Abstract:

The performance of reinforcing steel bars (rebars) coated with two different rust conversion coatings was analysed by means of electrochemical methods. Two exposure conditions were investigated, immersion in a pH 14 solution simulating pores in standard concrete, and immersion in a pH 9 solution simulating pore environments in carbonated concrete. The rebar corrosion potential (Ecorr), the corrosion rate (CR) and the electrochemical impedance (Z) were measured over 3 weeks. None of the products investigated helped to improve the resistance of steel against corrosion. Some parameters even indicated a detrimental action, particularly as the alkalinity of the solutions increased. Therefore, the application of this type of coating cannot be recommended during repair procedures of reinforced concrete structures due to the extremely alkaline environment provided by concrete.

Author affiliation: Guidoni, Griselda. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentina

Author affiliation: Vazquez, Marcela Vivian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentina

Abstract:

Asian soybean rust (ASR), caused by Phakopsora pachyrhizi, is the most destructive disease of soybean (Glycine max) in many areas of the world. ASR was first detected in Argentina during 2002 in a limited area in the northern region of the country (2). During the 2004 growing season, P. pachyrhizi spread rapidly throughout most soybean growing areas of northwestern and northeastern Argentina. ASR was also was found in some fields in Entre Ríos and Santa Fe provinces. In all areas, symptoms were expressed late in the 2004 season (growth stages R5.5 to R7) and yield losses were minimal. The objectives of this study were to quantify P. pachyrhizi infection in the canopy and morphologically characterize the fungus from fields where it had been previously detected by polymerase chain reaction (PCR) (3). Incidence (percentage of plants affected) and severity (percentage of leaf area affected, including chlorosis) were visually estimated for 10 plants arbitrarily collected (April 2004) from each of three fields located in Charata (Chacabuco), Chaco Province (Sample 1, collected in the R6 stage), La Paloma (Moreno), Santiago del Estero Province (Sample 2, stage R6 to R7), and Tolloche (Anta), Salta Province (Sample 3, stage R5.5). Disease assessments were made for the lower, middle, and upper canopy from 15 leaves per plant. The number of pustules per cm2 and uredinia per lesion were recorded from the undersides of central leaflets for each trifoliolate observed. Tissue sections were made to observe fructifications of P. pachyrhizi. Incidence of affected plants was 100% in all fields. Disease severity for Sample 1 was 45% (range 30 to 60%), 20% (10 to 30%), and 10% (5 to 20%) for the lower, middle, and upper canopy, respectively; for Sample 2: 60% (30 to 80%), 40% (25 to 50%), and 25% (15 to 40%) for the lower, middle, and upper canopy, respectively; and for Sample 3: 25% (10 to 50%), 15% (10 to 20%), and 10% (5 to 15%) for the lower, middle, and upper canopy, respectively. The number of pustules per cm2 for Sample 1 was 156/cm2 (range 88 to 200); Sample 2: 172/cm2 (128 to 232); and Sample 3: 120/cm2 (72 to 232). The number of uredinia per lesion for Sample 1 was 6 per lesion (range 1 to 15); Sample 2: 5.5 per lesion (1 to 13), and Sample 3: 2.8 per lesion (1 to 5). The two spore types that were commonly observed were urediniospores and teliospores. Telia were found on infected leaves mixed with uredinia in every sample. Urediniospores measured 16 to 22 μm (mean 18.5 μm) × 25 to 30 μm (mean 27 μm). Teliospores measured 8 to 11 μm (mean 9 μm) × 19 to 27 μm (mean 23.8 μm). Spores sizes are in the range described by Ono et al. (1). To our knowledge, this is the first report of epidemiological and morphological characterization of ASR in Argentina and the first report of the telial stage of P. pachyrhizi on soybean in South America.

Author affiliation: Carmona, Marcelo Anibal. Universidad de Buenos Aires. Facultad de Agronomía; Argentina

Author affiliation: Gally, Marcela Edith. Universidad de Buenos Aires. Facultad de Agronomía; Argentina

Author affiliation: Lopez, Silvia Edith. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Micología y Botánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Micología y Botánica; Argentina

Abstract:

