Resumen El cultivo de tomate genera grandes ganancias para México; sin embargo, la distribución del fruto enfrenta limitaciones debido a pérdidas postcosecha causadas por su rápido deterioro. La reducción en la firmeza del fruto se debe en parte a la degradación de la pectina localizada en la pared celular primaria. Varios frutos como fresa (Fragaria × ananassa), tomate (Solanum lycopersicum L.) y mango (Mangifera indica L.) muestran incremento en la expresión de genes que codifican para la enzima ramnogalacturonano liasa (RGL) durante la maduración. En tomate RGL es codificada por una familia de 13 multigenes, de los cuales tres están activos en fruto. Ramnogalacturonano I (RG-I) es un polisacárido que forma parte de las pectinas de la pared celular y que es degradado por la enzima RGL. En este sentido, el estudio de los cambios en expresión de genes que codifican para RGL durante el desarrollo y maduración del fruto de tomate ayudará a dilucidar la función fisiológica de esta familia de genes. El objetivo del presente estudio fue evaluar el perfil de expresión de los genes Solyc04g076630, Solyc04g076660 y Solyc11g011300 y la producción de etileno durante el desarrollo y maduración del fruto de tomate. El gen Solyc11g011300 mostró un incremento en actividad que correlacionó con el aumento en la producción de etileno del fruto, lo cual sugiere que este gen cumple una función en la pérdida de firmeza del fruto durante maduración. Los altos niveles de expression de los genes Solyc04g076630 y Solyc04g076660 registrados durante el desarrollo del fruto sugieren su participación en la re-ingeniería del polímero RG-I durante las etapas iniciales de desarrollo del fruto.

Summary Tomato cultivation generates great profits for Mexico; however, the distribution of the fruit faces limitations due to the postharvest losses caused by its rapid deterioration. The reduction in fruit firmness is due in part to the degradation of pectin located in the primary cell wall. Several fruits such as strawberry (Fragaria × ananassa), tomato (Solanum lycopersicum L.) and mango (Mangifera indica L.) show an increase in the expression of genes that code for the enzyme rhamnogalacturonan lyase (RGL) during ripening. In tomato RGL is encoded by a family of 13 multigenes, of which three are active in the fruit Rhamnogalacturonan l (RG-l) is a polysaccharide that is part of the pectins of the cell wall and is degraded by the RGL enzyme. Thus, the study of changes of RGL in the expression of genes that code for RGL during the development and ripening of tomato fruit will help to elucidate the physiological function of this family of genes. The objective of the present study was to assess the expression profile of genes Solyc04g076630, Solyc04g076660 and Solyc11g011300 and the ethylene production during the development and ripening of the tomato fruit. The Solyc11g011300 gene showed an increase in activity that correlated with the increase in ethylene production in fruits, suggesting that this gene plays a role in the loss of firmness of the fruit during ripening. The high levels of expression of genes Solyc04g076630 and Solyc04g076660 recorded during fruit development suggest their participation in the re-engineering of the RG-I polymer during the initial stages of fruit development.

ABSTRACT Winemaking waste contain a high number of bioactive compounds with antimicrobial properties that can be exploited in agriculture. In the present study, hydrolysates from three wine grape (Vitis vinifera L.) marcs were characterized and their antifungal activities against phytopathogenic fungi (Fusarium oxysporum and Alternaria spp.) were evaluated. Wine grape marcs (red, pink and white wine) collected from Ensenada, Baja California, Mexico, were subjected to an acid hydrolysis treatment. Skin hydrolysates of pink and white marcs obtained high concentrations of reducing sugars (5.8 ± 0.1 and 5.5 ± 0.2 g L-1, respectively). Meanwhile, the highest concentration of total sugars was obtained for skin hydrolysates of white marc (9.7 ± 0.08 g L-1). The seed hydrolysates of white marc obtained high concentrations of phenolic compounds (0.52 ± 0.1 mg mL-1). In addition, the highest antioxidant activity was found for skin hydrolysates of red marc (96 ± 0.61%). Results of in vitro antifungal assays clearly indicated a marked inhibition of the mycelial growth and spore viability of F. oxysporum (100% inhibition using red and white hydrolysates) rather than Alternaria spp. (58% inhibition exposed to pink hydrolysates), due to high concentration of phenols. According to HPLC analysis, phenolic acids such as gallic acid, hydroxybenzoic acid, vanillic acid and p-coumaric acid were predominant in the hydrolysates. This study demonstrated that the grape marc hydrolysates exhibit a potential antifungal activity, and highlights that the hydrolysates can be exploited in agriculture as a safe alternative of antifungal agents.

