Inoculum sources and Preservation in Soils of Phytophthora parasitica from Cherry Tomato in Continental Crop Areas in Southeast Spain

Inoculum sources and Preservation in Soils of Phytophthora parasitica from Cherry Tomato in Continental Crop Areas in Southeast Spain

Liberibacters associated with orange jasmine in Brazil: incidence in urban areas and relatedness to citrus liberibacters

Two surveys (2005/2006 and 2009) were conducted in the state of Sao Paulo, Brazil, to investigate the incidence of `Candidatus Liberibacter asiaticus` and `Ca. L. americanus`, two liberibacters associated with citrus huanglongbing (HLB) disease and both transmitted by Diaphorina citri, in orange jasmine (Murraya exotica), a widespread ornamental tree in cities and villages. The graft-transmissibility of the two species, and their DNA relatedness to citrus-associated liberibacters, were also investigated. Quantitative PCR was applied to PCR-positive orange jasmine and HLB-positive citrus growing in backyards and orchards to assess their inoculum source potentials. Liberibacters were detected in 91 of 786 sampled orange jasmine plants in 10 of 76 sampled locations. PCR-positive trees exhibited yellow shoots and/or dieback symptoms indistinguishable from those on PCR-negative trees. `Candidatus Liberibacter americanus` was more common in 2005/2006 (96 center dot 6%) and `Ca. L. asiaticus` in 2009 (84 center dot 8%). rplJ nucleotide sequences were identical within all populations of either species. Graft transmission succeeded only in homologous host combinations, including `Ca. L. americanus` (2/10) from/to orange jasmine and `Ca. L. americanus` (5/18) and `Ca. L. asiaticus` (5/9) from/to citrus. Symptoms were mild and developed less rapidly in orange jasmine than in citrus, probably as a result of lower liberibacter multiplication rates. Respective titres of `Ca. L. americanus` and `Ca. L. asiaticus` in orange jasmine averaged 4 center dot 3 and 3 center dot 0 log cells g-1 tissue, compared with 5 center dot 5 and 7 center dot 3 in citrus. The results indicate that orange jasmine does not favour liberibacter multiplication as much as citrus. However, its importance in HLB epidemics should not be underestimated as it is a preferred host of D. citri and is not under any strict tree-eradication programme or measures for insect control.

Survival of Botrytis cinerea as mycelium in rose crop debris and as sclerotia in soil

Botrytis blight caused by Botrytis cinerea is an important disease of rose (Rosa hybrida) grown in greenhouses in Brazil. As little is known regarding the disease epidemiology under greenhouse conditions, pathogen survival in crop debris and as sclerotia was evaluated. Polyethylene bags with petals, leaves, or stem sections artificially infected with B. cinerea were mixed with crop debris in rose beds, in a commercial plastic greenhouse. High percentage of plant parts with sporulation was detected until 60 days, then sporulation decreased on petals after 120 days, and sharply decreased on stems or leaves after 90 days. Sporulation on petals continued for 360 days, but was not observed on stems after 150 days or leaves after 240 days. Although the fungus survived longer on petals, stems and leaves are also important inoculum sources because high amounts of both are deposited on beds during cultivation. Survival of sclerotia produced on PDA was also quantified. Sclerotia germination was greater than 75% in the initial 210 days and 50% until 360 days. Sclerotia weight gradually declined but they remained viable for 360 days. Sclerotia were produced on the buried petals, mainly after 90 days of burial, but not on leaves or stems. Germination of these sclerotia gradually decreased after 120 days, but lasted until 360 days. Higher weight loss and lower viability were observed on sclerotia produced on petals than on sclerotia produced in vitro