Rust fungi are one of the most devastating pathogens of crop plants. The biotrophic fungus Puccinia sorghi Schwein (Ps) is responsible for maize common rust, an endemic disease of maize (Zea mays L.) in Argentina that causes significant yield losses in corn production. In spite of this, the Ps genomic sequence was not available. We used Illumina sequencing to rapidly produce the 99.6 Mb draft genome sequence of Ps race RO10H11247, derived from a single-uredinial isolate from infected maize leaves collected in the Argentine Corn Belt Region during 2010. High quality reads were obtained from 200 bp paired-end and 5000 bp mate-paired libraries and assembled in 15,722 scaffolds. A pipeline which combined an ab initio program with homology-based models and homology to in planta enriched ESTs from four cereal pathogenic fungus (the three sequenced wheat rusts and Ustilago maydis) was used to identify 21,087 putative coding sequences, of which 1599 might be part of the Ps RO10H11247 secretome. Among the 458 highly conserved protein families from the euKaryotic Orthologous Groups (KOG) that occur in a wide range of eukaryotic organisms, 97.5% have at least one member with high homology in the Ps assembly (TBlastN, E-value ⩽ e−10) covering more than 50% of the length of the KOG protein. Comparative studies with the three sequenced wheat rust fungus, and microsynteny analysis involving Puccinia striiformis f. sp. tritici (Pst, wheat stripe rust fungus), support the quality achieved. The results presented here show the effectiveness of the Illumina strategy for sequencing dikaryotic genomes of non-model organisms and provides reliable DNA sequence information for genomic studies, including pathogenic mechanisms of this maize fungus and molecular marker design.

Author affiliation: Rochi, Lucia. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Genética; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas; Argentina

Author affiliation: Dieguez, Maria Jose. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Genética; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas; Argentina

Author affiliation: Burguener, Germán Federico. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Author affiliation: Darino, Martin Alejandro. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Genética; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas; Argentina

Author affiliation: Pergolesi, María Fernanda. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Genética; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas; Argentina

Author affiliation: Ingala, Lorena Romina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Genética; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas; Argentina

Author affiliation: Cuyeu, Alba Romina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Genética; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas; Argentina

Author affiliation: Turjanski, Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Author affiliation: Kreff, Enrique Domingo. Pioneer Hi-Bred Internationa; Argentina

Author affiliation: Sacco, Francisco. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Genética; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas; Argentina

Abstract:

Leaf rust is one of the main diseases affecting wheat yield production. Considering the physiological variables that determine yield, diseases could affect radiation capture and/or radiation use efficiency. Reductions in radiation use efficiency may be mediated through effects on photosynthesis rate and related variables (i.e. dark respiration rate, stomatal conductance or photosynthesis events per se). The aim of this study was to analyze the effects of leaf rust on wheat leaves photosynthesis rate and to understand which processes determining photosynthesis are affected by this pathogen. Gas exchange measurements were taken on flag leaves with various rust severity levels in experiments carried out on two locations which included different nitrogen fertilization rates and sowing dates. Leaf rust reduced net photosynthesis rate at light saturation through reductions in gross photosynthesis (average reduction: 6.1μmolCO2m-2greenareas-1) rather than through increases in dark respiration rate (average increase: 0.7μmolCO2m-2greenareas-1). Changes in leaf nitrogen concentration did not modify the effects of leaf rust on net photosynthesis rate. Although net photosynthesis rate at light saturation was reduced, no effects were observed at low irradiance levels. The reduction of photosynthesis was due to effects on non-stomatal processes; indeed, important reductions of SPAD units (i.e. chlorophyll) were observed on green areas of diseased leaves. SPAD values on diseased leaves were 26.4±0.98 and 27.6±1.05 for N0 and N1 treatments, respectively; while on healthy leaves, values were 32.0±0.83 and 38.6±0.41, respectively. © 2011 Elsevier B.V.

Author affiliation: Carretero, Ramiro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cerealicultura; Argentina

Author affiliation: Bancal, Marie Odile. Institut National de la Recherche Agronomique; Francia

Author affiliation: Miralles, Daniel Julio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cerealicultura; Argentina

Abstract:

