Scielo RSS <![CDATA[Investigación Agraria]]> http://scielo.iics.una.py/rss.php?pid=2305-068320210001&lang=en vol. 23 num. 1 lang. en <![CDATA[SciELO Logo]]> http://scielo.iics.una.py/img/en/fbpelogp.gif http://scielo.iics.una.py <![CDATA[Use of antibiotic streptomycin sulphate to the control in vitro contamination of nodal segments of <em>Eugenia involucrate</em>]]> http://scielo.iics.una.py/scielo.php?script=sci_arttext&pid=S2305-06832021000100001&lng=en&nrm=iso&tlng=en RESUMO A descontaminação dos explantes é requisito para a eficiência da micropropagação. O trabalho teve como objetivo avaliar o modo de utilização do antibiótico sulfato de estreptomicina (SE) no controle de bactérias endógenas em segmentos nodais micropropagados de Eugenia involucrata. Os tratamentos foram: T1 (explantes sem contaminação prévia); T2 (explantes com contaminação prévia); T3 (explantes sem contaminação e imersos em solução de SE a 100 mg L-1 durante 5 min); T4 (explantes com contaminação e imersos em solução de SE a 100 mg L-1 durante 5 min); T5 (explantes sem contaminação e inoculados em meio contendo 100 mg L-1 de SE); e T6 (explantes com contaminação e inoculados em meio contendo 100 mg L-1 de SE). Decorridos 30 dias de cultivo in vitro não houve efeito significativo sobre as variáveis sobrevivência (média de 94,44%) e contaminação fúngica (média 6,94%). As maiores contaminações bacterianas foram observadas em T3 e T4 (100%), já em T5 (16,67%) observou-se a menor média. Ocorreu maior número de folhas em T5 (3,83), que diferiu estatisticamente de T2 e T4, os quais apresentaram a menor média. A imersão não controla a proliferação de bactérias. A inoculação na ausência de contaminação prévia controla a proliferação, mas não reduz as bactérias quando há contaminação. O desenvolvimento das folhas é prejudicado pela presença de bactérias.<hr/>ABSTRACT Decontamination of explants is a requirement for micropropagation efficiency. The aim of this work was to evaluate the use of the antibiotic streptomycin sulfate (SE) in the control of endogenous bacterias in micropropagated nodal segments of Eugenia involucrata. The treatments were: T1 (explants without previous contamination); T2 (explants with previous contamination); T3 (explants without contamination and immersed in SE solution at 100 mg L-1 for 5 min); T4 (contaminated explants and immersed in SE solution at 100 mg L-1 for 5 min); T5 (explants without contamination and inoculated in a medium containing 100 mg L-1 of SE); and T6 (contaminated explants and inoculated in medium containing 100 mg L-1 of SE). After 30 days of in vitro culture, there was no significant effect on the variables survival (mean 94.44%) and fungal contamination (mean 6.94%). The highest bacterial contamination was observed in T3 and T4 (100%), whereas in T5 (16.67%) the lowest average was observed. In T5 was observed the greatest number of leaves (mean 3.83), which differed statistically from T2 and T4, which presented the lowest averages. Immersion does not control the bacteria proliferation. Inoculation in the absence of prior contamination controls bacteria proliferation whereas inoculation with contaminated explants does not reduce it. Leaf development is hindered by the presence of bacteria. <![CDATA[Spatial analysis of soil physical properties in the Suárez river watershed, Boyacá - Santander (Colombia), using principal component analysis]]> http://scielo.iics.una.py/scielo.php?script=sci_arttext&pid=S2305-06832021000100008&lng=en&nrm=iso&tlng=en RESUMEN El uso de técnicas estadísticas multivariadas como el análisis de componentes principales permite resumir un grupo numeroso de variables en unas pocas que recogen un alto porcentaje de la variabilidad total. En este trabajo, se utilizó dicha técnica combinada con las herramientas de geoestadística para analizar el comportamiento conjunto de las propiedades físicas del suelo en la Hoya del río Suárez en relación con el uso de la tierra en