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Physiological and molecular implications of plant polyamine metabolism during biotic interactions

JUAN FRANCISCO JIMENEZ BREMONT MARIA DE LA LUZ GUERRERO GONZALEZ DIANA SANCHEZ RANGEL MARGARITA RODRIGUEZ Y DOMINGUEZ KESSLER (2014, [Artículo])

"During ontogeny, plants interact with a wide variety of microorganisms. The association with mutualistic microbes results in benefits for the plant. By contrast, pathogens may cause a remarkable impairment of plant growth and development. Both types of plant microbe interactions provoke notable changes in the polyamine (PA) metabolism of the host and/or the microbe, being each interaction a complex and dynamic process. It has been well documented that the levels of free and conjugated PAs undergo profound changes in plant tissues during the interaction with microorganisms. In general, this is correlated with a precise and coordinated regulation of PA biosynthetic and catabolic enzymes. Interestingly, some evidence suggests that the relative importance of these metabolic pathways may depend on the nature of the microorganism, a concept that stems from the fact that these amines mediate the activation of plant defense mechanisms. This effect is mediated mostly through PA oxidation, even though part of the response is activated by non-oxidized PAs. In the last years, a great deal of effort has been devoted to profile plant gene expression following microorganism recognition. In addition, the phenotypes of transgenic and mutant plants in PA metabolism genes have been assessed. In this review, we integrate the current knowledge on this field and analyze the possible roles of these amines during the interaction of plants with microbes."

Polyamines Spermidine Spermine Putrescine Thermospermine Plant pathogen Mutualism BIOLOGÍA Y QUÍMICA CIENCIAS DE LA VIDA

Heterologous expression of a novel psychrophilic Cu/Zn superoxide dismutase from Deschampsia antarctica

SERGIO ANGEL GARCIA ECHAURI LEANDRO GABRIEL ORDONEZ ACEVEDO JUAN ANTONIO ROJAS CONTRERAS ANA PAULINA BARBA DE LA ROSA ANTONIO DE LEON RODRIGUEZ (2009, [Artículo])

"Superoxide dismutase (SOD) catalyzes the conversion of the superoxide radical (O2−) into oxygen and hydrogen peroxide. Deschampsia antarctica is a plant that grows in Antarctica and survives to extreme low temperature and high UV radiation, thus it is an ideal model to study novel antioxidants. A cDNA Cu/Zn-SOD gene from D. antarctica was cloned into a pET vector and expressed in Escherichia coli BL21-SI. 112 mg/L of recombinant Cu/Zn-SOD was attained in batch cultures in bioreactor. Using Ni-affinity gel chromatography, the recombinant Cu/Zn-SOD was recovered with a purity of 90% and a specific enzyme activity of 749 at 25 °C. However, zymogram test showed that the enzyme has more activity at 4 °C. This D. antarctica SOD could be used to reduce the oxidation of refrigerated and frozen foods."

Antioxidant Plant Extremophil Psychrophilic enzyme Photo-oxidation Oxidative stress CIENCIAS AGROPECUARIAS Y BIOTECNOLOGÍA

Genetic variability in Rhizoctonia solani isolated from Vitis vinifera based on amplified fragment length polymorphism

AMPARO MEZA MOLLER MARTIN CANDELARIO ESQUEDA VALLE LORENZO FELIPE SANCHEZ TEYER GEORGINA VARGAS ROSALES ALFONSO ANTERO GARDEA BEJAR MARTIN ERNESTO TIZNADO HERNANDEZ (2011, [Artículo])

Problem statement: Rhizoctonia solani is a potential grapevine pathogen. In order to develop effective methods of control, it is necessary to document its genetic diversity. Approach: The objective of this study was to analyze the genetic variability of R. solani isolated from the rhizosphere of ungrafted V. vinifera var. perlette seedless planted in Sonora, Mexico using Amplified Fragment Length Polymorphism (AFLP). Results: In the selective amplification using eight primer combinations we obtained a total of 446 AFLP markers with a 100% polymorphism. Out of 41 isolates, 36 different AFLP patterns were observed and five were replicates of the same pattern. The dendrogram shows inter- and intrapopulation similarity indexes of 0.26, 0.98 and 0.31, 0.98, respectively. Six groups emerged from the principal components analysis, five of which were clearly defined, while the other one was spread out. Conclusion: We conclude that R. solanigrowing in Sonoran vineyards shows a high degree of genetic variability, even under similar environmental conditions.

