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Tesis para la obtención del grado de Magíster en Bioseguridad con Mención en Salud Animal, otorgado por la Universidad Nacional de Rosario, en septiembre de 2022 La provisión de pollitos a la industria avícola ocurre por medio de granjas de abuelos y reproductores que abastecen a las plantas de incubación, y los procesos que allí ocurren generan grandes cantidades de residuos orgánicos, formados principalmente por pollitos de descarte y muertos, huevos no nacidos, cáscaras y plumón (RI). La eliminación de estos residuos de forma segura y viable económicamente es una de las grandes preocupaciones actuales del sector avícola, ya que presentan alta carga de materia orgánica (MO) y son potencialmente patógenos. El compostaje es una opción económica y simple para su tratamiento ya que estabiliza la MO y destruye la mayoría de los parásitos, patógenos y virus contenidos en estos residuos, generando un producto con capacidad fertilizante en vegetales. En el presente trabajo se estudiaron el material disponible para realizar una mezcla que presente una relación de Carbono y Nitrógeno (C/N) adecuada para el proceso de compostado (C/N: 25-30). Se realizaron determinaciones fisicoquímicas de RI, cama usada (CU) y viruta de madera (VM) proveniente de los galpones de reproductores. Se realizó un ensayo con aireación estática en caseta utilizando pasto de corte y CU como fuente de Carbono (C). Con este método, las temperaturas (T°) alcanzadas demostraron ser independientes a las ambientales y suficientes para realizar el saneamiento del material. Además, se compostaron RI con VM en pilas a cielo abierto. En este caso las T° también resultaron independientes de las ambientales y a su vez las necesarias para el saneamiento del material. En el transcurso del proceso se observó una disminución de la MO y de la respiración basal, con un aumento del índice de germinación. Los estudios microbiológicos realizados determinaron un compost apto para ser utilizado o vertido en el medio ambiente. Con los compost obtenidos de estas experiencias se efectuaron ensayos de fertilización en maíz (Zea mays) y lechuga (Lactuca sativa L.) con el objeto de comprobar su capacidad fertilizante. En ambos se obtuvieron índices productivos alentadores. El grano de maíz obtenido se estudió en sus características nutricionales (Energía Metabolizable Verdadera), y se realizó análisis proximal y perfil de aminoácidos. Los compost resultaron aptos para uso agronómico como fertilizante orgánico. The provision of chicks to the poultry industry occurs through grandparent and breeder farms that supply the hatcheries, and the processes that occur there generate large amounts of organic waste, formed mainly by discarded and dead chicks, unborn eggs, shells and chick down (poultry hatchery waste or PHW). The elimination of these residues in a safe and economically viable way is one of the great current concerns of the poultry sector, since they present a high load of organic matter (OM) and are potentially pathogenic. Composting is an inexpensive and simple option for its treatment since it stabilizes OM and destroys most of the parasites, pathogens and viruses contained in this waste, generating a product with fertilizer capacity in vegetables. In the present work, the available material was studied to make a mixture that presents a Carbon to Nitrogen (C/N) ratio suitable for the composting process (C/N 25-30). Physicochemical determinations of PHW, poultry litter (PL) and wood shavings (WS) from the breeder houses were made. A test was carried out with static aeration in a shed using cut grass and PL as a source of Carbon (C). The temperatures (T°) reached with this method proved to be independent of the ambient T° and sufficient to sanitize the material. In addition, PHW with WS were composted in open-air piles. In this case, the T° were also independent of the environmental ones and in turn those necessary for the sanitation of the material. During the process, a decrease in OM and basal respiration was observed, with an increase in the germination index. The microbiological studies carried out determined a compost suitable to be used or dumped in the environment. With the compost obtained from these experiences, fertilization tests were carried out on corn (Zea mays) and lettuce (Lactuca sativa L.) in order to verify their fertilizing capacity. Encouraging productive indices were obtained in both. The corn grain obtained was studied for its nutritional characteristics (True Metabolizable Energy), and a proximal analysis and an amino acid profile were performed. The compost was suitable for agronomic use as organic fertilizer. EEA Pergamino Fil: Fain Binda, Virginia. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Pergamino. Sección Avicultura; Argentina

La horticultura argentina es una actividad de relevancia como productora de alimentos indispensables en la dieta y motor de economías regionales. La lechuga (Lactuca sativa L.) ocupa el cuarto lugar entre las principales hortalizas cultivadas en el país. Factores pre-cosecha, tales como el genotipo, las condiciones ambientales y el sistema productivo, afectan tanto la composición química como las propiedades biológicas de esta especie. El objetivo del presente trabajo fue evaluar el contenido de compuestos fenólicos y actividad antioxidante de diferentes genotipos de lechuga producidos en campo e invernadero. Se observaron diferencias significativas para el contenido de compuestos fenólicos totales y la actividad antioxidante entre tipos de lechuga para cada sistema de producción y entre genotipos pertenecientes a un mismo tipo (p < 0,05). El análisis de correlación entre la actividad antioxidante in vitro y el contenido de compuestos fenólicos totales, evidenció una relación significativa y positiva entre estas variables. Los datos obtenidos evidencian una marcada variabilidad entre los distintos genotipos, lo que podría contribuir a la selección de cultivares con mayores mejores propiedades funcionales. Es fundamental identificar los sistemas de producción óptimos. Argentina horticulture is a relevant activity since it produces essential vegetables for human consumption and promotes regional economies. Lettuce (Lactuca sativa L.) ranks fourth among the main vegetables grown in the country. Pre-harvest factors, such as genotype, environmental conditions and production system affect chemical composition and biological properties of lettuce. The aim of this work was to evaluate the total phenolic content and antioxidant activity of lettuce genotypes produced in field and greenhouse cultivation systems. Significant differences were observed for total phenolic content and antioxidant activity among lettuce’s types for each production system and genotypes of the same type (p

Este ensayo surge a partir de la consulta de un productor de plantines respecto a la composición química del sustrato utilizado en producción. El sustrato utilizado en los plantines de lechuga ¿Qué características físicas y químicas tiene? ¿ Permitirá obtener un plantin de calidad? EEA Catamarca Fil: Ignes, Carlos Mariano. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Catamarca. Agencia de Extensión Rural Paclin; Argentina Fil: Carrasco, Franca Denise. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Catamarca; Argentina Fil: Balbi, Fernando Dario. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Catamarca. Agencia de Extensión Rural Paclin; Argentina Fil: Silva, Luis. Cultivos Hidropónicos de Hoja “Los Yuyos”; Argentina

Composting is an aerobic process used to treat organic residues, which results in a high quality product, able to be adopted as plant substrate or soil amendment. In the present study, the performance of compost on the germination and biomass of Lactuca sativa var Grand rapids seedlings, with and without fertilization, was evaluated. The two types of composts used were prepared from two different raw materials: grape marc and a mixture of grape marc, goat manure, leaves and alfalfa. The experiment was carried out in seedling trays, in a split plot design with two factors (fertilization and substrate) and four repetitions. Sand were used as control and a commercial substrate as traditional treatment. Results indicated that fertilization had not significant effect on germination, but increased seedling biomass. Both compost also increased lettuce biomass, with the highest values obtained in mixture compost treatments. Only sand produced the lowest germination values, while no differences were detected among the other substrates. Compost mixture showed the highest seedling biomass, suggesting a higher quality as a plant substrate. It is necessary to perform further analyses and studies with different organic residues in order to determine physico-chemical and biological properties to evaluate the quality of the product obtained. El compostaje permite reducir y reciclar residuos orgánicos, generando un producto apto para ser utilizado como sustrato para el crecimiento de plantines florales y hortí-colas o como enmienda de suelos. En el presente trabajo, se evaluó el efecto del compost elaborado a partir de orujo de uva agotado y de una mezcla de orujo, guano de cabra, hojas y alfalfa, sobre la germinación y biomasa de plantines de Lactuca sativa var Grand rapids, con y sin fertilización. Se trabajó en bandejas de siembra con un diseño de parcelas divididas con dos factores (sustrato y fertilización), utilizando, arena como control y un sustrato comercial como tratamiento tradicional. Los resultados indicaron que la fertilización no tuvo efecto significativo sobre la germinación, obteniéndose los menores valores con la arena, sin encontrarse diferencias entre el resto de los sustratos. Por otro lado, ambos tipos de compost produjeron mayor biomasa que el sustrato comercial y la arena, efecto que se incrementó con la fertilización. El compost mezcla fue el sustrato que produjo el mayor crecimiento de plantines de lechuga, lo que indicaría una mayor calidad para ser utilizado como sustrato. Es necesario continuar con estudios para determinar las propiedades fisicoquímicas y biológicas del compost que permitan evaluar la calidad de producto obtenido. EEA Mendoza Fil: Funes Pinter, Mariano Ivan. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Mendoza; Argentina. Universidad Nacional de Cuyo. Facultad Ciencias Agrarias; Argentina Fil: Aguado, German Dario. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Mendoza; Argentina Fil: De Biazi, Federico Sebastian. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Mendoza; Argentina. Fil: Fernández, Ana Sofía. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Mendoza; Argentina. Fil: Martinez, Laura Elizabeth. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Mendoza; Argentina. Universidad Nacional de Cuyo. Facultad Ciencias Agrarias; Argentina Fil: Uliarte, Ernesto Martin. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Mendoza; Argentina

