The effect of potato variety mixtures on epidemics of late blight, in relation to plot size and level of resistance

Potatoes of a number of varieties of contrasting levels of resistance were planted in pure or mixed stands in four experiments over 3 years. Three experiments compared the late blight severity and progress in mixtures with that in pure stands. Disease on susceptible or moderately resistant varieties typical of those in commercial use was similar in mixtures and pure stands. In 2 of 3 years, there were slight reductions on cv. Sante, which is moderately susceptible, in mixture with cv. Cara, which is moderately resistant. Cara was unaffected by this mixture. Mixtures of an immune or near-immune partner with Cara or Sante substantially reduced disease on the latter. The effect of the size of plots of individual varieties or mixtures on blight severity was compared in two experiments. Larger plots had a greater area under the disease progress curve, but the average rate of disease progress was greater in smaller plots; this may be because most disease progress took place later, under more favourable conditions, in the smaller plots. In one experiment, two planting densities were used. Density had no effect on disease and did not interact with mixture effects. The overall conclusion is that, while mixtures of potato varieties may be desirable for other reasons, they do not offer any improvement on the average of the disease resistance of the components.

The citrus flavanone naringenin inhibits inflammatory signalling in glial cells and protects against neuroinflammatory injury

Neuroinflammation plays an integral role in the progression of neurodegeneration. In this study we investigated the anti-inflammatory effects of different classes of flavonoids (flavanones, flavanols and anthocyanidins) in primary mixed glial cells. We found that the flavanones naringenin and hesperetin and the flavols (+)-catechin and (-)-epicatechin, but not the anthocyanidins cyanidin and pelargonidin, attenuated LPS/IFN-gamma-induced TNF-alpha production in glial cells. Naringenin also inhibited LPS/IFN-gamma-induced iNOS expression and nitric oxide production in glial cells, thus showing the strongest antiinflammatory activity among all flavonoids tested. Moreover, naringenin protected against inflammatory-induced neuronal death in a primary neuronal-glial co-culture system. Naringenin also inhibited LPS/IFN-gamma-induced p38 mitogen-activated protein kinase (MAPK) phosphorylation and downstream signal transducer and activator of transcription-1 (STAT-1) in LPS/IFN-gamma stimulated primary mixed glial cells. Taken together, our results suggest that naringenin may produce an anti-inflammatory effect in LPS/IFN-gamma stimulated glial cells that may be due to its interaction with p38 signalling cascades and the STAT-I trascription factor. (C) 2009 Elseiver Inc. All rights reserved.

The differential tissue distribution of the citrus flavanone naringenin following gastric instillation

Citrus flavonoids have been investigated for their biological activity, with both anti-inflammatory and -carcinogenic effects being reported. However, little information is known on the bioavailability of these compounds in vivo. The objectives of this study were to determine the tissue distribution of naringenin after gastric gavage of [H-3]-naringenin to rats. Unlabelled naringenin was also used to quantify the levels of naringenin and its major metabolites in tissues and eliminated in the urine and faeces. Significant radioactivity was detected in the plasma as well as all tissues examined 2 h post-gavage. After 18 h, higher levels of radioactivity were retained in plasma and tissues (55% of the administered radioactivity). Investigation of the nature of metabolites, using unlabelled naringenin, revealed that the glucuronides were the major components in plasma, tissues and urine, in addition to the colonic metabolite 3-(4- hydroxyphenyl) propionic acid, detected in the urine. The aglycone was the form extensively retained in tissues after 18 h post-gavage. Total identified metabolites detected after 18 h in most tissues were only 1-5% of the levels detected after 2 h. However, the brain, lungs and heart retained 27, 20 and 11%, respectively, relative to the total metabolites detected at 2 h. While radioactive detection suggests increased levels of breakdown products of naringenin after 18 h versus 2 h, the products identified using unlabelled naringenin are not consistent with this, suggesting that a predominant proportion of the naringenin breakdown products at 18 h are retained as smaller decomposition molecules which cannot yet be identified.

