This review sought to highlight the importance of natural products versus synthetic products, as bioactive molecules, towards the development of better management practices in aquaculture. The nature, structure, activity, and applications of these naturally-occurring high value-added compounds are described, as well as the methodology used for their study. Examples include the well-known rotenone, eugenol, forskolin, isatin, malyngamide, chlorodesmine, pachydictyol, fimbrolide, and other potentially active molecules in aquaculture.

The chemical screening carried out on Schizochytrium sp. biomass led the identification of 24 types of organic compounds belonging to n-alkanes, 1-alkenes, 1-alkanols, free fatty acids, methyl and ethyl esters of saturated and unsaturated fatty acids, saturated tri- and diglycerides, unsaturated monoglycerides, wax esters, sterols, triterpenes, and mono- and sesquiterpenes. Moreover, a sample containing fully saturated ethyl biodiesel was obtained experimentally with a yield of 28.72% w/w of the crude extract, and an average chain length of 15.52 carbons. This strain produced no toxins, but showed important nutrients, making it potentially applicable to the field of functional food, and biodiesel production.

Screening of biomass of a new marine-derived strain of Penicillium roqueforti, as produced by liquid-state fermentation, led to the identification of several volatile organic compounds active in the fatty acid pathway as well as fragments produced by their catabolism, terpenoids, and metabolites from the shikimic acid pathway. In addition, five non-volatile organic compounds, triolein, ergosterol peroxide, 9(11)-dehydroergosterol peroxide, 4-hydroxybenzaldehyde, and d-mannitol, were isolated and identified by spectroscopy. The results showed that this fungal strain did not produce any mycotoxin in the culture conditions applied, and thus is useful for industrial applications, where high value-added biomolecules are generated.

Common rust caused by Puccinia sorghi is one of the endemic diseases of corn in Argentina. It appears every year with different levels of severity depending on the genotype of the host, the biotypes of the pathogen, and the environmental conditions. Estimates of grain weight losses ranged from about 3 to 8% for 10% of the total leaf area affected. P. sorghi is a heteroic fungus that completes its cycle on an alternative host, Oxalis spp. Its complete cycle is feasible in mild winter regions around the world. The objective of this study was to describe the factors involved in the virulence of the pathogen in the interaction Zea mays-Puccinia sorghi. Using Rp isolines, 10 pathotypes of P. sorghi were identified from 16 isolates obtained from different locations in the provinces of Santa Fe (Oliveros, Venado Tuerto and Zavalla) and Buenos Aires (Pergamino). Polymorphisms in the DNA of the different isolates of P. sorghi from this core corn-growing region of Argentina were detected by RAPD methodology. These experiments showed the genetic heterogeneity of the pathogen in this area. A high consensus rate was determined (81.4 %) between the results obtained from the virulence biotypes and the results obtained by RAPD.

La roya común causada por Puccinia sorghi es una de de las enfermedades endémicas de maíz (Zea mays) en Argentina. Se presenta cada año con diferentes niveles de severidad dependiendo del genotipo del hospedante, el biotipo del patógeno y las condiciones ambientales. Se estima una pérdida en el peso del grano entre 3 y 8% por cada 10% del total de área afectada. P. sorghi es un hongo heteroico que completa su ciclo en un hospedante alternativo: Oxalis spp. El ciclo completo se produce en las regiones con inviernos favorables. El objetivo de este estudio fue describir los factores involucrados en la virulencia del patógeno en la interacción Zea mays-Puccinia sorghi. Usando isolíneas Rp se identificaron 10 patotipos de P. sorghi, a partir de 16 aislamientos de diferentes localidades de la Provincia de Santa Fe (Oliveros, Venado Tuerto and Zavalla) y Buenos Aires (Pergamino). Se detectaron polimorfismos en el ADN por la metodología de RAPD en los diferentes aislamientos de P. sorghi. Estos experimentos muestran la heterogeneidad genética del patógeno en esta zona. Se determinó un alto consenso (81,4%) entre los resultados obtenidos a través de las isolíneas Rp y RAPD.

