Abstract:

Multiple pathogens affect sugarcane, among them Puccinia melanocephala, the causal agent of brown rust. This disease was first reported in Cuba in 1979 when it was responsible for a severe attack on the main sugarcane variety B4362. The aims of the present study were to give an overview of sugarcane brown rust in Cuba and show the current disease situation in the country. A retrospective analysis regard to sugarcane cultivar composition resistant to brown rust in Cuba was carried out. In addition 154 genotypes, including the most used progenitors in the breeding program and commercial varieties were evaluated under natural infection conditions. The identity of P. melanocephala was verified by Polymerase Chain Reaction (PCR) and by sequencing the ITS1 region. After the introduction of P. melanocephala into Cuba, the susceptible variety, B4362, was replaced by Ja60-5 which remained resistant until 1998. Since 2002, a varietal policy supported by a governmental resolution establishing that any single cultivar cannot occupy more than 20 % of the production area for each production company, local area and province, has been applied. Out of the genotypes evaluated, 49 showed resistance to the disease and 35 intermediate behavior, while 39 were susceptible and 31, highly susceptible. P. melanocephala was detected by PCR in all symptomatic samples and its identify confirmed by sequencing the ITS1 region. The adopted measurement together with permanent phytosanitary monitoring and commercial release of resistant or intermediate cultivars succeeded in avoiding any new epidemic. Inoculum pressure was reduced, even on susceptible and highly susceptible varieties since, by resolution, they cannot occupy more than 10 % of the planted area.

Author affiliation: La O, María. Institute For Sugarcane Research; Cuba

Author affiliation: Perera, María Francisca. 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: 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: Acevedo, Ricardo. Institute For Sugarcane Research; Cuba

Author affiliation: Arias, Marta Eugenia. Universidad Nacional de Tucumán; Argentina. Universidad Nacional de Catamarca; Argentina

Author affiliation: Casas, Mario Alberto. Institute For Sugarcane Research; Cuba

Author affiliation: Pérez, Juana. Institute For Sugarcane Research; Cuba

Author affiliation: Puchades, Yaquelín. Institute For Sugarcane Research; Cuba

Author affiliation: Rodríguez, Eida. Institute For Sugarcane Research; Cuba

Author affiliation: Alfonso, Isabel. Institute For Sugarcane Research; Cuba

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 "Obispo Colombres"(p). Instituto de Tecnología Agroindustrial del Noroeste Argentino; 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:

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.

Instituto de Genética

Author affiliation: Rochi, Lucía. INTA. Instituto de Genética; Argentina

Author affiliation: Dieguez, María José. INTA. Instituto de Genética; Argentina

Author affiliation: Burguener, Germán. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Author affiliation: Darino, Martín Alejandro. INTA. Instituto de Genética; Argentina

Author affiliation: Pergolesi, Marí­a Fernanda. INTA. Instituto de Genética; Argentina

Author affiliation: Ingala, Lorena Romina. INTA. Instituto de Genética; Argentina

Author affiliation: Cuyeu, Alba Romina. INTA. Instituto de Genética; Argentina

Author affiliation: Turjanski, Adrián. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Author affiliation: Kreff, Enrique D. Pioneer Hi-Bred International; Argentina

Author affiliation: Sacco, Francisco. INTA. Instituto de Genética; Argentina

Abstract:

Tan spot [Pyrenophora tritici-repentis (Died.) Drechs., anamorph Drechslera tritici-repentis) (Died.) Shoem.] and leaf rust (Puccinia triticina Eriks) are major diseases worldwide and some of the main biotic causes of yield and quality reduction in wheat (Triticum aestivum L.). Although wheat crop losses due to foliar diseases have already been studied based on an ecophysiological approach, none of these studies analyzed the independent effects of foliar pathogens with different nutritional habits. The aim of the present study was to determine the independent effects of (i) Py. tritici-repentis (necrothroph) and (ii) Puccinia triticina (biotroph) on the physiological components of biomass production: accumulated intercepted by green tissue photosynthetic active radiation (IGPAR), radiation use efficiency calculated by intercepted radiation (RUEint) as well as by intercepted by green tissue (RUEgt) in a wide range of Argentine commercial bread wheat cultivars growing in two field environments. Field experiments were carried out during two consecutive years combining a large range of wheat bread commercial cultivars and two levels of inoculation to promote infection of Tan spot and Leaf rust diseases, including a control without inoculation. Treatments were arranged in an experimental split-split plot design with three replications, where the main plots were both diseases, subplots corresponded to inoculation treatments 1- without inoculation (WI), 2- low concentration of inoculum of each disease (LC), 3- high concentration of inoculum of each disease (HC) and ten Argentine bread wheat commercial cultivars were the sub-subplots. Area under disease progress (AUDPC), area under percentage of non-green leaf area (AU %NGLA), crop growth rate (CGR) and healthy area duration (HAD) were calculated. Green leaf area index (GLAI), aboveground biomass (AGB), IGPAR and RUE were measured at three different crop stages (GS39, GS61 and GS82). Increases of inoculum concentration decreased AGB between 8 and 20% mainly explained by reductions in HAD and decreases on IGPAR by 14–18% with higher reductions when the crop was inoculated with Py. tritici-repentis than with P. triticina. Although both diseases reduced the physiological components of accumulated biomass related to radiation interception (IGPAR), RUEint (−23%), RUEgt (−11%) and CGR (−29%) were more reduced, respect to WI, when plants were inoculated with P. triticina compared to Pyrenophora tritici-repentis. The differential responses in RUE could be associated with the nutritional habit of P. triticina that reduces leaf nitrogen concentration, enhance assimilates consume by leaf respiration, reducing radiation use efficiency.

Author affiliation: Schierenbeck, Matías. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Fleitas, María Constanza. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

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. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina

Author affiliation: Simon, Maria Rosa. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Abstract:

La roya marrón de la caña de azúcar afecta el sistema foliar de la planta y es producida por el hongo Puccinia melanocephala H. & P. Sydow. En Tucumán, esta enfermedad se presenta a partir de fines de diciembre y principio de enero(periodo de gran crecimiento del cultivo) y el periodo de mayor afección transcurre durante marzo y abril. La Sección Fitopatología de la Estación Experimental Agroindustrial Obispo Colombres realiza desde hace seis años prospecciones en el área cañera de Tucumán, para conocer la distribución y los niveles de severidad de la roya marrón. Para ello, se divide a la provincia entres zonas (norte, centro y sur) y, mediante observaciones visuales y utilizando una escala diagramática, se calculan los valores promedio de severidad.

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

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

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

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

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

A high genetic variability has been recognized in Puccinia sorghi in Argentina (Gonzalez et al. 2011), although its origin remains unclear since the different reported alternate hosts (Oxalis corniculata L., O. stricta L., O. bowiei Herb. ex Lindl.) have never been detected with this disease in the region. In the spring of 2013 and 2014, the spermagonium and aecial estages of a Puccina sp., were observed on O. conorrhiza Jacq. (syn. O. cordobensis R. Knuth) in Córdoba Province, in central Argentina. Those structures were found in 22 sampling sites, under natural infections, in a radius of 175 km of Córdoba City. O. conorrhiza is a bulbous perennial plant native to South America in the Oxalidaceae family, with a low, moderate growth habit. It is distributed in several provinces of central Argentina. O. conorrhiza can usually be found in alluvial flatlands, riverbanks, wasteland, roadsides, pastures, as well as farmlands. The confirmation of the O. conorrhiza species was carried out by the ACCOR Herbarium of the National University of Córdoba, Argentina. On approximately one-third of the leaves of each infected plant, ampulliform, subepidermal, amphigenous spermagonia, arranged in small clusters of 0.5 mm were observed. Spermagonia containing spermatia and receptive hyphae were golden yellow to orange yellow with abundant nectar exuding. Those in the center of the lesion are surrounded by annular groups of aecia, formed exclusively on the abaxial surface of the leaves. Aecia were orange, cylindrical short, with irregular opening at the apex. To determine the causal organism, aesciospores were inoculated in sweet corn plants. Fifty aeciospores from disease samples were suspended per ml of sterile water and sprayed on 5 sweet corn plants. As a negative control, 5 plants were inoculated with sterile water. All plants were kept in the dark at saturated humidity for 24 h at 24°C. After that, the plants were kept at 25 to 27°C and 70 to 80% humidity with a photoperiod of 16 h light. Seven days after inoculation, typical symptoms of corn common rust were observed: orange uredia with abundant urediospores production. At 21 days, typical teleutospores were observed. The rust matched the morphological characteristics of P. sorghi Schwein (Lindquist 1982). DNA from aeciospores from O. conorrhiza was extracted with NucleoSpin Plant II kit. A fragment from the 28S subunit regions rRNA gene was amplified and sequenced with primers Rust1 and F36 (Kropp et al. 1995). BLAST analysis of 28S sequence data (GenBank Accession Nos. HQ412650.1, GU057994.1, and AY114291.1) showed 99% identity to P. sorghi. To our knowledge, this is the first report of P. sorghi isolated from O. conorrhiza worldwide. The report contributes to an improved understanding of variability of P. sorghi which will be useful for exploring appropriate disease management, epidemiology, and breeding strategies.