El crecimiento demográfico progresivo genera la expansión de los centros urbanos hacia zonas donde comúnmente se ubican los cinturones hortícolas; este aumento poblacional ejerce una fuerte demanda de esas tierras productivas para destinarlas a proyectos de desarrollos urbanísticos. Ante esta situación, es necesaria la aplicación de tecnologías que permitan un mejor aprovechamiento del espacio cultivado, como la práctica de la intersiembra, que consiste en sembrar dos o más especies en la misma superficie para aumentar su productividad. El objetivo de este trabajo fue estudiar el efecto de la intersiembra sobre el rendimiento y características morfológicas en lechuga y rúcula usando diferentes distanciamientos entre líneas, en la localidad de Colonia Benítez, Chaco. Los tratamientos fueron: R= rúcula a 0,2 m entre líneas; L= lechuga a 0,4 m entre líneas; LR1= intersiembra lechuga–rúcula, lechuga a 0,4 m entre líneas y una línea de rúcula entre las líneas de lechuga y LR2= intersiembra lechuga–rúcula, lechuga a 0,4 m entre líneas y dos líneas de rúcula entre las líneas de lechuga. La cosecha de rúcula se realizó a los 30 días después de la siembra (DDS) y la de lechuga a los 62 DDS, evaluándose el peso fresco aéreo (PF), el peso fresco total (PFT) y la tasa de tierra equivalente (Land Equivalent Ratio; LER), la cual es definida como la superficie total de monocultivo necesaria para lograr el mismo rendimiento que en intersiembra. En ambos cultivos se contó el número total de hojas y en lechuga se midió la longitud de tallo, el peso seco de las hojas y el peso seco del tallo. La mayor producción total se observó en el tratamiento LR1, seguida por LR2 y L. La intersiembra tuvo un efecto negativo sobre el cultivo de lechuga, disminuyendo el rendimiento; este efecto fue mayor cuando fueron dos las líneas de rúcula intersembradas (LR2). En lechuga el número de hojas y la longitud del tallo también se vieron afectados. En LR1 la intersiembra no tuvo efecto en el rendimiento de rúcula; sin embargo, en LR2 el efecto fue negativo, tanto para lechuga como para rúcula. En ninguno de los tratamientos se detectó un efecto sobre el número de hojas de rúcula. El tratamiento de LR1 presentó un LER superior a 1, considerándose que este tratamiento tuvo mejor performance en cuanto a su productividad y calidad de plantas. Progressive demographic growth generates the expansion of urban centers towards areas where horticultural belts are commonly located; this population increase produces a hard demand for these productive lands to be used for urban development projects. Given this situation, it is necessary to apply technologies such as intercropping, that consists of planting two or more species on the same field to increase their productivity. The objective of this work was to study the effect of intercropping on yield and morphological characteristics of lettuce and rocket using different distances between rows at Colonia Benítez, Chaco. Treatments were: R=rocket at 0.2 m between rows; L= lettuce at 0.4 m between rows; LR1= lettuce-rocket intercropped, with lettuce at 0.4 m between rows and one row of rocket between lettuce rows and LR2= lettuce-rocket intercropped, with lettuce at 0.4 m between rows and two rows of rocket between lettuce plants. Rocket was harvested 30 days after sowing (DAS) and lettuce 62 DAS, when the above ground fresh weight (FW) and total fresh weight (TFW) were determined, and land equivalent ratio (LER), defined as the total land area of the sole crop required to achieve the same yields as the intercrops, was calculated. For both crops the total number of leaves was counted and stem length, leaf dry weight and stem dry weight were measured on lettuce. The highest total production was observed in the LR1 treatment, followed by LR2 and L. Intercropping had a negative effect on lettuce, decreasing yield; this effect was greater when there were two lines of rocket (LR2). In lettuce the number of leaves and the length of the stem were also affected. Rocket yield was not affected in LR1, however, in LR2 the effect was negative for both lettuce and rocket. There was no effect on the number of leaves of rocket in any of the treatments. LR1 presented a LER higher than 1. We consider that this was the treatment with the best performance in productivity and plants quality. EEA Colonia Benitez Fil: Shindoi, Mauro Masakichi Jere. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Colonia Benitez; Argentina. Fil: Avico, Eda Larisa. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Colonia Benitez; Argentina Fil: Sarco, Pamela Carolina. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Colonia Benitez; Argentina Fil: Monteros, Diego Ezequiel. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Colonia Benitez; Argentina

Se evaluaron dos variedades de lechuga crespa, en dos épocas de producción distintas. La primera se trasplantó el 7 de abril y se cosechó el 5 de junio. La segunda se trasplantó el 31 de Julio y se cosechó el 19 de Octubre. En ambas se utilizó un diseño de parcelas divididas en 4 bloques al azar. En cada parcela se trató un tipo de de acolchado: testigo, mulching natural, mulching blanco -de reverso negro- y mulching negro. Y en las subparcelas el tratamiento fue: una variedad (Brisa - Garde Giusti Chuchuy SA) y un híbrido (Isabela – Sakata) de lechuga crespa. Se utilizó como mulching natural, una mezcla de gramíneas secas (Cynodom sp., Paspalum sp., Setaria sp., entre otros). Fil: Corti, Alberto Fabian. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Reconquista; Argentina

El exceso de Na+, carbonatos y bicarbonatos presentes en el agua de riego incrementan el pH, la conductividad eléctrica (CE) y el porcentaje de sodio intercambiable (PSI), afectando el crecimiento de los cultivos. El objetivo de este trabajo fue cuantificar el impacto de prácticas de manejo con aplicación de yeso y drenaje en suelos petrocálcicos de La Pampa afectados por riego con aguas subterráneas bicarbonatadas sódicas. Se cultivó lechuga durante cuatro ciclos (500 días) en dos invernáculos diferenciados por la cantidad previa de años de riego, utilizando un diseño factorial completamente aleatorizado con 4 submuestras (unidades de medición). Los tratamientos en ambos túneles (2 años=B1 y 4 años=B2) fueron: 1) T0, testigo sin tratar; 2) T1, 3,5 Mg ha-1 de yeso agrícola, 3) T2, 3,5 Mg ha-1 de yeso agrícola + drenaje y 4) T3, drenaje. La incorporación de yeso disminuyó la concentración de Na+ y PSI signifi cativamente desde superficie hasta 0,4 m. También mejoró significativamente las condiciones físicas del suelo en el túnel B2, aspecto que se manifestó con un incremento de la productividad acumulada del cultivo de lechuga. En cambio no se encontraron diferencias significativas en el pH del suelo en ninguna de las profundidades evaluadas. Adicionalmente, la CE del suelo con los diferentes tratamientos disminuyó notablemente a partir del 2º ciclo de producción debido al incremento en la dosis de riego The excess of Na+, carbonates and bicarbonates present in irrigation water increases the pH, the electric conductivity (EC) and the exchangeable sodium percentage (ESP) in the soil, thus affecting crop growth. The aim of this work was to quantify the use of different techniques in petro-calcium soils of La Pampa affected by irrigation with sodium bicarbonate underground waters. Lettuce was grown during four cycles (500 days) in two greenhouses differentiated by years of irrigation, using a completely randomized factorial design with 4 sub-samples (units of measurement). Treatments in both tunnels (2=B1 and 4=B2 years) were: 1) T0, non-treated control; 2) T1, 3.5 Mg ha-1 of agricultural gypsum, 3) T2, 3.5 Mg ha-1 of agricultural gypsum + drainage, and 4) T3, drainage. Gypsum signifi cantly decreased the concentration of Na+ and ESP from the surface to 0.4 m. It also significantly improved the physical conditions of the soil in tunnel B2, which was manifested through an increase of the accumulated productivity of the lettuce crop. However, no significant differences were registered in soil pH in any of the evaluated depths. Additionally, the soil EC under the different treatments decreased notably from the 2nd production cycle onwards, due to the increase in the irrigation depth. EEA Anguil Fil: Muguiro, Alberto. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Anguil. Agencia de Extensión Rural General Pico; Argentina Fil: Alvarez, Cristian. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Anguil. Agencia de Extensión Rural General Pico; Argentina Fil: Babinec, Francisco Jose. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Anguil; Argentina Fil: Marano, Roberto Paulo. Universidad Nacional del Litoral. Facultad de Ciencias Agrarias; Argentina