La roya común, causada por el hongo biótrofo Puccinia sorghi Schwein. es una importante enfermedad del maíz. En la Argentina poco se conoce acerca de fuentes de resistencia, no existen híbridos comerciales identificados como portadores de resistencia durable a la enfermedad y se desconoce acerca de la estructura poblacional de P. sorghi presente en la zona núcleo de cultivo. Los objetivos del presente trabajo consistieron en: la identificación de fuentes de resistencia a la enfermedad mediante la evaluación de un set de líneas de maíz con 66 aislamientos del patógeno y con infecciones naturales a campo; evaluación de la variabilidad patogénica y molecular de los 66 aislamientos; y profundizar en el conocimiento acerca de las bases genéticas que controlan la resistencia durable en cereales para poder implementarlas en programas de mejoramiento de maíz, mediante el estudio de una variedad de trigo llamada Buck Poncho que fue identificada como portadora de resistencia durable a roya de la hoja (Puccinia triticina Erikss.). Las líneas de maíz Rp3-A, Rp1-K, Rp-GI, Rp-G5, Rp-G5JD, PIO19802, PIO28760 y PIO17570 resultaron resistentes a más del 75% de los aislamientos y en más del 78% de las localidades evaluadas. En las líneas PIO68752, PIO28427 y PIO36420 se identificó un nuevo tipo de resistencia cuya expresión comenzó en el estadio V4. Las líneas PIO12345 y PIO74876 mostraron resistencia parcial en el estadio V2. Se identificaron en la población de P. sorghi por lo menos 3 grupos de virulencia y 26 fenotipos de virulencia o razas que podrían ser 40 razas si se consideran los genotipos de AFLP. En Buck Poncho se detectaron la existencia de por lo menos tres genes de resistencia LrBP1, LrBP2 y LBP3. La combinación de los genes de resistencia detectados en las distintas líneas de maíz podría generar variedades comerciales que posean resistencia más durable. Los grupos de virulencia identificados en la población de P. sorghi no mostraron diferencias en el nivel molecular indicando que aislamientos pertenecientes a un mismo grupo de virulencia pueden tener distintos orígenes dentro de la población. La resistencia durable observada en Buck Poncho se puede explicar en parte por los efectos combinados de los genes LrBP1, LrBP2 y LrBP3 aunque no puede descartarse la presencia de genes menores y/o QTLs menores cuyos efectos sean detectados con poblaciones segregantes de mayor tamaño a la utilizada en este estudio.

Common rust caused by the biotrofic fungus Puccinia sorghi Schwein. is an important disease of maize. In Argentina little is known about maize lines carrying resistance to the disease, the existence of corn hybrids with durable resistance and about the existence of distinct virulence groups in the P. sorghi population. The objectives of this work were: the evaluation of a set of maize lines with 66 isolates of the pathogen and with natural pathogen population present in field in order to identify resistance sources to the diseases; the study of the population structure of P. sorghi population; and in order to deepen the knowledge about the genetic basis that control durable resistance, genetic and molecular studies of a wheat variety called Buck Poncho that was identified as durable resistance to wheat leaf rust (Puccinia triticina Erikss.) were performed. Maize lines Rp3-A, Rp1-K, Rp-GI, Rp-G5, Rp-G5JD, PIO19802, PIO28760 and PIO17570 were resistant over the 75% of the isolates and over the 78% of the field locations where they were evaluated. A new class of resistance was identified in maize lines PIO68752, PIO28427 and PIO36420 whose expression of the resistance began at leaf stage V4. In inbred lines PIO12345 and PIO74876 showed partial resistance at leaf stage V2. At least, 3 virulence groups were identified, 26 virulent phenotypes or races were distinguished that could become 40 races if AFLPs genotypes are considered. Three leaf rust resistance genes, LrBP1, LrBP2 and LrBP3 were identified in Buck Poncho. Pyramiding the resistant genes detected in maize lines could be a useful strategy to increase durability of the resistance. The virulence groups identified in P. sorghi population did not differ at genetic level, indicating that isolates from each group could have different origins within the population. The durable resistance observed in Buck Poncho could be explained in part by the combination effects of LrBP1, LrBP2 and LrBP3 genes and the presence of minor genes or minor QTLs whose effects could perhaps be detected in segregant populations bigger than the one that was used in this study.

Author affiliation: Darino, Martín Alejandro. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Abstract:

Three leaf rust resistance genes were identified in the durable leaf rust resistant Argentinean wheat variety Sinvalocho MA: the seedling resistance gene Lr3 on distal 6BL and two adult plant resistance genes, LrSV1 and LrSV2, on chromosomes 2DS and 3BS, respectively. To develop a high-resolution genetic map for LrSV2, 10 markers were genotyped on 343 F2 individuals from a cross between Sinvalocho MA and Gama6. The closest co-dominant markers on both sides of the gene (3 microsatellites and 2 STMs) were analyzed on 965 additional F2s from the same cross. Microsatellite marker cfb5010 cosegregated with LrSV2 whereas flanking markers were found at 1 cM distal and at 0.3 cM proximal to the gene. SSR markers designed from the sequences of cv Chinese Spring BAC clones spanning the LrSV2 genetic interval were tested on the recombinants, allowing the identification of microsatellite swm13 at 0.15 cM distal to LrSV2. This delimited an interval of 0.45 cM around the gene flanked by the SSR markers swm13 and gwm533 at the subtelomeric end of chromosome 3BS.

