Molecular characerization of the interaction between the fungal pathogen Cladosporium fulvum and tomato

The fungus Cladosprium fulvum is a biotrophic leaf pathogen of tomato. The fungus develops in the intercellular space without forming specialized feeding structures and does not affect the leaf tissue. The outcome of the C. fulvum-tomato interaction can be described by the gene-for-gene model. Failure of infection is expressed by a hypersensitive response. Two fungal proteins, ECP1 and ECP2, have been isolated and their corresponding genes have been cloned. In a compatible interaction including many physiological races ECP1 and ECP2 are highly produced and a role in pathogenicity is suggestive. The ecp1 gene shows some homology with tumor necrosis factor receptors (TNFRs) while the ecp2 gene shows no homology with sequences known in data bases. However, disruption of one of the two genes showed no reduced pathogenicity of the fungus. Two race-specific elicitors, AVR4 and AVR9, have been isolated and their corresponding genes have been cloned. The avirulence genes Avr4 and Avr9 are only present in C. fulvum avirulent on Cf-4 and Cf-9 cultivars, respectively. The expression of these two genes is, like the expression of the ecp genes, highly induced when the fungus grows in planta. Disruption of the Avr9 gene in wild type avirulent races leads to virulence on tomato genotypes carrying the complementary resistance gene Cf-9. A single base-pair change in the avirulence gene Avr4 leads to virulence on tomato genotypes carrying the Cf-4 resistance gene. Isolation, characterization and possible function of ECP1, ECP2, AVR4, and AVR9 will be discussed.     

Evaluating evaporation from field crops using airborne radiometry and ground-based meteorological data

Summary Airborne measurements of reflected solar and emitted thermal radiation were combined with ground-based measurements of incoming solar radiation, air temperature, windspeed, and vapor pressure to calculate instantaneous evaporation (LE) rates using a form of the Penman equation. Estimates of evaporation over cotton, wheat, and alfalfa fields were obtained on 5 days during a one-year period. A Bowen ratio apparatus, employed simultaneously, provided ground-based measurements of evaporation. Comparison of the airborne and ground techniques showed good agreement, with the greatest difference being about 12% for the instantaneous values. Estimates of daily (24 h) evaporation were made from the instantaneous data. On three of the five days, the difference between the two techniques was less than 8%, with the greatest difference being 25%. The results demonstrate that airborne remote sensing techniques can be used to obtain spatially distributed values of evaporation over agricultural fields.     

Treatment of cereal products with a tailored preparation of trichoderma enzymes increases the amount of soluble dietary fiber

Nutritionists recommend increasing the intake of soluble dietary fiber (SDF), which is very low in most cereal-based products. Conversion of insoluble DF (IDF) into SDF can be achieved by chemical treatments, but this affects the sensorial properties of the products. In this study, the possibility of getting a substantial increase of SDF from cereal products using a tailored preparation of Trichoderma enzymes is reported. Enzymes were produced cultivating Trichoderma using durum wheat fiber (DWF) and barley spent grain (BSG) as unique carbon sources. Many Trichoderma strains were screened, and the hydrolysis conditions able to increase by enzymatic treatment the amount of SDF in DWF and BSG were determined. Results demonstrate in both products that it is possible to triple the amount of SDF without a marked decrease of total DF. The enzymatic treatment also causes the release of hydroxycinnamic acids, mainly ferulic acid, that are linked to the polysaccharides chains. This increases the free phenolic concentration, the water-soluble antioxidant activity, and, in turn, the phenol compounds bioavailability.     

Bioactive constituent production in St. John's Wort in vitro hairy roots. Regenerated plant lines

A wild strain of Agrobacterium rhizogenes was used to regenerate twelve in vitro plant lines from different hairy roots of H. perforatum (St. John's Wort). The production of the main bioactive constituents was observed even though their yields varied in the different plant lines. Two lines were selected for the hyperoside production (4.9-4.6 mg/gdw) while nine were characterized by significant yields of chlorogenic acid (ranged from 0.47 to 1.09 mg/gdw). Furthermore, one out of twelve lines showed a 10-fold higher hypericin content (0.25 mg/gdw) than that reported for the in vitro shoots in the literature. Morphological and phytochemical features were determined in order to select H. perforatum genotypes enriched in valuable bioactive compounds.     

