Dissertations / Theses on the topic 'Zea maiz'

El estudio tiene como finalidad establecer un diagnóstico actualizado del cultivo del maíz y sus proyecciones de mercado en el país, con especial énfasis en la Sexta Región. En este sentido, los objetivos del estudio son los siguientes: a) Realizar un diagnóstico actualizado del mercado interno del maíz (1990 – 2004); b) Realizar un diagnóstico del comercio exterior del maíz (1990 – 2004) y c) Analizar la situación actual y perspectivas del rubro maicero en la VI Región. La metodología utilizada está basada en elementos de estadística descriptiva, el análisis de serie de tiempo; y en la aplicación de dos encuestas, la primera a informantes calificados de la producción de maíz en la sexta región y la segunda dirigida a agentes públicos y privados que tienen relación con la industria maicera en la región Del Libertador para conocer de las fortalezas, oportunidades, debilidades y oportunidades del maíz. Los principales resultados en el periodo 1990-2004 son: a) Constatación del incremento de la superficie en el período de un 18%, aunque con fluctuaciones entre las 70.000 y 120.000 ha; b) Aumento de los rendimientos promedios de 81,4 a 110,7 qqm/ha; c) determinación de un 120% de aumento del consumo nacional de maíz, con un aumento consiguiente de 50 mil a 1.100.000 toneladas en las importaciones, y d) constatación de la tendencia a la baja del precio internacional del maíz que condiciona la rentabilidad del rubro en el país.

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A deriva de produtos fitossanitários e os efeitos sobre culturas-não-alvo são grandes preocupações na agricultura moderna, especialmente com produtos herbicidas que promovem efeitos com quantidades muito pequenas. Assim, o objetivo deste trabalho foi avaliar os efeitos de sub doses de glyphosate sobre seis híbridos de milho (Zea mays). Para tanto, foram conduzidos dois experimentos iniciais (Experimentos 01 e 02), com seis híbridos (Celeron, Fórmula, Impacto, Maximus, Speed e Status) e seis doses do herbicida glyphosate (formulação Roundup Ready®). No primeiro experimento foram avaliados os efeitos das doses 0, 25, 50, 75, 100 e 125 g e.a ha-1 e, no segundo experimento, as doses de 0, 100, 125, 150, 175 e 200 g e.a ha-1. Para avaliação de dose resposta um terceiro experimento (Experimento 03) foi conduzido com as doses de 0, 40, 80, 120, 160 e 200 g e.a ha-1 de glyphosate (Roundup Ready®) para os seis híbridos. Um quarto experimento (Experimento 04), também do tipo dose-resposta, envolvendo dois híbridos (Status e Impacto), as doses 0, 40, 80, 120, 160 e 200 g e.a ha-1 de glyphosate e as formulações Roundup Ready®, Roundup WG® e Zapp QI®. As plantas de milho foram cultivadas em vasos com mistura de terra, areia e esterco e a aplicação do glyphosate sempre ocorreu em plantas no estádio de quatro folhas totalmente expandidas. No experimento 01 foram avaliadas as variáveis fotossintéticas, morfológicas e nutricionais nos tratamentos com maior efeito tóxico. No experimento 02 incluiu-se altura das plantas na avaliação. Nos experimentos 03 e 04 foram avaliadas apenas variáveis morfológicas. A atividade fotossintética aos 7 DAA foi favorecida pela aplicação de glyphosate em doses de até 50 g e.a ha-1 apenas nos híbridos Impacto e Fórmula. O híbrido Celeron apresentou maior acúmulo...
Pesticides drift and its effect on non-target crops are the major concerns in modern agriculture, especially with the use of herbicides promoting effects at very small quantities. The objective of this study was to evaluate the effects of sub doses of glyphosate on six corn (Zea mays) hybrids, Two initial tests (01 and 02) were conducted with six maize hybrids (Celeron, Fórmula, Impact, Maximus, Speed, and Status) and six doses of the herbicide glyphosate (Roundup-Ready ®). In the first experiment the effects of 0, 25, 50, 75, 100 and 125 g e.a ha-1 and in the second experiment, doses of 0, 100, 125, 150, 175 and 200 g e.a ha-1 were evaluated. A third test (test 03) was carried out toy evaluate the dose-response at 0, 40, 80, 120, 160 and 200 g e.a ha-1 of glyphosate (Roundup®) on the six maize hybrids. A fourth trial (Trial 04), also a dose-response approach was conducted, involving two hybrids (Status and Impact), using 0, 40, 80, 120, 160 and 200 g e.a ha-1 of glyphosate and the commercial formulations Roundup Ready ®, Roundup WG® and Zapp QI®. Maize plants were grown in 4-L pots with a mix of soil, sand and manure. Glyphosate spraying always occurred at four fully expanded leaves maize stage. In test 01 it was evaluated photosynthetic, morphological and nutritional variables, mainly in the treatments with major toxic symptoms. In experiment 02 it was included plant height in the evaluations. In tests 3 and 4 only morphological variables were evaluated. The photosynthetic activity at 7 days after spraying was enhanced by application of glyphosate at doses up to 50 g e.a ha-1 only for the hybrids ‘Impact’ and ‘Fórmula’. The ‘Celeron’ showed greater leaf area and higher accumulation of dry mass of stem and leaf compared with the other genotypes and doses up to 50 g e.a ha-1 glyphosate favored this performance. Hybrids... (Complete abstract click electronic access below)