Mal de Río Cuarto virus produces a wheat disease, resulting from the combined action of this pathogen and its main vector, Delphacodes kuscheli. Knowing that viruses and insects cause a severe symptomatology in different genotypes, the objective of this work was to determine the possible physiological alterations in three phenological stages of wheat (cv ProINTA Federal) inoculated by two geographically distant MRCV isolates and exposed to non viruliferous insects. Treatments were run at three plant stages: first leaf emergence through coleoptile, four and five unfolded leaves. The health status of these plants was confirmed by ELISA. Physiological alterations were observed in both infected plants and plants exposed to non viruliferous insects (PS). The total soluble sugar, starch and soluble protein contents increased remarkably in the plants infected by MRCV. While chlorophyll content decreased considerably in PS and MRCV infected plants, malondialdehyde levels increased in both cases. These variations could indicate oxidative damage associated to biotic stress in these plants. The physiological alterations were similar on the different phenological stages. Only the starch increase was significantly higher in plants infected at the first leaf emergence from the coleoptile.

Mal de Río Cuarto virus en trigo provoca una enfermedad resultante de la acción combinada con su principal vector, Delphacodes kuscheli. La severa sintomatología inducida por virus e insecto condujo a determinar la posible existencia de alteraciones fisiológicas en el cultivar de trigo ProINTA Federal, infectado artificialmente con dos aislamientos geográficamente distantes del MRCV y sometido a picadura de insectos no virulíferos, respectivamente, en tres estadios fenológicos. ProINTA Federal fue picado por insectos no virulíferos e inoculado en la primera hoja emergiendo del coleóptilo, en la cuarta y quinta hojas desplegadas, respectivamente. La condición sanitaria de los diferentes tratamientos fue constatada mediante ELISA. Las plantas tratadas manifestaron alteraciones fisiológicas con similares variaciones entre estadios fenológicos. Azúcares solubles totales, almidón y proteínas solubles incrementaron significativamente su contenido en plantas infectadas por MRCV. En plantas PS y con MRCV, el contenido de clorofilas disminuyó marcadamente y lo inverso sucedió con el malondialdehído, lo que indicaría daño oxidativo por estrés en las mismas. No existieron diferencias entre estadios fenológicos y las variaciones de los indicadores de alteraciones fisiológicas considerados, excepto para el incremento de almidón, significativamente superior en plantas inoculadas en la primera hoja emergiendo del coleóptilo.

Maize plants infected with Spiroplasma kunkelii show symptoms similar to that of plants in a magnesium-deficient soil, and it has been shown that the spiroplasma alters the plants' magnesium absorption. In the current study we compared changes associated to either spiroplasma infection, two soil magnesium levels and their combinations. Plant symptoms were recorded and correlated with transmission electron microscopy observations. Plants grown on a high magnesium treatment showed no macroscopical alterations nor organelle ultrastructural alterations, while plants on a low magnesium treatment showed macroscopical vein yellowing and, ultrastructurally, they had most chloroplasts and mitochondrial membranes altered. Infected plants on a low magnesium treatment had an ageing aspect, ultrastructurally showed chloroplasts and mitochondrial alterations similar to those non-infected and grown on a low magnesium treatment, and spiroplasma cells were found in phloem cells, but outside their cytoplasm. Infected plants on a high magnesium treatment showed similar symptoms and ultrastructural alterations as either non-infected plants on the low magnesium treatment or in infected plants on the low magnesium treatment, but differ from them in that the spiroplasma cells were located inside the cytoplasm. Results suggest that magnesium is involved in the plant-pathogen interaction.

Among diseases reported worldwidely for sweet potato (Ipomoea batatas (L) Lam) crop, one of the most frequent is the Sweet potato virus disease (SPVD), caused by sweet potato chlorotic stunt virus (SPCSV) and sweet potato feathery mottle virus (SPFMV) co-infection. In Argentina, there exists the sweet potato chlorotic dwarf (SPCD), a sweet potato disease caused by triple co-infection with SPCSV, SPFMV and sweet potato mild speckling virus (SPMSV). Both diseases cause a synergism between the potyviruses (SPFMV and SPMSV) and the crinivirus (SPCSV). Up to date, studies carried out on the interaction among these three viruses have not described their localization in the infected tissues. In single infections, virions of the crinivirus genus are limited to the phloem while potyviral virions are found in most tissues of the infected plant. The purpose of this work was to localize the heat shock protein 70 homolog (HSP70h), a movement protein for genus crinivirus, of an Argentinean SPCSV isolate in its single infection and in its double and triple co-infection with SPFMV and SPMSV. The localization was made by in situ hybridization (ISH) for electron microscopy (EM) on ultrathin sections of sweet potato cv. Morada INTA infected tissues. The results demonstrated that viral RNA coding HSP70h is restricted to phloem cells during crinivirus single infection, while it was detected outside the phloem in infections combined with the potyviruses involved in chlorotic dwarf disease.