Prácticas culturales para el manejo de la Sigatoka negra en bananos y plátanos

Black sigatoka (Mycosphaerella fijiensis) control consists in the continuous use of fungicide sprays and cultural practices. Cultural control reduces inoculum sources of the pathogen and favorable environmental conditions for its development, as well as it increases the vigor of the plants. In order to manage the disease it is necessary to know its behavior through the time, its relationship with the weather and the crop management. The most important cultural practice to reduce the inoculum source is the removal of the whole affected leaves or only the diseased portions of the leaves. The removed tissue is placed over the ground and the use of urea is feasible to accelerate its decomposition. An alternative practice is the "mini-composting" that consists in forming small heaps with the dead leaves and harvested plants for its quick degradation, which allows to reduce the pathogen inoculum and to incorporate nutrients and organic matters into the soil. The early pruning of the tips of the Young leaves before they show symptoms of the disease and the quick elimination of harvested plants reduce the inoculum. Also, the agronomic management of the crop helps to reduce the favorable conditions and to increase the vigor of the plants: this management considers plantation density, drainage systems, irrigation methods, control of weeds, chemical-biological fertilization, and nematode control.

Inferência filogenética revela a complexa etiologia das manchas areolada e foliar em seringueira e em outras espécies cultivadas na Amazônia

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Podridão floral dos citros: variabilidade, sobrevivência e controle do agente causal, Colletotrichum acutatum

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Biological Hydrogen production from environmental sample in tropical countries

The hydrogen gas is regarded as clean and renewable energy source, since it generates only water during combustion when used as fuel. It shows 2.75 times more energy content than any hydrocarbon and it can be converted into electrical, mechanical energy or heat. Inoculum sources have been successfully tested for hydrogen biological production in temperate climate countries as sludge treatment plants sewage, sludge treatment plant wastewater, landfill sample, among others. However, hydrogen biologic production with inoculum from environmental samples such as sediment reservoirs, especially in tropical countries like Brazil, is rarely investigated. Reservoirs and fresh water lake sediment may contain conditions for the survival of a wide variety of microorganisms which use different carbon sources mainly glucose and xylose, in the fermentation. Glucose is an easily biodegradable, present in most of the industrial effluents and can be obtained abundantly from agricultural wastes. A wide variety of wastewater resulting from agriculture, industry and pulp and paper processed from wood may contain xylose in its constitution. Such effluent contains glucose and xylose concentrations of about 2 g/L. In this sense, this work verified hydrogen biological production in anaerobic batch reactor (1L), at 37 ° C, initial pH 5.5, headspace with N2 (100%), Del Nery medium, vitamins and peptone (1 g/L), fed separately with glucose (2g/L) and xylose (2 g/L). The inoculum was taken from environmental sample (sediment reservoir Itupararanga - Ibiúna - SP-Brazil). It was previously purified in serial dilutions at H2 generation (10-5, 10-7, 10-10), and heat treated (90º C - 10 min) later to inhibited the H2 consumers. The maximum H2 generations obtained in both tests were observed at 552 h, as described below. At the reactors fed with glucose and xylose were observed, respectively, 9.1 and 8.6 mmol H2/L, biomass growth (0.2 and 0.2 nm); consumption of sugar concentrations 53.6% (1.1 glucose g/L) and 90.5% (1.8 xylose g/L); acetic acid generation (124.7 mg/L and 82.7 mg/L), butyric acid (134.0 mg/L and 230.4 mg/L) and there wasn’t methane generation in the reactors. Microscopic analysis of biomass in anaerobic reactors showed the predominance of Gram positive rods and rods with endospores, whose morphology is characteristic of H2-generating bacteria, in both tests. These species were selected from the natural environment. In DGGE analysis performed difference were observed between populations from inoculum and in tests. This analysis confirmed that some species of bacteria were selected which remained under the conditions imposed on the experiment. The efficiency of the pre-treatment of inoculum and the imposition of pH 5.5 inhibited methane-producing microorganisms and the consumers of H2. Therefore, the experimental conditions imposed allowed the attainment of bacterial consortium of producer H2 taken from an environmental sample with concentration of xylose and glucose similar to the ones of the industrial effluents.