RHIZOCTONIA SOLANI THANATEPHORUS CUCUMERIS MOLECULAR MARKERS VINEYARDS GENETIC VARIABILITY AMPLIFIED FRAGMENT LENGTH POLYMORPHISM GRAPEVINE PATHOGEN PERLETTE SEEDLESS SIMILARITY INDEXES BIOLOGÍA Y QUÍMICA BIOLOGÍA Y QUÍMICA

Participación de Dscam en el sistema de defensa contra patógenos en Crassostrea gigas y C. corteziensis

LILIAN ARZETA PINO (2018, [Tesis de doctorado])

"En insectos y crustáceos el gen de Dscam (molécula de adhesión celular del síndrome de Down) ha sido ampliamente estudiado. La participación de Dscam en el sistema inmune se ha reportado en la mosca de la fruta, camarón, mosquitos, y cangrejos entre otros. El gen Dscam puede dar origen a numerosas isoformas mediante splicing alternativo, con capacidad de responder de manera patógeno-específica. En moluscos bivalvos existe poca información acerca de la expresión, localización, existencia de isoformas y participación en la respuesta frente a patógenos. En este trabajo se logró amplificar todos los dominios de Dscam de Crassostrea gigas, C. corteziensis y C. sikamea. La secuencia de Dscam de Crassostrea spp. mostró una organización estructural similar a la descrita en otros invertebrados. Se logró la identificación de dos regiones conservadas que permitieron el diseño de sondas y oligonucléotidos específicos para las técnicas de hibridación in situ y PCR cuantitativa (qPCR). Dscam se expresa en branquias y manto de C. gigas y C. corteziensis sanos. La localización de Dscam en C. gigas infectados con herpes virus tipo 1 (OsHV-1) y C. corteziensis con Perkinsus marinus no se limita a branquias y manto también se observó en intestino, glándula digestiva y gónada. Los resultados de qPCR en C. gigas y C. corteziensis sanos e infectados sugieren que la expresión de Dscam podría estar relacionada con el patógeno al que fueron expuestos. La expresión de Dscam en branquias infectadas incrementa considerablemente respecto al control en ambas especies. Por otra parte, en manto no se observa diferencia, particularmente en presencia de P. marinus se observó una inhibición de la expresión. Para evaluar la participación de Dscam durante la exposición a un patógeno, se midieron los niveles de expresión de Dscam en branquias y manto de C. gigas adultos expuestos a E. coli. Además se determinaron los niveles de expresión de otros genes de respuesta inmune como FREP, TLR2 e interleucina 17 (IL-17-3). En general, los niveles de expresión de Dscam en manto fueron mayores en comparación con branquias. Los patrones de expresión fueron tejido-específico, en manto, un incremento gradual en la expresión de Dscam se observó de las 0 a 12 h, mientras que en branquias, no se observó un patrón de expresión particular. Los picos de máxima expresión se observaron a las 12 h posteriores en ambos tejidos. Los niveles de expresión de TLR2 fueron altos durante todas las horas evaluadas..."