Ex situ collections in genebanks conserve many old cultivars that had disappeared from mainstream agriculture before modern genebanks were established. The collections incorporated cultivars from many sources, such as botanical gardens and working collections, sometimes with little further information on their origin. Many old cultivars with identical or synonymous names are maintained in multiple collections and often more than once within collections. This research investigates the authenticity of old cultivars in genebanks using a large lettuce (Lactuca sativa L.) collection as a case study. Accessions presumed to be identical, based on the cultivar names accompanying the accessions, were compared for their DNA marker profiles, based on amplified fragment length polymorphisms (AFLPs). Using the genetic similarity of these accessions, the probability of authenticity of the old cultivars maintained in the collection was estimated. Separate analyses were done for different classes of cultivars, on the basis of the year of release or the donor history of the cultivar. The two largest cultivar groups within the collection, Sans Rivale à Graine Blanche and Maikönig, were analyzed in detail. Nonauthenticity of the investigated cultivars appeared to be high. This was especially true for the oldest cultivars, but even for the cultivars released from the 1960s to 1990 it was estimated that approximately 10% was not authentic. Recommendations to improve authenticity of cultivars in ex situ collections were presented

El uso de sustrato con lombricompuesto favorece el crecimiento en cultivos hortícolas, siendo importante conocer sus propiedades para dosificar la cantidad adecuada. Este trabajo tuvo como objetivo analizar las modificaciones producidas en un sustrato según la dosis de lombricompuesto adicionado y evaluar el efecto de las mezclas sobre la calidad del plantín de lechuga. El ensayo se realizó en un invernadero en Luján, Argentina (34°36’ S, 59°04’ W). Se sembró lechuga mantecosa cv. Tizona, utilizando sustratos compuestos por distintas combinaciones porcentuales de lombricompuesto y una mezcla comercial formulada con turba y perlita: 1) 0% lombricompuesto, 2) 20% lombricompuesto, 3) 40% lombricompuesto. Las mezclas se analizaron físicoquímicamente. En las plantas se midió número de hojas, peso fresco y seco de parte aérea, raíz y total. El diseño fue en bloques completos aleatorizados con 4 repeticiones. Se realizó análisis de la varianza, evaluando diferencias entre medias por la prueba de Tukey y análisis de regresión para estudiar el tipo de respuesta en los parámetros físicoquímicos de los sustratos por la incorporación de lombricompuesto en el rango de 0 a 40%. La adición de lombricompuesto en los sustratos aumentó linealmente el pH, la conductividad eléctrica, el nivel de nutrientes, la densidad aparente y la porosidad total, y disminuyó linealmente la materia orgánica y cuadráticamente el porcentaje de poros ocupados por agua. Las plantas respondieron al agregado de lombricompuesto adquiriendo mayor tamaño con 20%. Substrates with vermicompost added promote growth in horticultural crops. Therefore, it is important to know its properties in order to apply proper amounts of it. This work aims to analyze substrate changes according to vermicompost doses and evaluate the effect of the mixtures on lettuce seedling quality. The essay was carried out under greenhouse conditions in Luján, Argentina (34°36’S, 59°04’W). Butterhead lettuce cv. Tizona was sown using substrates with different amounts of vermicompost added and a commercial mix of peat and perlite: 1) 0% vermicompost, 2) 20% vermicompost, 3) 40% vermicompost. The substrates were analyzed physically and chemically. Palabras clave: almácigo, vermicompuesto, Eisenia foetida. The number of leaves and both fresh and dry weights of leaves, roots and plant were determined. The treatments were established in a complete randomized block design with four replications. Data were evaluated by analysis of variance, while the difference between means was studied by Tukey`s Test. Regression analysis was used to study the response of substrate physical and chemical parameters to the addition of vermicompost, ranging from 0 to 40%. The addition of vermicompost resulted in a linear increased in pH, electrical conductivity, nutrient level, bulk density and total porosity of the substrate, while organic matter decreased linearly and quadratically the percentage of pores occupied by water. The plants responded to the addition of vermicompost, with a 20% increase in size. Instituto de Floricultura Fil: Tombion, Leticia. Universidad Nacional de Luján. Departamento de Tecnología; Argentina Fil: Puerta, Analia Veronica. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Floricultura; Argentina Fil: Barbaro, Lorena Alejandra. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Floricultura; Argentina Fil: Karlanian, Monica. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Floricultura; Argentina Fil: Sangiacomo, Miguel Angel. Universidad Nacional de Luján. Departamento de Tecnología; Argentina Fil: Garbi, Mariana. Universidad Nacional de Luján. Departamento de Tecnología; Argentina

Tesis para obtener el grado de Maestría en Horticultura, presentada en la Facultad de Ciencias Agrarias, Universidad Nacional de Cuyo en 2016 El manejo adecuado del riego es fundamental para el éxito de un cultivo bajo invernadero. Regar con agua de mala calidad puede ocasionar la acumulación de sales y cationes dispersantes como el sodio, que afecta negativamente algunas propiedades físicas del suelo como la conductividad hidráulica y la infiltración, causando una reducción de su capacidad productiva. El objetivo fue evaluar la incidencia de la aplicación de yeso y azufre sobre la mejora de las condiciones físico-químicas del suelo y en la productividad del cultivo de lechuga bajo cubierta. El ensayo se realizó durante cinco ciclos consecutivos, en un invernadero regado con agua bicarbonatada sódica. Se establecieron dos ambientes de riego (R1=Etc y R2=1,30 Etc) y tres tratamientos de enmiendas (testigo, yeso y azufre). Se evaluaron variables físico – químicas del suelo: CE, pH, CIC, Ca2+, Mg2+, Na+, K+, PSI, infiltración, conductividad hidráulica y productividad del cultivo: kg m-2 y peso fresco por planta. Se determinó que el contenido de sodio en el suelo se acrecienta a lo largo del tiempo cuando se riega con agua de mala calidad. El agregado de enmiendas inorgánicas reduce sustancialmente el aumento del PSI en el suelo, siendo el azufre el que mejor efecto produce. Regar con agua de elevado RAS disminuye la infiltración al final de los cinco ciclos de cultivo de lechuga. Existe un efecto positivo de ambas enmiendas sobre la infiltración. El uso de yeso como enmienda causa una menor disminución de la conductividad hidráulica en el suelo. El riego continuado con agua bicarbonatada sódica produce una disminución en los rendimientos del cultivo de lechuga a lo largo del tiempo. Con el agregado de yeso se obtuvieron los mejores rendimientos. El efecto de las enmiendas es positivo en relación al tamaño de las plantas cosechadas. Proper irrigation management is critical for successful greenhouse cultivation. Water with poor quality can cause the accumulation of salts and dispersants cations such as sodium, which affects negatively some physical soil properties such as hydraulic conductivity and infiltration, and as consequence reduces productivity. The objective of this work was to evaluate the impact of the application of gypsum and sulfur on lettuce crop productivity grown under greenhouse conditions. The trial was performed during five consecutive cycles in a greenhouse irrigated with sodium bicarbonate water. Two main irrigation environments (R1 = Etc and R2 = 1.30 Etc) and three treatments (control, gypsum and sulfur) were established. Physical and chemical soil variables were evaluated (EC, pH, CEC, Ca2+, Mg2+, Na+, K+, PSI, infiltration, hydraulic conductivity) and also crop productivity expressed as kg.m-2 and fresh weight per plant. Sodium content in the soil increases over time when irrigated with water of poor quality. The addition of inorganic amendments substantially reduces the PSI (exchangeable sodium percentage) on the soil. Sulfur produced better effect. The high RAS (sodium adsorption ratio) of the water decreases infiltration after cropping lettuce during five cycles. There is a positive effect of both amendments on infiltration. The use of gypsum as an amendment causes a minor decrease in soil hydraulic conductivity. Continued irrigation with sodium bicarbonate water causes a decrease in lettuce yields over time. The best yields were obtained using gypsum. The amendments have a positive effect in the size of the harvested plants. EEA Mendoza Fil: Lang, María De La Cruz. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Mendoza. Agencia de Extensión Rural Guaymallén; Argentina