agricultura. Se consideraron cinco variables físicas, como son: el porcentaje de arenas, el diámetro medio ponderado de los agregados, la capacidad de retención de agua disponible, la densidad aparente y la densidad real. Esta información se obtuvo de la base de datos de la hoya citada, que incluyó 932 puntos de observación de una grilla de 70x70 m sobre el terreno. Con las variables citadas se aplicó el análisis de componentes principales, y con los componentes más relevantes se realizó el análisis de variabilidad espacial. Se observó que el primer componente principal explicó el 40,5% de la varianza total de las características físicas evaluadas, asociándolo a procesos de compactación del suelo en la región de estudio, mientras que el segundo componente explicó el 21,7% de la varianza total, ligándose a la posible susceptibilidad del suelo a la erosión. Con estos componentes y el análisis espacial se elaboraron mapas que permitieron caracterizar las zonas de la hoya en estudio por problemas de compactación y erodabilidad, lo cual permitirá a futuro proponer esquemas diferenciales de prácticas de conservación del suelo.<hr/>ABSTRACT The principal component analysis is a multivariate statistical procedure used to reduce a set of numerous variables into a few ones that can explain a great percentage of the original variability. In this article, the principal component analysis combined with geostatistical tools were used to characterize different zones from the watershed known as “Hoya del río Suarez”, for differential agricultural management. Five physical properties were used from the watershed database: sand content in percentage, mean weighted diameter of soil aggregates, available water holding capacity, bulk density and particle density. There were used 932 points of observations from a grid of 70x70 m on the terrain. The two first principal components were used in the analysis of spatial variability. The first component was associated with the soil compaction, and it explained 40.5% of the total variance of the physical variable set. The second component was associated with soil erodibility, and it explained 21.7% of the total variance. The maps built using these components were useful to characterize the watershed soils for compaction and erodibility problems. This result will be useful to propose differential soil conservation management practices. <![CDATA[Comparison of samplers in the evaluation of soil physical properties]]> http://scielo.iics.una.py/scielo.php?script=sci_arttext&pid=S2305-06832021000100017&lng=en&nrm=iso&tlng=en ABSTRACT One of the methods most used in obtaining undisturbed soil samples is the volumetric ring method. Undeformed samples are used, for example, in the evaluation of soil physical properties, such as soil bulk density and porosity. However, there is a diversity of volumetric rings used in the research, which makes it difficult to compare results obtained in these studies. Thus, the objective of this investigation was to compare the values of soil bulk density, microporosity and total porosity, determined from sampling with volume volumetric rings of 100 and 272 cm³, and establish the correlation between them, verifying if the comparison is valid. Soil samples were taken in 25 cultivation sites in Hapludox, which differed in the tillage, culture and/or management system, in the municipality of Rio Paranaíba, MG, at different depths. Data were submitted to Pearson correlation analysis. The correlation between the volumetric rings for all variables was significant, described by the correlation equations y=0.3788+0.7054*x (R=0.68), y=0.1342+0.6582*x (R=0.62), and y=0.1107+0.6071*x (R=0.67), for the variables density, total porosity and microporosity, respectively. It is concluded that it is possible to compare values for the variables determined from the sampling with the two volumetric rings tested.