"The Dscam (Down syndrome cell adhesion molecule) gene has been widely studied in insects and crustaceans. Its role in immunity has been reported in the fruit fly, shrimp, mosquitoes, bees and crabs, among others. It is known that Dscam potentially gives rise to numerous isoforms by alternative splicing, which are able to respond in a pathogen-specific manner. In bivalve molluscs, information about Dscam expression, localization, isoforms and its role in the immune response is scarce. In this work, the Dscam domains from Crassostrea gigas, C. corteziensis and C. sikamea were amplified. Sequence analysis showed that the structural organization of Dscam from Crassostrea spp. was similar to other invertebrates. Two conserved regions were found and used to design specific primers and probes to perform in situ hybridization and quantitative PCR (qPCR). Dscam was expressed in gills and mantle from healthy individuals of C. gigas and C. corteziensis. Dscam localization in C. gigas infected with herpes virus type 1 (OsHV-1) and in C. corteziensis infected with Perkinsus marinus was not limited to gills and mantle, since it was also found in intestine, digestive gland and gonad. Quantitative PCR results in healthy and infected C. gigas and C. corteziensis suggest that Dscam expression could be related to pathogen exposure. Dscam expression in infected gills increased substantially in comparison with healthy individuals in both species. On the other hand, the mantle showed no differences in Dscam expression; even more, a decreased expression was observed in C. corteziensis infected with P. marinus. In a controlled bioassay using gills and mantle from adults of C. gigas challenged with Escerichia coli the expression of Dscam, together with other immune-related genes such as Toll-like receptor, FREP and IL-17-3 was measured by qPCR. In general, the expression levels of Dscam were higher in mantle than in gills. The expression profiles were tissue-specific, in mantle, a gradual increase of expression was observed from 0 to 12 h, while in gills, the expression profile did not show any pattern. A delayed response of Dscam in gills and mantle was observed, with highest expression levels at 12 h post-infection. TLR2 expression levels were higher through all the experiment in both tissues. FREP expression showed a gradual increase from 8 h to 24 h in gills, and the higher expression levels were found in mantle at 4, 24 and 48 h..."

Dscam, Crassostrea spp., Sistema inmune, Patógeno Immune system, Pathogen BIOLOGÍA Y QUÍMICA CIENCIAS DE LA VIDA BIOLOGÍA ANIMAL (ZOOLOGÍA) INMUNOLOGÍA INMUNOLOGÍA

Revision of Begomovirus taxonomy based on pairwise sequence comparisons

JUDITH K. BROWN JESUS NAVAS CASTILLO ENRIQUE MORIONES ROBERTO RAMOS SOBRINHO JOSE C. F. SILVA ELVIRA FIALLO OLIVE ROB W. BRIDDON CECILIA HERNANDEZ ZEPEDA Ali Idris V. G. MALATHI RAFAEL FRANCISCO RIVERA BUSTAMANTE SHIGENORI UEDA Arvind Varsani (2015, [Artículo])

Viruses of the genus Begomovirus (family Geminiviridae) are emergent pathogens of crops throughout the tropical and subtropical regions of the world. By virtue of having a small DNA genome that is easily cloned, and due to the recent innovations in cloning and low-cost sequencing, there has been a dramatic increase in the number of available begomovirus genome sequences. Even so, most of the available sequences have been obtained from cultivated plants and are likely a small and phylogenetically unrepresentative sample of begomovirus diversity, a factor constraining taxonomic decisions such as the establishment of operationally useful species demarcation criteria. In addition, problems in assigning new viruses to established species have highlighted shortcomings in the previously recommended mechanism of species demarcation. Based on the analysis of 3,123 full-length begomovirus genome (or DNA-A component) sequences available in public databases as of December 2012, a set of revised guidelines for the classification and nomenclature of begomoviruses are proposed. The guidelines primarily consider a) genus-level biological characteristics and b) results obtained using a standardized classification tool, Sequence Demarcation Tool, which performs pairwise sequence alignments and identity calculations. These guidelines are consistent with the recently published recommendations for the genera Mastrevirus and Curtovirus of the family Geminiviridae. Genome-wide pairwise identities of 91 % and 94 % are proposed as the demarcation threshold for begomoviruses belonging to different species and strains, respectively. Procedures and guidelines are outlined for resolving conflicts that may arise when assigning species and strains to categories wherever the pairwise identity falls on or very near the demarcation threshold value.

BEGOMOVIRUS GENOME, VIRAL PHYLOGENY PLANT DISEASES PLANTS SEQUENCE ALIGNMENT BIOLOGÍA Y QUÍMICA BIOLOGÍA Y QUÍMICA

Métodos de endurecimiento que modifican las características morfofisiológicas en plántulas de pino producidas en vivero

MARIA LUISA AVILA ANGULO (2015, [Tesis de doctorado])

Tesis (Doctorado en Ciencias, especialista Forestal).- Colegio de Postgraduados, 2015.