Author affiliation: Diéguez, M. J.. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Genética; Argentina

Author affiliation: Pergolesi, M. F.. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Genética; Argentina

Author affiliation: Velásquez, Silvia Melina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; Argentina

Author affiliation: Ingala, Lorena Romina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Genética; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: López, M.. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Genética; Argentina

Author affiliation: Darino, Martin Alejandro. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Genética; Argentina

Author affiliation: Paux, E.. Institut National de la Recherche Agronomique; Francia. Centre National de la Recherche Scientifique; Francia

Author affiliation: Feuillet, C.. Institut National de la Recherche Agronomique; Francia. Centre National de la Recherche Scientifique; Francia

Author affiliation: Sacco, F.. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Genética; Argentina

Abstract:

In April 2015, lesions typical of orange rust were observed in a commercial sugarcane field in Fachinal, Misiones Province, Argentina, on a nonidentified cultivar (a complex hybrid of Saccharum spp.). Symptoms on leaves differed from those of brown rust of sugarcane (Puccinia melanocephala), commonly observed in the region. Leaf samples were analyzed both at the EEAOC and INTA Plant Pathology laboratories in Tucumán, Argentina. Light microscope studies revealed that uredinia and urediniospore were similar morphologically to those described for the fungus Puccinia kuehnii E. J. Butler, causal agent of sugarcane orange rust (Virtudazo et al. 2001a). Uredinial lesions were orange and variable in size, hypophyllous, ellipsoidal to fusiform in shape, and distinctly lighter than pustules of P. melanocephala that were present along with P. kuehnii. Urediniospores were mostly obovoid to pyriform, variable in size (29 to 41 × 19 to 26 μm), and moderately echinulate with mostly evenly distributed spines 2 to 4.5 μm apart. Walls were orange-to-light cinnamon brown with a pronounced apical wall thickening as much as 7 μm. Paraphyses, telia, and teliospores were not observed. Identification of the pathogen was confirmed by molecular studies. The internal transcribed spacer region (ITS1-5.8S-ITS2) of the rust infecting a nonidentified sugarcane cultivar (GenBank Accession No. KT261382) was sequenced. The sequence was identical to sequences of P. kuehnii and distinct from known sequences of P. melanocephala (Virtudazo et al. 2001b). Orange rust, initially reported in the Asia-Pacific region, has caused important losses in Australia in 2000. In the Western Hemisphere, it was first reported in Florida in 2007 (Comstock et al. 2008). Since being reported in Brazil in 2009 (Barbasso et al. 2010), annual surveys have been conducted in all three sugarcane production regions of Argentina: Northern (Salta and Jujuy provinces); Northeast (Santa Fe and Misiones provinces); and Tucumán Province. At present, the only focus of orange rust infection detected is the one in Misiones Province, 1,200 km from Tucumán, the main sugarcane-growing region of the country. To our knowledge, this is the first report of P. kuehnii infecting sugarcane in Argentina. The possible economic impact of orange rust on sugarcane production in the country is still unknown, but considering its destructive potential, the disease may pose a serious threat to sugarcane production if environmental conditions favor its establishment during the early growth stages of the crop.

Author affiliation: Funes, C.. Gobierno de Tucumán. Ministerio de Desarrollo Productivo. Estación Experimental Agroindustrial Obispo Colombres; Argentina

Author affiliation: Pérez Gómez, S. G.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Tucuman-Santiago del Estero. Estación Experimental Agropecuaria Famaillá; Argentina

Author affiliation: Henriquez, D. D.. Gobierno de Tucumán. Ministerio de Desarrollo Productivo. Estación Experimental Agroindustrial Obispo Colombres; Argentina

Author affiliation: Di Pauli, V.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Tucuman-Santiago del Estero. Estación Experimental Agropecuaria Famaillá; Argentina

Author affiliation: Bertani, Romina Priscila. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Tecnología Agroindustrial del Noroeste Argentino. Provincia de Tucumán. Ministerio de Desarrollo Productivo. Estación Experimental Agroindustrial "Obispo Colombres"(p). Instituto de Tecnología Agroindustrial del Noroeste Argentino; Argentina

Author affiliation: Fontana, D. P.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Tucuman-Santiago del Estero. Estación Experimental Agropecuaria Famaillá; Argentina