<hr/>RESUMEN Uno de los métodos más utilizados para obtener muestras de suelo inalterado es el método de anillo volumétrico. Las muestras inalteradas se utilizan, por ejemplo, en la evaluación de las propiedades físicas del suelo, como la densidad y la porosidad. Sin embargo, existe una diversidad de anillos volumétricos utilizados en investigación, lo que dificulta la comparación de los resultados obtenidos en estos estudios. Así, el objetivo de esta investigación fue comparar los valores de densidad, microporosidad y porosidad total, determinados a partir de muestreos con anillos volumétricos con un volumen de 100 y 272 cm³, y establecer la correlación entre ellos, verificando si la comparación es válida. Se tomaron muestras de suelo en 25 sitios de cultivo en Hapludox, los cuales se diferenciaron en el sistema de labranza, cultivo y / o manejo, en el municipio de Rio Paranaíba, MG, a diferentes profundidades. Los datos obtenidos se sometieron al análisis de correlación de Pearson. La correlación entre los anillos volumétricos para todas las variables fue significativa, descrita por las ecuaciones de correlación y = 0.3788 + 0.7054 * x (R = 0.68), y = 0.1342 + 0.6582 * x (R = 0.62) e y = 0.1107 + 0.6071 * x (R = 0,67), para las variables densidad, porosidad total y microporosidad, respectivamente. Se concluye que la comparación de valores de las variables determinadas a partir del muestreo con los dos anillos volumétricos ensayados es válida. <![CDATA[Bromatological and morphological characteristic of forage plants]]> http://scielo.iics.una.py/scielo.php?script=sci_arttext&pid=S2305-06832021000100022&lng=en&nrm=iso&tlng=en ABSTRACT To a better decision in relation to the choice of forages, it is important to know its bromatological and morphological characteristics, since this knowledge can lead to greater productivity and quality of dry mass forage. This work aimed to evaluate the morpho-physiological characteristics of forage plants, specifically Urochloa brizantha cv. Xaraés/MG-5; Urochloa brizantha cv. Marandu; Panicum maximum cv. Mombaça; Urochloa brizantha cv. BRS/Piatã; Urochloa brizantha cv. Paiaguás. The experiment was carried out at the College of Agricultural and Technological Sciences, Dracena, São Paulo, Brazil, May 2015. Bromatological, physiological and morphological analyses of the leaves were performed. The cultivar Urochloa brizantha cv. Marandu excelled in mineral matter (MM%); and Xaraés for dietary fiber in acid detergent (FDA%). The cultivar Urochloa brizantha cv. Xaraés/MG-5 was distinguished in the parameter thickness of the adaxial epidermis (TAdE), mesophyll thickness (MT); diameter of leaf phloem (LDP) and diameter of leaf xylem (LDX). The cultivar Urochloa brizantha cv. Paiaguás highlighted in the parameter thickness of the abaxial epidermis (TAbE). In general, the cultivar Urochloa brizantha cv. Xaraés/MG-5 presented the best results regarding the morphological characteristics of the studied forage plants.<hr/>RESUMEN Para una mejor decisión en relación con la elección de los forrajes, es importante conocer sus características bromatológicas y morfológicas, ya que este conocimiento puede llevar a una mayor productividad y calidad del forraje de masa seca. Este trabajo tuvo como objetivo evaluar las características morfofisiológicas de las plantas forrajeras, específicamente Urochloa brizantha cv. Xaraés / MG-5; Urochloa brizantha cv. Marandu; Panicum maximo cv. Mombaça; Urochloa brizantha cv. BRS / Piatã; Urochloa brizantha cv. Paiaguás. El experimento se llevó a cabo en la Facultad de Ciencias Agrícolas y Tecnológicas, Dracena, São Paulo, Brasil, mayo de 2015. Se realizaron análisis bromatológicos, fisiológicos y morfológicos de las hojas. El cultivar Urochloa brizantha cv. Marandu sobresalió en materia mineral (MM%); y Xaraés para fibra dietética en detergente ácido (FDA%). El cultivar Urochloa brizantha cv. Xaraés / MG-5 se distinguió en el parámetro de espesor de la epidermis adaxial (TAdE), espesor de mesofila (MT); diámetro