The effects of stale seedbed preparations and several weed control methods on the emergence of weeds in lettuce were studied. The specific goal was to evaluate the use of a stale seedbed in combination with chemical or mechanical weed control methods in the field. Depending on location and year, stale seedbed preparations followed by weed control prior to planting reduced the amount of weeds during crop growth by 43¿83%. Control of the emerged seedlings after a stale seedbed preparation was more effective with glyphosate than with a rotary harrow. Covering the rotary harrow during control to prevent light reaching the soil improved its effect on the weed density during crop growth in two of 3 years. Radiation with far red light (FR) did not reduce the number of emerging weeds in this study. Mechanical control by finger weeder, torsion weeder and hoe was applied without stale seedbed preparations. These measures reduced the weed densities by 88¿99%, compared with the untreated control and were more effective than chemical weed control with carbetamide and chlorpropham. The results show that the stale seedbed technique in combination with mechanical control of emerging weeds can reduce the weed population during crop growth as effectively as chemical control. The technique may therefore help reduce the use of herbicides in lettuce crops in the future.

In the autumn of 2014 many companies specialized in protected lettuce cultivation were confronted with severe plant damage. In several lettuce greenhouses garden centipedes were detected. This explorative study summarizes the available knowledge of garden centipedes, and describes new possibilities for their control (chapter 1). It also tested one of the new control options, i.e. luring the garden centipedes with CO2-capsules, in a laboratory set-up (chapter 2). At the concentration tested, no luring effect of the CO2-capsules on the garden centipedes could be detected.At the same time it was found that many damaged lettuce plants suffered from Fusarium root damage. From research by the NVWA (Netherlands Food and Consumer Product Safety Authority) Fusarium was eventually identified as F. oxysporum lactucae. Finally, this seemed to be the most important culprit of the observed plant damage.

In the autumn of 2014 many companies specialized in protected lettuce cultivation were confronted with severe plant damage. In several lettuce greenhouses garden centipedes were detected. This explorative study summarizes the available knowledge of garden centipedes, and describes new possibilities for their control (chapter 1). It also tested one of the new control options, i.e. luring the garden centipedes with CO2-capsules, in a laboratory set-up (chapter 2). At the concentration tested, no luring effect of the CO2-capsules on the garden centipedes could be detected.At the same time it was found that many damaged lettuce plants suffered from Fusarium root damage. From research by the NVWA (Netherlands Food and Consumer Product Safety Authority) Fusarium was eventually identified as F. oxysporum lactucae. Finally, this seemed to be the most important culprit of the observed plant damage. In het najaar van 2014 werden veel slateelt-bedrijven geconfronteerd met een grote uitval van planten en veel schade. Bij verschillende bedrijven werd ook wortelduizendpoot gesignaleerd. In een verkennend project is daarom de bestaande kennis over wortelduizendpoot samengevat, en zijn nieuwe mogelijkheden voor bestrijding van wortelduizendpoten in kaart gebracht. Vervolgens is één van de nieuwe bestrijdingsmogelijkheden, nl. het weglokken van wortelduizendpoten met CO2 capsules, getest in een laboratoriumopstelling. Bij de geteste concentratie hadden de CO2 capsules geen aanlokkend effect op de wortelduizendpoten. Tegelijkertijd werden bij veel slateelt-bedrijven aantasting van wortels door Fusarium waargenomen. Uit onderzoek door de NVWA is de Fusarium uiteindelijk geïdentificeerd als zijnde F. oxysporum lactucae. Deze leek de belangrijkste boosdoener van de uitval.

Gegevens in bijgaande tabellen: 1) Opbrengst krop (ton/ha) bij 4 kalitoestanden en een gift van 240 kg/ha K20; 2) Opbrengst krop (ton/ha) bij een gift van 0,60, 120, 240, en 480 kg/ha K2O; 3) Kali-opname in de krop (kg K20 per ha); 4) K-opname van de krop (kg K2O per ha) bij 4 kalitiestanden en een gift van 240 kg/ha K2O; 5) K-HCI-30 cm einde teelt bij kalitoestanden en een gift van 240 kg/ha K2O; 6) K-HCI 0-30 cm einde teelt bij kaligiften van 0, 60, 240, 480 kg/ha K2O

Resultaten van drie jaar ontwikkeling van een geintegreerd prei-kropsla bedrijf. De gestelde streefopdrachten, kwaliteitsproductie, verliesnormen (MINAS) voor droge zandgronden en onkruidbestrijding staan in tabellen weergegeven

El objetivo del trabajo fue investigar la respuesta biológica y demográfica de los áfidos en cuatro cultivares de lechuga. En cámara climatizada a 10 más menos 1 oC, HR cercana al 90 por ciento y fotoperíodo de 14 h se criaron cohortes sobre plantulas. Los atributos biológicos y parámetros demográficos se analizaron mediante Kruskal-Wallis y el test de Wilcoxon con ƒ igual a 0,05. El período ninfal de Aulacorthum solani fue más largo en Veneza Roxa y Amarillo mientras que el reproductivo y la longevidad fueron menores en HMX 8574. Similar tendencia se observo en Nasonovia ribisnigri, excepto en Amarillo. La tasa intrinseca de crecimiento natural ((rm)de A. solani resultó significativamente baja sobre Amarillo, HMX y V. Roxa contrastando con Raider. En N. ribisnigri la menor rm ocurrió sobre V. Roxa y las mayores en Amarillo. A. solani podría alcanzar niveles poblacionales más altos sobre Raider y N. ribisnigri sobre Amarillo The aim of the present work is to investigate the biological and demographic response of the aphids on four lettuce commercial cultivars. The bio-assays were carried out in a climate chamber at 10 ± 1 ºC, near 90% RH and 14:10 h L:D cycle reared cohorts on seedlings. Biological attributes and demographic parameters, were analyzed with Kruskal-Wallis and Wilcoxon test with α = 0,05. Aulacorthum solani showed longer nymphal period on Veneza Roxa and Amarillo and shorter reproductive period and longevity on HMX 8574. Similar trend was observed in Nasonovia ribisnigri, on these cultivars except on Amarillo where the nymphal period was shorter. The intrinsic rate of natural increase (rm) of A. solani was significantly lower on Amarillo, HMX 8574 and V. Roxa contrasting with Raider. In N. ribisnigri the smaller rm occurred on V. Roxa and it was significantly higher on Amarillo. A solani could reach higher population levels on Raider and N. ribisnigri on Amarillo Instituto de Microbiología y Zoología Agrícola Fil: Vasicek, Araceli. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales. Cátedra de Zoología Agrícola; Argentina Fil: La Rossa, Francisco Ruben. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Microbiología y Zoología Agrícola; Argentina Fil: López, María Carolina. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales. Cátedra de Zoología Agrícola; Argentina

Using historical seed catalogues in combination with molecular fingerprinting data, diversity trends of lettuce, representing an important vegetable with active breeding programmes, were studied. Seed catalogues originating from France and the Netherlands from five different decades, the earliest dating from the 1840s, were checked for the occurence of lettuce cultivars. A total of 225 catalogues, with 7,311 records of lettuce, representing 878 different cultivars were found. The number of unique cultivars on offer by French and Dutch companies showed a small continuous increase until the 1960s, after which the number of cultivars on offer more than doubled to a total of 534 in the 1990s. Only a relatively small overlap between France and the Netherlands in the range of cultivars offered was observed. The 1960s appeared to be a period with many changes: the lowest genetic diversity in lettuce cultivars was found for this decade, whereas after the 1960s the number of companies supplying lettuce seeds reduced dramatically. The percentage of companies in a decade offering an identical cultivar decreased over time, and in the 1990s almost all cultivars were unique to only a single company. The possible relations of the observed trends with the developments in plant variety protection and in the plant breeding industry are discussed.