The ability of first and third-instar Delphacodes kuscheli Fennah (Hemiptera: Delphacidae) nymphs to acquire and transmit Mal de Río Cuarto virus (MRCV), under controlled conditions, was investigated. First and third-instar nymphs were allowed acquisition feeding separately on infected wheat plants for 48 hours. The insects were then placed in groups of three for serial transmissions to healthy wheat plants, using inoculation periods of 24 hours. Both instars of D. kuscheli were demonstrated to acquire and subsequently transmit the virus. Nevertheless, transmission trials showed highest transmission efficiency and shortest latent period when MRCV was acquired by first-instar nymphs.

Se comparó la capacidad de ninfas de primer y tercer estadío de Delphacodes kuscheli Fennah (Hemiptera: Delphacidae) para adquirir y posteriormente transmitir el Mal de Río Cuarto virus (MRCV), bajo condiciones controladas. Ninfas I y III avirulíferas se alimentaron separadamente de plantas de trigo infectadas durante 48 horas, para luego ser colocadas en subgrupos de tres individuos sobre plantas de trigo sanas. Se realizaron transmisiones seriales utilizando períodos de inoculación de 24 horas. Ambos estadií os lograron adquirir y transmitir el MRCV, pero se evidenció una mayor cantidad de subgrupos infectivos cuando la adquisición se efectuó como ninfas I, así como una disminución significativa en la duración del período de latencia del virus respecto de los insectos que adquirieron el MRCV durante el tercer estadio ninfal.

O objetivo deste trabalho foi avaliar a incidência de viroses e enfezamentos e estimar as perdas causadas por enfezamentos na cultura do milho safrinha. Os diagnósticos baseados em sintomas foram confirmados por PCR ou RTPCR. Em todas as lavouras, foram identificadas plantas com sintomas de enfezamentos, em incidência de 6,2% a 49,9% (média de 20,7%). Na identificação de insetos vetores desses patógenos, a cigarrinha Dalbulus maidis foi detectada em 20 lavouras das 24 amostradas, constituindo 66,6% do total de espécimens de cigarrinhas coletadas. A perda potencial causada pelos enfezamentos no período foi estimada em cerca de 16,5 milhões de dólares. A ocorrência de plantas com sintomas de "Maize rayado fino virus" e "Maize dwarf mosaic virus" foi baixa e o diagnóstico confirmado por RTPCR. A análise de 441 amostras suspeitas de infecção por "Mal de Río Cuarto virus", por DASELISA, mostrou ausência desse vírus. Resultados de PCR indicaram a presença de um possível fitoplasma distinto de "Maize bushy stunt phytoplasma" em duas plantas apresentando nanismo acentuado, folhas estreitas, enrijecidas, com deformações, e grãos na inflorescência, havendo necessidade de mais estudos para a confirmação da identidade desse possível novo fitoplasma.

The objective of this work was to evaluate the occurence and yield losses by corn stunting diseases and maize viruses in "safrinha" season. Disease diagnostics based on plant symptoms were confirmed by PCR or RTPCR assays. Insect samples were collected in 24 fields for identification of vectors of the pathogens. Corn stunting diseases symptoms were observed in all crops evaluated, with incidence levels ranging from 6.2% to 49.9% (average 20.7%) and the presence of the leafhopper Dalbulus maidis, was detected in 20 of the 24 areas evaluated. This insect species was prevalent, representing 66,6% of total leafhoppers specimens collected. The potential yield losses caused by mollicutes was estimated around US$ 16.5 million. Few plants showing Maize rayado fino virus and Maize dwarf mosaic virus symptoms were found and virus infection was confirmed by RTPCR. Mal de Río Cuarto virus was not detected in all 441 plants analyzed by DASELISA. Results of PCR assays indicated the presence of a possible phytoplasma different from maize bushy stunt phytoplasma in two stunting maize plants showing leaves distortions and grain in the inflorescence. However, new studies should be done to confirm the identity of this possible new phytoplasma.