Podredumbre parda del melocotonero (Monilinia spp.) : detección, identificación de especies y contribución a la epidemiología de la enfermedad

Monilinia spp. (M. laxa, M. fructigena y M. fructicola) causa marchitez en brotes y flores, chancros en ramas y podredumbre de la fruta de hueso provocando pérdidas económicas importantes en años con climatología favorable para el desarrollo de la enfermedad, particularmente en variedades tardías de melocotonero y nectarino. En estos huéspedes en España, hasta el momento, la especie predominante es M. laxa y, en menor proporción, M. fructigena. La reciente introducción en Europa de la especie de cuarentena M. fructicola hace necesaria una detección e identificación rápida de cada una de las especies. Además, hay diversos aspectos de la etiología y epidemiología de la enfermedad que no se conocen en las condiciones de cultivo españolas. En un primer objetivo de esta Tesis se ha abordado la detección e identificación de las especies de Monilinia spp. causantes de podredumbre parda. El estudio de las bases epidemiológicas para el control de la enfermedad constituye el fin del segundo objetivo. Para la detección del género Monilinia en material vegetal por PCR, diferenciándolo de otros hongos presentes en la superficie del melocotonero, se diseñaron una pareja de cebadores siguiendo un análisis del ADN ribosomal. La discriminación entre especies de Monilinia se consiguió utilizando marcadores SCAR (región amplificada de secuencia caracterizada), obtenidos después de un estudio de marcadores polimórficos de ADN amplificados al azar (RAPDs). También fue diseñado un control interno de amplificación (CI) basado en la utilización de un plásmido con secuencias de los cebadores diferenciadores del género, para ser utilizado en el protocolo de diagnóstico de la podredumbre parda con el fin de reconocer falsos negativos debidos a la inhibición de PCR por componentes celulares del material vegetal. Se disponía de un kit comercial que permitía distinguir Monilinia de otros géneros y M. fructicola del resto de especies mediante anticuerpos monoclonales utilizando la técnica DAS-ELISA. En esta Tesis se probaron diferentes fuentes de material como micelio ó conidias procedentes de cultivos en APD, o el micelio de la superficie de frutas o de momias frescas, como formas de antígeno. Los resultados obtenidos con ELISA se compararon con la identificación por métodos morfológico-culturales y por PCR con los cebadores desarrollados en esta Tesis. Los resultados demostraron la posibilidad de una detección temprana en frutas frescas por este método, realzando las posibilidades de una diagnosis temprana para una prevención más eficaz de M. fructicola en fruta de hueso. El estudio epidemiológico de la enfermedad comenzó con la determinación de las principales fuentes de inóculo primario y su importancia relativa en melocotoneros y nectarinos del valle del Ebro. Para ello se muestrearon 9 huertos durante los años 2003 a 2005 recogiendo todas las momias, frutos abortados, gomas, chancros, y brotes necróticos en los árboles. También se recogieron brotes aparentemente sanos y muestras de material vegetal situados en el suelo. En estas muestras se determinó la presencia de Monilinia spp. Los resultados mostraron que la fuente principal de inóculo son las momias que se quedan en los árboles en las que la supervivencia del hongo tras el invierno es muy alta. También son fuentes de inóculo las momias del suelo y los brotes necróticos. De aquí se deriva que una recomendación importante para los agricultores es que deben eliminar este material de los huertos. Un aspecto no estudiado en melocotonero o nectarino en España es la posible relación que puede darse entre la incidencia de infecciones latentes en los frutos inmaduros a lo largo del cultivo y la incidencia de podredumbre en los frutos en el momento de la recolección y en postcosecha. Esta relación se había observado previamente en otros frutales de hueso infectados con M. fructicola en diversos países del mundo. Para estudiar esta relación se realizaron ensayos en cinco huertos comerciales de melocotonero y nectarino situados en el Valle del Ebro en cuatro estados fenológicos durante los años 2000-2002. No se observaron infecciones latentes en botón rosa, dándose la máxima incidencia en precosecha, aunque en algunos huertos se daba otro pico en el endurecimiento del embrión. La especie prevaleciente fue M. laxa. Se obtuvo una correlación positiva significativa entre la incidencia de infecciones latentes y la incidencia de podredumbre en postcosecha. Se desarrolló también un modelo de predicción de las infecciones latentes en función de la temperatura (T) y el periodo de humectación (W). Este modelo indicaba que T y W explicaban el 83% de la variación en la incidencia de infecciones latentes causadas por Monilinia spp. Por debajo de 8ºC no se predecían latentes, necesitándose más de 22h de W para predecir la ocurrencia de latentes con T = 8ºC, mientras que solo se necesitaban 5h de W a 25ºC. Se hicieron también ensayos en condiciones controladas para determinar la relación entre la incidencia de las infecciones latentes, las condiciones ambientales (T y W), la concentración de inóculo del patógeno (I) y el estado de desarrollo del huésped (S) y para validar el modelo de predicción desarrollado con los experimentos de