Investigación Agraria

Digital mapping: new approach on soil survey

O uso cada vez mais intensivo do solo e sua ocupação desordenada resultam em sua degradação. Existe uma grande carência de informações mais detalhadas de solos e seus levantamentos. Por apresentarem informações básicas sobre esse recurso natural e sua distribuição na paisagem, os mapeamentos são fundamentais para o manejo sustentável das terras. A produção de mapas de classes e atributos, com maior nível de detalhamento, só será possível com a utilização de geotecnologias combinadas com dados coletados no campo. Assim, o objetivo desta revisão foi ressaltar a importância dos levantamentos de solos dentro de um novo paradigma, definido como Mapeamento Digital de Solos (MDS). A prática de MDS requer que: i) os dados utilizados tenham sua origem em coletas de campo e resultados analíticos de laboratório, incluindo dados legados e novas coletas; ii) o processo de inferência e espacialização inclui a proposição de modelos matemáticos e estatísticos entre as observações do solo, as covariáveis ambientais e os demais fatores scorpan; e, iii) os resultados estejam na forma de um sistema espacial em solos, com dados contínuos e/ou discretos, agregados à incerteza dessas informações, podendo ser atualizados sempre que novas observações estiverem disponíveis. A aplicação do MDS irá permitir que informações espaciais em solos, de atributos e classes, sejam geradas e prontamente disponibilizadas em formatos digitais e com a incerteza associada. Entre os desafios para uma maior aplicação das várias estratégias disponíveis em MDS está a capacitação e formação das futuras gerações de pedólogos.

Increasingly intensive use of soil and its disorganized occupancy result in its degradation. There is a lack of more detailed information on soils and on soil surveys. Soil mappings are key for land sustainable management because they provide basic information about this natural resource and its distribution on the landscape. The production of highly detailed soil class and attribute maps, will only be possible using geotechnologies in combination with field data. The objective of this review was to emphasize the importance of soil surveys within a new paradigm, defined as Digital Soil Mapping (DSM). DSM requires: i) the use of data from field sampling and analytical results from laboratories, including existing as well as newly collected data ii) the process of inference and of spacing includes a proposition of mathematical and statistical models based on soil observation, environmental covariates and other scorpan factors iii) results should be presented as soil spatial system format with continuous and/or discrete data, added to the uncertainty of this information, which could be updated whenever new observations become available. The application of DSM will make it possible for soil spatial information, attributes and classes to be generated and be readily available in digital format with its associated uncertainty. Among the challenges for further implementation of several strategies available in DSM, the training of future generations of soil scientists should be a priority.

Rural extension in Paraguay: Problems and conceptions of extension analysis

El artículo presenta una investigación que tuvo por objetivo analizar los problemas y concepciones de extensión de los agentes de la Dirección de Extensión Agraria (DEAg) del Paraguay desde su propio punto de vista. Teniendo en cuenta la importancia de los servicios de extensión en los procesos de desarrollo rural y los elevados índices de pobreza rural de Paraguay, se destaca el interés de la investigación realizada. Es dable mencionar que con el advenimiento del neoliberalismo económico en los 80 y 90, los servicios de extensión a nivel del MERCOSUR se redujeron a su mínima expresión, observándose en los últimos tiempos un resurgir de la extensión pública en diversos países de la región. A nivel metodológico, se realizó una revisión bibliográfica sobre la temática y se encuestó a 26 extensionistas que trabajan en la DEAg. Los resultados de las encuestas fueron categorizados siguiendo los lineamientos de la Teoría Fundamentada. Se identificaron como los principales problemas percibidos el bajo nivel educativo del productor, la adopción de actitudes pasivas y asistencialistas, la escasa apropiación de proyectos de extensión, el uso de tecnologías inapropiadas y la dificultad para el asociativismo. Varios de estos problemas, como la escasa participación en proyectos y la adopción de posicionamientos pasivos, se relacionan con una concepción difusionista de la extensión, la cual pone a los beneficiarios en un lugar subordinado, limitando sus dinamismos y sus posibilidades de influir en el diseño de los proyectos para que se adapten a sus necesidades.