Orientador: Robinson Antonio Pitelli
Banca: Ricardo Victoria Filho
Banca: Itamar Ferreira de Souza
Banca: Silvano Bianco
Banca: Claudinei da Cruz
Resumo: A deriva de produtos fitossanitários e os efeitos sobre culturas-não-alvo são grandes preocupações na agricultura moderna, especialmente com produtos herbicidas que promovem efeitos com quantidades muito pequenas. Assim, o objetivo deste trabalho foi avaliar os efeitos de sub doses de glyphosate sobre seis híbridos de milho (Zea mays). Para tanto, foram conduzidos dois experimentos iniciais (Experimentos 01 e 02), com seis híbridos (Celeron, Fórmula, Impacto, Maximus, Speed e Status) e seis doses do herbicida glyphosate (formulação Roundup Ready®). No primeiro experimento foram avaliados os efeitos das doses 0, 25, 50, 75, 100 e 125 g e.a ha-1 e, no segundo experimento, as doses de 0, 100, 125, 150, 175 e 200 g e.a ha-1. Para avaliação de dose resposta um terceiro experimento (Experimento 03) foi conduzido com as doses de 0, 40, 80, 120, 160 e 200 g e.a ha-1 de glyphosate (Roundup Ready®) para os seis híbridos. Um quarto experimento (Experimento 04), também do tipo dose-resposta, envolvendo dois híbridos (Status e Impacto), as doses 0, 40, 80, 120, 160 e 200 g e.a ha-1 de glyphosate e as formulações Roundup Ready®, Roundup WG® e Zapp QI®. As plantas de milho foram cultivadas em vasos com mistura de terra, areia e esterco e a aplicação do glyphosate sempre ocorreu em plantas no estádio de quatro folhas totalmente expandidas. No experimento 01 foram avaliadas as variáveis fotossintéticas, morfológicas e nutricionais nos tratamentos com maior efeito tóxico. No experimento 02 incluiu-se altura das plantas na avaliação. Nos experimentos 03 e 04 foram avaliadas apenas variáveis morfológicas. A atividade fotossintética aos 7 DAA foi favorecida pela aplicação de glyphosate em doses de até 50 g e.a ha-1 apenas nos híbridos Impacto e Fórmula. O híbrido Celeron apresentou maior acúmulo... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Pesticides drift and its effect on non-target crops are the major concerns in modern agriculture, especially with the use of herbicides promoting effects at very small quantities. The objective of this study was to evaluate the effects of sub doses of glyphosate on six corn (Zea mays) hybrids, Two initial tests (01 and 02) were conducted with six maize hybrids (Celeron, Fórmula, Impact, Maximus, Speed, and Status) and six doses of the herbicide glyphosate (Roundup-Ready ®). In the first experiment the effects of 0, 25, 50, 75, 100 and 125 g e.a ha-1 and in the second experiment, doses of 0, 100, 125, 150, 175 and 200 g e.a ha-1 were evaluated. A third test (test 03) was carried out toy evaluate the dose-response at 0, 40, 80, 120, 160 and 200 g e.a ha-1 of glyphosate (Roundup®) on the six maize hybrids. A fourth trial (Trial 04), also a dose-response approach was conducted, involving two hybrids (Status and Impact), using 0, 40, 80, 120, 160 and 200 g e.a ha-1 of glyphosate and the commercial formulations Roundup Ready ®, Roundup WG® and Zapp QI®. Maize plants were grown in 4-L pots with a mix of soil, sand and manure. Glyphosate spraying always occurred at four fully expanded leaves maize stage. In test 01 it was evaluated photosynthetic, morphological and nutritional variables, mainly in the treatments with major toxic symptoms. In experiment 02 it was included plant height in the evaluations. In tests 3 and 4 only morphological variables were evaluated. The photosynthetic activity at 7 days after spraying was enhanced by application of glyphosate at doses up to 50 g e.a ha-1 only for the hybrids 'Impact' and 'Fórmula'. The 'Celeron' showed greater leaf area and higher accumulation of dry mass of stem and leaf compared with the other genotypes and doses up to 50 g e.a ha-1 glyphosate favored this performance. Hybrids... (Complete abstract click electronic access below)
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Avaliaram-se o consumo, a digestibilidade, o pH e concentração de amônia ruminais e a taxa de passagem em bovinos recebendo dietas contendo feno de capim-tifton 85 (FT) e silagem de milho (SM) em diferentes proporções. Utilizaram-se quatro animais, castrados, com peso médio de 523 kg, fistulados no rúmen, distribuídos em um quadrado latino 4 x 4, recebendo 60% de volumoso e 40% de concentrado, na base da matéria seca. O volumoso consistiu das seguintes proporções: 100 TIF:0 SM; 67 TIF:33 SM; 33TIF:67 SM; e 0 TIF:100 SM (%). Os consumos (kg/dia) de matéria seca (MS), matéria orgânica (MO), matéria orgânica digestível (MOD), proteína bruta (PB), fibra em detergente neutro (FDN), carboidratos totais (CHOT) e digeríveis (CHOD) não foram influenciados pelas diferentes proporções de feno de capim-tifton 85:silagem de milho nas dietas, registrando-se valores médios de 9,2; 8,7; 6,4; 1,1; 3,7; 7,3; e 5,4 kg/dia, respectivamente. O consumo de extrato etéreo (EE) aumentou linearmente com o incremento da silagem de milho nas dietas. As digestibilidades aparentes de MS, MO, PB, EE e CHO também não foram influenciadas pelas diferentes proporções de silagem de milho, registrando-se, respectivamente, valores médios de 71,8; 73,0; 69,5; 69,2; e 73,9%. Para a digestibilidade da FDN, observou-se efeito quadrático, estimando-se valor máximo de 65,2% para dietas contendo 30,98% de silagem de milho. Estimaram- se concentração máxima de amônia de 12,0 mg/100 mL e valor mínimo de pH de 5,98 às 2,44 e 6,82 horas após a alimentação, respectivamente. A taxa de passagem não foi influenciada pelas diferentes proporções de feno:silagem, no volumoso, registrando-se valor médio de 4,2%/hora. Conclui-se que as dietas se equivaleram nutricionalmente.
This work was carried out to assess the intake, digestibility, ruminal pH, ammonia content and rate of passage in steers fed rations containing Tifton 85 bermudagrass hay (T85H) and corn silage (CS) in different proportions of the roughage portion of the diet, which contained 60:40 roughage: concentrate proportions in dry matter basis. Four rumen fistulated steers with 523 kg live weight were used and a 4x4 latin square design was adopted. The roughage portion consisted of: 100 T85H: 0 CS; 67 T85H: 33 CS; 33:67 CS T85H and 0 T85H: 100 CS. The dry matter (DM), organic matter (OM), digestible organic matter (DOM), crude protein (CP), neutral detergent fiber (NDF), total carbohydrates (TC) and total digestible carbohydrates (TDC) intakes were not affected by different T85H:CS proportions and averaged 9.2, 8.7, 6.4, 1.1, 3.7, 7.3 and 5.4 kg/day, respectively. The extract ethereal (EE) intake increased with increasing corn silage proportion in diets. The DM, OM, CP, EE and TC apparent digestibilities were not affected by increasing percentage of corn silage on rations and averaged 71.8, 73.0, 69.5, 69.2 and 73,9%, respectively. The NDF digestibility decreased 0,1454 units to each unit of increasing on corn silage proportion in diets. The N-ammonia maximum content (12.0 mg/100 ml) and minimum value of pH (5.98) were estimated 2.44 and 6.82 hours after feeding, respectively. The rate of passage, which was not affected by changing T85H:CS proportions in the roughage, averaged 4.2 %/hour. It is concluded that the diets are nutritionally similar.