Los procesos de degradación de los bosques han generado grandes áreas con disturbios intensos y recurrentes, por consecuencia la vegetación no recupera su estado original de forma natural, y es necesario realizar reforestaciones. En el proceso de producción en vivero es importante la resistencia de las plantas a factores ambientales de estrés (sequía y heladas) para asegurar la supervivencia de las plantaciones; dicha resistencia se produce principalmente durante la etapa de endurecimiento. Para las especies de pinos en México no se tiene claro el efecto del endurecimiento, por lo cual la presente investigación tuvo como finalidad evaluar tres técnicas convencionales de endurecimiento (reducción del riego, exposición a condiciones ambientales y reducción de la fertilización nitrogenada) en plántulas de Pinus oaxacana Mirov y Pinus rudis Endl. En la etapa de vivero se evaluó la morfología y la fisiología por medio del potencial de crecimiento de raíz y daño por desecación de la raíz. Durante la plantación se evaluó la supervivencia y el crecimiento durante el primer año. El endurecimiento por reducción del riego y exposición a condiciones ambientales modificaron la morfología y fisiología de las especies estudiadas. El endurecimiento mediante reducción de la fertilización nitrogenada no tuvo efecto en la supervivencia en un sitio de condiciones restrictivas. Las condiciones físico ambientales del sitio de plantación tiene un efecto marcado en la supervivencia y crecimiento de Pinus rudis Endl. En un sitio de condiciones favorables el endurecimiento no tiene efecto en la supervivencia y crecimiento de Pinus rudis Endl. _______________ HARDENING METHODS TO MODIFY THE CHARACTERISTICS MORPHOPHYSIOLOGICAL PRODUCED IN PINE SEEDLINGS IN NURSERY. ABSTRACT: The processes of forest degradation have generated large areas with severe and recurrent disturbances, consequently the vegetation does not recover its original state naturally, and reforestation is needed. In the production process nursery resistance of plants to environmental stresses (drought and frost) to ensure the survival of plantations is important; said resistance occurs primarily during the hardening step. For species of pines in Mexico there is no clear effect of hardening, so this research aimed to evaluate three conventional hardening techniques (reduction of irrigation, exposure to environmental conditions and reduction of nitrogen fertilization) in seedlings Pinus oaxacana Mirov and Pinus rudis Endl. In the nursery stage morphology and physiology through root growth potential and damage by drying the root was evaluated. When planting survival and growth was assessed during the first year. The hardening reduction of irrigation and exposure to environmental conditions changed the morphology and physiology of the species studied. The hardening by reduction of nitrogen fertilization had no effect on survival in a restrictive site conditions. Environmental physical conditions of the planting site has a marked effect on survival and growth of Pinus rudis Endl. In a favorable site hardening has no effect on the survival and growth of Pinus rudis Endl.

Estrés hídrico Potencial de crecimiento de raíz Calidad de planta Water stress Root growth potential Plant quality Ciencias Forestales Doctorado CIENCIAS AGROPECUARIAS Y BIOTECNOLOGÍA

Productividad de grano y semilla de híbridos trilineales, cruzas simples adroestériles y fértiles de maíz

ENRIQUE INOSCENCIO CANALES ISLAS (2014, [Tesis de maestría])

Tesis (Maestría en Ciencias, especialista en Genética).- Colegio de Postgraduados, 2014.