This article presents the results of a research aimed at analyzing the problems and conceptions about rural extension held by the Directorate of Agricultural Extension (DEAg )s practitioners in Paraguay, according to their own point of view. The interest of the research lies in the importance of agricultural extension for rural development processes as well as in the high levels of rural poverty in Paraguay. It should be mentioned that with the advent of economic neo-liberalism during the 80s and 90s, rural extension services at MERCOSUR were cut down to its lowest levels. However, it is noteworthy to point out that it has been noticed a resurgence of public extension services in several countries in the region during the last years. At a methodological level, a literature review on the topic was carried out and 26 Agricultural Extension (DEAg )s practitioners were surveyed. Replies to the surveys were categorized following Grounded Theorys principles. Among the main problems detected were the following: small farmerss low level of education, adoption of passive and welfare dependant attitudes, scarce commitment to extension projects, use of inappropriate technologies and struggle to take part in associative work. Some of these problems, such as scarce involvement in projects and the adoption of passive attitudes, are related to a diffusionist conception of extension, which places beneficiaries in a subordinate position, thus limiting their dynamisms and restricting their possibilities to influence tailoring project´s design to meet their needs.

**Potential of steel slag in the induction of resistance to foliar disease on wheat (Triticum aestivum L.)**

Las enfermedades foliares del trigo reducen 20 a 30% la productividad del cultivo. Con el fin de encontrar nuevas alternativas de manejo se evaluó el grado de inducción de resistencia de la escoria siderúrgica sobre la intensidad de las enfermedades foliares. Se realizó un experimento en el Campo Experimental de la Facultad de Ciencias Agrarias de la Universidad Nacional de Asunción que consistió en identificar los patógenos asociados a esta etiología, determinar la intensidad de la enfermedad (% severidad) con la ayuda de escalas diagramáticas, el índice de área foliar (IAF), el contenido de clorofila y el rendimiento. Los tratamientos utilizados fueron dosis crecientes de escoria siderúrgica, un testigo absoluto y un testigo químico, que fueron dispuestos en un diseño completamente al azar con 4 repeticiones. Los datos obtenidos fueron sometidos al análisis de varianza al 5% de probabilidad de error. Las plantas sintomáticas fueron llevadas al laboratorio y se identificaron los patógenos: Drechslera tritici-repentis; Bipolaris sorokiniana; Septoria tritici y Puccinia triticina. El IAF se cuantificó mediante el equipo medidor AAC-100, el contenido de clorofila mediante el medidor portátil SPAD® y el rendimiento expresado en kg ha-1. Se determinóel potencial efecto inductor en la dosis de 500 kg ha-1 al presentar menor severidad de enfermedades, aunque no se encontró diferencias significativas tanto en el rendimiento como en el IAF al aumentar la dosis de escoria siderúrgica. La concentración de clorofila aumenta al utilizar dosis bajas de escoria siderúrgica en el suelo.

Foliar diseases reduce 20-30% of crop productivity. In order to find new management options, steel slag´s resistance induction degree on wheat plants (Triticum aestivum L.) foliar disease intensity was assessed. A research, using diagrammatic scales, was carried out at the FCA-UNA Experimental Field with the aim of identifying pathogens associated to this aetiology and of determining disease intensity (severity %). The variables evaluated were Leaf area index (LAI) chlorophyll content and yield. Treatments consisted of increasing steel slag doses with an absolute control and a chemical one. The experimental design was completely randomized with four replications. Data was subjected to analysis of variance with 5% error probability. Laboratory analysis of symptomatic plants identified the pathogens Drechslera tritici-repentis; Bipolaris sorokiniana; Septoria tritici and Puccinia triticina. Leaf area index (LAI) was measured by an AAC-100 measuring device; chlorophyll content was assessed by SPAD® portable meter and yield was expressed by kg ha-1. Potential inducing effect was determined to be at a 500 kg ha-1 dose given that it exhibited the lowest disease severity. No significant difference in either yield or Leaf area index were found when increasing steel slag doses. Chlorophyll concentration increased when lowering steel slag content in soil.