A agricultura irrigada tem passado por constantes desafios voltados ao consumo racional dos recursos naturais, em especial para a cultura de milho que mesmo sendo um produto estratégico nos sistemas de produção agropecuários, tem sua viabilidade questionada em decorrência dos elevados custos de produção associado aos altos riscos relacionados as condições climáticas. O presente trabalho tem como objetivo determinar a necessidade, e propor estatégias de manejo de irrigação, baseados no balanço hídrico e na produtividade deplecionada de milho em dez épocas de semeadura, para dez municípios do estado do Rio Grande do Sul. O balanço hídrico do solo foi gerado com uma série histórica de dados de 17 a 25 anos de observação, a necessidade de irrigação foi determinada com base no deficit hídrico acumulado, e as estratégias de manejo de irrigação foram simuladas nas seguintes condições: (A) irrigação com base no fator de depleção de água no solo e na previsão de chuva, com irrigações ao longo de todo o ciclo, (B) manutenção da capacidade de água disponível (CAD) do solo em 80% ao longo de todo o ciclo, e (C) manutenção da CAD a 80% entre a floração e a maturidade fisiológica. Os dados foram submetidos a análise de variância com teste de regressão para os efeitos relacionado as épocas e teste de médias para determinar a melhor estratégia de irrigação. A partir dos resultados conclui-se que há necessidade de irrigação para todos os municípios e épocas estudadas, sendo que os valores de deficit hídrico acumulados foram de 312, 239, 260, 247, 286, 215, 206, 302, 240 e 264 mm para Bagé, Cruz Alta, Encruzilhada do Sul, Ibirubá, Iraí, Júlio de Castilhos, Passo Fundo, Santa Maria, Santa Rosa e São Luiz Gonzaga, respectivamente. Entre as épocas de semeadura o deficit hídrico acumulado variou de 143 a 360 mm.ciclo-1 e a evapotranspiração potencial da cultura entre 473 e 593 mm.ciclo-1, sendo as semeaduras de agosto responsáveis pelos menores valores e outubro pelos maiores, na média entre as épocas e locais o deficit hídrico acumulado foi de 257 mm.ciclo-1, ao passo que o excedente hídrico apresentou valor superior ao deficit ao longo do ciclo para todas situações estudadas. Quanto as estratégias de manejo de irrigação, foi possível concluir que o manejo A: foi responsável pela menor produtividade sob condição irrigada e pela menor lâmina de irrigação, sendo que o ganho de produtividade (GP) médio foi de 18,9 kg.mm-1, manejo B apresentou os maiores valores de produtividade sob condição irrigada, lâmina de irrigação e o menor GP 19,6 kg.mm-1 e o manejo C promoveu um incremento de 127% na produtividade em relação as condições de sequeiro, com uma lâmina de irrigação de 170 mm, e um GP de 30,1 kg.mm-1. Por fim, a produtividade potencial sofreu uma redução de 71% em decorrência do deficit hídrico, demonstrando a necessidade de suplementação hídrica através da irrigação e a melhoria das condições de armazenamento de água e exploração do perfil de solo para maior aproveitamento da água perdida no excedente hídrico.
Irrigated agriculture has been a constant challenge aiming at the rational consumption of natural resources, especially for the corn crop, which even though being a strategic product in agricultural production systems, has its viability questioned due to high production costs. In order to determine the need to propose irrigation management strategies based on the concept of water balance, the depleted yield of maize in ten sowing seasons was used for ten cities in the state of Rio Grande do Sul, Brazil. Soil water balance was generated with a historical data series of 17 to 25 years of observation, the need for irrigation was determined based on the accumulated water deficit, and irrigation management strategies were: (A) irrigation based on the water depletion factor along of the whole cycle; (B) maintaining soil water holding capacity (SWHC) at 80% throughout the cycle; and (C) maintaining 80% SWHC between flowering and physiological maturation. From the results, it can be concluded that irrigation is needed for all studied cities and seasons, and the accumulated water deficit values were 312, 239, 260, 247, 286, 215, 206 , 240 and 264 mm for Bagé, Cruz Alta, Encruzilhada do Sul, Ibirubá, Iraí, Júlio de Castilhos, Passo Fundo, Santa Maria, Santa Rosa and São Luiz Gonzaga, respectively. Among sowing times, the accumulated water deficit ranged from 143 to 360 mm.cycle-1 and the potential evapotranspiration of the crop between 473 and 593 mm.cycle-1, with August sowings accounting for the lowest values and October presenting the highest value on average between the seasons and localities. The accumulated water deficit was 257 mm.cycle-1, while the water surplus presented a value higher than the deficit over the cycle for all situations. Regarding the irrigation management strategies, it was possible to conclude that: (A) they were responsible for the lowest irrigated productivity and the lowest irrigation depth, and the mean gain of productivity (GP) was 18.9 kg.mm-1; (B) presented the highest productivity values for Irrigation, and the lowest GP 19.6 kg.mm-1 and (C) promoted a 77% increase in productivity in relation to rainfed conditions, with an irrigation depth of 170 mm, and a GP of the order of 30.1 kg.mm-1. Finally, potential productivity fell by 71% due to the water deficit, so that this result demonstrates the need for water supplementation through irrigation and improvement of water storage conditions, and soil profile exploration for better use of the water lost in the water surplus.

En el Valle de Toluca se disponen de pocas variedades sintéticas de maíz de testa blanca como amarilla; registrada y disponible para los productores. Uno de los pasos iniciales para su registro es la descripción fenotípica de cada material generado, por lo que se requiere que se describan fenotípicamente tres genotipos blancos y cinco genotipos amarillos originados, del programa de mejoramiento genético de la Universidad Autónoma del Estado de México y del Colegio de Posgraduados, y que se han adaptado a las condiciones ambientales del Valle de Toluca y que exprese tolerancia al carbón de la espiga del maíz. El objetivo del presente trabajo fue evaluar las características agronómicas en ocho variedades sintéticas de maíz resistente al carbón de la espiga. Se estableció una parcela de durante el ciclo primavera-verano del 2016 en la facultad de ciencias agrícolas de la UAEM. La distribución de los tratamientos se realizó con un diseño de bloques completamente al azar con cuatro repeticiones. Las variables registradas fueron: número de plantas, color de espigas (blancas ó rojas), altura de la planta, numero de elote, numero de hileras de la mazorca, diámetro de la mazorca, peso total de la mazorca, peso total de seis mazorcas, longitud de la mazorca, numero de mazorcas cosechadas y peso de grano. Los resultados indicaron que los ocho materiales sintéticos mostraron diferencia significativa entre los caracteres evaluados, destacando el genotipo Amarillo 21 y el genotipo blanco 25 para la producción de grano. Mientras que el genotipo amarillo 23 presentó características fenotípicas adecuadas para la producción de forraje.