En los programas de mejoramiento genético de maíz (Zea mays L.) y de generación de híbridos de la Facultad de Estudios Superiores Cuautitlán (FESC-UNAM) y del Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias (INIFAP-CEVAMEX), se emplean la esterilidad masculina y la incorporación de este carácter, en las líneas élites como una alternativa para facilitar la producción de semillas, favorecer el mantenimiento de la calidad genética, y disminuir costos de producción de semilla, al liberarse comercialmente para su uso extensivo y abastecimiento de semilla de nuevos híbridos. En estos programas, desde 1992, se trabaja con androesterilidad, contándose con híbridos trilíneales, para productores de maíz de los Valles Altos de México (2200 a 2600 msnm), cuyos progenitores tienen el carácter de androesterilidad. Con base en ello, se consideró necesario evaluar un grupo de híbridos trilíneales así como las cruzas simples progenitoras, para definir la estabilidad del rendimiento, y determinar la interacción genotipo x ambiente de los híbridos en diferentes ambientes de prueba, con el propósito de establecer una recomendación adecuada y apoyar su liberación comercial en ambientes específicos. Adicionalmente, para estos híbridos se tuvo como objetivos, en un trabajo paralelo, a) definir la capacidad productiva de estos híbridos trilíneales de maíz, en sus versiones androestéril y fértil; b) determinar la mejor proporción de mezcla de semilla androestéril (AE) y fértil (F), bajo dos densidades de población (50 000 y 70 000 plantas por hectárea); c) identificar a los híbridos trilineales y sus cruzas simples progenitoras que tuvieran mejor estabilidad del rendimiento de grano, utilizando para ello los Parámetros de Estabilidad de Eberhart y Russell, y el modelo AMMI, y d) definir al modelo que mejor describa la interacción genotipo por ambiente para poder lo recomendar la liberación comercial de los híbridos trilineales. En el análisis de varianza para rendimiento, se obtuvieron diferencias altamente significativas para ambientes, genotipos y densidades; en la interacción Genotipo x Ambiente resultó significativa. Los mejores rendimientos los tuvo el híbrido H-53, con 7438 kg ha-1; mientras que el ambiente con el mejor rendimiento fue Cuautitlán Izcalli en la segunda fecha de siembra. La mejor densidad de población fue 70 000 plantas por hectárea. Las proporciones de semilla 33%AE y 67%F, con 6290 kg ha-1; y 66%AE y 34%F con 6200 kg ha-1, fueron mejores que otras mezclas de semilla androestéril y fértil y que la versión 100% fértil. En la parte de la evaluación de la estabilidad y la interacción genotipo x ambiente, el modelo AMMI identificó como estables a los híbridos trilineales H-57 y Puma 1183 AEC2, así como a las cruzas simples H-57 AE y H-57 F; en cuanto a los parámetros de estabilidad los híbridos trilineales H-53, Puma 1183 AEC1 y Puma 1183 AEC2, y las cruzas simples H-57 AE, Puma 1183 AEC1 AE, y Puma 1183 AEC1 F resultaron estables. Los niveles de correspondencia entre ambos modelos, para los híbridos trilineales y las cruzas simples, fue del 50% y 20%, respectivamente. Ambos modelos identificaron por lo menos a un híbrido trilineal y una cruza simple, como estable. Se concluye que el modelo AMMI describió mejor la interacción genotipo por ambiente. _______________ GRAIN AND SEED PRODUCTIVITY OF SINGLE AND THREE-WAY AND SINGLE CROSSES OF ANDROESTERILE AND FERTILE MAIZE. ABSTRACT: The maize (Zea mays l.) breeding project and the hibrid development program the Faculty of Superior Studies Cuautitlan (FESC-UNAM) and the National Institute for Forestry, Agricultural and Animal Research (CEVAMEX-INIFAP) uses the male sterility system for the incorporation of this character to the elite inbred lines. This alternative facilitates the production of seed and also favored the maintenance of the genetic quality and lowered the cost of seed production on commerciall maize released for extensive use and for seed supplying of new hybrids. Since 1992, the project has developed tree-way hybrids to be grown by maize farmers for the High Valleys of Mexico (2200-2600 meters above sea level), whose parents have the character of male sterility. Based on this, it was necessary to assess a group of three-way maize hybrids as well as single crosses in order to study their yield stability, and genotype x environment interaction of hybrids across different test environments to establish a proper recommendation and to support their commercial release to specific environments. Other objective of this work were: a) to study the productivity potencial of the androsterile an fertile versions of the hybrids; b) to determine the best proportion of male-sterile (MS) and fertile (F) seed mixtures, under two plant densities (50 000 and 70 000 plants per hectare); c) to identify the best hybrids and their progenitor single crosses with de best grain yield stability by means of the Eberhart and Russell´s parameters of stability, and the AMMI model, and d) to define the model that best describes the genotype by environment interaction, allowing to recommend the commercial release of the three-way maize hybrids. For the analysis of variance for yield, there were highly significant differences among environments, genotypes and densities for grain yield and that the genotype x environment interaction was significant. The hybrid H-53 had the highest yield, 7438 kg ha-1, and the best environment was Cuautitlán Izcalli in the second planting date. The best population density was 70,000 plants per hectare. The best mix proportions of seed were 33% MS and 67 %F, with 6,290 kg ha-1; and the mix of 66% MS and 34 %F, with 6,200 kg ha-1. For the evaluation of the stability and genotype x environment interaction, the model AMMI identified to the three-way Hybrids H-57 and Puma 1183 AEC2, and the single crosses H-57 AE and H-57 F, as the stablest ones. Considering the stability parameters, the three-way hybrids H-53, Puma 1183 1183 AEC1 and Puma AEC2, and the single crosses H-57 AE, 1183 AEC1, AE and Puma 1183 F AEC1 were considered as stables. The levels of correspondence between the two models, for the three-way hybrids and the single crosses were 50% and 20%, respectively. Both models al least identified one three-way and one single cross hybrid as stable. It is concluded that the AMMI model described better the genotype by environment interaction.