ABSTRACT The rhamnogalacturonan I (RGI) is part of pectin plant cell wall, and currently there is scarce information about the elicitor effect of its fragments in the fruit defense mechanism. In this work, the effect of the fragments of RGI on the defense mechanism in tomato (Solanum lycopersicum L.) fruits was evaluated. Three fragments of RGI released from enzymatic degradation by RG lyase were characterized according to their physical-chemical and structural characteristics. Two of RGI fragments (F-1 and F-2) were selected and applied on tomato fruits during 48 h. At different exposure times (0, 0.5, 1, 6, 24, and 48 h) tomato samples were taken, and the enzymatic activity of chitinase was assessed by fluorometry, and β-1,3-glucanase and peroxidase by spectrophotometry (UV-visible). The absorption bands determined by Fourier transform infra-red (FT-IR) spectroscopy in the RGI fragments, was different concerning RGI no fragmented. The RGI had a molecular weight of 64 kDa and an intrinsic viscosity of 40.9 mL g-1; while the molecular weight of F-1 and F-2 fragments were 20 and 16 kDa, and an average intrinsic viscosity of 27 and 26 mL g-1, respectively. The content of galacturonic acid decreased, and the neutral sugars increased concerning the time of enzymatic degradation. F-1 and F-2 fragments induced an increase in the level of β -1,3-glucanase activity in tomato fruits; however, an increase in the enzymatic activity of chitinase and peroxidase was observed after 0.5 h of exposure to F-2 fragment. It was concluded that the RGI fragments were structurally different from the RGI no fragmented and induced the natural defense mechanism of the tomato fruit.

ABSTRACT The aim of the present work is to evaluate the changes on the phenylalanine ammonia lyase (PAL) activity, phenolic compounds accumulation and photochemical efficiency in leaves of P. glandulosa treated with Cd2+ (0.001 M) and Cu2+ (0.52 M) concentrations for 96 h under hydroponic conditions. The results showed that only leaves treated with copper had a decrease in photochemical efficiency and leaf epidermal polyphenols in P. glandulosa leaves after 96 h of exposure. On the other hand the reverse-phase HPLC analysis revealed higher levels of phenolic compound (gallic, vanillic and caffeic acids) and flavonoids (rutin and kaempferol-3-O-glucosides) in plant leaves from Cu and Cd-treatments with respect to control plants. Finally, highest increments in PAL activity was observed in extracts of leaves treated with Cu and Cd (about 205 and 284%), respectively, with respect to control plants after 96 h treatment. These suggest that activation of phenylpropanoid pathway represent a source of nonenzymatic antioxidants that protect at P. glandulosa against oxidative stress when exposed to cadmium and copper. Hence future studies are necessary to elucidate the participation of phenylpropanoid pathway in the reduction of metal toxicity in Prosopis species.

ABSTRACT Alternaria alternata (Fr.) Keissl. 1912 is one of the main fungal pathogens that infect tomato (Solanum lycopersicum L.) during cold storage affecting postharvest quality and marketing. During fungal infections, fruits and fungi release specific volatile metabolites (VM) that could alter the fruit aroma, or could mediate resistance response in the fruit, or they also could suggest the possible status of fungal attack. The detection of the VM released during the tomato-Alternaria interaction could contribute to the development of ecofriendly and harmless strategies for its control. In this study, the profile of VM of fresh tomatoes inoculated with A. alternata, were analyzed by solid phase microextraction and gas chromatography-mass spectrometry (SPME-GC-MS) during storage at 15 and 20 °C for 48 h, respectively. Changes in the profile of VM were observed between control and inoculated fruit since the first few hour post-inoculation. Some VM (3-methyl-2-butenal, dimethyl disulfide, 1-butenol, hexanol, 2-methyl-1-butanol acetate, among others) were only detected in inoculated fruit, so they appear to be synthesized by the presence of the pathogen. Also, a marked increase of 3-methyl-1-butanol and 6-methyl-5-hepten-1-one were observed in inoculated fruit, and they were progressive over time particularly at 20 °C. In conclusion, A. alternata induced changes in the profile of volatile metabolites released by tomato fruit. Some of the VM released during tomato-A. alternata interaction, were synthesized or stimulated by the fungal attack. These results contribute to the current knowledge about the profile of VM released during the fruit-pathogen interaction.