Author affiliation: Guerra, Fernando Andres. Universidad Católica de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Brücher, Elsa. Universidad Católica de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: de Rossi, Roberto Luis. Universidad Católica de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Plazas, M. C.. Universidad Católica de Córdoba; Argentina

Author affiliation: Guerra, Gustavo Dario. Universidad Católica de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Ducasse, Daniel Adrián. Universidad Católica de Córdoba; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias. Instituto de Patología Vegetal; 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:

Leaf rust caused by Puccina triticina is one of the most destructive fungal diseases of wheat (Triticum aestivum). Adult plant resistance (APR) is an effective strategy to achieve long-term protection from the disease. In this study, findings are reported from a genome-wide association study (GWAS) using a panel of 96 wheat cultivars genotyped with 874 Diversity Arrays Technology (DArT) markers and tested for adult leaf rust response in six field trials. A total of 13 quantitative trait loci (QTL) conferring APR to leaf rust were identified on chromosome arms 1BL, 1DS, 2AS, 2BL, 2DS, 3BS, 3BL, 4AL, 6BS (two), 7DS, 5BL/7BS and 6AL/6BS. Of these, seven QTLs mapped close to known resistance genes and QTLs, while the remaining six are novel and can be used as additional sources of resistance. Accessions with a greater number of combined QTLs for APR showed lower levels of disease severity, demonstrating additive and significant pyramiding effects. All QTLs had stable main effects and they did not exhibit a significant interaction with the experiments. These findings could help to achieve adequate levels of durable resistance through marker-assisted selection and pyramiding resistance QTLs in local germplasm.

Author affiliation: Gerard, Guillermo Sebastián. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Agrarias y Forestales. Centro de Investigacion para la Sustentabilidad de Los Suelos Agrícolas y Forestales; Argentina

Author affiliation: Kobiljski, B.. Biogranum; Serbia

Author affiliation: Lohwasser, U.. Leibniz‐Institut für Pflanzengenetik und Kulturpflanzenforschung; Alemania

Author affiliation: Börner, A.. Leibniz‐Institut für Pflanzengenetik und Kulturpflanzenforschung; Alemania

Author affiliation: Simon, Maria Rosa. Universidad Nacional de la Plata. Facultad de Ciencias Agrarias y Forestales. Centro de Investigacion para la Sustentabilidad de Los Suelos Agrícolas y Forestales; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentina

Abstract:

Tesis de doctorado para obtener el título de Doctor en Ciencias Agrarias presentada en la Universidad Nacional de Mar del Plata; Facultad de Ciencias Agrarias, Balcarce, Buenos Aires, Argentina en 2015.

