ABSTRACT Pathogenic fungi generate crop diseases, and affect yield and food production. The use of phytosanitary products to control fungal diseases can pose a risk to human health and the environment. In this context, the use of plant metabolites as potential bio-controls for pathogens turns out to be a sustainable alternative. The objective of this study was to evaluate the anti-fungal action of six compounds of plant origin: daidzein, genistein, two chalcones, vanillin and iso-vanillin, on the in vitro growth of pathogens. The Minimum Inhibitory Concentration (MIC) and the Minimum Fungicidal Concentration (CFM) of each chemical compound were evaluated by the broth micro-dilution method against five fungal genera: Alternaria sp., Cladosporium sp., Fusarium (F. graminearum, F. subglutinans, F. proliferatum, F. oxysporum), Phomopsis longicolla, and Rhizopus stolonifer. The results indicated that daidzein, genistein, iso-vanillin and CH1 did not show an inhibitory and / or fungicidal action at concentrations lower that 250 mL-1. CH2 was characterized by inhibiting four isolates belonging to three genera in different concentrations, and presenting fungicidal activity on two of them. Vanillin proved to be effective to inhibit and / or eliminate all of the isolates (nine) included in the five fungal genera evaluated at concentrations below 250 mL-1. It is concluded that metabolites of plant origin such as vanillin and CH2 presented antifungal capacity in different degrees and specificity on the isolates.

RESUMEN Los hongos patógenos generan enfermedades en distintos cultivos y afectan el rendimiento y producción de alimentos. El control mediante fitosanitarios puede implicar un riesgo para la salud humana y el ambiente. En este contexto la utilización de los metabolitos vegetales como potenciales bio-controles de patógenos son una alternativa sustentable. El objetivo de este estudio fue evaluar la acción antifúngica de seis compuestos de origen vegetal, daidzeína, genisteína, dos chalconas, vainillina e iso-vainillina, sobre el crecimiento in vitro de patógenos que actúan en cultivos de interés alimentario. Se evaluó la Concentración Inhibitoria Mínima (CIM) y la Concentración Fungicida Mínima (CFM) de cada compuesto químico mediante el método de microdilución en caldo frente a cinco géneros fúngicos: Alternaria sp., Cladosporium sp., Fusarium (F. graminearum, F. subglutinans, F. proliferatum, F. oxysporum), Phomopsis longicolla, y Rhizopus stolonifer. Los resultados indicaron que daidzeína, genisteína, iso-vainillina y CH1 no presentaron acción inhibitoria y/o fungicida en concentraciones menores a 250 mL-1. CH2 se caracterizó por inhibir a cuatro aislamientos pertenecientes a tres géneros en diferentes concentraciones y presentar actividad fungicida sobre dos de los mismos. La vainillina demostró ser efectiva para inhibir y/o eliminar la totalidad de los aislamientos (nueve) incluidos en los cinco géneros fúngicos evaluados con concentraciones menores a 250 mL-1. Se concluyó que los metabolitos de origen vegetal como la vainillina y CH2 presentaron capacidad antifúngica en diferente grado y especificidad sobre los aislamientos.

Soybean asian rust (SAR) caused by the fungus Phakopsora pachyrhizi was confirmed in Argentina for the first time during the 2002-2003 growing season. Then, the disease spread to the Northern and Eastern provinces, reaching the central area of Santa Fe, which is one of the main agricultural areas of the country. However, the disease has been usually detected at the end of the growing season (late March to early April), causing little or no impact on grain and seeds production. The objectives of this study were: i) characterize, molecularly and morphologically, the isolates of P. pachyrhizi from this area; ii) evaluate the effect of two environmental combinations (a typical for the region and other optimal as a control) on the germination of urediniospores in laboratory conditions; and iii) assess the infecting capacity of the inoculum obtained and the disease progress promoted under greenhouse conditions. Morphologic, molecular and pathometric characteristics of uredinia and urediniospores allowed verifying P. pachyrhizi identity. Uredospores exposed to daily temperatures ranging from 35 to 25°C, combined with a photoperiod and humidity conditions similar to those typical of the central area of Santa Fe during the crop cycle, decreased germination and appressoria formation and, consequently, SAR symptoms and uredinia production. These biological and epidemiological features would explain the erratic occurrence of SAR in the central producing area of Santa Fe, Argentina. Therefore, these could be used as references to design crop management strategies aimed at decreasing disease impact in other production areas.