The objective of the present study was to evaluate the activity of phenylalanine ammonia-lyase (PAL), peroxidase (POX) and the production of phenolic compounds and flavonoids in transgenic cotton plants in response to inoculation with Trichoderma longibrachiatum (ICA-4). Ninety days after inoculation with T. longibrachiatum, leaves of the cotton plants were collected and the enzymes PAL, POX and phenolic compounds were determined. The results showed that inoculation increased the content of phenolic compounds and flavonoids by 18% and 45%, respectively, compared to non-inoculatedplants. The activity of the enzymes peroxidase (4.88 Ux10-5/mg protein), and phenylalanine ammonia-lyase (0.0176 U/mg protein) showed significant differences compared to the enzymatic activity of uninoculated plants (3, 48x10-5 U/mg proteinfor POX and 0.01 U/mg proteinfor PAL). These results suggest the induction of a systemic resistance response induced by seed inoculation with the Trichoderma ICA-4 strain.

El objetivo del presente estudio fue evaluar la actividad de las enzimas fenilalanina amonio-liasa (PAL), peroxidasa (POX) y la producción de compuestos fenólicos y flavonoides en plantas de algodón transgénico en respuesta a la inoculación con Trichoderma longibrachiatum (ICA-4). Noventa días después de la inoculación con T. longibrachiatum, hojas de las plantas de algodón fueron colectadas y las enzimas PAL, POX y los compuestos fenólicos fueron determinados. Los resultados mostraron que la inoculación aumentó el contenido de compuestos fenólicos y flavonoides en 18% y 45%, respectivamente; comparadas con plantas no inoculadas. La actividad de las enzimas peroxidasa (4,88 Ux10-5/mg de proteína), y fenilalanina amonia-liasa (0,0176 U/mg de proteína) mostraron diferencias significativas en comparación con la actividad enzimática de plantas no inoculadas (3,48x10-5 U/mg proteína para POX y 0,01 U/mg de proteína para PAL). Estos resultados sugieren la inducción de una respuesta de resistencia sistémica inducida por la inoculación de las semillas con la cepa Trichoderma ICA-4.

Abstract Dahlias, in addition to their use as ornamental flowers, are consumed in a wide variety of foods. However, once harvested their shelf life is less than three days. The aim of this study was to evaluate the antimicrobial effect of 0.25 % cinnamaldehyde on edible dahlias held in polyethylene terephthalate (PET) and low-density polyethylene (LDPE) packages stored at 8 and 25 °C. Also, the ripening and quality of treated flowers were evaluated. The total population of yeasts and molds, mesophilic aerobic bacteria and psychrophilic bacteria increased during storage. Both packaging materials and cinnamaldehyde influenced the microbial count; however, microbial development was not totally controlled. The lowest weight loss was observed with PET, regardless of storage temperature. The lowest respiration rate was obtained in dahlias stored at 8 °C, regardless of packaging material. Ethylene production was not influenced by packaging material or storage temperature. In general, phenolic compounds and antioxidant capacity remained unchanged during storage. However, further studies are needed to improve control of pathogenic microorganisms in this commodity.

Resumen Las dalias, además de su uso como flores de ornato, se consumen en gran variedad de alimentos; no obstante, una vez que se cosechan su vida útil es menor a tres días. El objetivo de este trabajo fue evaluar el efecto antimicrobiano del cinamaldehído a 0.25 % en dalias comestibles, en empaques de tereftalato de polietileno (PET) y polietileno de baja densidad (LDPE) almacenadas en 8 y 25 °C. Además, se evaluó la maduración y calidad de las flores tratadas. La población total de hongos y levaduras, bacterias mesofílicas aerobias y bacterias psicrofílicas se incrementó durante el almacenamiento. Ambos materiales de empaque y el cinamaldehído influyeron en la cuenta microbiana; sin embargo, no se controló totalmente el desarrollo microbiano. La pérdida menor de peso se observó con el PET, independientemente de la temperatura de almacenamiento. La menor tasa de respiración se obtuvo en dalias almacenadas a 8 ºC, independientemente del empaque. La producción de etileno no se vio influenciada por el empaque ni por la temperatura de almacenamiento. En general, los compuestos fenólicos y la capacidad antioxidante se mantuvieron durante el almacenamiento. Es necesario llevar a cabo otros estudios que aumenten el control de microorganismos en este producto.