Aphids are serious pests of crop plant species, and host plant resistance is often the most effective and environmentally friendly control strategy to control these pests. One of these aphid pests is the black currant - lettuce aphid, Nasonovia ribisnigri (Mosely), an economically important pest of cultivated lettuce, Lactuca sativa L. Host plant resistance has been used since 1982 to control this aphid species and is mediated by the Nr-gene, originating from wild lettuce Lactuca virosa L. However, this resistance is not effective anymore, since N. ribisnigri aphids virulent to the Nr-resistance have been reported since 2007. The aim of this thesis was to unravel the mechanism of resistance mediated by the Nr-gene against N. ribisnigri, by behavioural studies on the aphids on both resistant and susceptible lettuce, to allow lettuce breeders to accelerate their resistance breeding programmes. Although the exact mechanism of Nr-mediated resistance remains unknown, the data in this thesis provide insight into this mechanism. The active site of the Nr-mediated resistance is mainly located in the phloem and some resistance might be encountered by the aphids along the pathway to the phloem. The inability of the avirulent aphids to feed from the resistant plant could be caused by the failure of aphids to suppress the wound response of the sieve element. The resistance factor(s) are only produced in the shoot, because grafts with resistant shoots and susceptible roots were resistant, whereas grafts with susceptible shoots and resistant roots remained susceptible. An intact vascular system is needed for full resistance, because both detached leaves and leaf disks of resistant lettuce plants were less resistant. Variation in virulence was observed among populations of different geographical origin. Aphids from a highly virulent population performed equally well on both resistant and susceptible lettuce plants, whereas semi-virulent aphids performed better on susceptible lettuce plants. Both short-term and long-term virulence loss were observed for virulent aphid populations differing in virulence level, which indicates this virulence is associated with fitness costs. A possible mechanism underlying virulence in N. ribisnigri to the Nr-resistance is the presence of an effector protein in the salivary secretion of the aphids suppressing resistance. Virulent aphids seemed to actively suppress the resistance in lettuce against the avirulent aphids. The original donor or the Nr-resistance, L. virosa accession IVT 280, was tested as possible source of new resistance against the virulent biotypes of N. ribisnigri and was foundfully resistant against virulent aphids, and can be exploited as a source of resistance in breeding for new resistance in cultivated lettuce.

In Botanical Files, a study of the real chances for gene flow from cultivated plants to the wild a system of dispersal codes (Dpdf) was introduced (see text box Dpdf).³7 They are indications of already occurring gene flow from cultivated plants to the wild flora, as can be deduced from herbarium collections and florisdc archives. These codes apply to the Netherlands only. One of the crops of which the real chances for gene flow could not be determined, because of uncertainties regarding the relationship between the cultivated plant and its wild relatives, is Lettuce (Lactuca sativa L.). Its relationship with the wild L. serriola L. is accepted to be very close, but the species are considered to be distinguishable. In a field trial, using 350 specimens from 67 genetically different populations, the distinction between the two species proved to depend largely on character states usually connected to domestication, like absence or presence of prickles, retention of achenes, leaf texture and colour. The consequences are that both wild and cultivated lettuce must be considered to belong to the same species. The finding of some ‘domesticated’ character states in ‘wild’ lettuces indicates an already ongoing gene flow between cultivated lettuce and the wild flora, and the Dp(jf-code is adapted accordingly, indicating a substantial chance for gene flow from cultivated lettuce to its wild relative in the Netherlands. If the scope of Dispersal codes as in Botanical Files is extended to Europe, European Dpdf-codes are needed. In this report a model is proposed using a plant geographical division of Europe into six vegetational regions. For each species six Dpdf-codes, summarizing the chances for gene flow to each of the regions, should be developed. For the major part of the species this can be done using the information already present in national herbarium collections.

Uit mineralenbalansen van teelten op kunstmatige substraten in de glastuinbouw is gebleken dat de aanvoer van stikstof (N) via recirculerende voedingsoplossingen wat hoger is dan de afvoer van N via oogstprodukten en gewasresten. In deze studie zijn de ammoniak-vervluchtiging, denitrificatie en lachgas-emissie bij de teelt van sla gekwantificeerd

Onderzoek naar de vector van slabobbelblad en slakringnecrose, virusziekten die door bodemschimmels kunnen worden overgebracht

Four lettuce (Lactuca saliva L.) varieties ('Benita’, ‘Wendy’, ‘Mirena’, and ‘Jacky') were grown for 43 days in a pH‐controlled complete nutrient solution without cadmium (Cd) or with either 0.01 or 0.03 mg Cd/1 and with NH4 or NO3 as the form of nitrogen nutrition. Cadmium did not affect dry matter yield. ‘Wendy’ had a significantly higher total dry matter production when grown on NO3 compared to NH4, whereas growth of ‘Mirena’ was best on NH4 (P

Dos experimentos fueron efectuados para comparar, el crecimiento de plantines hortícolas de espinaca cv Amadeo INTA , lechugas cv divina o cv maravilla, acelga cv bressane, remolacha cv detroit, y repollo cv corazón de buey, en contenedores de poliestireno expandido (80 cm3), termoformado (25 cm3 o 60cm3), polipropileno ( 60cm3) y celulosa biodegradable (100 cm3), con tres mezclas de sustratos, en diferentes proporciones de, vermicompost, turba, perlita (M1, M2, M3). En el primero de ellos (año 1999) se compararon, contenedores termoformados (25 cm3) vs celulosa biodegradable (100 cm3), siendo el % de parte aérea (%PA), mayor en los últimos, siempre que en la mezcla existió una mayor proporción de vermicompost (M3). En cv Amadeo INTA, cv divina, cv bressane, cv detroit, las mezclas de sustratos, con vermicompost en proporciones de 50% (M2) o 75% (M3), demostraron pesos medios a cosecha superiores que aquellas con 25% (M1). En el segundo (año 2000), se efectuaron comparaciones de contenedores de diferente geometría, de 60 a 100 cm3. En plantines el mayor % de la parte aérea (%PA) se obtuvo, en el siguiente orden: poliestireno expandido (80 cm3), termoformado (60 cm3), y celulosa biodegradable (100cm3). El mayor % de raíces, se observó, en los de polipropileno (60cm3). Posteriormente a campo, en el transplante, hubo una respuesta diferencial por especie. En cv amadeo INTA y lechuga cv maravilla, los de mayor %PA en plantín, tuvieron un mayor peso medio de planta a cosecha, y en cv detroit, todos se igualaron. En general, las mezclas con 50% o 75% de vermicompost, tuvieron pesos medios a cosecha superiores, independiente del tipo de contenedor utilizado. Los resultados vistos permiten concluir que hortalizas de hojas, en el rango de 25-100 cm3, con mezclas de sustratos, de no menos de 50% de vermicompost, no manifestaron restricción radicular, que afectara, los rendimientos posteriores. EEA San Pedro Fil: Ullé, Jorge Ángel. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria San Pedro; Argentina