El objetivo de esta tesis fue cuantificar la importancia de las enfermedades foliares del girasol en el sudeste bonaerense, y generar conocimientos y herramientas para el manejo de la mancha de la hoja por A. helianthi (ALT) y la mancha negra del tallo por P. macdonaldii (MNT). El trabajo se dividió en tres capítulos donde se estudiaron: 1- La prevalencia e intensidad de ALT y MNT, y su impacto sobre componentes fisiológicos del rendimiento en ambientes y manejos de cultivo; 2-La eficiencia de fungicidas y la protección de diferentes estratos de hojas mediante prueba de activos, dosis y momentos de aplicación; y 3- La relación entre variables meteorológicas (Vmet) y la tasa de progreso de MNT (rMNT). Los experimentos se realizaron en la EEA Balcarce en lotes con antecedentes de ALT y MNT y agregado de rastrojo infectado. Se evaluaron cultivares, fechas de siembra y combinaciones de dosis de activos de fungicida (pyraclostrobin y metconazole) y de estadios de aplicación. Se incluyó un testigo protegido (dos a cuatro aplicaciones) y uno sin fungicida. Se evaluaron síntomas de enfermedad, componentes fisiológicos y de rendimiento, y se registraron Vmet. La MNT fue la enfermedad de mayor predominio y asociación con disminución en peso y número de aquenios. La MNT provocó senescencia anticipada de hojas, disminución en radiación interceptada y en eficiencia de conversión. La senescencia provocada por las enfermedades foliares fue importante en hojas medias o superiores. La siembra tardía presentó más MNT y ALT con relación a la temprana, observándose en algunos casos epifitias severas de ALT y roya negra. Metconazole no controló MNT y ALT. La protección con pyraclostrobin varió con la dosis, el estadio de aplicación y la hoja o estrato. La curva exponencial negativa de dosis-respuesta se ajustó para ALT, mientras que para MNT no hubo respuesta con más de 50 g.ha-1. Una alta eficiencia de control de ALT se obtuvo con aplicaciones en distintos estadios y hoja según: R2-hoja12, R4-hoja20 y R6-hoja28. La aplicación en R6 presentó menor incidencia de MNT en el estrato medio, en relación a R2 y R4. Ante una epifitia severa de ALT, el área foliar y el rendimiento fueron mayores con aplicaciones en R4 o R6 y dosis mínimas de 100 g.ha-1. Los mayores ajustes Vmet vs rMNT se observaron con las variables hídricas, y fueron lineales y positivos. La cantidad de precipitaciones durante el período de llenado de aquenios presentó el mayor valor predictivo.

The goal of this thesis was to estimate the importance of foliar sunflower diseases in the southeast of Buenos Aires, and generate knowledge for management of diseases caused by A. helianthi (ALT) and P. macdonaldii (MNT). This work was divided into three sections: 1- The prevalence and intensity of ALT and MNT, and their impact on physiological and yield components in different years and crop management systems; 2- The effective fungicide dose through the crop phonological stages; y 3- The relationship between meteorological variables (VMET) and the rate of MNT progress (rMNT). The experiments were performed in EEA Balcarce on fields with history of ALT and MNT and with the addition of infected stubble. Planting dates, cultivars, doses combinations of active ingredients (pyraclostrobin and metconazole) and spray phenological times were evaluated. Protected control (two to four fungicide applications) and check without fungicide were included. Disease symptoms, physiological and yield components were evaluated and the VMET were recorded. MNT was the most prevalent disease and had the highest association with decrese in weight and number of achenes. MNT caused early leaf senescence, decreasing the interception of the incidence radiation and the radiation use efficiency. Senescence caused by foliar diseases was important in upper or high leaves. The late sowing had more MNT and ALT than early sowing, and in some cases severe epidemics of ALT and black rust were observed. Metconazole did not control MNT or ALT. The efficiency of pyraclostrobin protection varied with the dose, the spray time and the leaf layer or stratum. The negative exponential dose-response curve was adjusted to ALT, whereas there was no response to MNT over 50 g ha-1. High efficiency control of ALT was obtained at spraying times and leaf: R2-leaf12, R4-leaf20 and R6-leaf28. R6 spray time had lower incidence of MNT in the middle leaves stratum, in relation to R2 and R4. Under severe epidemics of ALT, greater leaf area and yield was achieved with applications in R4 or R6 and 100 g ha-1 or higher doses. Higher regression between VMET and rMNT were observed with hydric variables and were linear and positive. The amount of rainfall during the filling period had the highest predictive value. Keywords: leaf senescence; radiation use efficiency; rate of disease progress; effective fungicide doses; black rust.

EEA Balcarce

Author affiliation: Quiróz, Facundo José. INTA. Estación Experimental Agropecuaria Balcarce, Argentina.