Los sistemas modernos de formulación de raciones para el ganado vacuno se basan en los conceptos de proteína digestible y el aporte de aa al intestino delgado del rumiante. De la calidad total de proteína sintetizada en el rumen y que llega al intestino delgado del rumiante, una proporción importante, aunque variable, corresponde a la proteína microbiana, la cual proviene, fundamentalmente, de las bacterias. Aunque la mayor parte de las bacterias están unidas a la parte solida B(AS), en la mayoría de los estudios realizados se utilizan muestras de bacterias obtenidas de la fracción líquida del contenido ruminal (BAL). Existe información en la literatura que indica la diferencia en la composición quimica entre BAL y BAS, las cuales pueden estar relacionadas con importantes errores en la predicción del flujo de proteína y aa de origen microbiano. Otro factor importante que se debe tomar en cuenta se relaciona con la dieta (forraje:concentrado, nivel de fibra, tamaño de partícula, consumo de alimento…etc.) ya que pueden afectar la fermentación y el metabolismo proteico y con ello disminuir el aporte parcial de BAL y BAS y con ello el flujo de proteína o aa de origen microbiano. De igual forma, el flujo de BAL y BAS se ve alterada por los cambios producidos a nivel ruminal debido a variaciones en la dieta o en el tiempo de alimentación (pH, tasa de dilución). El estudio de los problemas antes mencionados in vivo es complicado, ya que la fermentación puede confundir la interpretación de los resultados. Existen diversos sistemas in vitro que nos ofrecen la oportunidad de estudiar cada uno de los factores de forma aislada. El objetivo del presente estudio, fue evaluar los diferentes métodos de digestibilidad y condiciones de fermentación, así como, el flujo de nutrientes y el perfil y flujo de aa de origen microbiano utilizando la excreción de derivados púricos (DP).

Plant genetic engineering approaches are of pivotal importance to both basic and applied research. However, rapid commercialization of genetically engineered crops, especially maize, raises several ecological and environmental concerns largely related to transgene flow via pollination. In most crops, the plastid genome is inherited uniparentally in a maternal manner. Consequently, a trait introduced into the plastid genome would not be transferred to the sexually compatible relatives of the crops via pollination. Thus, beside its several other advantages, plastid transformation provides transgene containment, and therefore, is an environmentally friendly approach for genetic engineering of crop plants. Reliable in vitro regeneration systems allowing repeated rounds of regeneration are of utmost importance to development of plastid transformation technologies in higher plants. While being the world’s major food crops, cereals are among the most difficult-to-handle plants in tissue culture which severely limits genetic engineering approaches. In maize, immature zygotic embryos provide the predominantly used material for establishing regeneration-competent cell or callus cultures for genetic transformation experiments. The procedures involved are demanding, laborious and time consuming and depend on greenhouse facilities. In one part of this work, a novel tissue culture and plant regeneration system was developed that uses maize leaf tissue and thus is independent of zygotic embryos and greenhouse facilities. Also, protocols were established for (i) the efficient induction of regeneration-competent callus from maize leaves in the dark, (ii) inducing highly regenerable callus in the light, and (iii) the use of leaf-derived callus for the generation of stably transformed maize plants. Furthermore, several selection methods were tested for developing a plastid transformation system in maize. However, stable plastid transformed maize plants could not be yet recovered. Possible explanations as well as suggestions for future attempts towards developing plastid transformation in maize are discussed. Nevertheless, these results represent a first essential step towards developing chloroplast transformation technology for maize, a method that requires multiple rounds of plant regeneration and selection to obtain genetically stable transgenic plants. In order to apply the newly developed transformation system towards metabolic engineering of carotenoid biosynthesis, the daffodil phytoene synthase (PSY) gene was integrated into the maize genome. The results illustrate that expression of a recombinant PSY significantly increases carotenoid levels in leaves. The beta-carotene (pro-vitamin A) amounts in leaves of transgenic plants were increased by ~21% in comparison to the wild-type. These results represent evidence for maize to have significant potential to accumulate higher amounts of carotenoids, especially beta-carotene, through transgenic expression of phytoene synthases. Finally, progresses were made towards developing transformation technologies in Peperomia (Piperaceae) by establishing an efficient leaf-based regeneration system. Also, factors determining plastid size and number in Peperomia, whose species display great interspecific variation in chloroplast size and number per cell, were investigated. The results suggest that organelle size and number are regulated in a tissue-specific manner rather than in dependency on the plastid type. Investigating plastid morphology in Peperomia species with giant chloroplasts, plasmatic connections between chloroplasts (stromules) were observed under the light microscope and in the absence of tissue fixation or GFP overexpression demonstrating the relevance of these structures in vivo. Furthermore, bacteria-like microorganisms were discovered within Peperomia cells, suggesting that this genus provides an interesting model not only for studying plastid biology but also for investigating plant-microbe interactions.
Pflanzliche Gentechnik spielt sowohl in der Grundlagenforschung als auch der Biotechnologie eine große Rolle. Allerdings bringt die landwirtschaftliche Nutzung gentechnisch veränderter Pflanzen (GM) ökologische Umweltrisiken mit sich, wie z.B. die Kreuzung GM Pflanzen mit sexuell kompatiblen Verwandten durch Fremdbestäubung. Gegenüber den Kerntransformanden haben Plastidtransformanden für die biotechnologische Nutzung große Vorteile, unter anderem da die Vererbung des Plastidgenoms bei höheren Angiospermen ausschließlich maternal geschieht. Somit kann ein Gentransfer transplastomischer Pflanzen über Pollen ausgeschlossen werden. Zuverlässige in-vitro-Regenerationssysteme, die wiederholte Regenerationsrunden erlauben, sind von großem Wert für die Etablierung der Plastidentransformationstechnologie. Trotz Sein die Hauptgetreidenahrungsmittel der Welt, Zerealie Pflanzen gehören zu schwierigsten in der Gewebekultur zu handeln, die Annäherungen der genetischen Technik streng begrenzt. Im Mais werden hauptsächlich junge zygotische Embryonen für die Herstellung der Regenerations-kompetenten Kalluskulturen benutzt. Der Arbeitsaufwand dafür ist hoch und die Prozedur schwierig und von den Gewächshausbedingungen abhängig. Im Rahmen dieser Arbeit wurden neue Gewebekultursysteme für Mais etabliert, welches junge Blattgewebe nutzt und somit unabhängig von Embryonen und Gewächshaus ist. Weiterhin wurden die aus Blättern gebildeten Kalluskulturen für die Generierung der genetisch veränderten Maispflanzen benutzt. Ebenso wurden verschiedene Selektionsmethoden für die Entwicklung eines Plastidentransformationssystems in Mais getestet. Jedoch konnten keine transplastomischen Maispflanzen erhalten werden. Sowohl die möglichen Ursachen als auch Vorschläge für weiterführende Versuche diesbezüglich werden im Rahmen dieser Arbeit diskutiert. Dennoch stellt diese Arbeit den ersten wesentlichen Schritt für die Entwicklung eines Plastidentransformationssystems in Mais vor. In einem zweiten Teil dieses Projekts wird die erfolgreiche Integration der Narzissen Phytoene Synthase in das Maisgenom durch das neu entwickelte nukleäre Transformationssystem gezeigt. Dadurch konnte eine signifikante Steigerung um 17% des Gesamtcarotinoid- und 21% des Beta-Carotengehalts in Maisblättern beobachtet werden. Schließlich wurden Fortschritte für die Entwicklung eines Transformationssystems für Peperomia (Piperaceae) durch die Etablierung eines Regenerationssystems aus Blättern gemacht. Außerdem wurden Faktoren, die die Plastidengröße und –zahl bestimmen, untersucht. Diese Ergebnisse geben Hinweise darauf, dass die Organellengröße und –zahl eher gewebespezifisch als in Abhängigkeit vom Plastidentyp reguliert wird.

