Effectiveness of Chemical and Thermal Treatments on Control Rhizopus stolonifer Fruit Infection Comparing Tomato Cultivars with Different Sensitivities to Cracking

Tomatoes are among the most important horticultural crops; however, it is estimated that 30% of tomato yield is lost due to postharvest rot due to Rhizopus stolonifer, a fungus which requires lesions to initiate the infectious process. Tomato fruit cracking is a physiopathy which causes significant economic losses, since cracking is the door used by the fungus. In this experiment, 14 cultivars of tomato of different types were used. Fruit sampling was carried out in the middle of the crop cycle, coinciding with the peak of yield; then, the fruits were divided into two groups: one group was inoculated with Rhizopus in order to assess the effectiveness of washing, whilst the other was treated with sterile water. The fruits of each group were divided into lots to be treated with six washing treatments: dipping in hot water at 20, 40 and 60 °C for 20 s; the fruits were then sprayed with the following solutions: 0.6% of Hydrogen Peroxide 23% + Peracetic acid 15%; commercial bleach at 0.5% and 2% of Hydrogen Peroxide 50%. The control sample was not washed. The results show that there was an influence of cultivar on fruit cracking, which was strongly related with Rhizopus infection. Three cultivars were not susceptible to cracking, and therefore, were not sensitive to Rhizopus infection. The effectiveness of different washing treatments of tomato fruits depends on several factors; nonetheless, hot water treatment has been shown to be more effective than the use of chemical products such as commercial bleach or hydrogen peroxide. Another factor, the susceptibility of cultivars to cracking, determines the effectiveness of the washing treatment. The results provide an important basis for making decisions about the washing management of tomato fruits in packaging houses

Analysis of a suppressive subtractive hybridization library of Alternaria alternata resistant to 2-propenyl isothiocyanate

AbstractBackgroundIsothiocyanates (ITCs) are natural products obtained from plants of the Brassicas family. They represent an environmentally friendly alternative for the control of phytopathogenic fungi. However, as it has been observed with synthetic fungicides, the possibility of inducing ITC-resistant strains is a major concern. It is, therefore, essential to understanding the molecular mechanisms of fungal resistance to ITCs. We analyzed a subtractive library containing 180 clones of an Alternaria alternata strain resistant to 2-propenyl ITC (2-pITC). After their sequencing, 141 expressed sequence tags (ESTs) were identified using the BlastX algorithm. The sequence assembly was carried out using CAP3 software; the functional annotation and metabolic pathways identification were performed using the Blast2GO program.ResultsThe bioinformatics analysis revealed 124 reads with similarities to proteins involved in transcriptional control, defense and stress pathways, cell wall integrity maintenance, detoxification, organization and cytoskeleton destabilization; exocytosis, transport, DNA damage control, ribosome maintenance, and RNA processing. In addition, transcripts corresponding to enzymes as oxidoreductases, transferases, hydrolases, lyases, and ligases, were detected. Degradation pathways for styrene, aminobenzoate, and toluene were induced, as well as the biosynthesis of phenylpropanoid and several types of N-glycan.ConclusionsThe fungal response showed that natural compounds could induce tolerance/resistance mechanisms in organisms in the same manner as synthetic chemical products. The response of A. alternata to the toxicity of 2-pITC is a sophisticated phenomenon including the induction of signaling cascades targeting a broad set of cellular processes. Whole-transcriptome approaches are needed to elucidate completely the fungal response to 2-pITC

Efectos de cadmio en compuestos fenolicos totales y flavonoides de Euglena gracilis