Zea mays L. Androesterilidad Densidad de población Producción de semillas Híbridos de maíz Proporciones de semilla Parámetros de estabilidad AMMI Rendimiento Male sterility Plant density Seed production Maize hybrids Seed ratios Parameters of stability Yield Genética Maestría CIENCIAS AGROPECUARIAS Y BIOTECNOLOGÍA

Producción hidropónica de freesia x hybrida bajo diferentes cubiertas plásticas

ERIKA MIRANDA VILLAGOMEZ (2012, [Tesis de maestría])

Tesis (Maestría en Ciencias, especialista en Fruticultura).- Colegio de Postgraduados, 2012.

La freesia es una especie florícola poco comercializada en México, con alto potencial como flor de corte, tolera bajas temperaturas, presenta amplia diversidad de colores y su aroma es agradable. En esta investigación se evaluó el efecto de malla negra (25 % transmitancia), malla roja (15 % transmitancia) y cubierta plástica (70 % transmitancia) en el crecimiento, desarrollo y calidad del tallo flora del freesia para corte. También se determinó el efecto de la concentración de la solución nutritiva Steiner (25, 50, 75 y 100 %) bajo malla sombra roja en estas variables. El estudio se llevó a cabo en el Campo Experimental del Colegio de Postgraduados, en Montecillo, México. En ambos experimentos se probaron dos fechas de siembra (22 de septiembre y 18 de octubre de 2010) y las plantas fueron cultivadas bajo sistema hidropónico. Se usaron cormos de Freesia x hybrida cv. Patio. Los tratamientos fueron la combinación factorial tres ambiente y dos fechas de siembra (3 x 2), el segundo consistió en cuatro concentraciones de SN y dos fechas de siembra (4 x 2), ambos experimentos en un diseño completamente al azar. Durante el ciclo del cultivo se midieron variables micrometeorológicas, fenológicas, morfológicas y fisiológicas. A la cosecha se midió altura y grosor de tallo floral, longitud y número de flores de la espiga. La vida de florero se evaluó mediante el consumo de agua, peso fresco, número de flores abiertas y días a senescencia de cada tallo. En el experimento 1, la altura de planta (62.6 cm), longitud de tallo (61.4 cm), área foliar (351.5 cm2) y biomasa total (4.75 g) fueron mayores en plantas cultivadas bajo la malla roja. En el experimento 2, con 100 % de la solución Steiner se obtuvo menor altura de planta (49 cm), longitud del tallo floral (37 cm), área foliar por planta (170 cm2), unidades SPAD (62), longitud de la espiga (8.5 cm) y grosor del tallo (3.6 mm), mientras que con la concentración de 25 % se obtuvo la mayor altura de planta (59.4 cm), unidades SPAD (71.7), longitud del tallo floral (61 cm), longitud de la espiga (11 cm), número de flores por espiga (12), grosor del tallo (5.0 mm) y número de días de vida de florero (12 d). Al inicio de la floración, las plantas cultivadas con 100 % de la solución Steiner fueron las que acumularon menor biomasa de tallo, hoja y total. La eficiencia cuántica máxima del fotosistema II (Fm/Fv) fue igual entre tratamientos (P > 0.05) en ambas fechas de medición y varió de 0.80 a 0.83. El consumo de agua, peso de biomasa en fresco, número de flores abiertas y días a senescencia en postcosecha fueron iguales entre tratamientos. _______________ HYDROPONIC PRODUCTION OF Freesia x hybrida UNDER DIFFERENT PLASTIC COVERS. ABSTRACT: Freesia is a floricultural species almost unknown in Mexico, with high potential for cut flower; it tolerates low temperatures, its blooms have a wide range of hues, and produce a delicate scent. The