The glutathione transferases (GSTs) of maize have been the most studied GSTs in plants, however much is still not known about these enzymes. In the course of the current study six GST subunits (Zm GSTs I, II and III, which have been reported previously, and Zm GSTs V, VI and VII, which have not been previously reported) have been identified in the dimers Zm GST I-I, I-II, I-III, V-V, V-VI and V-VII. Maize GSTs are known to be important in herbicide detoxification and the purified maize enzymes were each found to have differing activities toward a number of herbicides, and also a range of other potential GST substrates. Additionally, Zm GST I II and Zm GST V-V possessed glutathione peroxidase activity. The developmental regulation and chemical inducibility of maize GSTs were studied in maize seedlings using western blotting, with different subunits showing markedly different responses. Zm GST I was constitutively present in all plant parts and unaffected by chemical treatment, Zm GST II was only detected in young roots but was induced in roots and shoots by many different chemical treatments, and Zm GST V was present at low levels throughout maize plants, with levels enhanced greatly by treatment with the safener dichlormid but not by other chemicals tested. cDNA clones corresponding to Zm GST subunits I, III, V, VI and VII were isolated by library screening using antibody or DNA probes. The cDNA sequences for Zm GST subunits V, VI and VH were different from those of previously cloned type I (theta class) maize GSTs and were most similar to the auxin-regulated GST family (type III or tau class GSTs) previously only identified in dicotyledonous species. The cloned GSTs were expressed as recombinant proteins in E. coli, allowing further characterisation, including detailed kinetic analysis for recombinant Zm GST I-I and Zm GST V-V.

Thesis (Ph. D.) University of Missouri-Columbia, 2006.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 3, 2007) Includes bibliographical references.

Las variedades tradicionales de maíz se han adaptado a través de los años al manejo, selección y a las condiciones climáticas donde son cultivadas, encontrándose en ellas características de adaptación y resistencia, así como una base genética más amplia que las variedades comerciales. La caracterización morfológica permite un entendimiento de las relaciones genético-ambientales existentes entre las poblaciones, facilitando así el uso de ellas por parte de mejoradores. En este trabajo se evaluó la variabilidad morfológica de 34 accesiones de maíces nativos de raza Choclero, recolectados entre la III y VIII región. El ensayo se realizó durante la temporada primavera-verano de 2005-2006 utilizando semilla obtenida del Banco Base de Germoplasma de INIA, CRI- Intihuasi. El diseño experimental se basó en bloques completos al azar con tres repeticiones, midiéndose un total de 37 caracteres morfológicos de tipo reproductivo, vegetativo y fenológico de acuerdo a los descriptores establecidos por el IPGRI (International Plant Genetic Resources Institute). Las pruebas de hipótesis indicaron diferencias significativas para todos los caracteres cuantitativos a excepción del índice de macollamiento y el número de mazorcas por macollo. Los coeficientes de correlación fueron calculados para todas las variables cuantitativas, descartando aquellas que se encontraron altamente correlacionadas (r >0,6). Once caracteres fueron escogidos por esta vía, y con ellos se realizó un análisis de componentes principales (ACP) en base a la matriz de correlaciones y un análisis de conglomerados, previa estandarización de las variables. El dendrograma arrojado mostró tres grupos principales, los cuales tuvieron cierta correspondencia con el agrupamiento observado en la figura de los dos primeros ejes del ACP. La descripción de los grupos fue complementada con descripciones de caracteres cualitativos relevantes para cada grupo. Los resultados mostraron la existencia de variabilidad inter poblacional dentro de la raza Choclero evidenciada por la formación de grupos claramente diferenciables explicados en parte por la diversidad de ambientes de recolección, siendo tres los principales: maíz pequeño (grupo A), con accesiones precoces a intermedias y mazorcas gruesas y cortas, principalmente del tipo cónico, sus zonas de origen son de altas temperaturas y baja humedad relativa; maíz intermedio-grande (grupo C) con plantas intermedias- altas, tallos gruesos, panojas grandes, granos de alto peso y mazorcas de tamaños intermedio a largo; maíz intermedio (grupo B), con características menos acorde para la raza probablemente debido a la introgresión de genes de otras razas como Diente de Caballo, mazorcas de menor diámetro, de tamaño intermedio a largo y panojas pequeñas de pocas ramificaciones, así como algunas accesiones con mazorcas cilíndricas y con hileras irregulares a regulares. Para validar el agrupamiento obtenido se realizó un análisis discriminante con los grupos formados a dos distancias diferentes en el análisis de conglomerados. Éste clasificó correctamente la mayoría de los grupos salvo en los grupos 5 y 6 (grupo C), donde la diferenciación no fue clara. Dentro de las explicaciones posibles está la distancia genética que pudiera existir entre ellos o la falta de discriminación de los caracteres elegidos.