campo. Estos ensayos se llevaron cabo con flores y frutos de nectarino procedentes de un huerto comercial en seis estados fenológicos en los años 2004 y 2005, demostrándose que la incidencia de podredumbre en postcosecha y de infecciones latentes estaba afectada por T, W, I y S. En los frutos se producían infecciones latentes cuando la T no era adecuada para el desarrollo de podredumbre. Una vez desarrollado el embrión eran necesarias más de 4-5h de W al día y un inóculo superior a 104 conidias ml-1 para que se desarrollase o podredumbre o infección latente. La ecuación del modelo obtenido con los datos de campo era capaz de predecir los datos observados en estos experimentos. Para evaluar el efecto del inóculo de Monilinia spp. en la incidencia de infecciones latentes y de podredumbre de frutos en postcosecha se hicieron 11 experimentos en huertos comerciales de melocotonero y nectarino del Valle del Ebro durante 2002 a 2005. Se observó una correlación positiva entre los números de conidias de Monilinia spp. en la superficie de los frutos y la incidencia de infecciones latentes De los estudios anteriores se deducen otras dos recomendaciones importantes para los agricultores: las estrategias de control deben tener en cuenta las infecciones latentes y estimar el riesgo potencial de las mismas basándose en la T y W. Deben tener también en cuenta la concentración de esporas de Monilinia spp. en la superficie de los frutos para disminuir el riesgo de podredumbre parda. El conocimiento de la estructura poblacional de los patógenos sienta las bases para establecer métodos más eficaces de manejo de las enfermedades. Por ello en esta Tesis se ha estudiado el grado de diversidad genética entre distintas poblaciones de M. laxa en diferentes localidades españolas utilizando 144 marcadores RAPDs (59 polimórficos y 85 monomórficos) y 21 aislados. El análisis de la estructura de la población reveló que la diversidad genética dentro de las subpoblaciones (huertos) (HS) representaba el 97% de la diversidad genética (HT), mientras que la diversidad genética entre subpoblaciones (DST) sólo representaba un 3% del total de esta diversidad. La magnitud relativa de la diferenciación génica entre subpoblaciones (GST) alcanzaba 0,032 y el número estimado de migrantes por generación (Nm) fue de 15,1. Los resultados obtenidos en los dendrogramas estaban de acuerdo con el análisis de diversidad génica. Las agrupaciones obtenidas eran independientes del huerto de procedencia, año o huésped. En la Tesis se discute la importancia relativa de las diferentes fuentes evolutivas en las poblaciones de M. laxa. Finalmente se realizó un muestreo en distintos huertos de melocotonero y nectarino del Valle del Ebro para determinar la existencia o no de aislados resistentes a los fungicidas del grupo de los benzimidazoles y las dicarboximidas, fungicidas utilizados habitualmente para el control de la podredumbre parda y con alto riesgo de desarrollar resistencia en las poblaciones patógenas. El análisis de 114 aislados de M. laxa con los fungicidas Benomilo (bencimidazol) (1Bg m.a ml-1), e Iprodiona (dicarboximida) (5Bg m.a ml-1), mostró que ninguno era resistente en las dosis ensayadas. Monilinia spp. (M. laxa, M. fructigena and M. fructicola) cause bud and flower wilt, canker in branches and stone fruit rot giving rise important economic losses in years with appropriate environmental conditions, it is particularly important in late varieties of peach and nectarine. Right now, M. laxa is the major species for peach and nectarine in Spain followed by M. fructigena, in a smaller proportion. The recent introduction of the quarantine organism M. fructicola in Europe makes detection and identification of each one of the species necessary. In addition, there are different aspects of disease etiology and epidemiology that are not well known in Spain conditions. The first goal of this Thesis was the detection and identification of Monilinia spp. causing brown rot. Study of the epidemiology basis for disease control was the second objective. A pair of primers for PCR detection was designed based on the ribosomal DNA sequence in order to detect Monilinia spp. in plant material and to discriminate it from other fungi colonizing peach tree surface. Discrimination among Monilinia spp. was successful by SCAR markers (Sequence Characterized Amplified Region), obtained after a random amplified polymorphic DNA markers (RAPDs) study. An internal control for the PCR (CI) based on the use of a mimic plasmid designed on the primers specific for Monilinia was constructed to be used in diagnosis protocol for brown rot in order to avoid false negatives due to the inhibition of PCR as consequence of remained plant material. A commercial kit based on DAS-ELISA and monoclonals antibodies was successfully tested to distinguish Monilinia from other fungus genera and M. fructicola from other Monilinia species. Different materials such as micelium or conidias from APD cultures, or micelium from fresh fruit surfaces or mummies were tested in this Thesis, as antigens. Results obtained by ELISA were compared to classical identification by morphologic methods and PCR with the primers developed in this Thesis. Results demonstrated the possibility of an early detection in fresh fruits by this method for a more effective prevention of M. fructicola in stone