In the present study the production of phenolic acids and flavonoid compounds by E. gracilis exposed to two cadmium concentrations (0.02 and 0.14 mM) was evaluated using high-performance liquid chromatography (HPLC). The results showed that E. gracilis exposed to 0.02 mM Cd+2 increased significantly the total content of phenolic compounds (798.46 ± 12.61 ?g GA/g) and total flavonoids (241.34 ± 47.63 ?g QE/g) with respect to the control (137.34 ± 19.80 ?g QE/g DW and 549.00 ± 8.57 ?g GA/g DW, respectively). However, no significant increase in the total content of phenolic compounds (568.54 ± 17.42 ?g GA/g DW) and total flavonoids (141.11 ± 9.36 ?g QE/g DW) were observed in E. gracilis exposed to 0.14 mM Cd+2. Further research is necessary to determine the specific role of flavonoids in E. gracilis exposed to high concentrations of Cd+2.En el presente estudio la producción de compuestos fenolicos y flavonoides producidos por E. gracilis expuesto a dos concentraciones de cadmio fue evaluado usando cromatografía liquida de alta precisión (HPLC). Los resultados mostraron que 0.02 mM de Cd+2 incrementaba significativamente el contenido total de compuestos fenolicos (798.46 ± 12.61 ?g GA/g) y flavonoides (241.34 ± 47.63 ?g QE/g) con respecto al control (137.34 ± 19.80 ?g QE/g DW y 549.00 ± 8.57 ?g GA/g DW) respectivamente. Sin embargo, incrementos no significativos en el contenido de compuestos fenolicos (568.54 ± 17.42 ?g GA/g DW) y flavonoides totales (141.11 ± 9.36 ?g QE/g DW) fueron observados en E. gracilis expuestas a 0.14 mM de Cd+2. Futuros estudios son necesarios para determinar la función especifica de los flavonoides en E. gracilis expuesto a altas concentraciones de Cd+2

Cambios en la calidad de turiones de espárrago verde irradiados con UV-C

El espárrago es una hortaliza importante por su valor comercial. Es un producto altamente perecedero, debido a que en el ápice presenta una actividad metabólica alta. Para extender su vida postcosecha, existen tecnologías como la refrigeración y atmósferas controladas y modificadas con resultados inconsistentes. Por otro lado, la radiación UV-C se ha empleado en papa, rábano y zanahoria para disminuir la brotación y mantener su calidad postcosecha. El objetivo del presente trabajo fue evaluar el efecto de la radiación UV-C sobre la calidad postcosecha en turiones de espárrago cv. Brock. Se irradiaron turiones con UV-C sobre el meristemo apical durante 5 y 10 min y se incluyó un testigo. Posteriormente, los espárragos se almacenaron a 2 y 5°C a 90% HR por 20 días. Se evaluó cada 4 días la curvatura del turión (°), crecimiento (mm), apariencia (brotación de yemas), color (L*, °Hue y croma), acidez titulable (AT, % de ácido cítrico), pH, y contenido de sólidos solubles totales (SST). El color, AT, pH y SST se determinaron en las zonas basal y apical. La radiación UVC no tuvo un efecto significativo en el curveado, crecimiento, ángulo Hue°, AT y pH de los turiones después de 20 días de almacenamiento. Por otro lado, los tratamientos con UV-C (5 y 10 min) mostraron valores de L* (brillo) y croma más bajos con respecto al control en ambas zonas. Los SST fueron mayores en la parte apical que en la basal y disminuyeron con el tiempo, sin efecto significativo. Hubo mayor brotación de las yemas laterales en el testigo que en los tratados. Se concluyó que la radiación UV-C aplicada al meristemo apical del turión no presentó efectos importantes en todas las variables a excepción de L* del espárrago en ambas zonas, además de disminuir la brotación de yemas laterales

Analysis of a suppressive subtractive hybridization library of Alternaria alternata resistant to 2-propenyl isothiocyanate

Background: Isothiocyanates (ITCs) are natural products obtained from plants of the Brassicas family. They represent an environmentally friendly alternative for the control of phytopathogenic fungi. However, as it has been observed with synthetic fungicides, the possibility of inducing ITC-resistant strains is a major concern. It is, therefore, essential to understanding the molecular mechanisms of fungal resistance to ITCs. We analyzed a subtractive library containing 180 clones of an Alternaria alternata strain resistant to 2-propenyl ITC (2-pITC). After their sequencing, 141 expressed sequence tags (ESTs) were identified using the BlastX algorithm. The sequence assembly was carried out using CAP3 software; the functional annotation and metabolic pathways identification were performed using the Blast2GO program. Results: The bioinformatics analysis revealed 124 reads with similarities to proteins involved in transcriptional control, defense and stress pathways, cell wall integrity maintenance, detoxification, organization and cytoskeleton destabilization; exocytosis, transport, DNA damage control, ribosome maintenance, and RNA processing. In addition, transcripts corresponding to enzymes as oxidoreductases, transferases, hydrolases, lyases, and ligases, were detected. Degradation pathways for styrene, aminobenzoate, and toluene were induced, as well as the biosynthesis of phenylpropanoid and several types of N-glycan. Conclusions: The fungal response showed that natural compounds could induce tolerance/resistancemechanisms in organisms in the same manner as synthetic chemical products. The response of A. alternata to the toxicity of 2-pITC is a sophisticated phenomenon including the induction of signaling cascades targeting a broad set of cellular processes. Whole-transcriptome approaches are needed to elucidate completely the fungal response to 2-pITC

Insecticidal and repellent effect of extracts of Pluchea sericea (Nutt.) on adults of Bemisia tabaci (Genn.)