Author affiliation: Rago, Alejandro Mario. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias. Instituto de Patología Vegetal; Argentina

Author affiliation: Joya, Constanza María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Tecnología Agroindustrial del Noroeste Argentino. Provincia de Tucumán. Ministerio de Desarrollo Productivo. Estación Experimental Agroindustrial "Obispo Colombres"(p). Instituto de Tecnología Agroindustrial del Noroeste Argentino; Argentina

Author affiliation: Sopena, R. A.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Tucuman-Santiago del Estero. Estación Experimental Agropecuaria Famaillá; Argentina

Author affiliation: González, V. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Tecnología Agroindustrial del Noroeste Argentino. Provincia de Tucumán. Ministerio de Desarrollo Productivo. Estación Experimental Agroindustrial "Obispo Colombres"(p). Instituto de Tecnología Agroindustrial del Noroeste Argentino; Argentina

Author affiliation: Babi, H.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Tucuman-Santiago del Estero. Estación Experimental Agropecuaria Famaillá; Argentina

Author affiliation: Erazzú, Luis Ernesto. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Tucuman-Santiago del Estero. Estación Experimental Agropecuaria Famaillá; Argentina

Author affiliation: Cuenya, María Inés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Tecnología Agroindustrial del Noroeste Argentino. Provincia de Tucumán. Ministerio de Desarrollo Productivo. Estación Experimental Agroindustrial "Obispo Colombres"(p). Instituto de Tecnología Agroindustrial del Noroeste Argentino; Argentina

Author affiliation: Ploper, Leonardo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Tecnología Agroindustrial del Noroeste Argentino. Provincia de Tucumán. Ministerio de Desarrollo Productivo. Estación Experimental Agroindustrial "Obispo Colombres"(p). Instituto de Tecnología Agroindustrial del Noroeste Argentino; Argentina

Abstract:

Background: Many previous studies have shown that soybean WRKY transcription factors are involved in the plant response to biotic and abiotic stresses. Phakopsora pachyrhizi is the causal agent of Asian Soybean Rust, one of the most important soybean diseases. There are evidences that WRKYs are involved in the resistance of some soybean genotypes against that fungus. The number of WRKY genes already annotated in soybean genome was underrepresented. In the present study, a genome-wide annotation of the soybean WRKY family was carried out and members involved in the response to P. pachyrhizi were identified.Results: As a result of a soybean genomic databases search, 182 WRKY-encoding genes were annotated and 33 putative pseudogenes identified. Genes involved in the response to P. pachyrhizi infection were identified using superSAGE, RNA-Seq of microdissected lesions and microarray experiments. Seventy-five genes were differentially expressed during fungal infection. The expression of eight WRKY genes was validated by RT-qPCR. The expression of these genes in a resistant genotype was earlier and/or stronger compared with a susceptible genotype in response to P. pachyrhizi infection. Soybean somatic embryos were transformed in order to overexpress or silence WRKY genes. Embryos overexpressing a WRKY gene were obtained, but they were unable to convert into plants. When infected with P. pachyrhizi, the leaves of the silenced transgenic line showed a higher number of lesions than the wild-type plants.Conclusions: The present study reports a genome-wide annotation of soybean WRKY family. The participation of some members in response to P. pachyrhizi infection was demonstrated. The results contribute to the elucidation of gene function and suggest the manipulation of WRKYs as a strategy to increase fungal resistance in soybean plants.

Author affiliation: Bencke Malato, Marta. Universidade Federal do Rio Grande do Sul; Brasil

Author affiliation: Cabreira, Caroline. Universidade Federal do Rio Grande do Sul; Brasil

Author affiliation: Wiebke Strohm, Beatriz. Universidade Federal do Rio Grande do Sul; Brasil

Author affiliation: Bücker Neto, Lauro. Universidade Federal do Rio Grande do Sul; Brasil

Author affiliation: Mancini, Estefania. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Agrobiotecnología de Rosario; Argentina

Author affiliation: Osorio, Marina B.. Universidade Federal do Rio Grande do Sul; Brasil

Author affiliation: Homrich, Milena S.. Universidade Federal do Rio Grande do Sul; Brasil

Author affiliation: Turchetto Zolet, Andreia C.. Universidade Federal do Rio Grande do Sul; Brasil

Author affiliation: De Carvalho, Mayra C.C.G.. Ministerio da Agricultura Pecuaria e Abastecimento de Brasil. Empresa Brasileira de Pesquisa Agropecuaria; Brasil