Piriformospora indica reduces Fusarium head blight disease severity and mycotoxin DON contamination in wheat under UK weather conditions

Piriformospora indica (Sebacinaceae) is a cultivable root endophytic fungus. It colonises the roots of a wide range of host plants. In many settings colonisation promotes host growth, increases yield and protects the host from fungal diseases. We evaluated the effect of P. indica on Fusarium head blight (FHB) disease of winter (cv. Battalion) and spring (cv. Paragon, Mulika, Zircon, Granary, KWS Willow and KWS Kilburn) wheat and consequent contamination by the mycotoxin deoxynivalenol (DON) under UK weather conditions. Interactions of P. indica with an arbuscular mycorrhizal fungus (Funneliformis mosseae), fungicide application (Aviator Xpro) and low and high fertiliser levels were considered. P. indica application reduced FHB disease severity and incidence by 70%. It decreased mycotoxin DON concentration of winter and spring wheat samples by 70% and 80% respectively. P. indica also increased above ground biomass, 1000 grain weight and total grain weight. P. indica reduced disease severity and increased yield in both high and low fertiliser levels. The effect of P. indica was compatible with F. mosseae and foliar fungicide application. P. indica did not have any effects on plant tissue nutrients. These results suggest that P. indica might be useful in biological control of Fusarium diseases of wheat.

Early changes in apoplast composition associated with defence and disease in interactions between Phaseolus vulgaris and the halo blight pathogen Pseudomonas syringae pv. phaseolicola

The apoplast is the arena in which endophytic pathogens such as Pseudomonas syringae grow and interact with plant cells. Using metabolomic and ion analysis techniques, this study shows how the composition of Phaseolus vulgaris leaf apoplastic fluid changes during the first six hours of compatible and incompatible interactions with two strains of Pseudomonas syringae pv. phaseolicola (Pph) that differ in the presence of the genomic island PPHGI-1. Leaf inoculation with the avirulent island-carrying strain Pph 1302A elicited effector-triggered immunity (ETI) and resulted in specific changes in apoplast composition, including increases in conductivity, pH, citrate, γ-aminobutyrate (GABA) and K+, that are linked to the onset of plant defence responses. Other apoplastic changes, including increases in Ca2+, Fe2/3+ Mg2+, sucrose, β-cyanoalanine and several amino acids, occurred to a relatively similar extent in interactions with both Pph 1302A and the virulent, island-less strain Pph RJ3. Metabolic footprinting experiments established that Pph preferentially metabolizes malate, glucose and glutamate, but excludes certain other abundant apoplastic metabolites, including citrate and GABA, until preferred metabolites are depleted. These results demonstrate that Pph is well-adapted to the leaf apoplast metabolic environment and that loss of PPHGI-1 enables Pph to avoid changes in apoplast composition linked to plant defences.

Comparative analysis by protocol and key of seed storage behaviour of sixty Vietnamese tree species

Seed storage behaviour of 5 1 native and 9 introduced tree species in Vietnam was investigated using a brief protocol developed to aid biodiversity conservation in circumstances where little is known about the seeds. Of the 60 species, 34 appeared to show orthodox (Acacia auriculaeformis, Adenanthera pavonina, Afzelia xylocarpa, Bauhinia purpurea, Callistemon lanceolatus, Cananga odorata, Canarium nigrum, Cassia fistula, Cassia javanica, Cassia splendida, Chukrasia tabularis, Dalbergia bariaensis, Dialium cochinchinensis, Diospyros mollis, Diospyros mun, Dracuntomelon duperreanum, Erythrophleum fordii, Khaya senegalensis, Lagerstroemia speciosa, Leucaena leucocephala, Livistona cochinchinensis, Markhamia stipulata, Melaleuca cajuputi, Millettia ichthyotona, Peltophorum pterocarpum, Peltophorum tonkinensis, Pinus khasya, Pinus massoniana, Pinus merkusii, Pterocarpus macrocarpus, Sindora siamensis, Sophora tonkinense, Sterculia foetida, Swietenia macrophylla), 13 recalcitrant (Avicennia alba, Beilschmiedia roxburghiana, Caryota mitis, Dimocarpus sp., Diospyros malabarica, Dipterocarpus chartaceus, Dypsis pinnatifrons, Hopea odorata, Lithocarpus gigantophylla, Machilus odoratissimus, Melanorrhoea laccifera, Melanorrhea usitata, Syzygium cinereum) and 13 intermediate (Anisoptera cochinchinensis, Aphanamixis polystachya, Averrhoa carambola, Carissa carandas, Chrysopylum cainito, Cinnamomum camphora, Citrofortunella microcarpa, Citrus grandis var. grandis, Elaeis guineensis, Hydnocarpus anthelmintica, Madhuca floribunda, Manilkara achras, Mimusops elengi) seed storage behaviour. A double-criteria key to estimate likely seed storage behaviour showed good agreement with the above: the key can reduce the workload of seed storage behaviour identification considerably.

