishment of plant resistance. In this review the latest developments implicating salicylic acid as a signal molecule in systemic resistance are discussed and contrasted with new signalling pathways which, seemingly, are based on alternative mechanisms.

In recent years, the interest in the possible use of natural alternatives to food additives to prevent bacterial and fungal growth has notably increased. Plants and plant products can represent a source of natural alternatives to improve... more

In recent years, the interest in the possible use of natural alternatives to food additives to prevent bacterial and fungal growth has notably increased. Plants and plant products can represent a source of natural alternatives to improve the shelf-life and the safety of food. Some of these compounds, i.e. hexanal, hexanol, 2-(E)-hexenal and 3-(Z)-hexenol, produced throughout the lipoxygenase pathway have important roles in plant defence with a protective action towards microbial proliferation in wounded areas. Otherwise, hexanal and 2-(E)-hexenal have evidenced a marked antimicrobial activity against food spoilage and pathogenic microbial species both in model and real systems. The precise mechanisms of action of all these antimicrobial compounds are not yet clear. Because the usage of these compounds as antimicrobials in foods has to be supported by the comprehension of mechanisms of action of these compounds, the overall purpose of this work was to study the modifications of the cell membrane and volatile compounds of Listeria monocytogenes, Staphylococcus aureus, Salmonella enteritidis and Escherichia coli during the growth in the presence of sub-lethal doses of these two aldehydes. The results obtained evidenced that the tested molecules induced noticeable modifications of the composition of cell membrane and the volatile compounds produced during the growth. Although specific differences in relation to the species considered were identified, 2-(E)-hexenal and hexanal induced a marked increase of some membrane associated fatty acids, both linear and branched fatty acids as well as unsaturated fatty acids, and released free fatty acids.

Plant disease control is mainly based on the use of fungicides, bactericides, and insecticides-chemical compounds toxic to plant invaders, causative agents, or vectors of plant diseases. However, the detrimental effect of these chemicals... more

Plant disease control is mainly based on the use of fungicides, bactericides, and insecticides-chemical compounds toxic to plant invaders, causative agents, or vectors of plant diseases. However, the detrimental effect of these chemicals or their degradation products on the environment and human health strongly imposes the search for novel, harmless means of disease control. Therefore, it is essential to introduce environmentally-friendly alternative measures for management of plant diseases. Induced plant resistance is one of the promising non-chemical strategies for the effective management of diseases. The host plant mediated resistance is governed by defense response genes encoding for production of various pathogenesis-related (PR) proteins. This review chiefly explains the biochemical response of plant defense mechanism pertaining to defense-related enzymes which have been identified as PR proteins.

SUMMARY Control of grapevine virus and phytoplasma diseases is currently based on prophylactic measures and cultur- al practices. Certification programs aim to avoid the in- troduction of diseased grapevines into healthy vine- yards, and... more

SUMMARY Control of grapevine virus and phytoplasma diseases is currently based on prophylactic measures and cultur- al practices. Certification programs aim to avoid the in- troduction of diseased grapevines into healthy vine- yards, and cultural practices aim to reduce the popula- tions of virus vectors to limit virus spread. These ap- proaches however are of limited effectiveness. Addition- ally, there

Plant-insect interactions are not just influenced by interactions between plants and the actively feeding stages, but also by the close relationships between plants and insect eggs. Here, we review both effects of plants on insect eggs... more

Plant-insect interactions are not just influenced by interactions between plants and the actively feeding stages, but also by the close relationships between plants and insect eggs. Here, we review both effects of plants on insect eggs and, vice versa, effects of eggs on plants. We consider the influence of plants on the production of insect eggs and address the role of phytochemicals for the biosynthesis and release of insect sex pheromones, as well as for insect fecundity. Effects of plants on insect oviposition by contact and olfactory plant cues are summarised. In addition, we consider how the leaf boundary layer influences both insect egg deposition behaviour and development of the embryo inside the egg. The effects of eggs on plants involve egg-induced changes of photosynthetic activity and of the plant's secondary metabolism. Except for gall-inducing insects, egg-induced changes of phytochemistry were so far found to be detrimental to the eggs. Egg deposition can induce h...

SUMMARY The objective of this paper is to describe the various measures investigated to secure the behaviour of Oman-UAE interconnected power system when facing large disturbances. When occurring, the activation of the defence plan... more

SUMMARY The objective of this paper is to describe the various measures investigated to secure the behaviour of Oman-UAE interconnected power system when facing large disturbances. When occurring, the activation of the defence plan maintains or restores the stability of the interconnected system but also to limit the spreading of the disturbance or the instability phenomena to large portions of the power system. The main defence plan and emergency actions of concern are: • Defence actions against frequency instabilities which lead (most of the time) to the activation of the Under Frequency Load Shedding (UFLS). The paper assesses the need to harmonize the two existing UFLS plans to avoid unnecessary power transfer during transients involving the activation of UFLS plans. • Defence actions against loss of synchronism which could take place following various circumstances such as the occurrence of faults with delayed clearing or uncontrolled development of undamped power swings between various parts of the interconnected system. The most common loss of synchronism defence action is the detection and splitting of the portion of the system that lost synchronism. In the frame of the Oman-UAE interconnection, it would consist of the disconnection of the interconnector or the portions of the system that would have lost synchronism. A large number of severe contingencies have been simulated to locate the coherent group of generators following a loss of synchronism. These have been achieved by the simulation of 3-phase faults cleared in backup time close to 220 kV substations leading to the loss of two circuits or one 220 kV circuit and one transformer. The cases leading to the loss of synchronism of a set of generators have been detected. These cases should be addressed with adequately located and tuned out of step protections. In some situations the system splits into two or more coherent groups of generators. Simulations of faults cleared in backup time have shown that in very unlikely Oman exporting situations, the transmission system or part of it may lose synchronism with respect to the UAE system.