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 μg GA/g) and total flavonoids (241.34 ± 47.63 μg QE/g) with respect to the control (137.34 ± 19.80 μg QE/g DW and 549.00 ± 8.57 μg GA/g DW, respectively). However, no significant increase in the total content of phenolic compounds (568.54 ± 17.42 μg GA/g DW) and total flavonoids (141.11 ± 9.36 μg 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 μg GA/g) y flavonoides (241.34 ± 47.63 μg QE/g) con respecto al control (137.34 ± 19.80 μg QE/g DW y 549.00 ± 8.57 μg GA/g DW) respectivamente. Sin embargo, incrementos no significativos en el contenido de compuestos fenolicos (568.54 ± 17.42 μg GA/g DW) y flavonoides totales (141.11 ± 9.36 μg 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.

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.

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/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.

The use of repeated insecticide applications in agricultural crops to control Bemisia tabaci (Genn.) has resulted in resistance problems and environmental pollution. Inputs from plant species are an alternative to reduce this problem. Plants are a source of bioactive chemicals that can have insecticidal, repellent, attractant, anti-feeding or growth regulator effects. The aim of this study was to determine the insecticidal and repellent activity of ethanolic, acetonic and aqueous extracts of both leaves and stems of Pluchea sericea (Nutt.) on Bemisia tabaci (Genn.). The LC50 of each of the extracts on adult whiteflies was estimated using bioassays with the residual film technique. Also, the repellent effect from the LC50 of each extract was evaluated, and the repellency index (RI) was estimated. If RI = 1 the effect is neutral, if RI <1 the effect is repellent and if RI > 1 the effect is attractant. The leaf-ethanol, leaf-water and leaf-acetone extracts showed the lowest LC50 values of 700, 1,190 and 1,250 ppm respectively, indicating high efficiency on B. tabaci, followed by the stem-water extract and lastly the stem-ethanol and stem-acetone extracts showed the least effectiveness. All extracts had repellent action, regardless of the solvent and plant organ at 24 and 48 h. However, water-based extracts may have greater potential for whitefly control in integrated pest management systems because they presented insecticidal and repellent effects, and the solvent is harmless and inexpensive.

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 repelente e 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.

The effect of phenolic and carotenoid extracts from chiltepin fruits on mycelial growth and the inhibition of conidial germination of Alternaria alternata and Fusarium oxysporum were investigated in the present work. Phenolic extracts inhibited mycelial growth of A. alternata by 38.46%, and significantly reduced conidial germination on the fifth day after treatment to 92% in relation to control. No significant changes were observed in the inhibition of mycelial growth in Fusarium oxysporum; however, the number of germinated conidia was reduced, showing 85% inhibition five days after treatment in relation to control. Moreover, carotenoid extracts showed 38.5% inhibition of mycelial growth and 85.3% inhibition of conidial germination of A. alternata, five days after treatment. Carotenoid extracts showed less inhibition of mycelial growth (20.3%) in F. oxysporum, with respect to A. alternata; while there was greater inhibition of conidial germination (96%) on the fifth day after treatment. Phenolic and carotenoid extracts from chiltepin may be a promising alternative as a natural fungicide against fungi of agricultural importance.

En el presente estudio se evaluó el efecto de extractos fenólicos y de carotenoides procedentes de frutos de chiltepín sobre el crecimiento micelial y la germinación de conidios de Alternaria alternata y Fusarium oxysporum, 2 importantes hongos causantes de podredumbres en frutas y hortalizas. Los extractos fenólicos presentaron una inhibición en el crecimiento micelial de A. alternata del 38,46 %, y redujeron significativamente la germinación de conidios al quinto día después del tratamiento al 92 % en relación al control. No se observaron cambios significativos en el crecimiento micelial de F. oxysporum, pero sí se redujo significativamente al 85 % en relación al control, el número de conidios germinados a los 5 días de tratamiento. Los extractos de carotenoides mostraron una inhibición del 38,5 % en el crecimiento micelial y del 85,3 % en la germinación de conidios de A. alternata, 5 días después del tratamiento. Frente a F. oxysporum, dichos extractos presentaron menor inhibición del crecimiento micelial (20,3 %), mientras que hubo una mayor inhibición en la germinación de conidios (96 %). Los extractos fenólicos y de carotenoides de chiltepín pueden ser una alternativa promisoria de importancia agrícola como fungicidas naturales.