Aquesta tesi doctoral s'engloba dins d'un projecte general d'estudi de gens implicats en l'embriogènesi del blat de moro. L'embriogènesi del blat de moro, i en general la de totes les plantes superiors, es dóna en tres etapes: una primera etapa on es diferencien tots els diversos teixits que formaran l'embrió, una segona etapa on l'embrió acumula productes de reserva i un tercer període, la dormància, que finalitza quan les condicions ambientals són les idònies per a la germinació. En el laboratori estàvem interessats, concretament, en l'estudi de gens implicats en la primera etapa morfogenètica, on els diferents teixits i estructures embrionàries queden definides. Per tal d'estudiar gens que s'expressaven en aquest període, una de les estratègies que es va realitzar fou un crivellat diferencial entre teixit embrionari i teixit de planta adulta. D'entre els diferents clons obtinguts, un corresponia a un clon parcial que presentava similitud amb receptors quinasa i que fou objecte d'estudi. A partir d'aquest clon es va obtenir el clon complet i es va anomenar MARK (per Maize Atypical Receptor Kinase).
MARK presenta una estructura típica d'un receptor quinasa amb un domini extracel.lular, que conté 6 còpies imperfectes de LRR (Leucine- Rich Repeats), un únic domini transmembrana i un domini quinasa intracel.lular. El domini quinasa de MARK presenta, però, algunes variacions en els residus aminoacídics que es consideren claus per a la funció catalítica dels dominis quinasa. En concret cinc dels aminoàcids considerats essencials per a la fosforilació es troben substituits en el domini quinasa de MARK (DK-MARK). Els experiments de fosforilació in vitro que es van realitzar al laboratori, van mostrar com MARK era incapaç de fosforilar in vitro. Aquesta característica no és, però, exclusiva de MARK. Una búsqueda en les bases de dades ens van permetre identificar altres seqüències que també presentaven els mateixos o altres canvis en aquestes posicions aminoacídiques. En les bases de dades de plantes es van identificar un conjunt de seqüències genòmiques o ESTs amb aquestes característiques i només una d'elles, la proteïna TMKL1 d'Arabidopsis, ha sigut descrita com un receptor quinasa incapaç de fosforilar in vitro. Respecte a la búsqueda de receptors similars a MARK en les bases de dades d'animals, es van identificar també un conjunt de proteïnes que, en alguns casos, s'ha descrit que no tenen activitat quinasa in vivo. Per exemple, un dels casos més ben estudiats és el del receptor erbB3 que forma part de la família de receptors del EGF (Epidermal Growth Factor). Aquesta família de receptors està formada per 4 receptors: erbB1, erbB2, erbB3 i erbB4, dels quals només l'erbB3 no presenta activitat catalítica. S'ha descrit que erbB3 és capaç, tot i no fosforilar in vivo, de participar activament en la transducció del senyal formant heterodímers amb els altres membres de la família. Així, erbB3 és fosforilat pel seu partner i pot iniciar la cascada de transducció del senyal. La participació d'erbB3 en la transducció del senyal és essencial ja que embrions de ratolí knock-out pel gen erbB3 són inviables. Així doncs, el fet que receptors quinasa catalíticament inactius participin en les cascades de transducció del senyal, suggereix l'existència de nous mecanismes d'acció per a la transducció del senyal. Per tant, l'objectiu d'aquest treball fou l'estudi del mecanisme d'acció de MARK mitjançant la caracterització les proteïnes capaces d'interaccionar amb el seu domini quinasa. Per tal d'assolir aquest objectiu, es va realitzar un crivellat de doble-híbrid amb una llibreria de cDNA d'embrions de blat de moro de 7 DAP. D'aquest crivellat es va obtenir un conjunt de possibles clons positius que foren seqüenciats i entre els quals es van escollir per un estudi més detallat aquells que s'havien obtingut més vegades com a clons independents. Aquests clons codificaven per: una SAMDC (S-Adenosil Descarboxilasa), una eIF5 (Eukaryotic translation initiation), una hypothetical protein, una unknown protein, una gamma-adaptina i una MAP4K. Amb aquests 6 clons es van fer estudis in vitro i in vivo per tal de confirmar al seva interacció amb DK-MARK. Els estudis in vivo es van realitzar amb la soca de llevat AH109, una soca més astringent que la utilitzada en el crivellat, ja que presenta tres gens marcadors: Histidina, Adenina i Lacz. Els resultats obtinguts van mostrar que els clons codificants per SAMDC i eIF5 no van créixer en un medi selectiu per His i Ade i, per tant o es tracta de falsos positius del sistema o la seva interacció amb DK-MARK és dèbil. D'altra banda, la resta dels clons analitzats (proteïna hipotètica, una proteïna de funció desconeguda, la gamma-adaptina i una MAP4K) van créixer en medis en absència de Histidina i Adenina. Els assatjos de b-galactosidasa van ser tots positius a excepció de la proteïna hipotètica suggerint que potser aquesta interacció sigui més feble. D'altra banda també es van realitzar estudis in vitro amb la tècnica del pull-down. Els resultats obtinguts amb aquesta tècnica van recolzar els obtinguts en cèl.lules de llevat, ja que tots els clons analitzats a excepció dels codificants per SAMDC i eIF5 van donar un resultat d'interacció amb KD-MARK in vitro positiu. Davant aquests resultats ens vam centrar en l'estudi de la proteïna similar a MAP4K, doncs algunes proteïnes de la seva família s'han relacionat amb receptors de membrana. Els clons que es va obtenir del crivellat codificaven per una proteïna similar amb el domini C-terminal a les proteïnes BnMAP4Ka1 i a2 de Brassica napus. Aquestes proteïnes presenten una forta similitud de seqüència amb proteïnes de la família GCK/SPS1 que formen part d'un grup particular de MAPK relacionades amb la proteïna Ste20 (sterile 20 protein) de llevat. Ste20p activa la MAP3K de llevat Ste11 directament per fosforilació, transduint d'aquesta manera el senyal del receptor de feromones de creuament de les cèl.lules de llevat i es pot, doncs, considerar com una proteïna del tipus MAP4K (mitogen-activated protein kinase kinase kinase kinase). En els darrers anys, s'han identificat un gran nombre de proteïnes similars a Ste20: fins a una trentena en mamífers, en Drosophila, en Caenorhabditis elegans i en altres organismes. Segons la seva estructura aminoacídica, la família Ste20 s'ha classificat en dues subfamílies: les proteïnes STE20/PAK (p21-activated kinases) i la subfamília GCK/SPS1 (germinal center kinases). Les dues subfamílies estan formades per proteïnes que contenen un domini quinasa i un domini regulador, però, mentre que les proteïnes PAK presenten el domini quinasa en la part C-terminal, les GCKs el presenten en la regió N terminal. Les proteïnes GCK presenten una elevada diversitat estructural en el domini regulador permetent la seva classificació en 6 subfamílies. Mitjançant la tècnica del RACE es va obtenir el clon de cDNA complet que es va anomenar MIK (MARK Interacting Kinase). Amb la tècnica del Southern blot es va poder determinar que el gen MIK és un gen de còpia única en el genoma de blat de moro. Per tal d'analitzar la possible interacció entre DK-MARK i MIK, es va estudiar tant el patró d'expressió d'ambdós gens com el seu patró d'acumulació d'ambdues proteïnes durant l'embriogènesi del blat de moro. El patró d'expressió, analitzat per Northen blot va mostrar uns patrons coincidents al llarg de l'embriogènesi des del seu inici fins als 20 DAP amb una acumulació màxima de mRNA en embrions de 15 DAP. D'altra banda per tal d'estudiar el patró d'acumulació de la proteïna MIK així com per comparar-lo amb el de MARK, es van realitzar estudis de Westerns blot. Els resultats també van mostrar una coincidència en el temps de l'acumulació de les proteïnes MARK i MIK durant l'embriogènesi de blat de moro amb una major acumulació en embrions de 15 i 20 DAP. Es van dur a terme també estudis d'immunolocalitzacions sobre embrions de blat de moro de 15 DAP per tal d'estudiar en quins teixits s'acumulaven ambdues proteïnes. Les immunolocalitzacions van mostrar una major acumulació tant de MARK com de MIK en les zones meristemàtiques i en el teixit vascular sobretot del coleòptil on s'aprecia una forta co-localització de MARK i MIK. Totes aquestes dades són compatibles, doncs, amb una possible interacció de les proteïnes MARK i MIK, tot i que no la demostren. Per tal de demostrar la interacció es van realitzar experiments d'immunoprecipitació in vivo a partir d'extractes d'embrions. Malauradament, els resultats no són clars i en aquests moments en el laboratori s'estan posant a punt aquests experiments.
També es van realitzar estudis comparatius de seqüència amb diferents proteïnes de la família GCK, mostrant una major similitud amb les proteïnes de la subfamília GCK-III. La subfamília GCK-III ha estat molt poc estudiada i en formen part un conjunt de proteïnes amb funcions molt diverses des de l'apoptosi, la citoquinesi o l'anòxia cel.lular. Per tant, la similitud de seqüència possiblement fa referència a una conservació en el mecanisme d'acció més que no pas a una conservació funcional. La possible interacció de MARK amb el domini C-terminal de MIK (el domini regulador) podria activar aquesta última iniciant una cascada de transducció del senyal en un model en el que una proteïna del tipus GCK-III faria de lligam directa entre un receptor de membrana i una cascada de senyalització intracel.lular. Aquest tipus de lligam entre un recepctor de membrana i mòduls intracel.lulars de senyalització s'ha descrit per a altres proteïnes GCK, si bé no directament sinó a través de proteïnes adaptadores. D'altra banda, la interacció directa de MARK, un receptor quinasa atípic que no té activitat catalítica, amb MIK suggereix un mecanisme on receptors atípics podrien interaccionar en la transducció del senyal activant la via de les MAPK.