del floema de la hoja (LDP) y diámetro del xilema de la hoja (LDX). El cultivar Urochloa brizantha cv. Paiaguás resaltó en el parámetro espesor de la epidermis abaxial (TAbE). En general, el cultivar Urochloa brizantha cv. Xaraés / MG-5 presentó los mejores resultados en cuanto a las características morfológicas de las plantas forrajeras estudiadas. <![CDATA[Aphid vectors of barley yellow dwarf (BYDV) virus in wheat crop in Paraguay]]> http://scielo.iics.una.py/scielo.php?script=sci_arttext&pid=S2305-06832021000100028&lng=en&nrm=iso&tlng=en RESUMEN El Barley yellow dwarf virus o Virus del Enanismo Amarillo de la Cebada (BYDV) es una de las enfermedades transmitidas por áfidos presente en muchas regiones productoras de trigo del mundo, causando mermas importantes en la producción. Identificar las especies que transmiten la enfermedad es de suma importancia, a fin de encarar tácticas de manejo, para evitar la diseminación de la misma. El estudio tiene como objetivo identificar especies de áfidos transmisores del BYDV en cultivos de trigo de las zonas de mayor producción del Paraguay. Los trabajos de trampeo de especímenes se realizaron desde el inicio de la emergencia de las plántulas hasta la etapa final del cultivo de trigo que comprendió entre los meses de mayo hasta octubre del año 2014. Los insectos fueron capturados semanalmente en cada una de las parcelas seleccionadas en trampas tipo Moericke. Los datos fueron sometidos a análisis faunísticos. Se identificaron cinco especies de áfidos, Rhopalosiphum padi, Rhopalosiphum maidis, Sitobion avenae, Schizaphis graminum, Rhopalosiphum rufiabdominalis, todas las especies identificadas son consideradas transmisoras de virus.<hr/>ABSTRACT The Barley yellow dwarf virus or Barley Yellow Dwarf Virus (BYDV) is one of the aphid-borne diseases present in many wheat-producing regions of the world, causing significant losses. Identifying the species that transmit the disease is very important, in order to management tactics and to avoid its spread. The object of this study is to identify BYDV-transmitting aphid species in wheat crops in the areas of highest production in Paraguay; Alto Paraná, Itapúa, Caaguazú and San Pedro. The research was carried out from the start of the seedling emergence to the final stage of wheat cultivation, which ranged from May to October 2014. The insects were captured weekly in each of the selected plots in Moericke-type traps. The data were subjected to fauna analysis. Five species of aphids were identified: Rhopalosiphum padi, Rhopalosiphum maidis, Sitobion avenae, Schizaphis graminum, Rhopalosiphum rufiabdominalis, all identified species are considered virus transmitters. <![CDATA[Chemical control of <em>Fusarium</em> head blight of wheat and its effect on grain production and seed quality]]> http://scielo.iics.una.py/scielo.php?script=sci_arttext&pid=S2305-06832021000100032&lng=en&nrm=iso&tlng=en RESUMEN La fusariosis de la espiga del trigo (FET) producida principalmente por Fusarium graminearum, es una de las enfermedades más importantes para la producción del trigo en Paraguay, no solo por las pérdidas de rendimiento que ocasionan sino por la presencia de micotoxinas en granos. El objetivo del experimento fue evaluar distintos grupos químicos de fungicidas y sus mezclas para el control de FET y su relación con el rendimiento y niveles de micotoxina dioxinivalenol (DON) en granos de trigo. Los fungicidas fueron aplicados en tres estados de desarrollo del cultivo: espigazón, antesis y grano lechoso en la variedad Canindé 13. Todos los fungicidas evaluados (Tebuconazole, Metconazole + Epoxiconazole, Azoxystrobin, Fluxapyroxad + Epoxyconazole + Pyraclostrobin, Azoxystrobin + Benzovindiflupir) disminuyeron significativamente en promedio los niveles de índice de infección del FET y aumentaron el rendimiento y peso de mil granos comparados al testigo sin control químico. La mayoría de los tratamientos que incluyeron estrobilurinas en su composición resultaron con los niveles más altos de DON (4,07-4,27 ppm) en granos de trigo. Entre los fungicidas evaluados, el Tebuconazole presentó el menor (1-1.5 ppm) nivel de concentración de DON en granos.