fruit. The epidemiology study of the disease started with the determination of the main sources of primary inoculum and its relative importance in peach trees and nectarines in the Ebro valley. Nine orchards were evaluated during years 2003 to 2005 collecting all mummies, aborted fruits, rubbers, cankers, and necrotic buds from the trees. Apparently healthy buds and plant material located in the ground were also collected. In these samples presence of Monilinia spp. was determined. Results showed that the main inoculum sources are mummies that stay in the trees and where fungus survival after the winter is very high. Mummies on the ground and the necrotics buds are also sources of inoculum. As consequence of this an important recommendation for the growers is the removal of this material of the orchards. An important issue not well studied in peach or nectarine in Spain is the possible relationship between the incidence of latent infections in the immature fruits and the incidence of fruit rot at harvesting and postharvesting. This relationship had been previously shown in other stone fruit trees infected with M. fructicola in different countries over the world. In order to study this relationship experiments were run in five commercial peach and nectarine orchards located in the Ebro Valley in four phenologic states from 2000 to 2002. Latent infections were not observed in pink button, the maxima incidence arise in preharvest, although in some orchards another increase occurred in the embryo hardening. The most prevalence species was M. laxa. A significant positive correlation between the incidence of latent infections and the incidence of rot in postharvest was obtained. A prediction model of the latent infections based on the temperature (T) and the wetness duration (W) was also developed. This model showed that T and W explained 83% of the variation in latent infection incidence caused by Monilinia spp. Below 8ºC latent infection was not predicted, more than 22h of W with T = 8ºC were needed to predict latent infection occurrence of, whereas at 25ºC just 5h of W were enough. Tests under controlled conditions were also made to determine the relationship among latent infections incidence, environmental conditions (T and W), inoculum concentration of the pathogen (I) and development state of the host (S) to validate the prediction model developed on the field experiments. These tests were made with flowers and fruits of nectarine coming from a commercial orchard, in six phenologic states in 2004 and 2005, showing that incidence of rot in postharvest and latent infections were affected by T, W, I and S. In fruits latent infections took place when the T was not suitable for rot development. Once developed the embryo, more than 4-5h of W per day and higher inoculums (104 conidia ml-1) were necessary for rot or latent infection development. The equation of the model obtained with the field data was able to predict the data observed in these experiments. In order to evaluate the effect of inoculum of Monilinia spp. in the incidence of latent infections and of rot of fruits in postharvest, 11 experiments in commercial orchards of peach and nectarine of the Ebro Valley were performed from 2002 to 2005. A positive correlation between the conidial numbers of Monilinia spp. in the surface of the fruits and the incidence of latent infections was observed. Based on those studies other two important recommendations for the agriculturists are deduced: control strategies must consider the latent infections and potential risk based on the T and W. Spores concentration of Monilinia spp. in the surface of fruits must be also taken in concern to reduce the brown rot risk. The knowledge of the population structure of the pathogens determines the bases to establish more effective methods of diseases handling. For that reason in this Thesis the degree of genetic diversity among different M. laxa populations has been studied in different Spanish locations using 144 RAPDs markers (59 polymorphic and 85 monomorphics) on 21 fungal isolates. The analysis of the structure of the population revealed that the genetic diversity within the subpopulations (orchards) (HS) represented 97% of the genetic diversity (HT), whereas the genetic diversity between subpopulations (DST) only represented a 3% of the total of this diversity. The relative magnitude of the genic differentiation between subpopulations (GST) reached 0.032 and the considered number of migrantes by generation (Nm) was of 15.1. The results obtained in dendrograms were in agreement with the analysis of genic diversity. The obtained groupings were independent of the orchard of origin, year or host. In the Thesis the relative importance of the different evolutionary sources in the populations from M. laxa is discussed. Finally a sampling of resistant isolates in different orchards from peach and nectarine of Ebro Valley was made to determine the existence of fungicide resistance of the group of benzimidazoles and the dicarboximidas, fungicides used habitually for the control of rot brown and with high risk of resistance developing in the pathogenic populations. The analysis of 114 isolated ones of M. laxa with the fungicides Benomilo (bencimidazol) (1Bg m.a ml-1), and Iprodiona (dicarboximida) (5Bg m.a ml-1), showed no resistant in the doses evaluated.