Detailed knowledge ofthe genetic diversity among maize (Zea mays L.) gennplasm is useful for their systematic and efficient use in breeding programmes. The objectives of the study were to (i) characterize Ghanaian landraces for agronomic and morphological traits, (ii) use amplified fragment length polymorphisms (AFLPs) and agro-morphological traits to detennine the variability of the local landraces and (iii) evaluate the landraces for adaptation to two major maize-growing zones in Ghana. In the molecular studies involving 90 landraces and four improved cultivars, twelve higIily informative AFLP primer combinations produced a total of 536 fragments of which 447 (83%) were polymorphic. Jaccard's similarity coefficients among the accessions ranged from 0.13 to 0.66. Analysis of molecular variance (AMOVA) indicated that 96% of the variability resided among accessions within groups rather r/ than among groups (4%), necessitating intra-accession variability assessment of two selected landraces, AA007F and AA098F. Euclidean distance estimates from agromorphological traits averaged 6.49 over all accessions and ranged from 2.30 to 13.61, indicating high phenotypic variability among them. Principal component analysis (PCA) showed that the first six principal components explained 79.2% of the total variability among the accessions. In the intra-Iandrace variability study, Jaccard's similarity coefficients ranged from 0.05 to 0.83 (AA007F) and 0.20 to 0.75 (AA098F). Euclidean distance estimates ranged from 1.90 to 18.80 for AA007F and 2.30 to 14.41 for AA098F, indicating high phenotypic variability within the landraces. There was no significant a~sociation between agronomic performance and the genetic diversity estimates from AFLP. The results will help in maintaining the landrace accessions and serve as a guide in designing breeding strategies that utilize Ghanaian maize genetic resources effectively.

When chilled, plants produce greater amounts of toxic oxygen compounds than they do under non-stressed conditions. These toxic oxygen compounds have the potential to cause severe damage to plants. Plants have evolved antioxidant systems which can scavenge these toxic oxygen compounds and thus allow for the avoidance of their detrimental effects. The purpose of this thesis was to characterize antioxidant capacities of differentially chilling sensitive lines of maize (Zea mays L.) in order to test the hypothesis that the most chilling sensitive lines would have less antioxidant capacity and, hence, less ability to scavenge damaging toxic oxygen compounds, than the more tolerant lines. Three objectives were set to test this hypothesis. The first objective was to select out relatively chilling sensitive and tolerant inbred maize based on their physiological responses to chilling. This first objective was successfully met by subjecting the inbred lines to laboratory chilling tests at the germination stage and early growth stages. Field trials which assessed physiological parameters at both the emergence and early growth phases were then carried out which confirmed laboratory results. The second objective of this thesis was to test if the selected chilling sensitive inbred maize lines had less antioxidant capacities than the tolerant. To this end, activities of the antioxidant enzymes catalase (CAT; EC 1.11.1.6), ascorbate peroxidase (ASPX; EC 1.11.1.11), superoxide dismutase (SOD; EC 1.15.1.1), monodehydroascorbate reductase (MDHAR; EC 1.6.5.4), and glutathione reductase (GR; EC 1.6.4.2), along with concentrations of the antioxidant compounds ascorbate, glutathione, $\beta$-carotene, and $\alpha$-tocopherol and levels of the general metabolic indicators of chilling stress (carbohydrates, chlorophyll, and soluble proteins) were assessed. These parameters were assessed at three developmental stages (first, third and fifth leaf stages) and under control (25$\sp\circ$C) and both short- and long-term chilling ($11\sp\circ$C) regimes. This second objective was successfully met. Significantly lower percent of control activities of the antioxidant enzymes ASPX, MDKAR, and CAT, were observed in the most chilling sensitive inbred line as compared to the tolerant at the first leaf stage of development. The third objective of this thesis was designed to determine if there were similar results for antioxidant capacities and metabolic indicator concentrations for the chilled hybrids as there were for the inbred maize lines. Thus, a complete diallel cross between the above selected inbreds was made, and the resulting hybrids then classified as relatively chilling sensitive or tolerant depending upon how they performed in the laboratory germination and early growth stage screening tests with confirmation in the field. The hybrids were grown until the third leaf stage under short-term chilling (11$\sp\circ$C) and assessed for activities of the antioxidant enzymes and concentrations of antioxidant compounds and metabolic stress indicators. This third objective was successfully met. The chilling sensitive maize hybrids were found to have lower, although not significantly so, percent of control activities of CAT, MDHAR, and ASPX than the chilling tolerant hybrids, paralleling the results of the parental inbreds. (Abstract shortened by UMI.)