Modulation of peroxynitrite-induced fibroblast injury by hesperetin: a role for intracellular scavenging and modulation of ERK signalling

Peroxynitrite is thought to contribute to the progression of many diseases including cardiovascular disease, cancer, and neurodegenerative disorders. We report that pre-treatment of fibroblasts with the citrus flavanone, hesperetin, prior to peroxynitrite exposure protects against peroxynitrite-mediated cytotoxicity. This protection was partially mediated by the intracellular scavenging of peroxynitrite by hesperctin as exposure of fibroblasts to peroxynitrite following hesperetin loading led to the formation of two intracellular nitrohesperetin derivatives. In addition, protection appeared to be mediated by hesperetin-induced changes in MAP kinase signalling. Exposure of fibroblasts to hesperetin led to concentration-dependent increases in the phosphorylation of ERK1/2 and was observed to restore peroxynitrite-mediated decreases in ERK1/2 phosphorylation. We propose that the protective potential of hesperetin in fibroblasts may be mediated both by intracellular scavenging of peroxynitrite and by modulation of fibroblast signalling. (c) 2006 Elsevier Inc. All rights reserved.

Neuroprotective effects of hesperetin in mouse primary neurones are independent of CREB activation

Dietary flavonoids, including the citrus flavanone hesperetin, may have stimulatory, effects on cytoprotective intracellular signalling pathways. In primary mouse cortical neurone cultures, but not SH-SY5Y human neuroblastoma cells or human primary dermal fibroblasts (Promocells), hesperetin (100-300 nM, 15 min) caused significant increases in the level of ERK1/2 phosphorylation, but did not increase CREB phosphorylation. Administration of hesperetin for 18 h did not alter gene expression driven by the cyclic AMP response element (CRE), assessed using a luciferase reporter system, but 300 nM hesperetin partially reversed staurosporine-induced cell death in primary neurones. Our data show that hesperetin is a neuroprotective compound at concentrations where antioxidant effects are unlikely to predominate. The effects of hesperetin are cell-type dependent and, unlike the flavanol (-)epicatechin, neuroprotection in vitro is not associated with enhanced CREB phosphorylation or CRE-mediated gene expression. (C) 2008 Elsevier Ireland Ltd. All rights reserved.

Confocal imaging of pseudomonas syringae pv. phaseolicola colony development in bean reveals reduced multiplication of strains containing the genomic island PPHGI-1.

Pseudomonas syringae pv. phaseolicola is the seed borne causative agent of halo blight in the common bean Phaseolus vulgaris. Pseudomonas syringae pv. phaseolicola race 4 strain 1302A contains the avirulence gene hopAR1 (located on a 106-kb genomic island, PPHGI-1, and earlier named avrPphB), which matches resistance gene R3 in P. vulgaris cultivar Tendergreen (TG) and causes a rapid hypersensitive reaction (HR). Here, we have fluorescently labeled selected Pseudomonas syringae pv. phaseolicola 1302A and 1448A strains (with and without PPHGI-1) to enable confocal imaging of in-planta colony formation within the apoplast of resistant (TG) and susceptible (Canadian Wonder [CW]) P. vulgaris leaves. Temporal quantification of fluorescent Pseudomonas syringae pv. phaseolicola colony development correlated with in-planta bacterial multiplication (measured as CFU/ml) and is, therefore, an effective means of monitoring Pseudomonas syringae pv. phaseolicola endophytic colonization and survival in P. vulgaris. We present advances in the application of confocal microscopy for in-planta visualization of Pseudomonas syringae pv. phaseolicola colony development in the leaf mesophyll to show how the HR defense response greatly affects colony morphology and bacterial survival. Unexpectedly, the presence of PPHGI-1 was found to cause a reduction of colony development in susceptible P. vulgaris CW leaf tissue. We discuss the evolutionary consequences that the acquisition and retention of PPHGI-1 brings to Pseudomonas syringae pv. phaseolicola in planta.