Certaines souches de Fusarium oxysporum sont pathogènes de différentes espèces végétales avant et après leur récolte, et sont responsables de graves pertes économiques. La gestion de ce champignon passe souvent par l'utilisation de produits chimiques dangereux pour l'environnement. Toutefois, d'autres composés biodégradables tels que les isothiocyanates (ITCs) ont montré leur potentiel nématicide, bactéricide et fongicide. Dans cette recherche, l'effet fongitoxique in vitro des ITCs allyle, benzyle, phényle, phényléthyle et propyle à des concentrations de 0, 0,1, 0,3, 0,5, 1,0, 1,5 et 2,0 uL-1 a été évalué sur plusieurs isolats de F. oxysporum obtenus à partir de bulbes de glaïeuls, de graines de jatropha, de feuilles de manguier, de fruits de la papaye et de fruits du coahuayote. La croissance quotidienne du mycélium et la germination des conidies des cinq isolats ont été évalués à différentes périodes d'incubation. Pour vérifier la réponse fongicide ou fongistatique, le champignon a été repiqé dans un milieu nutritif exempt des ITCs. En moyenne, les conidies de F. oxysporum étaient plus sensibles que le mycélium à des ITCs. À la fin de la période d'incubation, il y avait des différences significatives (P < 0,05) entre la croissance du mycélium de champignons traités avec des ITCs par rapport aux non traités. Les isolats de F. oxysporum les plus sensibles au benzyle ITC étaient ceux obtenus à partir des feuilles de manguier et de fruits de coahuayote. Les isolats de manguier étaient également très sensibles au phényléthyle ITC. A des concentrations entre 1,0 et 2,0 μ L-1, l'allyle ITC a également supprimé la croissance de F. oxysporum isolé de la papaye et du coahuayote. A part pour l'ITC phényle dans le fruit de coahuayote, la germination des conidies de F. oxysporum n'a pas eu lieu sous l'influence d'ITC rémanent alors que le traitement controle atteint 100% de germination. En moyenne la concentration appliquée n'affecte pas la croissance des champignons. Une fois que la source d'ITCs a été retirée des boîtes de Pétri, la germination et croissance des champignons ont eu lieu. En conclusion, les ITCs examinés diffèrent dans la bioactivité, et le mycélium et les conidies de différents isolats de F. oxysporum varient dans leur sensibilité et tolérance à ces composants.

Some strains of Fusarium oxysporum are pathogenic to different plant species during their pre- and postharvest stages and are responsible for serious economic losses. Management of this fungus is usually with the aid of environmentally-harmful chemicals. However, other biodegradable compounds such as isothiocyanates (ITCs) have demonstrated their nematicidal, bactericidal and fungicidal potential. In this research, the in vitro fungitoxic effect of ITCs of allyl, benzyl, phenyl, phenylethyl and propyl at concentrations of 0, 0.1, 0.3, 0.5, 1.0, 1.5 and 2.0 μ L-1 was tested on various isolates of F. oxysporum obtained from gladiolus corms, jatropha seeds, mango leaves, papaya and coahuayote fruit. Daily mycelial growth and conidial germination of these five isolates was evaluated at different incubation period. To verify the fungistatic or fungicidal response, the ITCs were removed and the fungi were re-grown only in nutrient media. As average, conidia of F. oxysporum were more sensitive to the ITCs than mycelium. At the end of the incubation period, there were significant differences (P < 0.05) in mycelia growth of the ITC-treated fungi compared to the untreated ones. The F. oxysporum isolates that were the most sensitive to the benzyl ITC were those obtained from mango leaves and coahuayote fruit. The mango isolate was also very sensitive to phenylethyl ITC. At concentrations ranging from 1.0 to 2.0 μ L-1, the allyl ITC also suppressed the growth of F. oxysporum isolated from papaya and coahuayote fruit. Except for the phenyl ITC in the coahuayote fruit, conidial germination of F. oxysporum did not occur under the influence of the remaining ITCs, whilst in the control treatment germination reached 100%. As average, the concentration applied did not influence the growth of the fungi. Once the source of the ITCs was removed from the Petri plate re-growth and germination took place in all fungi. In conclusion, the ITCs tested differed in bioactivity and the mycelium and conidia of the different F. oxysporum isolates varied in their susceptibility and tolerance to these compounds.