La roya asiática de la soja (RAS) causado por el hongo Phakopsora pachyrhizi fue citado por primera vez en Argentina durante la campaña 2002-2003. Luego la enfermedad se diseminó a las provincias del norte del país y la región centro norte de Santa Fe. RAS ocurre usualmente al final del período reproductivo del cultivo (finales de marzo hasta principios de abril) causando poco o ningún impacto sobre la producción de granos y semillas. Los objetivos de este estudio fueron: i) caracterizar molecular y morfológicamente los aislamientos de P. pachyrhizi del área central de Santa Fe, ii) evaluar el efecto de dos combinaciones ambientales (una típica de la región y otra óptima como control) sobre la germinación de las urediniosporas en laboratorio; y iii) evaluar la capacidad infectiva del inóculo obtenido y el progreso de la enfermedad generado bajo condiciones de invernadero. La caracterización molecular y morfológica de uredinios y urediniosporas permitieron verificar la identidad de P. pachyrhizi. Las esporas expuestas al rango térmico diario 35/25°C con fotoperíodo y humedad similares a las condiciones típicas del centro de Santa Fe, disminuyeron la germinación y formación de apresorios y, en consecuencia, la aparición de síntomas y producción de uredinios de RAS. Los resultados biológicos y epidemiológicos obtenidos podrían explicar la baja frecuencia de ocurrencia de RAS en la región central de Santa Fe, Argentina, y pueden ser tomados como referencia al diseñar estrategias de manejo de cultivo orientadas a minimizar el impacto de la enfermedad en otras áreas productivas.

ABSTRACT Spartina argentinensis and Panicum prionitis are herbaceous grasses that dominate many communities used for livestock production systems. High amounts of biomass accumulate in these communities without being grazed by cattle due to their low digestibility. Hence, farmers often burn these rangelands in order to stimulate higher quality regrowth. This type of biomass could be used to produce bioethanol. As a biomass pretreatment is necessary to increase the efficiency of the hydrolysis process. The use of ligninolytic enzymes commonly produced by some fungi could be an alternative. In this paper, the fungal genera present in both grasses from different locations and with different degrees of decomposition were surveyed. According to the literature, the following isolated fungal genera show ligninolytic capacity: Alternaria, Aspergillus, Chaetomium, Cladosporium, Epicoccum, Fusarium, Nigrospora, Penicillium, Pestalotia y Phoma. Most of them were found in both hosts. Ligninolytic enzymes could be obtained from these fungi in order to improve the efficiency of ethanol production of this kind of biomass.

Los pastizales de Spartina argentinensis y de Panicum prionitis son comunidades herbáceas utilizadas para la producción ganadera en Argentina. En estas comunidades se acumula gran cantidad de biomasa senescente no aprovechable por el ganado por su baja digestibilidad, siendo la quema una práctica recurrentemente utilizada para estimular el rebrote de pasto más tierno. Este tipo de biomasa podría usarse para producir bioetanol, pero para ello es necesario hacer un pretratamiento para aumentar la eficiencia del proceso de hidrólisis. Un posible pretratamiento es el uso de enzimas ligninolíticas que son comúnmente producidas por algunos grupos de hongos. En este trabajo, se relevaron los géneros fúngicos asociados a ambas especies botánicas presentes en distintas localidades y con diferente grado de descomposición. Se encontró predominancia de géneros fúngicos con citada capacidad ligninolítica tales como Alternaria, Aspergillus, Chaetomium, Cladosporium. Epicoccum, Fusarium, Nigrospora, Penicillium, Pestalotia y Phoma. La mayoría de las mismas se encontraron en ambos hospedantes. A partir de estos hongos podrían obtenerse enzimas ligninolíticas que contribuirían a mejorar la eficiencia de la producción de bioetanol lignocelulósico.