The impact of fruit flavonoids on memory and cognition

There is intense interest in the studies related to the potential of phytochemical-rich foods to prevent age-related neurodegeneration and cognitive decline. Recent evidence has indicated that a group of plant-derived compounds known as flavonoids may exert particularly powerful actions on mammalian cognition and may reverse age-related declines in memory and learning. In particular, evidence suggests that foods rich in three specific flavonoid sub-groups, the flavanols, anthocyanins and/or flavanones, possess the greatest potential to act on the cognitive processes. This review will highlight the evidence for the actions of such flavonoids, found most commonly in fruits, such as apples, berries and citrus, on cognitive behaviour and the underlying cellular architecture. Although the precise mechanisms by which these flavonoids act within the brain remain unresolved, the present review focuses on their ability to protect vulnerable neurons and enhance the function of existing neuronal structures, two processes known to be influenced by flavonoids and also known to underpin neuro-cognitive function. Most notably, we discuss their selective interactions with protein kinase and lipid kinase signalling cascades (i.e. phosphoinositide-3 kinase/Akt and mitogen-activated protein kinase pathways), which regulate transcription factors and gene expression involved in both synaptic plasticity and cerebrovascular blood flow. Overall, the review attempts to provide an initial insight into the potential impact of regular flavonoid-rich fruit consumption on normal or abnormal deteriorations in cognitive performance.

Pseudomonas syringae pv. phaseolicola: from ‘has bean’ to supermodel

Pseudomonas syringae pv. phaseolicola causes halo blight of the common bean, Phaseolus vulgaris, worldwide and remains difficult to control. Races of the pathogen cause either disease symptoms or a resistant hypersensitive response on a series of differentially reacting bean cultivars. The molecular genetics of the interaction between P. syringae pv. phaseolicola and bean, and the evolution of bacterial virulence, have been investigated in depth and this research has led to important discoveries in the field of plant-microbe interactions. In this review, we discuss several of the areas of study that chart the rise of P. syringae pv. phaseolicola from a common pathogen of bean plants to a molecular plant-pathogen supermodel bacterium. Taxonomy: Bacteria; Proteobacteria, gamma subdivision; order Pseudomonadales; family Pseudomonadaceae; genus Pseudomonas; species Pseudomonas syringae; Genomospecies 2; pathogenic variety phaseolicola. Microbiological properties: Gram-negative, aerobic, motile, rod-shaped, 1.5 µm long, 0.7-1.2 µm in diameter, at least one polar flagellum, optimal temperatures for growth of 25-30 °C, oxidase negative, arginine dihydrolase negative, levan positive and elicits the hypersensitive response on tobacco. Host range: Major bacterial disease of common bean (Phaseolus vulgaris) in temperate regions and above medium altitudes in the tropics. Natural infections have been recorded on several other legume species, including all members of the tribe Phaseoleae with the exception of Desmodium spp. and Pisum sativum. Disease symptoms: Water-soaked lesions on leaves, pods, stems or petioles, that quickly develop greenish-yellow haloes on leaves at temperatures of less than 23 °C. Infected seeds may be symptomless, or have wrinkled or buttery-yellow patches on the seed coat. Seedling infection is recognized by general chlorosis, stunting and distortion of growth. Epidemiology: Seed borne and disseminated from exudation by water-splash and wind occurring during rainfall. Bacteria invade through wounds and natural openings (notably stomata). Weedy and cultivated alternative hosts may also harbour the bacterium. Disease control: Some measure of control is achieved with copper formulations and streptomycin. Pathogen-free seed and resistant cultivars are recommended. Useful websites: Pseudomonas-plant interaction http://www.pseudomonas-syringae.org/; PseudoDB http://xbase.bham.ac.uk/pseudodb/; Plant Associated and Environmental Microbes Database (PAMDB) http://genome.ppws.vt.edu/cgi-bin/MLST/home.pl; PseudoMLSA Database http://www.uib.es/microbiologiaBD/Welcome.html.

An assessment of the prebiotic potential of single and blended substrates in anaerobic in vitro batch culture fermentations using canine faecal samples as inocula