A incidência de doenças causadas por molicutes e por vírus foi avaliada em lavouras de milho (Zea mays) nas Províncias de Tucumán e de Córdoba, na Argentina, em fevereiro de 2000. Na Província de Tucumán verificou-se que 44% das lavouras apresentaram altos níveis de incidência de plantas com sintomas de enfezamentos causados por molicutes (50 a 100%), em altitudes variando de 300 a 2.000 m. A presença de fitoplasma e de espiroplasma foi confirmada em amostras de folhas de plantas com sintomas de enfezamentos, através dos testes de PCR e de "Western blotting". Constatou-se, porém, que a eficiência desses testes para detecção destes patógenos, quando os sintomas apresentados pelas plantas eram muito acentuados, foi da ordem de 70%, e de apenas 30% quando os sintomas eram menos acentuados. Na localidade Jesus Maria, foram encontradas plantas apresentando acentuado nanismo, folhas estreitas e com deformações. Dentre quatro amostras destas plantas, submetidas a testes de PCR, em duas foi detectada a presença de fitoplasma, possivelmente d istinto do "Maize Bushy Stunt Phytoplasma". A cigarrinha Dalbulus maidis, inseto vetor dos molicutes, foi encontrada apenas em Tucumán, estando ausente em Córdoba. O Mal de Rio Cuarto virus foi detectado em seis lavouras em Córdoba, e em três em Tucumán. A cigarrinha Delphacodes kuscheli foi detectada em todas as lavouras em Córdoba, e em apenas três lavouras em Tucumán. O Maize dwarf mosaic virus foi detectado em cerca de 60% das lavouras amostradas nas duas Províncias e o Maize rayado fino virus em apenas uma localidade em Tucumán.

The incidence of "corn stunt diseases" and maize (Zea mays) viruses was evaluated in maize fields located at the Provinces of Tucumán and Córdoba in Argentina in February 2000. A high number of plants infected with "corn stunt disease" were observed in Tucumán (up 50 to 100%) in 44% of maize crops surveyed in areas varying from up 300 to 2000 m high. The presence of Maize Bushy Stunt Phytoplasma (MBSP) and Corn Stunt Spiroplasma (CSS) was confirmed by PCR and Western blotting tests. In plants showing typical symptoms of MBSP or CSS, the pathogens were detected in 70% of the samples. However, when symptoms were weak, the efficiency of detection dropped to approximately 30%. In Rio Cuarto, Province of Córdoba, the presence of phytoplasma was detected only in three plants showing red leaf symptoms. In Jesus Maria locality, plants showing symptoms different from those caused by MBSP, were demonstrated to be infected by phytoplasma when analyzed by PCR using universal primers. The leafhopper Dalbulus maidis, vector of MBSP and CSS, was found only in Tucumán. The Mal de Rio Cuarto virus (MRCV) was found in six maize fields in Córdoba and in three maize fields located at 1970 to 2.000 m high in Tucumán. The plant hopper Delphacodes kuscheli, vector of MRCV, was found in both provinces sampled. The Maize dwarf mosaic virus (MDMV) was found in 60% of maize crops in both Provinces and the Maize rayado fino virus (MRFV)was found only in one location in Tucumán.

The Mal de Río Cuarto disease is caused by Mal de Río Cuarto virus (MRCV) transmitted by Delphacodes kuscheli. Comparative studies were carried out on the cytopathological alterations produced by MRCV in corn (Zea mays), wheat (Triticum aestivum) and barley (Hordeum vulgare), as seen with a transmission electron microscope. Corn plants were infected with viruliferous D. kuscheli collected from the endemic disease area (i.e. Río Cuarto County, Córdoba, Argentina). For the viral transmission to small grain cereal plants, laboratory rared insects were used. In this case, the inoculum source was wheat and barley plants infected with MRCV isolate grown in a greenhouse. Leaf samples with conspicuous symptoms were collected: enations and size reduction in corn; crenatures, swelling veins and dark green color in small grain cereals. Viral infection was corroborated by DAS-ELISA. Viroplasms containing complete and incomplete virus particles and fibrillar material were found in the cytoplasm of infected cells in all species. Mature virions were between 60 and 70 nm diameter. In wheat and barley, viroplasms and dispersed particles were observed only in phloem, while in corn virions were also found in cells of the bundle sheath. Crystalline arrays of particles were detected in corn enation constitutive cells. Tubular inclusions were found only in wheat samples. The three species showed abnormalities in the chloroplasts of affected cells. The results showed that MRCV cytopathology has similarities with other viruses from the genus Fijivirus, family family Reoviridae, but slight differences depending upon the host plant.