<hr/>ABSTRACT Fusarium head blight (FHB), produced mainly by Fusarium graminearum, it is one of the most relevant diseases for wheat production in Paraguay which continues to threaten the economic sustainability of crop producers, causing losses in grain yield and quality. The objective of the experiment was to evaluate different chemical groups of fungicides for the control of Fusarium head blight and its effect on yield and mycotoxin deoxynivalenol levels in wheat grains. The fungicides were applied in three wheat growth stages: head emergence, anthesis and milky grains. All fungicides evaluated (Tebuconazole, Metconazole + Epoxiconazole, Azoxystrobin, Fluxapyroxad + Epoxyconazole + Pyraclostrobin, Azoxystrobin + Benzovindiflupir) significantly decreased the infection levels of Fusarium head blight and increased the yield and thousand grains weight compared with the non-sprayed control. Treatments that included strobilurins in their composition resulted in the highest levels of DON (4.07-4.27 ppm) in wheat grains. Among the fungicides evaluated, Tebuconazole showed the lowest level of DON concentration in grain (1-1.5 ppm). <![CDATA[Culture media and effect of melaleuca essential oil in <em>Stemphylium</em> sp. micelial growth]]> http://scielo.iics.una.py/scielo.php?script=sci_arttext&pid=S2305-06832021000100040&lng=en&nrm=iso&tlng=en RESUMO Espécies do gênero Stemphylium são responsáveis por uma série de doenças de plantas, como as solanáceas, com destaque para a queima-de-estenfílio, que afeta a produtividade de culturas carentes em fungicidas disponíveis. Diante disso, propôs-se com esse trabalho a determinação de um meio de cultura que viabilizasse o crescimento micelial de Stemphylium sp. isolado de cebola para posterior avaliação do efeito do óleo de melaleuca (M. alternifolia), sob diferentes concentrações in vitro, no desenvolvimento desse patógeno. Para isso, no primeiro ensaio foram testados oito meios de cultura: Batata-Dextrose-Ágar (BDA); Suco V-8® Ágar a 5%; Suco V-8® Ágar a 10%; Suco V-8® Ágar a 20%; Suco de Tomate a 5% (ST5%); Suco de Tomate a 10% (ST10%); Suco de Tomate a 20% (ST20%) e Extrato de Malte Ágar 2%. Aos 10 dias e aos 15 dias o maior crescimento foi identificado com os tratamentos ST20% e BDA e opostamente, os tratamentos V8-5% e V8-10% o menor crescimento. No segundo ensaio, o óleo de melaleuca foi testado em cinco concentrações (0; 0,2; 0,4; 0,6 e 0,8%) diluído em BDA e se determinou o IVCM (índice de velocidade do crescimento micelial). O óleo essencial de melaleuca reduziu significativamente o crescimento micelial de Stemphylium sp. com melhor ajuste à equação quadrática y = 28,074x2 - 46,136x + 19,94. Conclui-se que o meio de cultura ST20% proporcionou o maior crescimento in vitro e que o óleo de melaleuca adicionado ao meio de cultura nas concentrações de 0,6 e 0,8% foram capazes de reduzir o IVCM, podendo representar alternativa promissora para o controle deste patógeno.<hr/>ABSTRACT Species of Stemphylium genus are responsible for many plant diseases, as solanaceas in which stemphylium leaf blight, which productivity of these crops can be negatively affected due lacking in available fungicides. Therefore, the purpose of this work was to determine a culture medium that would allow of Stemphylium sp. mycelial growth isolated from onion for a later evaluation of melaleuca oil (M. alternifolia) effect under different in vitro concentrations. For this, in the first test eight culture media were tested: Potato-Dextrose-Agar (PDA); Juice V-8® 5% Agar; V-8® Juice 10% Agar; Juice V-8® Agar 20%; Tomato Juice 5% (ST5%); Tomato Juice 10% (ST10%); Tomato Juice 20% (ST20%) and Malt Extract Agar 2%. At ten days and fifteen days, the highest growth was identified