Author affiliation: Stolf, Renata. Ministerio da Agricultura Pecuaria e Abastecimento de Brasil. Empresa Brasileira de Pesquisa Agropecuaria; Brasil

Author affiliation: Weber, Ricardo L.M.. Universidade Federal do Rio Grande do Sul; Brasil

Author affiliation: Westergaard, Gastón. Instituto de Agrobiotecnología de Rosario (indear); Argentina

Author affiliation: Castagnaro, Atilio Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Tecnología Agroindustrial del Noroeste Argentino. Provincia de Tucumán. Ministerio de Desarrollo Productivo. Estación Experimental Agroindustrial ; Argentina

Author affiliation: Abdelnoor, Ricardo V.. Ministerio da Agricultura Pecuaria e Abastecimento de Brasil. Empresa Brasileira de Pesquisa Agropecuaria; Brasil

Author affiliation: Marcelino Guimarães, Francismar C.. Ministerio da Agricultura Pecuaria e Abastecimento de Brasil. Empresa Brasileira de Pesquisa Agropecuaria; Brasil

Author affiliation: Margis Pinheiro, Márcia. Universidade Federal do Rio Grande do Sul; Brasil

Author affiliation: Bodanese Zanettini, Maria H.. Universidade Federal do Rio Grande do Sul; Brasil

Abstract:

Author affiliation: López, Micaela Valeria. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Abstract:

Brown rust (Puccinia melanocephala) and orange rust (P. kuehnii) cause important yield loss in global sugarcane production. Due to the difficulties of distinguishing between the two diseases to the naked eye, it is essential to use molecular techniques for an accurate rust diagnosis. A major gene, Bru1, which confers resistance to a broad spectrum of P.melanocephala strains in different parts of the world, has been described, and molecular markers closely associated with this allele have been developed. The aims of the present study were: (1) to optimise a PCR-based method to diagnose and characterise the causal agent of both rusts in Tucumán; (2) to determine the usefulness of the Bru1 gene in the Sugarcane Breeding Program of “Estación Experimental Agroindustrial Obispo Colombres” (EEAOC) by studying its association with resistant and susceptible phenotypes; and (3) to assess the frequency of the Bru1 allele in the sugarcane germplasm of the EEAOC. Conditions for both rust diagnoses were optimised. Out of 129 genotypes evaluated to study the usefulness of the Bru1 allele, 49 were found to be resistant to brown rust, but only eight of these resistant genotypes were positive for the Bru1 allele. Also frequency of appearance of the Bru1 allele was analysed in 191 sugarcane accessions of the EEAOC germplasm, and its presence was detected in only 7 % of the genotypes evaluated. In conclusion, although results showed that Bru1 markers enable positive selection of this character, additional source(s) of resistance are available in the EEAOC Sugarcane Breeding Program.

Author affiliation: Racedo, Josefina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Gobierno de Tucumán. Ministerio de Desarrollo Productivo. Estación Experimental Agroindustrial Obispo Colombres; Argentina

Author affiliation: Perera, María Francisca. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Gobierno de Tucumán. Ministerio de Desarrollo Productivo. Estación Experimental Agroindustrial Obispo Colombres; Argentina

Author affiliation: Bertani, Romina Priscila. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Gobierno de Tucumán. Ministerio de Desarrollo Productivo. Estación Experimental Agroindustrial Obispo Colombres; Argentina

Author affiliation: Funes, C.. Gobierno de Tucumán. Ministerio de Desarrollo Productivo. Estación Experimental Agroindustrial Obispo Colombres; Argentina

Author affiliation: González, V.. Gobierno de Tucumán. Ministerio de Desarrollo Productivo. Estación Experimental Agroindustrial Obispo Colombres; Argentina

Author affiliation: Cuenya, María Inés. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Gobierno de Tucumán. Ministerio de Desarrollo Productivo. Estación Experimental Agroindustrial Obispo Colombres; Argentina

Author affiliation: D'Hont, A.. Centre de Coopération Internationale en Recherche Agronomique pour le Développement; Francia

Author affiliation: Welin, Bjorn. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Gobierno de Tucumán. Ministerio de Desarrollo Productivo. Estación Experimental Agroindustrial Obispo Colombres; Argentina

Author affiliation: Castagnaro, Atilio Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Gobierno de Tucumán. Ministerio de Desarrollo Productivo. Estación Experimental Agroindustrial Obispo Colombres; Argentina