Prácticas culturales para el manejo de la Sigatoka negra en bananos y plátanos

Black sigatoka (Mycosphaerella fijiensis) control consists in the continuous use of fungicide sprays and cultural practices. Cultural control reduces inoculum sources of the pathogen and favorable environmental conditions for its development, as well as it increases the vigor of the plants. In order to manage the disease it is necessary to know its behavior through the time, its relationship with the weather and the crop management. The most important cultural practice to reduce the inoculum source is the removal of the whole affected leaves or only the diseased portions of the leaves. The removed tissue is placed over the ground and the use of urea is feasible to accelerate its decomposition. An alternative practice is the "mini-composting" that consists in forming small heaps with the dead leaves and harvested plants for its quick degradation, which allows to reduce the pathogen inoculum and to incorporate nutrients and organic matters into the soil. The early pruning of the tips of the Young leaves before they show symptoms of the disease and the quick elimination of harvested plants reduce the inoculum. Also, the agronomic management of the crop helps to reduce the favorable conditions and to increase the vigor of the plants: this management considers plantation density, drainage systems, irrigation methods, control of weeds, chemical-biological fertilization, and nematode control.

Exploring the potential of novel biomixtures and Lentinula edodes fungus for the degradation of selected pesticides. Evaluation for use in biobed systems