aim of this research was to evaluate the effect of different covers as black netting (transmittance of 25 %) red netting (transmittance of 15 %) and greenhouse covered in plastic (transmittance of 70 %) on growth, development and flower stem quality of freesia for cut flower. Also, the effect of the Steiner concentration (25, 50, 75 and 100 %) on these variables was tested. The study was carried out in the Experimental Field of the Postgraduates College, in Montecillo, Mexico, using corms of Freesia x hybrida cv. Patio planted under a hydroponic system. There were two planting dates (22th of September and 18th of October 2010). Treatments were the factorial combination of three production environments and two planting dates (3 x 2), in the first experiment, and four Steiner solution concentrations and two planting dates (4 x 2), in the second experiment, both in a complete random design. Meteorological, phenological, morphological and physiological variables were measured during the growth period. Height and thickness of flower stem, and length and number of flowers in the spike were measured at harvest. Also, water consumption, fresh weight, number of open flowers and days to senescence were evaluated at post-harvest. In the first experiment, plant height (62.6 cm), stem length (61.4 cm), leaf area (351.5 cm2) and total biomass (4.75 g) were larger in plants cultivated under red netting. In the second experiment, 100 % of Steiner solution (SN) produced the lowest plant height (49 cm), floral stem length (37 cm), leaf area per plant (170 cm2), SPAD units (62), spike length (8.5 cm) and stem thickness (3.6 mm) whereas 25 % of SN produced the largest plant height (59.4 cm), SPAD units (71.7), floral stem length (61 cm), spike length (11 cm), number of flowers per stem (12), stem thickness (5.0 mm) and flower vase life (12 d). Leaf number per plant was similar between treatments. The lowest leaf, stem and total dry biomass at harvest was produced by the complete SN, but root dry weight was similar between treatments. The maximum quantum efficiency of photosystem II (Fm/Fv) was similar in all treatments (0.80 to 0.83) meaning plants from all the treatments were not under stress. Water consumption fresh biomass weight, number of open flowers, and vase life were similar between treatments.

Freesia x hybrida Sistema hidropónico Solución nutritiva Crecimiento Calidad del tallo floral Malla sombra Hydroponic system Nutrient solution Plant growth Floral stem quality Shade net Fruticultura Maestría CIENCIAS AGROPECUARIAS Y BIOTECNOLOGÍA

Successful community-based seed production strategies

Peter Setimela (2004, [Libro])

Designed to address the issues that limit the access of small-scale farmers in sub-Saharan Africa to quality, affordable seed of the crops on which they depend for food security and livelihoods, this collection of articles describes successful principles for and experiences in community-based seed production. Among other things, the manuscripts analyze current seed production systems and models; propose ways to design successful community-based seed production schemes; describe proper seed production practices for selected cereals, vegetatively propagated plants, and other crops; and outline basic business practices for seed producers.

CIENCIAS AGROPECUARIAS Y BIOTECNOLOGÍA Quality Business management Food security Partnerships Plant propagation Crops Models Seed production Small farms Farmers