Para el control de Bemisia tabaci (Genn.) en los cultivos agrícolas se usan repetidas aplicaciones de insecticidas, lo que ha provocado problemas de resistencia y contaminación ambiental. Los insumos provenientes de especies vegetales son una alternativa para reducir esta problemática. Las plantas son una fuente de químicos bioactivos, que pueden tener efecto insecticida, repelente, atrayente, antialimenticio o regulador de crecimiento. El objetivo fue determinar la actividad insecticida y repelente de extractos etanólicos, acetónicos y acuosos, tanto de hojas como de tallos de Pluchea sericea (Nutt.) sobre Bemisia tabaci (Genn.). Se estimó la CL50 de cada uno de los extractos, mediante bioensayos con la técnica de película residual, sobre adultos de mosquita blanca. Además, se evaluó el efecto repelente a partir de la CL50 de cada extracto, se estimó el índice de repelencia (IR), si IR = 1 el efecto es neutro, IR 1, el efecto es atrayente. Los extractos de hoja-etanol, hoja-agua y hoja-acetona presentaron valores menores de CL50 700, 1,190 y 1,250 ppm respectivamente, lo que indica alta eficiencia sobre B. tabaci, seguidos del extracto tallo-agua, por último los extractos tallo-etanol y tallo-acetona presentaron menor efectividad. Todos los extractos tuvieron acción repelente, independientemente del disolvente y órgano de la planta a 24 y 48 h. Sin embargo, los extractos a base de agua podrían tener mayor potencial para el control de la mosquita blanca en sistemas de manejo integrado de plagas, debido a que presentaron efecto insecticida y repelente, además el disolvente es inocuo y de bajo costo

Compuestos fenólicos y capacidad antioxidante presentes en tres variedades de berenjena cultivadas en el valle de Mexicali, Baja California

In the present study our evaluated the quality biochemistry of three varieties of eggplant (Versatil, Barcelona and Esculentum) with the potential to be grown in a greenhouse in the Mexicali Valley. Since ripe fruit respectively, was determined the content of total phenolic compounds and antioxidant capacity. The results showed that the variety Esculentum showed higher antioxidant activity (23.43 mg/ml of extract) but not of total phenolic compounds where the Versatile was the one that showed the greatest levels of these compounds (8.13 mg/mg fresh weight). Which indicates that the antioxidant activity could be influenced by the presence of other bioactive compounds. However, the presence of bioactive compounds in fruits of eggplant could be a quality parameter, which could help to increase their cultivation and production in the Mexicali Valley. Future studies should be directed to the identification of other bioactive compounds that could contribute to the antioxidant activity of eggplant varieties evaluated and its impact on consumer health.En el presente trabajo se evaluó la calidad bioquímica de tres variedades de berenjena (Versátil, Barcelona y Esculentum) con potencial de ser cultivadas en condiciones de invernadero en el valle de Mexicali. A partir de frutos maduros se determinó el contenido de compuestos fenólicos totales y capacidad antioxidante. Los resultados mostraron que la variedad Esculentum fue la que presentó mayor contenido de actividad antioxidante (23,43 μg/mL de extracto) no así de compuestos fenólicos totales en donde la variedad Versátil (8,13 μg/mg de peso fresco) fue la que mostró los mayores niveles de estos compuestos. Lo que nos indica que la actividad antioxidante podría estar influenciada por la presencia de otros compuestos bioactivos. No obstante, la presencia de compuestos bioactivos en frutos de berenjena representa un parámetro de calidad, lo que podría ser útil para incrementar su cultivo y valor de producción en el valle de Mexicali. Futuros estudios deben ser encaminados para la determinación de otros compuestos bioactivos que podrían contribuir en la actividad antioxidante de las variedades de berenjena evaluadas y su impacto en la salud del consumidor

Arabinoxylans Release from Brewers’ Spent Grain Using Extrusion and Solid-State Fermentation with <i>Fusarium oxysporum</i> and the Antioxidant Capacity of the Extracts