Survival of the green fluorescent protein-transformed human pathogens Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium was studied in a laboratorysimulated lettuce production chain. Dairy cows were fed 3 different roughage types: high digestible grass silage + maize silage (6:4), low digestible grass silage and straw. Each was adjusted with supplemental concentrates to a high and low crude protein level. The pathogens were added to manure which was subsequently mixed (after 56 and 28 d for resp. E. coli O157:H7 and Salmonella serovar Typhimurium) with 2 pairs of organically and conventionally managed loamy and sandy soil. After another 14 d, iceberg-lettuce seedlings were planted and checked for pathogens after 21 d of growth. Survival data were fitted to a logistic decline function (exponential for E. coli O157: H7 in soil). Roughage type significantly influenced the decline rate of E. coli O157: H7 in manure with the fastest decline in manure from the pure straw diet and the slowest in manure from the grass-silage + maize-silage diet. Roughage type showed no effect on the rate of decline of Salmonella serovar Typhimurium, although decline was significantly faster in the manure derived from straw compared to the manure from the grass-silage + maize-silage diet. The pH and fiber content of the manure were significant explanatory factors and were positively correlated with the rate of decline. With E. coli O157:H7 there was a trend of faster decline in organic compared to conventional soils. No pathogens were detected in the edible lettuce parts. The results indicate that cattle diet and soil management are important factors with respect to the survival of human pathogens in the environment.

Survival of the green fluorescent protein-transformed human pathogens Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium was studied in a laboratorysimulated lettuce production chain. Dairy cows were fed 3 different roughage types: high digestible grass silage + maize silage (6:4), low digestible grass silage and straw. Each was adjusted with supplemental concentrates to a high and low crude protein level. The pathogens were added to manure which was subsequently mixed (after 56 and 28 d for resp. E. coli O157:H7 and Salmonella serovar Typhimurium) with 2 pairs of organically and conventionally managed loamy and sandy soil. After another 14 d, iceberg-lettuce seedlings were planted and checked for pathogens after 21 d of growth. Survival data were fitted to a logistic decline function (exponential for E. coli O157: H7 in soil). Roughage type significantly influenced the decline rate of E. coli O157: H7 in manure with the fastest decline in manure from the pure straw diet and the slowest in manure from the grass-silage + maize-silage diet. Roughage type showed no effect on the rate of decline of Salmonella serovar Typhimurium, although decline was significantly faster in the manure derived from straw compared to the manure from the grass-silage + maize-silage diet. The pH and fiber content of the manure were significant explanatory factors and were positively correlated with the rate of decline. With E. coli O157:H7 there was a trend of faster decline in organic compared to conventional soils. No pathogens were detected in the edible lettuce parts. The results indicate that cattle diet and soil management are important factors with respect to the survival of human pathogens in the environment.

Salmonella is among the most commonly known bacterial pathogens to cause human illness. Often Salmonellosis is associated with the consumption of contaminated foods like meat, eggs or egg products. However, during the last decades an increase of outbreaks is recognized to be caused by human pathogenic bacteria in association with fresh produce. The use of manure for production of vegetables, e.g. lettuce, contributes significantly to the risk of contamination of fresh produce. Enteric pathogens like Salmonella associated with manure can come in close contact with plants like lettuce, and a better understanding of the interaction between lettuce and Salmonella serovars during cultivation is necessary to be able to take preventive actions to reduce the risk for human health.This thesis describes the development of detection methods of Salmonellaenterica and Escherichia coli O157:H7 for routine diagnostic screening in the food production chain. Next to that, it describes the physiological and molecular interaction between Salmonella serovars and lettuce. Background information concerning Salmonella serovars in association with lettuce, like history of produce-associated outbreaks, approaches to detect the pathogen in food samples, pathogenesis, plant responses and the molecular interaction between plants and human pathogens, is discussed in Chapter one.Chapter two concerns the comparison of different molecular methods to detect S. enterica ( invA -gene) or E.coli O157:H7 ( stx -1, stx- 2 and eae -gene) with respect to sensitivity, precision and accuracy. Two basic methods were selected, both based on real-time Taqman PCR, a method that generates fluorescence upon specific DNA amplification. The increase in fluorescence during PCR is directly correlated to the amount of target DNA present after each amplification cycle. The detection and quantification methods were improved by the addition of a general internal amplification control (IAC), viz. comprised of DNA coding forgreenfluorescent protein ( gfp ), that allowed the identification of false negative results. The IAC provided insight in amplification efficiency and enabled a more accurate quantification. Implementation of the IAC did not affect the precision of the methods, although the sensitivity was reduced 10-fold. At least 1 pg of target DNA (equal to 200 CFU) was detected and quantified with high precision and accuracy. Qualitative detection was feasible even down to 10fgof target DNA (equal to 2 CFU) per reaction using both methods in which the IAC was incorporated. The methods enable a reduction in assay time to two days to test food samples, compared to five days required for the standardized procedures.To improve molecular methods to detect the pathogen in environmental substrates, five commercially available DNA extraction methods were evaluated in Chapter three with respect to DNA extraction efficiency of S. Enteriditis from soil, manure and compost. An internal procedural control (GIPC) for DNA extraction and amplification was developed. The GIPC was based on the same control DNA as used for the IAC in Chapter 1, incorporating gfp containing bacterial cells ( E. coli harboring a gfp-plasmid) in the sample prior to DNA extraction. Inclusion of the GIPC permitted a more accurate quantification of S. Enteriditis after DNA extraction and amplification and reduced the possibility of false-negatives. Using this protocol, the optimal extraction method differed forsoil (Mobio soil DNA extraction kit), manure (Bio101 soil DNA extraction kit) and compost (Mobio fecal DNA extraction kit).With each method, at least 2000 CFU of added S. Enteriditis/100 mg substrate could be detected bydirect DNA extraction and subsequent S. enterica specific Taqman PCR. After bacterial enrichment, as little as 1 CFU/100 mg of original substrate was detected. Using this approach a more reliable quantification was obtained for S. enterica initially present in environmental substrates.In Chapter four the physiological and molecular interactions between the human pathogenicS. Dublinand the commercially available mini Roman lettucecvTamburo are described. Investigation of the localization of S.Dublinon/in lettuce plants revealed the presence of significant populations on the surface and inside the plants. The latter was evidenced from significant residual concentrations after highly efficient surface disinfection (99.81%) and fluorescence microscopy ofS.Dublinin cross-sections of lettuce at the root-shoot transition region. A reduction in biomass was observed upon colonization of lettuce plants withS.Dublincompared to water-inoculated plants. Next to this physiological response, there were clear differential gene expression profiles between non-colonized and colonized lettuce plants based on transcriptome analysis by cDNA-AFLP. To confirm the results, generally and differentially expressed genes were selected, identified by sequence analysis and analyzed by RT-PCR to present the specific gene expression profiles in time. Functional grouping of the expressed genes indicated a correlation between colonization of the plants and an increase in expressed pathogenicity-related genes. From these results it was evident that lettuce plants respond to the presence ofS.Dublinat a physiological and molecular level. In addition, it was confirmed thatSalmonella serovars can colonize the interior of lettuce plants, thus potentially imposing a human health risk when contaminated lettuce is processed and consumed.The fact that the lettuce plants responded to the colonization by Salmonella serovars suggested that differences in susceptibility between cultivars or differences in colonization efficiency between Salmonella serovars might be present. In Chapter five, the differential interaction of S. Typhimurium, S. Enteritidis, S . Dublin, S. Newport and S. Montevideo with lettuce cultivars Cancan, Nelly and Tamburo is presented, in terms of prevalence and degree of endophytic colonization of lettuce by the Salmonella serovars. Besides a significant interaction, significant differences among serovars, but not among lettuce cultivars, were obtained when lettuce was grown under axenic conditions. When grown on soil, all three evaluated serovars S. Typhimurium, S. Enteritidis andS . Dublinwere able to colonize lettuce epiphytically, but to a lower extent than on axenically grown plants. OnlyS. Dublinwas able to colonize the plants endophytically when these were grown on contaminated soil. Species richness and diversity of the endophytic microbial community, determined from DGGE gels with DNA from Salmonella -colonized lettuce Cancan and Nelly, were negatively correlated with the number of Salmonella CFU / gram of lettuce. No correlation was observed for cultivar Tamburo. Thus, the microflora of lettuce cultivars Cancan and Nelly appeared more antagonistic to Salmonella serovars than that of cultivar Tamburo.Besides plant-associated colonization, also the active movement of Salmonella serovars towards lettuce roots was assessed. Movement was visualized using a metabolism marker (tetrazolium) for chemotaxis. Reduction of this marker suggested the presence of an organic compound in the lettuce root exudates that was used as carbon source by the Salmonella serovars. Subsequent micro-array analyses with DNA extracted from a broth culture of Salmonella with or without exudates identified genes of S. Typhimurium that were induced by root exudates. These genes, trehalose-6-phosphate synthase ( Ots A; utilizes glucose-6-phosphate as substrate), hexose phosphate utilization protein ( Uhp C; sensor for external glucose-6-phosphate), putative effector protein ( Ssa H; regulator of secretion of the type III secretion system),and putative anti-silencer RNA( Drs A; regulator of transcription to express rcs A promoter, responsible for capsular polysaccharide synthesis), imply a relation with a sugar-like carbon source and thus suggest an association with chemotaxis. The results described in Chapter 5 reveal different plant and microbial factors that influence the colonization efficiency of Salmonella serovars. The serovar and cultivar, but indirectly also the rhizosphere and the endophytic microflora of lettuce were most influential with respect to the risk of colonization and thus the risk for human health.Finally, an extensive discussion concerning the research of Chapters two to five is described in Chapter six, including future perspectives of risk for human health, route of infection and risk reduction in the production chain of Salmonella -associated lettuce.