Novel application of square-wave adsorptive-stripping voltammetry for the determination of xanthohumol in spent hops

This paper reports the development of a novel electrochemical assay for xanthohumol (XN) by square-wave adsorptive-stripping voltammetry (SWAdSV) with a hanging mercury drop electrode. The method showed good repeatability (CV < 2%) and linearity (between 10 and 250 μg L(-1)), as well as suitable limits of detection (2.6 μg L(-1)) and quantification (8.8 μg L(-1)). The method was applied for the quantification of this compound in spent hops, and the results obtained were compared with the HPLC-UV method. XN contents determined by the SWAdSV method were 16 ± 1 and 100 ± 4 μg L(-1) for aqueous and methanolic extracts, respectively. The developed new methodology considerably reduces the analysis time, approximately from 25 min (HPLC-UV method) to 7 min, enabling a high sample throughput. In addition, the detection and quantification limits were approximately 5-fold lower than those obtained with the chromatographic method.     

Characterization of flavonols in cranberry (Vaccinium macrocarpon) powder

Flavonoids were extracted from cranberry powder with acetone and ethyl acetate and subsequently fractionated with Sephadex LH-20 column chromatography. The fraction eluted with a 60% methanol solution was composed primarily of phenolic constituents with maximum absorbance at 340 nm. A high-performance liquid chromatography procedure was developed, which resolved 22 distinct peaks with UV/vis and mass spectra corresponding to flavonol glycoside conjugates. Six new constituents not previously reported in cranberry or in cranberry products were determined through NMR spectroscopy to be myricetin-3-beta-xylopyranoside, quercetin-3-beta-glucoside, quercetin-3-alpha-arabinopyranoside, 3'-methoxyquercetin-3-alpha-xylopyranoside, quercetin-3-O-(6' '-p-coumaroyl)-beta-galactoside, and quercetin-3-O-(6' '-benzoyl)-beta-galactoside. Quercetin-3-O-(6' '-p-coumaroyl)-beta-galactoside and quercetin-3-O-(6' '-benzoyl)-beta-galactoside represent a new class of cranberry flavonol compounds with three conjugated components consisting of a flavonol, sugar, and carboxylic acid (benzoic or hydroxycinnamic acids). This is also the first report identifying quercetin-3-arabinoside in both furanose and pyranose forms in cranberry. Elucidation of specific flavonol glycosides in cranberry is significant since the specificity of the sugar moiety may play a role in the bioavailability of the flavonol glycosides in vivo.     

In vitro bioaccessibility of soil-bound polycyclic aromatic hydrocarbons in successive digestive compartments in cows

Ruminants, which have a central place in the food chain, ingest soil that may contain pollutants. The bioaccessibility of three different polycyclic aromatic hydrocarbon compounds from soil was studied using an in vitro model based on the digestive tract of cows. For this purpose, pasture soil was spiked with (14)C radio-labeled compounds, aged, and then exposed to conditions which simulated the digestive compartments of the rumen, abomasum, and intestines. Our results show that aging generally reduced the bioaccessibility of all the compounds tested. Total bioaccessibilty in the first digestive compartment, i.e., the rumen, depended on the considered compound: elevated for phenanthrene (17-24%), moderate for pyrene (6.6-8.1%), and low for benzo[ a]pyrene (2.3-3.6%). Bioaccessibility was very low in abomasal acidity (generally <2%) and intestinal colloids (<8%). The liquid phases of intestinal medium successfully extracted compounds from freshly contaminated soil (25-28%), but the bioaccessibilty dropped markedly after aging (17% for phenanthrene and <9% for the more lipophylic compounds). Total bioaccessibilty in this in vitro model ranged from 11% for benzo[ a]pyrene in aged soil to 58% for phenanthrene in freshly contaminated soil, and the bioaccessibility of this latter compound was always higher compared to pyrene or benzo[ a]pyrene. Residual soil contained around half of the initial load, the highest residual levels being of benzo[ a]pyrene, which confirms the observed bioaccessibility.     

Lupine induced "crooked calf disease" in Washington and Oregon: identification of the alkaloid profiles in Lupinus sulfureus, Lupinus leucophyllus, and Lupinus sericeus

Several lupines (Lupinus spp.) present on western U.S. rangelands contain alkaloids that are teratogenic to livestock and cause congenital birth defects in calves (crooked calf disease). Periodically, large losses of calves due to lupine-induced "crooked calf disease" occur in northern Oregon and eastern Washington state. Five lupine populations from this area representing three species (L. leucophyllus, L. sulfureus, and L. sericeus) were evaluated taxonomically and by gas chromatography/mass spectrometry, and the major alkaloids in each lupine species were identified. The teratogenic alkaloid anagyrine was present in both of the lupine species responsible for the high outbreaks in east-central Washington and northeastern Oregon. However, the alkaloid profiles of the two lupines identified as L. leucophyllus were dissimilar, as were the alkaloid profiles of the two lupines identified as L. sulfureus. Botanical classification is not sufficient to determine potential teratogenicity, and it must be followed by chemical characterization to determine risk to livestock.