Brewers’ spent grain (BSG) is the most abundant byproduct generated from the beer-brewing process. BSG is a material rich in hemicellulose, composed of arabinoxylans (AX). However, the high crosslinking of this material causes low availability of AX, for which it is necessary to apply different treatments. The objective of this research is to increase the release of arabinoxylans through solid-state fermentation with Fusarium oxysporum f. sp. lycopersici using extruded brewery spent grain. First, the BSG is subjected to two types of physical treatments: extrusion at 20% moisture, 200 rpm and 50 °C (BSGe), and blade milling (BSGm). The chemical composition is determined for each sample (BSG, BSGe and BSGm). Subsequently, the solid-state fermentation process (SSF) is carried out on each sample. The fermentation kinetics at 30 °C are monitored for 7 days. Once the SSF concludes, AX are extracted, and the purity of AX is determined by the phloroglucinol colorimetric assay. Finally, the total phenolic compounds, phenolic acids and antioxidant capacity by DPPH are quantified. No significant differences (p ≥ 0.05) in the protein, lipid, ash or total dietary fiber contents are found among the samples. No significant difference (p ≥ 0.05) in the content of soluble fiber is found, although BSGe and BSGm have higher values than BSG. On the other hand, the yields of soluble AX exhibit significant differences (p ≤ 0.05) among nonfermented samples (BSG, 0.03%; BSGm, 0.53%; BSGe, 0.70%) and with SSF (BSG, 2.95%; BSGm, 6.24%; and BSGe, 9.58%). In addition, the contents of free phenolic compounds and free phenolic acids and the percent inhibition of free extracts by 2,2-diphenyl-1-picrylhydrazyl (DPPH) differ significantly (p ≤ 0.05) between samples subjected to SSF and nonfermented samples. Therefore, extrusion and SSF treatment increase AX release from BSG as well as the antioxidant capacity of the extracts

Composition, Physicochemical Features, and Covalent Gelling Properties of Ferulated Pectin Extracted from Three Sugar Beet (Beta vulgaris L.) Cultivars Grown under Desertic Conditions

Sugar beet is a potential source of pectin, competitive with traditional sources, that has recently acquired great relevance for its interesting covalent gelling and applications in food and biomedical industries. Pectins from three Sugar beet (Beta vulgaris L.) commercial cultivars (Cadet, Coronado large, and SV MEI) were grown under irrigated desertic conditions and the influence of cultivar, on pectin yield, composition, physicochemical and gelling characteristics was investigated. The composition and chemical properties of pectin from the three cultivars were in general, statistically different, especially in the Syngenta Cadet cultivar, presenting higher protein (10.3%), neutral sugars (21.6%), galacturonic acid (55%) and ferulic acid (5.5 mg/g) content, which are important parameters for gel formation. All pectins gelled via oxidative coupling and the main ferulic acid dimers found were 8-5&prime; and 8-O-4&prime;. Pectin from Cadet cultivar formed gels with higher hardness (6.65 N) and adhesiveness (12.2 N) values than the other two varieties. The results indicate that pectin composition is affected by the sugar beet cultivars reported herein, especially in ferulic acid content, which confer the covalent gelling capability. Sugar beet cultivars grown under desert conditions could be a source of gelling ferulated pectins for the food industry, as valuable as those obtained in temperate conditions

Toward Understanding the Molecular Recognition of Fungal Chitin and Activation of the Plant Defense Mechanism in Horticultural Crops

Large volumes of fruit and vegetable production are lost during postharvest handling due to attacks by necrotrophic fungi. One of the promising alternatives proposed for the control of postharvest diseases is the induction of natural defense responses, which can be activated by recognizing molecules present in pathogens, such as chitin. Chitin is one of the most important components of the fungal cell wall and is recognized through plant membrane receptors. These receptors belong to the receptor-like kinase (RLK) family, which possesses a transmembrane domain and/or receptor-like protein (RLP) that requires binding to another RLK receptor to recognize chitin. In addition, these receptors have extracellular LysM motifs that participate in the perception of chitin oligosaccharides. These receptors have been widely studied in Arabidopsis thaliana (A. thaliana) and Oryza sativa (O. sativa); however, it is not clear how the molecular recognition and plant defense mechanisms of chitin oligosaccharides occur in other plant species or fruits. This review includes recent findings on the molecular recognition of chitin oligosaccharides and how they activate defense mechanisms in plants. In addition, we highlight some of the current advances in chitin perception in horticultural crops