Catedra de Fitopatologia

José de San Martín, Argentina

Catedra de Fitopatologia

José de San Martín, Argentina
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O'Donnell K.,National United University | Sink S.,National United University | Scandiani M.M.,Laboratorio Agricola Rio Parana | Lenzi L.,Instituto Nacional de Tecnologia Agropecuaria | And 8 more authors.
Phytopathology | Year: 2010

Sudden death syndrome (SDS) of soybean has become a serious constraint to the production of this crop in North and South America. Phenotypic and multilocus molecular phylogenetic analyses, as well as pathogenicity experiments, have demonstrated that four morphologically and phylogenetically distinct fusaria can induce soybean SDS. Published molecular diagnostic assays for the detection and identification of these pathogens have reported these pathogens as F. solani, F. solani f. sp. glycines, or F. solani f. sp. phaseoli, primarily because the species limits of these four pathogens were only recently resolved. In light of the recent discovery that soybean SDS and Phaseolus and mung bean root rot (BRR) are caused by four and two distinct species, respectively, multilocus DNA sequence analyses were conducted to assess whether any of the published molecular diagnostic assays were species-specific. Comparative DNA sequence analyses of the soybean SDS and BRR pathogens revealed that highly conserved regions of three loci were used in the design of these assays, and therefore none were species-specific based on our current understanding of species limits within the SDS-BRR clade. Prompted by this finding, we developed a high-throughput multilocus genotyping (MLGT) assay which accurately differentiated the soybean SDS and two closely related Phaseolus and mung BRR pathogens based on nucleotide polymorphism within the nuclear ribosomal intergenic spacer region rDNA and two anonymous intergenic regions designated locus 51 and 96. The single-well diagnostic assay, employing flow cytometry and a novel fluorescent microsphere array, was validated by independent multilocus molecular phylogenetic analysis of a 65 isolate design panel. The MLGT assay was used to reproducibly type a total of 262 soybean SDS and 9 BRR pathogens. The validated MLGT array provides a unique molecular diagnostic for the accurate identification and molecular surveillance of these economically important plant pathogens.

Rivera M.C.,Catedra de Fitopatologia | Wright E.R.,Catedra de Fitopatologia | Salice S.,Catedra de Fitopatologia | Fabrizio M.C.,Metodos Cuantitativos Aplicados
Acta Horticulturae | Year: 2012

Plant preparations are commonly used in organic horticulture. Herbal teas and broths are considered to be plant growth stimulating and disease suppressive. However, scarce scientific support is available. The aims of this work were to evaluate the effect of onion (Allium cepa) and stinging nettle (Urtica dioica) preparations on the growth of lettuce crops. The experiments were carried out in the Experimental Organic Orchard of the Faculty of Agronomy University of Buenos Aires. The assays were planned as completely randomized blocks, with 6 replications per treatment. Lettuce (Lactuca sativa 'Criolla') was sown in continuous rows (3 kg seeds/ha) in each 1 m2 minimum tillage experimental unit. Manual thinning out was required to reach an optimum number of plants per area. Onion and nettle preparations were obtained as follows. Broths were prepared by boiling 1 kg of chopped bulbs or leaves, respectively, in 10 L of water during 20 min, fermenting during 15 days, filtering and adding water to complete 10 L. Teas were prepared by chopping 1 kg of bulbs or leaves, respectively, adding 10 L of water, fermenting during 15 days, filtering and adding water to complete 10 L. Each preparation (diluted 1:20) was applied to the corresponding experimental units 3 times per week, during the whole crop cycle. Controls were treated with water. Plots treated with onion tea showed the highest leaf area and fresh head weight. Variations in the analyzed chemical components of the different plant preparations can, at least, partially explain these results. Further research is needed on the presence and role of organic compounds present in these preparations.

Ramos A.M.,CONICET | Tadic L.F.,CONICET | Cinto I.,CONICET | Carmona M.,Catedra de Fitopatologia | Gally M.,Catedra de Fitopatologia
Mycotaxon | Year: 2013

Twenty-six isolates obtained from soybean crops (Glycine max) with typical anthracnose symptoms were identified as Colletotrichum truncatum (73 %) and C. destructivum (26 %). Their genetic relationships were studied using the AFLP method. A UPGMA phenogram divided the strains into two clusters corresponding with the two species. Genetic distances based on association coefficient were 0.71-0.89 among the 18 C. truncatum strains and 0.67-1 among the eight C. destructivum strains. Genetic variability within species, measured in terms of percentage of polymorphic loci, was high (<90%). Only two isolates showed 100% similarity, suggesting high intraspecific variability. © 2013. Mycotaxon, Ltd.

Boiteux J.J.,Catedra de Fitopatologia | Boiteux J.J.,National University of Cuyo | Hapon M.V.,Catedra de Fitopatologia | Hapon M.V.,National University of Cuyo | And 5 more authors.
Revista de la Facultad de Ciencias Agrarias | Year: 2015

Botrytis cinerea is a parasite fungus that causes destructive diseases over several crops and important economic damages. In grapes causes berry softy rots, which decreases both harvest yield and grape, must and wine quality. In order to ensure quality, different controls are used, such as cultural measure and fungicide applications. Last one, presents adverse effects in environment and its residue affect human health. Plant extracts are a valid alternative method. The objectives of this study were to determine the biological effect of aqueous extract of Geoffroea decorticans (chañar) on germination and germ tube growth of conidia of B. cinerea and to determine its efficiency in vivo control. To accomplish the objectives different concentrations of plant extract were tested over conidia of the pathogen. Efficiency of in vivo control on bunches of grapes cv. Red Globe was determined for different concentrations of plant extract. Also, control efficiency was compared with the chemical controls dicloran and sulfur dioxide. From these studies it was determined that the chañar extract inhibited germination and germ tube growth of conidia of B. cinerea. In vivo tests, under preventive treatments with chañar extract showed that the percentage of diseases berries decreases. © 2015, Universidad Nacional de Cuyo. All rights reserved.

Carmona M.,Catedra de Fitopatologia | Gally M.,Catedra de Fitopatologia | Sautua F.,Catedra de Fitopatologia | Abello A.,Catedra de Fitopatologia | Lopez P.,Catedra de Fitopatologia
Summa Phytopathologica | Year: 2011

Widely spread in Argentina, late season diseases (LSD), cause yield losses and seed quality changes. Leaf application of fungicides is an effective procedure to manage LSD under the current cropping conditions (monocrop and no-till system). The aims of the present study were 1) to determine causal agents of LSD, 2) to evaluate yield reduction caused by LSD and 3) to evaluate the efficiency of mixtures containing triazoles and strobirulins, sprayed during R3 or R5 reproductive stages to control LSD. Four experiments were carried out in a randomized complete block design, with four replicates in Armstrong, Santa Fe, Argentina, in a soybean cultivation area in the Pampeana Region. Two assays were performed in 2004/2005, and the remaining ones in 2005/2006 growing seasons. Two azoxystrobin mixtures, one with cyproconazole and the other with difenoconazole, and a mixture of the latter two were tested. The following pathogens were detected: Cercospora kikuchii, Colletotrichum truncatum, Septoria glycines, Glomerella glycines y Phomopsis sojae. All treatments presented higher yield than control, with 5% of statistic significance. It can be concluded that, under the present experimental conditions, characterized by frequent rains between R1 and R5.5, the tested mixtures efficiently controlled LSD.

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