Previously, using an in vitro static batch culture system, it was found that rice bran (RB), inulin, fibersol, mannanoligosaccharides (MOS), larch arabinogalactan and citrus pectin elicited prebiotic effects (in terms of increased numbers of bifidobacteria and lactic acid bacteria) on the faecal microbiota of a dog. The aim of the present study was to confirm the prebiotic potential of each individual substrate using multiple faecal donors, as well as assessing the prebiotic potential of 15 substrate blends made from them. Anaerobic static and stirred, pH-controlled batch culture systems inoculated with faecal samples from healthy dogs were used for this purpose. Fluorescence in situ hybridization (FISH) analysis using seven oligonucleotide probes targeting selected bacterial groups and DAPI (total bacteria) was used to monitor bacterial populations during fermentation runs. High-performance liquid chromatography was used to measure butyrate produced as a result of bacterial fermentation of the substrates. RB and a MOS/RB blend (1:1, w/w) were shown to elicit prebiotic and butyrogenic effects on the canine microbiota in static batch culture fermentations. Further testing of these substrates in stirred, pH-controlled batch culture fermentation systems confirmed the prebiotic and butyrogenic effects of MOS/RB, with no enhancement of Clostridium clusters I and II and Escherichia coli populations.

Orange juice–derived flavanone and phenolic metabolites do not acutely affect cardiovascular risk biomarkers: a randomized, placebo-controlled, crossover trial in men at moderate risk of cardiovascular disease

Background: Epidemiological data suggest inverse associations between citrus flavanone intake and cardiovascular disease (CVD) risk. However, insufficient randomized controlled trial (RCT) data limit our understanding of mechanisms by which flavanones and their metabolites potentially reduce cardiovascular (CV) risk factors. Objective: We examined the effects of orange juice or a dose-matched hesperidin supplement on plasma concentrations of established and novel flavanone metabolites and their effects on CV risk biomarkers in men at moderate CVD risk. Methods: In an acute, randomized, placebo-controlled crossover trial, 16 fasted participants (aged 51-69 y) received orange juice or a hesperidin supplement (both providing 320 mg hesperidin) or control (all matched for sugar and vitamin C content). At baseline and 5 h post-intake, endothelial function (primary outcome), further CV risk biomarkers (i.e. blood pressure, arterial stiffness, cardiac autonomic function, platelet activation and NADPH oxidase gene expression) and plasma flavanone metabolites were assessed. Prior to each intervention, a diet low in flavonoids, nitrate/nitrite, alcohol and caffeine was followed and a standardized low-flavonoid evening meal was consumed. Results: Orange juice intake significantly elevated mean (± SEM) plasma concentrations of 8 flavanone (1.75 ± 0.35 µmol/L, P < 0.0001) and 15 phenolic metabolites (13.27 ± 2.22 µmol/L, P < 0.0001) compared with control at 5 h post-consumption. Despite increased plasma flavanone and phenolic metabolite concentrations, CV risk biomarkers were unaltered. Following hesperidin supplement intake, flavanone metabolites were not different to control, suggesting altered absorption/metabolism compared with the orange juice matrix. Conclusions: Following single-dose flavanone intake within orange juice, we detected circulating flavanone and phenolic metabolites collectively reaching a concentration of 15.20 ± 2.15 µmol/L but observed no effect on CV risk biomarkers. Longer-duration RCTs are required to further examine the previous associations between higher flavanone intakes and improved cardiovascular health and to ascertain the relative importance of food matrix and flavanone-derived phenolic metabolites.

The identification of genes important in pseudomonas syringae pv. phaseolicola plant colonisation using in vitro screening of transposon libraries

The bacterial plant pathogen Pseudomonas syringae pv. phaseolicola (Pph) colonises the surface of common bean plants before moving into the interior of plant tissue, via wounds and stomata. In the intercellular spaces the pathogen proliferates in the apoplastic fluid and forms microcolonies (biofilms) around plant cells. If the pathogen can suppress the plant’s natural resistance response, it will cause halo blight disease. The process of resistance suppression is fairly well understood, but the mechanisms used by the pathogen in colonisation are less clear. We hypothesised that we could apply in vitro genetic screens to look for changes in motility, colony formation, and adhesion, which are proxies for infection, microcolony formation and cell adhesion. We made transposon (Tn) mutant libraries of Pph strains 1448A and 1302A and found 106/1920 mutants exhibited alterations in colony morphology, motility and biofilm formation. Identification of the insertion point of the Tn identified within the genome highlighted, as expected, a number of altered motility mutants bearing mutations in genes encoding various parts of the flagellum. Genes involved in nutrient biosynthesis, membrane associated proteins, and a number of conserved hypothetical protein (CHP) genes were also identified. A mutation of one CHP gene caused a positive increase in in planta bacterial growth. This rapid and inexpensive screening method allows the discovery of genes important for in vitro traits that can be correlated to roles in the plant interaction