Diaporthe(telomorfo) - Phomopsis(anamorfo) (DP) constituye un grupo fúngico de amplia diversidad genética con más de 900 especies distribuidas en un amplio rango de hospedantes que incluye especies cultivadas y no cultivadas, forestales, frutales y malezas. Los aislamientos de DP son hemi-biótrofos y disponen de diferentes fuentes de inóculo primario, como el rastrojo y las semillas, para reiniciar sus ciclos de parasitismo-saprofitismo. Ellos colonizan los tejidos del hospedante desde los estadios tempranos del desarrollo y establecen relaciones nutricionales de endofitia y necrotrofia fúngica. La plasticidad del género Phomopsisha favorecido su expansión a diferentes agro-ecosistemas y hospedantes constituyendo un importante riesgo epidemiológico. El objetivo fue validar la identidad y evaluar las relaciones biológicas de 12 aislamientos de P. longicollay D. phaseolorumvar. sojaeobtenidos en distintos agro-ambientes templados y subtropicales de Argentina, para analizar la variabilidad y estrategias de conservación de la bio-diversidad fúngica. Las cualidades macro-morfo-lógicas(textura y color de colonias, forma y distribución de estromas, desarrollo, forma y distribución de cuerpos fructíferos), y los caracteres micro-morfológicos(tamaño y forma de conidios, ascos y ascosporas) permitieron identificar a tres nuevos aislamientos de P. longicollaincluidos en el complejo D/P. El análisis molecular complementario corrigió las limitaciones derivadas de la caracterización basada sólo en marcadores morfológicos y logró reubicar al aislamiento AFP.8413 de identidad dudosa, en el nodo correspondiente a P. longicolla.De esta manera, la caracterización molecular definió la identidad de los aislamientos y los ubicó en los 4 taxones del complejo DP: diez aislamientos fueron incluidos en Plo(AFP.Gpo 4.4, AFP.Gpo 3.5, AFP.Gpo 4.3, AFP.Gpo 3.4, AFP.CaA, AFP. CaB, AFP.B5L16, AFP.B4L17, AFP.227B2, AFP.8413), un aislamiento incluido en Dps(AFP.Qcol7), un aislamiento en Dpc(AFP.Dpc16) y dos aislamientos incluidos en Dpm(AFP.Dpm109 y AFP.Dpm112). La adecuada identificación de P. longicollay el avance en el conocimiento de las relaciones biológicas (hibridaciones homo o heterotálicas) entre variedades de D. phaseolorum (P. phaseoli)y especies de Diaporthe- Phomopsispermiten comprender la plasticidad para colonizar un amplio rango de hospedantes, los mecanismos de variabilidad genética y la preservación de la diversidad fúngica.

Diaporthe(teleomorpho)-Phomopsis (anamorph) (DP) is a fungal group of great genetic diversity with over 900 species associated to a wide host range that includes cultivated and uncultivated species, forest, fruit trees and weeds. DP isolates are hemi-biotrophs and have different sources of primary inoculum as stubble and seeds to restart cycles of parasitism -saprophytism. They colonize host tissues from early plant stages and establish different nutritional relationships, acting as endophytic and necrotrophic fungi. The plasticity of the Phomopsisgenus has favored its expansion to different agro-ecosystems and various hosts constituting an epidemiological risk. The objective was to validate the identity and evaluate the biological relationships among 12 isolates of P. longicollaand D. phaseolorumvar. sojae(anamorph P. phaseolivar. sojae)obtained in different tempered and subtropical agro-environments of Argentina, in order to analyze the variability and strategies for preserving fungal biodiversity. Macro-morphological attributes (such as texture and color of colonies, stroma shape and distribution, pycnidia and perythecia shape and distribution) and micro-morphological characteristics (such as size and shape of conidia, asci and ascospores) allowed identifying three new isolates as P. longicolla.A complementary molecular analysis was also made to overcome the limitations derived from the morphological analysis, thus the AFP.8413 isolate was finally identified as P. longicolla.The molecular characterization was useful to identify the evaluated isolates and to group them in four taxa of the Diaporthe-Phomopsiscomplex: ten isolates were included in P. longicolla,one isolate was included in D. phaseolorumvar. sojae(anamorph P. phaseolivar. sojae),one isolate was identified as D. phaseolorumvar. caulivoraand two isolates were included in D. phaseolorumvar. meridi-onalis.The use of phenotipic and molecular tools have contributed to an accurate identification of P. longicolla,and comprehension about the biological relationships (homo or heterothallic hibridizations) among D. phaseolo-rumvarieties (P. phaseoli)and species of Diaporthe-Phomopsis.This allowed also a better understanding of the mechanisms of fungic plasticity, to colonize and expand their host range and genetic variability, promoting thus their biodiversity conservation.