Differential Expression of the gene fla 14 in soybean seed tegument

O tegumento apresenta uma função importante quanto à resistência das sementes e a sua deterioração. Sendo assim, torna-se necessário entender os mecanismos de genes responsáveis por caracteres que possam auxiliar no desenvolvimento de variedades com melhor qualidade. Nesse sentido, a análise da expressão do gene fla 14 que codifica para a proteína Arabinogalactana que esta relacionada diretamente com a síntese da parede celular no tegumento da semente de soja pode contribuir para o avanço dos estudos. Sendo assim, o objetivo do trabalho foi validar primers e analisar o perfil da expressão do gene fla 14 em quatro genótipos de soja, dois desses com tegumento preto (TP e IAC 222) e maior conteúdo de lignina, e outros dois com tegumento amarelo (CD 202 e Potência) e menor conteúdo de lignina. O tecido vegetal (tegumento) foi coletado aos 50 dias após a antese. Para a análise da expressão gênica dos genótipos, utilizou-se a técnica de qRT-PCR, onde foram testadas quatro combinações de primers construídos a partir de modelos de sequência de ESTs da soja. Os resultados da validação demostraram a eficiência dos primers FLA 14 p1 e FLA 14 p2para serem utilizados em estudos de expressão gênica. Em relação ao gene fla 14, pode-se observar queo perfil de expressão deste gene é quantitativamente superior nos genótipos de soja com tegumento preto e conteúdo superior de lignina quando relacionado com os genótipos com tegumento amarelo e menor teor de lignina.

The seed coat has an important role related to seed resistance and deterioration. Therefore, it becomes necessary to understand the mechanisms of genes responsible for traits which can assist developing cultivars with better seed quality. In this sense, the analysis of the expression of fla 14 gene, encoding for the Arabinogalactan protein, which is directly related to cell wall synthesis in soybean seed coat, can contribute to the advancement of this study. Thus, the aim of this work was to validate primers and analyze fla 14 gene expression profile in four soybean genotypes, two of these with black seed coat (TP and IAC 222) and higher lignin content, and two others with yellow seed coat (CD 202 and Potência) and lower lignin content. The plant tissue (seed coat) was collected 50 days after anthesis. qRT-PCR technique was used for genotypes gene expression analysis, through which four combinations of primersconstructed from soybean EST sequence models were tested. The validation results demonstrated the efficiency of FLA 14 p1 and FLA 14 p2 primers in gene expression studies. Regarding fla 14 gene, it was possible to notice that the expression profile of this gene is quantitatively superior in soybean genotypes with black coat and higher lignin content when comparing it with genotypes with yellow coat and lower lignin content.

**Effect of testa in vitro germination of Bipinnula pennicillata (Rchb. F.) Sisternas & Salazar (Orchidaceae)**

Bipinnula pennicillata es una orquídea terrestre que habita en pastizales de Entre Ríos (Argentina). El objetivo de este trabajo fue evaluar el efecto de la cubierta de la semilla en la germinación in vitro, de B. pennicillata en comparación a su viabilidad determinada por la técnica de tetrazolio (Tz). La viabilidad de las semillas almacenadas en frio (4ºC) se evaluó a los 24, 28, 32 y 35 meses, a través de la prueba de tetrazolio (24 h - 0,5% Tz). Con semillas conservadas en refrigerador durante 35 meses, se efectuó la siembra in vitro en un medio MS a la mitad de la concentración, previa desinfección de las semillas. Los tratamientos (T) evaluados fueron: T1, semillas enteras y T2, semillas cortadas. La viabilidad fue de 80%. La germinación, ocurrió a los 61 días después de la siembra (dds). A los 76 días se registró el máximo de germinación con 49% y 53% para los T1 y T2, respectivamente, no encontrándose diferencias significativas (p = 0,05) entre tratamientos; demostrando que la testa no limitó la germinación in vitro. La germinación en comparación con la viabilidad fue significativamente menor. La viabilidad de las semillas fue alta y disminuyó levemente (8%) en un periodo de 35 meses. La oxidación de los protocormos afectó levemente los porcentajes de germinación en ambos tratamientos. La testa no limita la germinación asimbiótica de las semillas en condiciones in vitro, sí lo hace en el tiempo de obtención de protocormos con yema apical y rizoides (61 dds), logrando un 8% más que las semillas enteras.

determined by the tetrazolium viability determination method (Tz). The viability of seeds stored in cold conditions (4 °C) was evaluated at 24, 28, 32 and 35 months, through tetrazolium testing method (24 hours - 0.5% Tz). In vitro planting was carried out using seeds preserved in refrigerator for 35 months, in a M and S medium at half the concentration. Seeds were disinfected before planting. Treatments (T) evaluated were T1 for whole seeds and T2 for cut seeds, obtained viability was 80%. Germination occurred 61 days after sowing (das). Maximum germination took place 76 days after sowing with 49% and 53% germination rate for T1 and T2 respectively, with no significant differences (p = 0.05) between treatments; showing that seed coat did not limit in vitro germination. Germination was significantly lower as compared with seed viability. Seed viability was high and it slightly decreased (8%) over a period of 35 months. Protocorms oxidation slightly affected germination rates in both treatments. It was concluded that seed coat does not limit asymbiotic seed germination under in vitro conditions, though it does when obtaining protocorms with apical bud and rhizoids (61 das), achieving 8% more than whole seeds.