An approach to reduce the contamination of water sourceswith pesticides is the use of biopurificaction systems. The active core of these systems is the biomixture. The composition of biomixtures depends on the availability of local agro-industrial wastes and design should be adapted to every region. In Portugal, cork processing is generally regarded as environmentally friendly and would be interesting to find applications for its industry residues. In this work the potential use of different substrates in biomixtures, as cork (CBX); cork and straw, coat pine and LECA (Light Expanded Clay Aggregates), was tested on the degradation of terbuthylazine, difenoconazole, diflufenican and pendimethalin pesticides. Bioaugmentation strategies using the white-rot fungus Lentinula edodes inoculated into the CBX, was also assessed. The results obtained from this study clearly demonstrated the relevance of using natural biosorbents as cork residues to increase the capacity of pesticide dissipation in biomixtures for establishing biobeds. Furthermore, higher degradation of all the pesticides was achieved by use of bioaugmented biomixtures. Indeed, the biomixtures inoculated with L. edodes EL1were able to mineralize the selected xenobiotics, revelling that these white-rot fungi might be a suitable fungus for being used as inoculum sources in on-farm sustainable biopurification system, in order to increase its degradation efficiency. After 120 days, maximum degradation of terbuthylazine, difenoconazole, diflufenican and pendimethalin, of bioaugmented CBX, was 89.9%, 75.0%, 65.0% and 99.4%, respectively. The dominant metabolic route of terbuthylazine in biomixtures inoculated with L. edodes EL1 proceeded mainly via hydroxylation, towards production of terbuthylazine-hydroxy-2 metabolite. Finally, sorption process to cork by pesticides proved to be a reversible process,working cork as a mitigating factor reducing the toxicity to microorganisms in the biomixture, especially in the early stages.

Influence of carbon source and inoculum type on anaerobic biomass adhesion on polyurethane foam in reactors fed with acid mine drainage

This paper analyzes the influence of carbon source and inoculum origin on the dynamics of biomass adhesion to an inert support in anaerobic reactors fed with acid mine drainage. Formic acid, lactic acid and ethanol were used as carbon sources. Two different inocula were evaluated: one taken from an UASB reactor and other from the sediment of a uranium mine. The values of average colonization rates and the maximum biomass concentration (C(max)) were inversely proportional to the number of carbon atoms in each substrate. The highest C(max) value (0.35 g TVS g(-1) foam) was observed with formic acid and anaerobic sludge as inoculum. Maximum colonization rates (v(max)) were strongly influenced by the type of inoculum when ethanol and lactic acid were used. For both carbon sources, the use of mine sediment as inoculum resulted in a v(max) of 0.013 g TVS g(-1) foam day(-1), whereas 0.024 g TVS g(-1) foam day(-1) was achieved with anaerobic sludge. (C) 2011 Elsevier Ltd. All rights reserved.

Effects of six carbohydrate sources on dog diet digestibility and post-prandial glucose and insulin response

The effects of six extruded diets with different starch sources (cassava flour, brewer`s rice, corn, sorghum, peas or lentils) on dog total tract apparent digestibility and glycemic and insulinemic response were investigated. The experiment was carried out on thirty-six dogs with six dogs per diet in a completely randomized design. The diets containing brewer`s rice and cassava flour presented the greatest digestibility of dry matter, organic matter and gross energy (p < 0.05), followed by corn and sorghum; pea and lentil diets had the lowest. Starch digestibility was greater than 98% in all diets and was greater for brewer`s rice and cassava flour than for lentils and peas diets (p < 0.05). Dogs` immediate post-prandial glucose and insulin responses (AUC <= 30 min) were greater for brewer`s rice, corn, and cassava flour diets (p < 0.05), and later meal responses (AUC >= 30 min) were greater for sorghum, lentil and pea diets (p < 0.05). Variations in diet digestibility and post-prandial response can be explained by differences in chemical composition of each starch source including fibre content and starch granule structure. The nutritional particularities of each starch ingredient can be explored through diet formulations designed to modulate glycemic response. However, more studies are required to support these.