with treatments ST20% and PDA and, conversely, treatments V8-5% and V8-10% the lowest growth. In the second trial, melaleuca oil was tested in five concentrations (0; 0, 2; 0,4; 0,6 and 0,8%) diluted in PDA and the MGR (mycelial growth rate) was determined. The melaleuca essential oil reduced the Stemphylium sp. mycelial growth with better fit to the quadratic equation y=28,074x2 - 46,136x + 19,94. The MGR was reduced by the oil added to culture medium and could represent a promising alternative for this pathogen control. <![CDATA[Agronomic evaluation of nitrogen-fixing bacteria isolated from Andean soils in lettuce and tomato seedlings]]> http://scielo.iics.una.py/scielo.php?script=sci_arttext&pid=S2305-06832021000100047&lng=en&nrm=iso&tlng=en RESUMEN El uso prolongado de fertilizantes químicos sintéticos produce efectos negativos en la fertilidad del suelo. Como alternativa, en los últimos años se ha propuesto la utilización de microorganismos en la agricultura. El objetivo de este ensayo fue evaluar la eficiencia agronómica de aislados de microorganismos de diferentes suelos con cultivos nativos andinos, en la germinación y el crecimiento de plántulas de tomate y lechuga. Para ello se aislaron y seleccionaron bacterias fijadoras de nitrógeno de vida libre utilizando medio Ashby en suelos y rizosfera de cultivos de amaranto (Amaranthus quitensis Kunth), mora (Rubus glaucus Bentham), zanahoria blanca (Arracacia xanthorriza Bancr.) y mashua (Tropaeolum tuberosum Ruiz &amp; Pav.). Posteriormente se realizaron pruebas fisiológicas y bioquímicas para seleccionar las bacterias que se asemejaban al género Azotobacter sp., y se inocularon en cultivos en invernadero de lechuga y tomate, de febrero a abril de 2018, donde se midieron los días a la germinación, altura de la planta, número de hojas, y se realizó un análisis de varianza y test de Tukey para evaluar si existían diferencias estadísticas entre los tratamientos. En la inoculación de 3 cepas en el cultivo del tomate se observó un adelanto significativo en el tiempo de germinación de 3-4 días. En 9 de los tratamientos se constató un aumento significativo en la altura de la planta tanto de tomate como de lechuga y el número de hojas aumentó significativamente en 6 tratamientos de lechuga y 3 de tomate. La cepa bacteriana que mejores resultados obtuvo fue aislada en la rizosfera del cultivo de mora.<hr/>ABSTRACT The prolonged use of synthetic chemical fertilizers produces negative effects on the fertility of the soil. As an alternative, the use of microorganisms in agriculture has been proposed in recent years. The objective of this trial was to evaluate the agronomic efficiency of isolates of microorganisms from different soils with native Andean crops in the germination and growth of tomato and lettuce plants. To do this, free-living nitrogen-fixing bacteria were isolated and selected using Ashby medium in soils and rhizosphere of amaranth (Amaranthus quitensis Kunth), blackberry (Rubus glaucus Bentham), white carrot (Arracacia xanthorriza Bancr.) And mashua (Tropaeolum tuberosum Ruiz &amp; Pav.). Subsequently, physiological and biochemical tests were carried out to select bacteria that resembled the genus Azotobacter sp., and were inoculated in greenhouse crops of lettuce and tomato, from February to April 2018, where the days to germination, plant height, and number of leaves were measured, and an analysis of variance and Tukey’s test were performed to assess whether there were statistical differences between the treatments. In the inoculation of 3 strains in the tomato crop, a significant advance in the germination time of 3-4 days was observed. In 9 of the treatments, a significant increase in the height of both tomato and lettuce plants was observed, and the number of leaves significantly increased in 6 lettuce and 3 tomato treatments. The bacterial strain that obtained the best results was isolated in the rhizosphere of the blackberry crop.