This thesis is about optimal greenhouse lettuce cultivations such that lettuce nitrate accumulation above EU imposed maximum concentrations is prevented at maximum profits. This case is an example of two general classes of problems: firstly, crop quality improvement through adjustment of environmental conditions during cultivation and secondly, optimal control of processes that are carried out with a significant number of limitations on process variables while being affected by disturbances. Finding solutions for this problem will be interesting for people working in the area of horticulture as well as for people working in the area of optimal control.This problem can be solved mathematically through the computation of optimal trajectories of greenhouse climate variables and their affecting controls. The variables of interest are greenhouse air temperature, relative humidity ratio and greenhouse air CO 2 -concentration while the control inputs are heating pipe temperatures, CO 2 -enrichment flow rates and ventilation rates.A so-called closed-loop suboptimal control algorithm is presented eventually. To build this algorithm, equations, cost functions, constraints and disturbances are presented first. Then results of open loop optimisations with perfect a-priori knowledge of disturbances are presented. These results are analysed for characteristic patterns. These patterns and necessary optimality conditions are applied to obtain operational modes for the design of the algorithm. Symbolic computations are also employed here. The modes can be evaluated very efficiently, which makes the algorithm highly efficient computationally.

This thesis is about optimal greenhouse lettuce cultivations such that lettuce nitrate accumulation above EU imposed maximum concentrations is prevented at maximum profits. This case is an example of two general classes of problems: firstly, crop quality improvement through adjustment of environmental conditions during cultivation and secondly, optimal control of processes that are carried out with a significant number of limitations on process variables while being affected by disturbances. Finding solutions for this problem will be interesting for people working in the area of horticulture as well as for people working in the area of optimal control.This problem can be solved mathematically through the computation of optimal trajectories of greenhouse climate variables and their affecting controls. The variables of interest are greenhouse air temperature, relative humidity ratio and greenhouse air CO 2 -concentration while the control inputs are heating pipe temperatures, CO 2 -enrichment flow rates and ventilation rates.A so-called closed-loop suboptimal control algorithm is presented eventually. To build this algorithm, equations, cost functions, constraints and disturbances are presented first. Then results of open loop optimisations with perfect a-priori knowledge of disturbances are presented. These results are analysed for characteristic patterns. These patterns and necessary optimality conditions are applied to obtain operational modes for the design of the algorithm. Symbolic computations are also employed here. The modes can be evaluated very efficiently, which makes the algorithm highly efficient computationally.

Het artikel geeft een verslag van proeven naar mogelijkheden van pilleren van slazaad ter bestrijding van luis. Het blijkt dat pilleren met een niet nader genoemd middel effectief is in de bestrijding van luis. Met toepassing van het middel zijn de luizen vrijwel verdwenen en is het oogstgewicht toegenomen t.o.v. onbehandeld of standaard behandeld. De hoeveelheid gebruikte actieve stof ligt op minder dan 10% van de normale gewasbespuitingen. Wel is de kieming van het gepilleerde zaad slechter maar het totale effect is zeker positief. Sleutelwoorden: PPO-agv, akkerbouw, tuinbouw, gewasbescherming, geïntegreerde bestrijding, groenteteelt, bladplanten, vollegrondsgroenten, geintegreerde teelt, duurzame teelt, slazaad, pilleren

Korte teeltbeschrijving als onderdeel van het project Screening nieuwe gewassen/productinnovatie waarin van relatief onbekende gewassen of innovaties de teeltkansen voor vollegrond in Nederland in kaart worden gebracht. Romeinse sla is een van oudsher bekende slasoort die op beperkte schaal in Nederland werd geteeld en voornamelijk werd gebruikt als stoofgroente. Door de veranderende vraag naar meer hardere, beter versnijbare slasoorten voor gemengde slasoorten, de vraag naar Romeinse sla bij de allochtone bevolkingsgroep en sterkere en resistente eigenschappen van de rassen biedt Romeinse sla de Nederlandse tuinder hernieuwde afzetmogelijkheden

In het najaar en de winter wordt in de teelt van sla op een aantal bedrijven wortelafsterving geconstateerd of valt een flink percentage planten uit. Het is niet duidelijk wat de oorzaak is van deze wortelafsterving. Het doel van dit onderzoek is te bepalen welke factoren een rol spelen bij deze wortelafsterving en plantuitval. Daarom zijn een aantal bedrijven bezocht en door middel van vraaggesprekken met telers en vragenlijsten gegevens over de teeltomstandigheden verzameld. Tevens zijn op de bedrijven monsters genomen van planten met wortelafsterving en/of van uitgevallen planten om deze te onderzoeken op de aanwezigheid van ziekteverwekkers. Bij drie adviseurs is informatie met betrekking tot uitval in sla verzameld. Op een oproep zich te melden als er op het bedrijf wegval of wortelafsterving werd geconstateerd hebben slechts 7 telers gereageerd. Uit ziek plantmateriaal van 5 bedrijven is Botrytis of Rhizoctonia geïsoleerd. In plantmateriaal met wortelafsterving afkomstig van de 2 overige bedrijven werden geen ziekteverwekkers gevonden. Het lijkt er het meest op dat een aantal teeltfactoren een rol spelen, waarbij plantactiviteit en waterhuishouding in het wortelmilieu belangrijke factoren zijn.

Korte teeltbeschrijving als onderdeel van het project Screening nieuwe gewassen/productinnovatie waarin van relatief onbekende gewassen of innovaties de teeltkansen voor vollegrond in Nederland in kaart worden gebracht. Romeinse sla is een van oudsher bekende slasoort die op beperkte schaal in Nederland werd geteeld en voornamelijk werd gebruikt als stoofgroente. Door de veranderende vraag naar meer hardere, beter versnijbare slasoorten voor gemengde slasoorten, de vraag naar Romeinse sla bij de allochtone bevolkingsgroep en sterkere en resistente eigenschappen van de rassen biedt Romeinse sla de Nederlandse tuinder hernieuwde afzetmogelijkheden

In het najaar en de winter wordt in de teelt van sla op een aantal bedrijven wortelafsterving geconstateerd of valt een flink percentage planten uit. Het is niet duidelijk wat de oorzaak is van deze wortelafsterving. Het doel van dit onderzoek is te bepalen welke factoren een rol spelen bij deze wortelafsterving en plantuitval. Daarom zijn een aantal bedrijven bezocht en door middel van vraaggesprekken met telers en vragenlijsten gegevens over de teeltomstandigheden verzameld. Tevens zijn op de bedrijven monsters genomen van planten met wortelafsterving en/of van uitgevallen planten om deze te onderzoeken op de aanwezigheid van ziekteverwekkers. Bij drie adviseurs is informatie met betrekking tot uitval in sla verzameld. Op een oproep zich te melden als er op het bedrijf wegval of wortelafsterving werd geconstateerd hebben slechts 7 telers gereageerd. Uit ziek plantmateriaal van 5 bedrijven is Botrytis of Rhizoctonia geïsoleerd. In plantmateriaal met wortelafsterving afkomstig van de 2 overige bedrijven werden geen ziekteverwekkers gevonden. Het lijkt er het meest op dat een aantal teeltfactoren een rol spelen, waarbij plantactiviteit en waterhuishouding in het wortelmilieu belangrijke factoren zijn.