The role of seeds and airborne inoculum in the initiation of leaf blotch (Rhynchosporium secalis) epidemics in winter barley

Both airborne spores of Rhynchosporium secalis and seed infection have been implied as major sources of primary inoculum for barley leaf blotch (scald) epidemics in fields without previous history of barley cropping. However, little is known about their relative importance in the onset of disease. Results from both quantitative real-time PCR and visual assessments indicated that seed infection was the main source of inoculum in the field trial conducted in this study. Glasshouse studies established that the pathogen can be transmitted from infected seeds into roots, shoots and leaves without causing symptoms. Plants in the field trial remained symptomless for approximately four months before symptoms were observed in the crop. Covering the crop during part of the growing season was shown to prevent pathogen growth, despite the use of infected seed, indicating that changes in the physiological condition of the plant and/or environmental conditions may trigger disease development. However, once the disease appeared in the field it quickly became uniform throughout the cropping area. Only small amounts of R. secalis DNA were measured in 24 h spore-trap tape samples using PCR. Inoculum levels equivalent to spore concentrations between 30 and 60 spores per m3 of air were only detected on three occasions during the growing season. The temporal pattern and level of detection of R. secalis DNA in spore tape samples indicated that airborne inoculum was limited and most likely represented rain-splashed conidia rather than putative ascospores.

Fermentation characteristics of several carbohydrate sources for dog diets using the in vitro gas production technique

Fermentable carbohydrates are an important part of the canine diet. They can improve gastrointestinal health by modifying gut microbial population and metabolic activity. The present study compared the fermentation characteristics and kinetic patterns of 10 carbohydrate sources using the in vitro gas production technique (IVGPT) with dog faecal inoculum. The substrates tested were: pure cellulose (PC), carboxymethylcellulose (CMC), sugar-cane fibre (SCF), beet pulp (BP), wheat bran (WB), fructooligosaccharides (FOS), inulin, yeast cell wall (YCW), ground psyllium seed (PS), pea hulls (PH). All substrates were incubated at 39°C under anaerobic conditions with faeces collected from dogs as microbial inoculum. Gas production of fermenting cultures was recorded and after 48 h, pH, shortchain fatty acids (SCFA) and organic matter disappearance (OMD) were determined. The results confirm high fermentation by dog faecal bacteria of FOS and inulin that produced high amounts of propionate and that underwent very rapid fermentation. Three substrates (SCF, CMC and PC) were not able to support bacterial growth, with low gas and SCFA production, and high BCFA formation. The PH and BP showed moderate OMD and SCFA production. Wheat bran B underwent rapid fermentation and generated a high proportion of butyrate. Psyllium seeds underwent slow fermentation with delayed gas production, supporting a high formation of SCFA, with an adequate amount of butyrate for bacterial growth while YCW, which showed a delayed fermentation, gave moderate SCFA production. The fermentation characteristics of PS and YCW suggest their potential use in promoting a more distal fermentation on intestinal tract. © Copyright S. Calabrò et al., 2013 Licensee PAGEPress, Italy.

Use of different carbon sources in cultivation of baker's yeast for production of glycerol-3-phosphate dehydrogenase

The physiological state of yeast cells changes during culture growth as a consequence of environmental changes (nutrient limitations, pH and metabolic products). Cultures that grow exponentially are heterogeneous cell populations made up of cells regulated by different metabolic and/or genetic control systems. The strain of baker's yeast selected by plating commercial compressed yeast was used for the production of glycerol-3- phosphate dehydrogenase. Glycerol-3-phosphate dehydrogenase (GPD) has been widely used in the enzyme assays with diverse compounds of industrial interest, such as glycerol or glycerol phosphate, as well as a number of important bioanalytical applications. Each cell state determines the level of key enzymes (genetic control), fluxes through metabolic pathways (metabolic control), cell morphology and size. The present study was carried out to determine the effects of environmental conditions and carbon source on GPD production from baker's yeast. Glucose, glycerol, galactose and ethanol were used as carbon sources. Glycerol and ethanol assimilations required agitation, which was dependent on the medium volume in the fermentation flask for the greatest accumulation of intracellular GPD. Enzyme synthesis was also affected by the initial pH of the medium and inoculum size. The fermentation time required for a high level of enzyme formation decreased with the inoculum size. The greatest amount of enzyme (0.45 U/ml) was obtained with an initial pH of 4.5 in the medium containing ethanol or glycerol. The final pH was maintained in YP-ethanol, but in the YP-glycerol the final pH increased to 6.9 during growth.