Effect of different temperatures on physiological quality of sesame seeds

En el proceso de germinación de las semillas, éstas pueden ser afectadas principalmente por la disponibilidad de agua, temperatura y luz, que influyen en la germinación. El objetivo del estudio fue evaluar la calidad fisiológica de semillas de cinco genotipos de sésamo sometidos a diferentes temperaturas. Se utilizaron cinco genotipos de semillas de sésamo producidas en Paraguay. El trabajo tuvo dos fases: en la primera, se evaluó la calidad física y en la segunda, la calidad fisiológica. El diseño experimental utilizado fue completamente al azar con arreglo bi-factorial donde el factor A fueron los genotipos (Kemasem, SH1, Escoba, Negro Paraguay y Dorado) y el factor B las temperaturas (cuatro niveles: 20°C, 25°C, 30°C y 35°C) con cuatro repeticiones, totalizando 80 unidades experimentales. Los resultados indicaron que el peso de mil semillas mostró un rango de 2,29 a 2,92 g siendo Kemasem el más sobresaliente; en la calidad fisiológica los genotipos Negro Paraguay, Kemasem y Escoba registraron mayor germinación tanto en el primer conteo y conteo final. Se observó que en las temperaturas de 25 y 30°C las semillas presentaron mejor desempeño germinativo en comparación, a las temperaturas 20 y 35°C que registraron germinaciones inferiores. Se concluye que la expresión de la germinación y el peso seco de la plántula total dependió más del genotipo utilizado; las temperaturas de 25 y 30°C son las que propician un mejor desempeño germinativo en los genotipos de sésamo del Paraguay; los genotipos de sésamo que registraron la mejor calidad física y fisiológica fueron: Negro Paraguay y Kemasem.

During seeds germination process, they may mainly be affected by the availability of water, temperature and light, which all influence germination. The objective of the study was to evaluate physiological quality of five sesame seeds genotypes subjected to different temperatures. The study was carried out using five sesame seeds genotypes produced in Paraguay. The research had two phases: in the first phase, seeds physical quality was evaluated and in the second one, seeds physiological quality. The experimental design was a completely randomized bifactorial arrangement with four replications, totaling 80 experimental units. The variables evaluated were seeds genotype, called factor A (Kemasen,SH1, Escoba, Negro Paraguay and Dorado) and temperature, called Factor B (four levels: 20°C, 25°C, 30°C and 35°C) Results showed that one thousand seeds yielded between 2.29 to 2.92 g weight being Kemasen the most outstanding genotype; Regarding physiological quality, Negro Paraguay, Kemasen and Escoba genotypes had the highest germination rate, both on the first and the last counting. As for the effect of temperature, it was observed that germination was better under temperatures of 25ºC and 30°C compared to temperatures of 20ºC and 35°C. It is concluded that germination rate and seedlings total dry weight depended more on seed genotype. Temperatures of 25ºC to 30°C are the best one for highest germination rate of Paraguayan sesame seed genotypes; The best physical as well as physiological quality were achieved by Negro Paraguay and Kemasem genotypes.

Foliar fertilization with boron on soybean crops

La soja es el cultivo de mayor importancia económica en Paraguay. Actualmente, la fertilización foliar constituye una de las técnicas más utilizadas para suplir las necesidades de micronutrientes, por su efectividad y eficiencia. Con el objetivo de evaluar la respuesta del cultivo de soja a la fertilización foliar con boro (B), en Itakyry, Alto Paraná, se realizó un ensayo en la que se utilizó el diseño experimental en bloques completos al azar, con 10 tratamientos y tres repeticiones. Los tratamientos fueron: 2,8; 3,7; 4,6; 5,6; 6,5; 7,4; 8,3; 9,3 y 10,2 g ha-1 de Baplicados en la floración. Se evaluó: altura de planta, número de vainas por planta, rendimiento de granos y peso de 1.000 granos. La altura de planta no presentó diferencia significativa a nivel estadístico variando los resultados entre 57,0 y 60,3 cm, el número de vainas por planta aumentó linealmente con la aplicación de B, pasando de 43,3 vainas en el testigo, hasta 48,3 vainas por plantas. El rendimiento de granos también aumentó linealmente pasando de 3.470 kg ha-1 a 3.819 kg ha-1, con un incremento de 349 kg. El peso de 1.000 granos pasó de 155 g a 160 g. El incremento del rendimiento con la dosis de 9,3 g ha-1 de B, comparada al testigo se muestra bastante ventajoso, principalmente cuando se considera la producción en escala.