Algunas cepas de Fusarium oxysporum son patogénicas en diferentes especies vegetales durante sus etapas pre y postcosecha y son responsables de serias pérdidas económicas. El manejo de este hongo es generalmente mediante la ayuda de químicos peligrosos al medio ambiente. Otros compuestos biodegradables como los isotiocianatos (ITCs) han demostrado su potencial nematicida, bactericida y fungicida. En esta investigación, el efecto fungitoxico in vitro de los ITCs de alilo, bencilo, fenilo, feniletilo y propilo a concentraciones de 0, 0.1, 0.3, 0.5, 1.0, 1.5, y 2.0 μL-1 se evaluaron sobre varias cepas de F. oxysporum aisladas de cormos de gladiolo, semillas de jatropha, hojas de mango y frutos de papaya y coahuayote. El crecimiento micelial diario y la germinación conidial de estos cinco aislados se evaluaron en diferentes períodos de incubación. Para verificar la respuesta fungicida o fungistática de los ITCs, estos se resembraron únicamente en medio nutritivo. En general, los conidios de F. oxysporum fueron más sensibles que el micelio a los ITCs. Al final del período de incubación, hubo diferencias significativas (P < 0.05) en el crecimiento micelial de los hongos tratados con los ITC comparados con los no tratados. Los aislados de F. oxysporum más sensibles al ITC de bencilo fueron los que se obtuvieron de hojas de mango y frutos de coahuayote. Los aislados de mango también fueron sensibles a ITC de feniletilo. A concentraciones entre 1.0 a 2.0 μL-1, el ITC de alilo también suprimió el crecimiento de F. oxysporum aislados de frutos de papaya y coahuayote. Con excepción del ITC de fenilo, en el aislamiento del fruto de coahuayote, la germinación conidial de F. oxysporum no ocurrió bajo la influencia de los ITCs restantes al mismo tiempo que el tratamiento control alcanzó una germinación del 100%. En general, la concentración aplicada no influyó sobre el crecimiento de los hongos. Una vez que la fuente de los ITCs se quitó de las cajas Petri, el crecimiento y la germinación de los hongos se reinició. En conclusión, los ITCs probados fueron diferentes en su bioactividad mientras que el micelio y los conidios de los diferentes aislados de F. oxysporum variaron en susceptibilidad y tolerancia a estos compuestos.

The isothiocyanates are natural compounds with potent antifungal activity produced by Brassicas as part of their defense system. These compounds represent an alternative to the utilization of chemical compounds for controlling fungal infections in agricultural products. The objective of the review was to analyze the published literature including studies of the fungal molecular mechanisms responding to the toxic effect of isothiocyanates. The studies in Alternaria brassicicola show the induction of genes playing a role in oxidative stress (cytochrome P450, thioredoxins and oxidoreductases), and genes playing a role in the elimination of isothiocyanates from the cell (glutathione-S-transferases, and ABC transporters). The fungus A. brassiciccola is a pathogen specialized in Brassicas, while Alternaria alternata is a generalist pathogen. However, in A. alternata it was also reported the induction of a gene encoding an ABC transporter. Based on the reviewed data, it can be concluded that the fungi response mechanism to isothiocyanates consists in the formation of an isothiocyanate-glutathione conjugate which is secreted by an ABC transporter. It is suggested that the utilization of isothiocyanates in combination with ABC transporter inhibitors, could avoid the fungal resistance and it could constitute a safe treatment for the environment as well as for human health.

Los isotiocianatos son compuestos naturales con potente actividad antifúngica producidos por Brassicas como parte de su sistema de defensa. Estos compuestos representan una alternativa a la utilización de compuestos químicos para el control de infecciones fúngicas en productos agrícolas. El objetivo de la revisión fue analizar los estudios publicados acerca de los mecanismos moleculares de la respuesta de hongos al efecto tóxico de los isotiocianatos. Los estudios en Alternaria brassicicola demuestran la inducción de genes cuyos productos cumplen funciones en estrés oxidativo (citocromo P450, tioredoxinas y oxidoreductasas), así como en la excreción de isotiocianatos (glutatión-S-transferasas y transportadores ABC). El hongo A. brassicicola es un patógeno especializado en Brassicas, mientras que Alternaria alternata es un patógeno generalista. Sin embargo, en A. alternata también se reportó la inducción de un gen codificando a un transportador ABC. En base a los datos de la revisión se puede concluir que el mecanismo de respuesta a isotiocianatos en hongos incluye la formación de un conjugado isotiocianato-glutatión que es excretado mediante un transportador ABC. Se sugiere que la utilización de isotiocianatos en combinación con inhibidores de transportadores ABC, podría evitar la resistencia fúngica y constituiría un tratamiento amigable con el ambiente y la salud humana.