La enfermedad denominada mal de Río Cuarto es causada por el Mal de Río Cuarto virus (MRCV) transmitido por Delphacodes kuscheli. Se reportan los resultados de un estudio de las alteraciones citopatológicas producidas por el MRCV en maíz (Zea mays), trigo (Triticum aestivum) y cebada (Hordeum vulgare), observadas en microscopio electrónico de transmisión. Las plantas de maíz fueron inoculadas con ejemplares infectivos de D. kuscheli colectados en la zona endémica de la enfermedad. Para la transmisión del virus a los cereales de grano fino se utilizaron insectos criados en laboratorio, siendo la fuente de inóculo plantas de trigo y cebada infectadas con un aislamiento del virus obtenido en Río Cuarto y mantenido en invernáculo. Se colectaron muestras de hojas con síntomas conspicuos en maíz, y en cereales de grano fino. La infección viral fue corroborada mediante DAS-ELISA. Se encontraron viroplasmas, conteniendo partículas virales completas e incompletas y material fibrilar, en el citoplasma de las células infectadas en todas las especies. Los viriones maduros midieron entre 60 y 70 nm de diámetro. En trigo y cebada, los viroplasmas y partículas dispersas fueron observados sólo en el floema, mientras que en maíz también se encontraron viriones en las células de la vaina. En maíz, se detectaron partículas formando arreglos cristalinos en las células de las enaciones. Exclusivamente en las muestras de trigo, se encontraron inclusiones tubulares. Las tres especies mostraron anomalías en los cloroplastos de las células afectadas. Los resultados obtenidos ponen de manifiesto que la citopatología propia del MRCV presenta semejanzas con la de otros fijivirus y pequeñas diferencias dependiendo de la planta hospedante.

The disease caused by the "Mal de Rio Cuarto virus" (MRCV) is one of the most important diseases among those affecting maize (Zea mays) crops in Argentina. The MRCV belongs to the Reoviridae family, within the Fijivirus genus. It is spread in nature by Delphacodes kuscheli (Hemiptera: Delphacidae). The manner of transmission of the members of this virus genus is persistent propagative. An efficient virus transmission system was arranged in order to perform the various characterisation studies. These studies were carried out with healthy vector populations raised in the laboratory. Different acquisition, latency and inoculation periods were tested and a range of differential hosts was also evaluated, by breeding in phytotrons and controlled atmosphere chambers. A sufficient number of virus-free insects could thus be obtained to perform work. Experimental transmission of MRCV was successfully accomplished under identical conditions with acquisition, latency and inoculation periods of two, 10 and one days for fine grain cereals and two, 10 and two days for maize respectively. The following species were infected in this manner: maize (Zea mays), barley (Hordeum vulgare), oats (Avena sativa), wheat (Triticum aestivum), rye (Secale cereale), grama rhodes (Chloris gayana) and birdseed (Phalaris canariensis). Virus detection in inoculated plants was performed by means of serological tests, electrophoresis of the dsRNA in polyacrylamide gel (which showed the 10 typical bands of the fijiviruses) and electron microscopy, which showed 60 - 70 nm isometric particles.

Entre las enfermedades que afectan al cultivo de maíz (Zea mays) en Argentina, la producida por el virus del mal de Río Cuarto (MRCV) es la más importante. El MRCV pertenece a la familia Reoviridae, género Fijivirus, y su propagación en la naturaleza es realizada por Delphacodes kuscheli (Hemiptera: Delphacidae). La modalidad de transmisión para los miembros de este género de virus es persistente propagativa. Se estableció la necesidad de ajustar un sistema de transmisión eficiente del virus para estudios de caracterización, partiendo de poblaciones libres de virus criadas en laboratorio, para lo cual se ensayaron distintos períodos de adquisición, latencia e inoculación, evaluándose además un rango de hospedantes diferenciales. Se lograron obtener insectos libres de virus en cantidad suficiente para llevar a cabo los trabajos, mediante su cría en fitotrones y cámaras aclimatadas. La transmisión experimental del MRCV se efectuó exitosamente, bajo idénticas condiciones, empleando períodos de adquisición, latencia e inoculación de dos, 10 y uno día respectivamente para los cereales de grano fino y de dos, 10 y dos días para el maíz. Se infectaron de este modo las siguientes especies: maíz, cebada (Hordeum vulgare), avena (Avena sativa), trigo (Triticum aestivum), centeno (Secale cereale), grama rhodes (Chloris gayana) y alpiste (Phalaris canariensis). La detección del virus en las plantas inoculadas se efectuó mediante pruebas serológicas, análisis de dsRNA en electroforesis en gel de poliacrilamida (obteniéndose las 10 bandas típicas de los fijivirus) y microscopía electrónica, detectándose las partículas isométricas de entre 60 y 70 nm de diámetro.