Soybean is the most important cash crop in Paraguay. Currently, foliar fertilization is one of the most used techniques to meet trace elements needs, due to its effectiveness and efficiency. In order to evaluate the response of soybean to foliar fertilization with boron (B) on a Rhodic Paleudalf in Itakyry, Alto Paraná, a trial design in randomized complete block with 10 treatments and three replications was performed. The treatments were: 0; 2,8; 3,7; 4,6; 5,6; 6,5; 7,4; 8,3; 9,3 y 10,2 g of B per hectare, applied at blooming. The variables evaluated were: plant height, number of pods per plant, grain yield and 1,000 seeds weight. Plant height showed no significant statistical difference in values between 57.0 and 60.3 cm, pod number per plant increased by applying B, from 43.3 pods in the control to 48.3 pods per plant. Grain yield also increased, from 3,470 kg ha-1 in the control to 3,819 kg ha-1, which implies an increase of 349 kg ha-1. The weight of 1000 seeds increased from 155 g in the control to 160 g. Yield growth with a B dose of 9.3 g/ ha-1, compared to that of the control is shown to be quite advantageous, especially when considering a scale production.

**Evaluation of plant extracts for the control of tomato leaf miner Tuta absoluta (Meyrick) growing undergreen house**

La Tuta absoluta (Meyrick), es una plaga importante del tomate en Paraguay, causante de daños significativos al cultivo. Su control depende principalmente de la aplicación continua de insecticidas convencionales, siendo una alternativa el empleo de extractos vegetales. El objetivo del experimento fue evaluar extractos vegetales en el control de T. absoluta (Meyrick) en el cultivo de tomate en condiciones de invernadero. El diseño experimental fue de bloques completos al azar con cinco tratamientos y cuatro repeticiones Los tratamientos fueron extractos de Melia azedarach L., Allium sativum L., Eucalyptus grandis W. Hill. (Ex. Maiden), Capsicum frutescens L. más jabón y un testigo sin aplicación. Las variables medidas fueron número de larvas vivas antes de aplicar los extractos, número de larvas vivas a las 2 y 24 h después de las aplicaciones de los extractos y rendimiento del tomate. La reducción poblacional de las larvas se observó a las 2 h después de la aplicación de los extractos de A. sativum y C. frutescens más jabón con 36 y 30% respectivamente; a las 24 h los extractos de C. frutescens más jabón y E. grandis fueron de 33 y 27% con relación al testigo, respectivamente. Los rendimientos de tomate en los tratamientos con aplicación de los extractos vegetales E. grandis y C. frutescens fueron de 61,16 y 70,39 kg/Parcela, respectivamente, siendo significativamente superiores al obtenido en el testigo, con 37,15 kg/Parcela. Los extractos vegetales presentan capacidad de control de Tuta absoluta (Meyrick) en el cultivo de tomate bajo condiciones de invernadero.

Tomato leaf miner, Tuta absoluta (Meyrick), is one of the main tomato pests in Paraguay, causing significant damage to crops. Current control measures primarily rely on continuous application of conventional insecticides. The use of plant extracts may be an alternative control measure instead of currently used insecticide. The aim of the experiment was to determine the efficacy of plant extracts in the control of T. absoluta in tomato (Lycopersicon esculentum Mill) grown under greenhouse conditions. The study was carried out at the Hernando Bertoni Research Center, in Caacupé-Paraguay from January to May 2012. The experimental design was randomized complete blocks with five treatments and four replications. Treatment consisted on Melia azedarach L., Allium sativum L., Eucalyptus grandis W. Hill., Capsicum frutescens extract with soap and a control with no treatment. The variables evaluated were number of larvae alive before extracts application, number of larvae alive at 2 and 24 hours after application, and tomato yield. Larvae population reduction were 36% and 30% respectively observed 2 hours after A. sativum and C. frutescens extract application with soap and 33% and 27% at 24 hours after C. frutescens and E. grandis extract application with soap compared to the control. Tomato yield with E. grandis y C. frutescens extract application treatments were 61.16 and 70.39 kg/plot respectively, significantly higher than the obtained in the control with no treatment which was 37,15 kg/plot. Plant extracts show efficacy in the control of T. absoluta in tomato (Lycopersicon esculentum Mill) grown under greenhouse conditions.