1. Climate change is expected to modify current ecological conditions sustaining the coexistence of species within cold-adapted plant communities. It will primarily act upon the existing structure of communities, whose response should... more

1. Climate change is expected to modify current ecological conditions sustaining the coexistence of species within cold-adapted plant communities. It will primarily act upon the existing structure of communities, whose response should depend on the functional differences governing coexistence among alpine species. We postulated that a possible trade-off between (1) plant growth in response to temperature , (2) plant competition and (3) resistance to herbivory, modulates the rate of plant community turnover under climate change. 2. We reviewed the literature investigating functional traits variability within communities along elevation gradients. Despite environmental filtering, our review indicates that interspecific plant functional variation within communities does not necessarily decrease with elevation. While the diversity of traits related to abiotic affinities or competition are well documented, the variability in species resistance to herbivory within communities is poorly known. 3. Using a Lotka–Volterra-based model, we simulated the impact of climate change on plant communities through (1) a direct effect on plant growth and competition and (2) an indirect effect via an increase in herbivore pressure. We showed that different shapes of trade-offs between temperature-related growth, competition and resistance to herbivory modulate community turnover under climate change. 4. We documented the existence of two independent trade-offs axes using a detailed dataset of functional traits within two alpine grasslands in the European Alps. Plant competitive traits (i.e. leaf area and height) where negatively associated to cold tolerance, whereas traits of the leaf economic spectrum were associated to traits related to the physical resistance to herbivory. 5. We propose that the immediate effect of climate change on alpine plant communities will depend on existing functional variability and how functional axes trade-off with each other. Documenting ecological constraints between plant functional axes should provide indications to anticipate winners and losers in alpine plant communities.

Abstract Background: Cyanogenic glucosides are common bioactive products that break down to release toxic hydrogen cyanide (HCN) when combined with specific β-glucosidases. In forage sorghum, high concentrations of the cyanogenic... more

The polyphagous obligate parasites Meloidogyne spp. devastate a wide range of crop plants including bananas and plantains. Their infestations impact agriculture worldwide. Therefore, an effective combating regime against this nematode... more

The polyphagous obligate parasites Meloidogyne spp. devastate a wide range of crop plants including bananas and plantains. Their infestations impact agriculture worldwide. Therefore, an effective combating regime against this nematode species and an in-depth understanding of plant-nematode interaction are essential. Early detection of infection by visual inspection is not possible. This hampers early control strategy efforts and makes in-depth research of the early infection and plant defence unfeasible. A simple and robust in planta PCR-based nematode detection method is described here as the first crucial step. This PCR-based detection assay exploits the existence of the Internal Transcribed Spacer 1 (ITS 1) region of the ribosomal DNA (rDNA) gene family in the nematodes for early detection of nematode penetration into the roots. The results demonstrate that this detection assay is suitable to serve as a molecular screening tool for plant root diagnostic purposes.

The concept ‘functional genomics’ refers to the methods used for the functional characterisation of genomes. The methods utilised provide new opportunities for studying the nature and role of defence mechanisms in plants. Unlike... more

The concept ‘functional genomics’ refers to the methods used for the functional characterisation of genomes. The methods utilised provide new opportunities for studying the nature and role of defence mechanisms in plants. Unlike Arabidopsis, poplar and rice, the full genomic sequence of barley is not available. In this case, the analysis of barley gene expression data plays a pivotal role for obtaining insight into the functional characterisation of individual gene products. Many genes are activated transcriptionally following attack by pathogens and these often contribute to the defence mechanisms which underlie disease resistance. The use of large-scale complementary DNA library constructions and genome-wide transcript profiles of plants exposed to biotic stress provide the data required to drive hypotheses concerning the function of newly identified genes. In this paper, we illustrate how publicly available gene expression data has proved valid for studies of plant defence responses; enabling a cost-effective workflow starting from isolated gene transcripts to elucidation of biological function upon biotic stress.

Globally, cassava is the second most important root crop after potatoes and the fifth most important crop overall in terms of human caloric intake. In addition to its growing global importance for feed, fuel, and starch, cassava has long... more

Globally, cassava is the second most important root crop after potatoes and the fifth most important crop overall in terms of human caloric intake. In addition to its growing global importance for feed, fuel, and starch, cassava has long been vital to food security in Sub-Saharan Africa. Climate change is expected to have its most severe impact on crops in food insecure regions, yet little is known about how cassava productivity will respond to climate change. The most important driver of climate change is globally increasing atmospheric CO2 concentration ([CO2]). However, the potential for cassava to enhance food security in an elevated [CO2] world is uncertain as greenhouse and open top chamber (OTC) study reports are ambiguous. Studies have yielded misleading results in the past regarding the effect of elevated [CO2] on crop productivity, particularly in cases where pots restricted sink growth. To resolve these conflicting results, we compare the response of cassava to growth at ambient (ca. 385 ppm) and elevated [CO2] (585 ppm) under field conditions and fully open air [CO2] elevation. After three and half months of growth at elevated [CO2], above ground biomass was 30% greater and cassava root tuber dry mass increased over 100% (fresh weight increased 89%). High photosynthetic rates and photosynthetic stimulation by elevated [CO2], larger canopies, and a large sink capacity all contributed to cassava’s growth and yield stimulation. Cassava exhibited photosynthetic acclimation via decreased Rubisco capacity early in the season prior to root tuber initiation when sink capacity was smaller. Importantly, and in contrast to a greenhouse study, we found no evidence of increased leaf N or total cyanide concentration in elevated [CO2]. All of our results are consistent with theoretical expectations; however, the magnitude of the yield increase reported here surpasses all other C3 crops and thus exceeds expectations.