Fusarium tucumaniae e F. virguliforme são agentes etiológicos primários da síndrome da morte súbita (sudden death syndrome - SDS) de soja na Argentina e nos Estados Unidos, respectivamente. Cinco isolados de F. tucumaniae e quatro isolados de F. virguliforme foram testados para agressividade relativa à soja, usando-se o método de ponta de palito de dente e duas versões do método de inoculação com solo infestado. A cultivar de soja parcialmente resistente RA629 e a cultivar suscetível A6445RG foram inoculadas separadamente com cada um dos nove isolados. Dois experimentos para cada método de inoculação foram realizados. A análise da variância identificou uma interação tripla significativa entre cultivar*experimento*patógeno SDS (P = 0,01), usando-se os três métodos. Quando os métodos de infestação de solo foram utilizados, F. virguliforme foi mais agressivo que F. tucumaniae. Entretanto, quando foi usado o método do palito de dente, isolados de F. virguliforme e F. tucumaniae foram igualmente agressivos. Embora os três métodos testados tenham discriminado níveis de resistência parcial dos genótipos à SDS, resultados do presente estudo indicam que inoculações no solo com grãos de sorgo infestados representam o melhor método para avaliação de resistência de cultivares de soja à SDS. A existência de interações entre o hospedeiro, patógeno e condições de ambiente destaca a necessidade de estudos adicionais para melhorar a reprodutibilidade de testes de seleção de germoplasmas de soja para resistência à SDS.

Fusarium tucumaniae and F. virguliforme are the primary etiological agents of sudden-death syndrome (SDS) of soybean in Argentina and the United States, respectively. Five isolates of F. tucumaniae and four isolates of F. virguliforme were tested for relative aggressiveness to soybean, using a toothpick inoculation method and two versions of a soil infestation inoculation method. Partially resistant soybean cultivar RA629 and susceptible cultivar A6445RG were inoculated separately with each of the nine isolates. Two experiments for each inoculation method were performed. Analysis of variance identified a significant three-way interaction of soybean cultivar*experiment*SDS pathogen (P = 0.01) using the different methods. When the two soil infestation methods were used, F. virguliforme was more aggressive than F. tucumaniae; however, when using the toothpick method, isolates of F. virguliforme and F. tucumaniae were equally aggressive. Although all three methods discriminated levels of partial resistance of the genotypes to SDS, results of the present study indicated that soil inoculations with sorghum infested grain represent the best method for evaluating soybean cultivar resistance to SDS. The existence of interactions among the host, pathogen and environmental conditions highlights the need for additional studies to improve the reproducibility of tests for screening soybean germplasm for resistance to SDS.

O objetivo deste trabalho foi avaliar o comportamento da primeira coleção do germoplasma introduzido de edamame sobre resistência/susceptibilidade ao Cancro da Haste da Soja (SSC), causado por Diaporthe phaseolorum var. meridionalis (Dpm) e D. phaseolorum var. caulivora (Dpc) no Pampa Húmido Argentino. Trinta genótipos de edamame foram avaliados em casa de vegetação e o delineamento experimental foi o de blocos completos com duas repetições. O germoplasma de edamame mostrou diferentes níveis de resistência a cinco isolados de Diaporthe phaseolorum. Determinaram-se diferenças na virulência de Dpm e Dpc, verificando assim que os genes que conferem resistência a Dpm e Dpc são diferentes. Este trabalho demonstra que existe variabilidade genética no germoplasma de edamame e será útil no melhoramento para resistência e tolerância.

The objective was to evaluate the reaction of introduced edamame edible soybean germplasm against Soybean stem canker (SSC), caused by Diaporthe phaseolorum var. meridionalis (Dpm) and D. phaseolorum var. caulivora (Dpc) in the humid Pampa of Argentina. Thirty edamame genotypes were evaluated in greenhouse conditions using an experimental design in blocks with two replications, over two years. Edamame germplasm showed a different degree of resistance to five Diaporthe phaseolorum isolates. The existence of inter- and intra-varietal differences in Dpm and Dpc virulence were also found, verifying that genes conferring resistance to Dpm and Dpc are different. This study showed that genetic variability does exist in edamame germplasm and would be useful in breeding for resistance or tolerance.