Teelthandleidingen voor biologisch geteelde consumptieaardappelen, granen, ijsbergsla, peen, prei, sluitkool en spruitkool. Het laatste hoofdstuk van het boek bestaat uit saldoberekeningen voor pootaardappel uit kleigebieden, vroege aardappelen, consumptieaardappelen uit kleigebieden, wintertarwe uit kleigebieden, zomertarwe uit kleigebieden, wintergerst uit kleigebieden, zomergerst uit kleigebieden, haver uit zandgebieden, winterrogge uit zandgebieden, triticale uit zandgebieden, ijssla (zomerteelt), bospeen (zomerteelt), grove peen (b-peen, bewaring), prei (vroeg herfst), witte kool (bewaring), witte kool (industrie), rode kool (bewaring), rode kool (industrie) en spruitkool (middenvroeg).

Teelthandleidingen voor biologisch geteelde consumptieaardappelen, granen, ijsbergsla, peen, prei, sluitkool en spruitkool. Het laatste hoofdstuk van het boek bestaat uit saldoberekeningen voor pootaardappel uit kleigebieden, vroege aardappelen, consumptieaardappelen uit kleigebieden, wintertarwe uit kleigebieden, zomertarwe uit kleigebieden, wintergerst uit kleigebieden, zomergerst uit kleigebieden, haver uit zandgebieden, winterrogge uit zandgebieden, triticale uit zandgebieden, ijssla (zomerteelt), bospeen (zomerteelt), grove peen (b-peen, bewaring), prei (vroeg herfst), witte kool (bewaring), witte kool (industrie), rode kool (bewaring), rode kool (industrie) en spruitkool (middenvroeg).

Door de nieuwe energiewet hebben tuinders die gewassen telen met een lage energiebehoefte te maken met veel hogere energiekosten. Als het totale energiegebruik en de hoge uurpieken in gasverbruik verminderd zouden kunnen worden, zou dit voor de betreffende telers gunstig uit kunnen pakken. In eerder PPO-onderzoek is aangetoond dat toepassing van temperatuurintegratie (TI) bij buisverwarming veel perspectief biedt. Omdat zo’n 80 à 90% van de sla- en radijstelers gebruik maakt van heteluchtverwarming is voor deze groep een apart onderzoek uitgevoerd.

Door de nieuwe energiewet hebben tuinders die gewassen telen met een lage energiebehoefte te maken met veel hogere energiekosten. Als het totale energiegebruik en de hoge uurpieken in gasverbruik verminderd zouden kunnen worden, zou dit voor de betreffende telers gunstig uit kunnen pakken. In eerder PPO-onderzoek is aangetoond dat toepassing van temperatuurintegratie (TI) bij buisverwarming veel perspectief biedt. Omdat zo’n 80 à 90% van de sla- en radijstelers gebruik maakt van heteluchtverwarming is voor deze groep een apart onderzoek uitgevoerd.

Najaar 2003 is er door PPO-Business Unit Glastuinbouw in Naaldwijk onderzoek uitgevoerd naar de werking van nieuwe bestrijdingsmiddelen tegen Bremia lactuca in sla. Deze proef is een herhaling van het onderzoek van begin 2003. Naast de 3 middelen uit die betreffende proef is een vierde middel in dit onderzoek opgenomen. Het betreft de plantversterker c.q. bladmeststof Kendal. De middelen die in dit onderzoek zijn getest, zijn voorgedragen door LTO, de slacommissie en het PPO in samenspraak met de betreffende fabrikanten. Dit onderzoek werd gefinancierd door het PT. De betreffende fabrikanten leverden de te testen producten en bijhorende proefontheffingen. Omdat de geteste middelen voor de slateelt geen toelating hebben, worden ze in dit verslag onder code vermeld.

Najaar 2003 is er door PPO-Business Unit Glastuinbouw in Naaldwijk onderzoek uitgevoerd naar de werking van nieuwe bestrijdingsmiddelen tegen Bremia lactuca in sla. Deze proef is een herhaling van het onderzoek van begin 2003. Naast de 3 middelen uit die betreffende proef is een vierde middel in dit onderzoek opgenomen. Het betreft de plantversterker c.q. bladmeststof Kendal. De middelen die in dit onderzoek zijn getest, zijn voorgedragen door LTO, de slacommissie en het PPO in samenspraak met de betreffende fabrikanten. Dit onderzoek werd gefinancierd door het PT. De betreffende fabrikanten leverden de te testen producten en bijhorende proefontheffingen. Omdat de geteste middelen voor de slateelt geen toelating hebben, worden ze in dit verslag onder code vermeld.

De laatste jaren loopt de verkoop van losse kroppen sla terug (Leegwater, 1999; Van den Berg, 1999). Meer en meer wordt er voorgesneden en verpakte sla verkocht. De traditionele botersla heeft hierbij als nadeel dat het erg snel na het snijden verlept. Er wordt dus gezocht naar alternatieve types sla. In het zuiden van Europa wordt voornamelijk bataviasla geteeld en gegeten. Deze sla is steviger en zou ook een betere smaak hebben dan botersla (Janse, 1999). Bindsla is een oudere slasoort die ook goed van smaak zou zijn en makkelijk te verwerken door snijderijen. In de winter van 2002 en 2003 is er door PPO Glastuinbouw gebruikswaarde onderzoek uitgevoerd aan enkele rassen bataviasla. Deze rassen zijn door het PPO expertpanel en consumentenpanel vergeleken met een monster bindsla en een monster botersla.

De laatste jaren loopt de verkoop van losse kroppen sla terug (Leegwater, 1999; Van den Berg, 1999). Meer en meer wordt er voorgesneden en verpakte sla verkocht. De traditionele botersla heeft hierbij als nadeel dat het erg snel na het snijden verlept. Er wordt dus gezocht naar alternatieve types sla. In het zuiden van Europa wordt voornamelijk bataviasla geteeld en gegeten. Deze sla is steviger en zou ook een betere smaak hebben dan botersla (Janse, 1999). Bindsla is een oudere slasoort die ook goed van smaak zou zijn en makkelijk te verwerken door snijderijen. In de winter van 2002 en 2003 is er door PPO Glastuinbouw gebruikswaarde onderzoek uitgevoerd aan enkele rassen bataviasla. Deze rassen zijn door het PPO expertpanel en consumentenpanel vergeleken met een monster bindsla en een monster botersla.

Versalg van gebruikswaardeonderzoek glasgroenten met als doel de teler steunen in de keuze van zijn rassen door het vergaren en presenteren van resultaten, verkregen uit objectief en betrouwbaar onderzoek dat in samenwerking met telers en veredelaars wordt uitgevoerd.

Versalg van gebruikswaardeonderzoek glasgroenten met als doel de teler steunen in de keuze van zijn rassen door het vergaren en presenteren van resultaten, verkregen uit objectief en betrouwbaar onderzoek dat in samenwerking met telers en veredelaars wordt uitgevoerd.

PRI onderzocht het effect van een meter brede strips luzerne op de aantallen bladluizen en hun natuurlijke vijanden in ijsbergsla. Alle belangrijke bladluissoorten op ijsbergsla en de belangrijkste bladluispredatoren werden geteld gedurende drie plantingen in het groeiseizoen. Behalve voor groene perzikluis werden geen duidelijke verschillen gevonden tussen teelten met en zonder luzernestroken