Memoria para optar al título profesional de: Ingeniero Agrónomo
El rendimiento del cultivo de maíz (Zea mays L.) está estrechamente relacionado con la condición fisiológica del cultivo, durante el período crítico de éste. Déficit de nitrógeno es uno de los factores que influyen en la disminución del rendimiento. Uno de los caracteres utilizados para determinar tolerancia a este tipo de estrés, por su alta relación con el rendimiento, es ASI, intervalo seda-antesis. El objetivo de este estudio fue determinar si los híbridos de maíz usados en Chile, más tolerantes a una condición de estrés, en este caso deficiencia de nitrógeno, son los que tienen un menor ASI. Los valores de rendimiento y ASI fueron medidos en híbridos de maíz DK619, Lerma, NK703, Río Cisnes, Río Maipo, Río Negro y Río Trancura lo que fue evaluado en dos ensayos, con y sin fertilización nitrogenada, los cuales se realizaron en la Estación Experimental Antumapu de la Universidad de Chile en la temporada 2011-2012 bajo condiciones de riego. El diseño experimental fue de bloques completos al azar con cuatro repeticiones para cada uno de los ensayos, los bloques se distribuyeron en forma perpendicular a la pendiente del sector. Al realizar un análisis combinado de varianza para ASI se detectó interacción entre híbrido y ensayo con fertilización nitrogenada (p≤0,05). El ASI no varió entre ensayos para los híbridos DK619 y Lerma siendo significativamente menor que los otros híbridos. Los híbridos que tuvieron mayor diferencia de ASI entre ensayos fueron Río Negro y Río Maipo, ambos con 4 días de diferencia. El rendimiento no tuvo interacción entre híbrido y ensayo con fertilización nitrogenada, por lo que el ranqueo de los híbridos no varió dentro de los ensayos. El rendimiento estuvo relacionado negativamente con el ASI, tanto en el ensayo con fertilización nitrogenada como en el ensayo sin fertilización nitrogenada, pero estas relaciones no fueron significativas para ninguno de los dos ensayos. Con la finalidad de evaluar el efecto de la deficiencia de nitrógeno ocurrida producto de la no fertilización, sobre el rendimiento del cultivo en los siete híbridos de maíz, se planteó cuantificar la disminución porcentual del rendimiento (DPR). La disminución porcentual del rendimiento fluctuó entre un 14% y 43%. Con la finalidad de evaluar el efecto de la deficiencia de nitrógeno ocurrida producto de la no fertilización, sobre el ASI de los híbridos de maíz, se cuantifico ∆ASI entre ensayos. Esta variable tuvo una relación positiva y significativa con la disminución de rendimiento porcentual bajo condición de estrés (r2 =0,75 y p-value=0,0069). Por lo tanto la limitante al rendimiento en la localidad evaluada es el déficit de nitrógeno para el cultivo. El mayor rendimiento se obtuvo en el ensayo con fertilización nitrogenada con el híbrido Río Maipo. Los híbridos que tuvieron una menor disminución porcentual de rendimiento en condiciones de deficiencia de nitrógeno son los que tuvieron un menor ASI.
The yield of maize (Zea mays L.) is closely related to the physiological condition of the crop during its critical period. Nitrogen deficiency is one of the factors influencing the yield's fall in. One of the characters used to determine stress tolerance due to its high correlation with yield, is ASI, anthesis - silk interval. The objective of this study was to determine whether corn hybrids used in Chile to a more tolerant stress condition, in this case nitrogen deficiency, are those with lower ASI. Yield and ASI for hybrids DK619, Lerma, NK703, Río Cisnes, Río Maipo, Río Negro y Río Trancura, was evaluated in two trials, with and without nitrogen fertilization, which were conducted at the Antumapu Experimental Station in University of Chile, in the 2011-2012 season, under irrigated conditions. Treatments were arranged as randomized complete block design with seven treatments replicated four times, the blocks are distributed perpendicular to the slope of the sector. When a combined analysis of variance for ASI was achieved, interaction between hybrid and nitrogen fertilization test ( p ≤ 0.05 ) was detected. The ASI did not differ between trials for hybrids DK619 and Lerma, being significantly lower than the other hybrids. The hybrids with a higher result as an ASI difference between trials, were Río Negro and Río Maipo, both 4 days apart from each other. The yield had not interaction between hybrid and nitrogen fertilization trial, thus the ranking of the hybrids did not vary within trials. The yield was negatively correlated with both ASI nitrogen fertilization test and in the test without nitrogen fertilization, but these correlations were not significant for none of the trials. In order to evaluate the effect of nitrogen deficiency occurred due to the un-fertilization on the crop yield, it was proposed to quantify the yield percentage reduction (YPR). The yield percentage reduction ranged between 14% and 43%. In order to evaluate the effect of nitrogen deficiency occurred due to the un-fertilization on the ASI hybrids, it was proposed to quantify the ∆ASI between trials. This variable had a positive and significant correlation with ASI under stress condition (r 2 =0,75 y p-value=0,0069). Therefore the bounding one to yield in the evaluated locality is the deficit of nitrogen for the crop. The major yield was obtained in the trial with nitrogen fertilization by the hybrid Rio Maipo. The hybrids had a lower percentage decrease of yield under nitrogen deficiency are those who had lower ASI .

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With the objective of comparing the efficiency of the natural reactive phosphate (NRP) and the triple super-phosphate (TSP) associated with the elementary sulfur in the ridge of the maize plantation and also evaluate the influence of the elementary sulfur in the solubility of the NRP it was installed a field experiment in Toledo-PR in a eutroferric Red Latosol (Oxisol). In the experiment used a totally randomized design, with two sources of phosphorus in four levels of phosphate-fertilizers (0, 100, 200, e 300 kg ha-1 of elementary sulfur) applied in the plantation ridge, in four repetitions. In the beginning of the culture blossom it was carried out collects of vegetable tissue to determine the content of phosphorus and sulfur in the foliar tissue. In the end of the plantation it was evaluated the insertion height and the spike size, the mass of grains in each spike is of 1000 grains, the number of lines and the grains in each spike and also the productivity of each allotment. It was collected some soil samples from 0-10 cm and 10-20 cm of depth to determine the contents of phosphorus, sulfur, potassium and pH. It was evaluated the index of agronomical efficiency (IAE), the equivalent in triple super-phosphate (EqTSP), the utilization factor of P and the efficiency of the fertilizer´s utilization (EFU). The triple super-phosphate provided greater income of grains in comparison to the Gafsa phosphate in the first year of plantation. The agronomical efficiency of NRP was of 43% with the elementary sulfur addition and of 33% in the absence of sulfur. The phosphorus content in the foliar tissue was inferior with the utilization of the Gafsa phosphate related to the smaller availability of phosphorus in the soil with NRP application. The dose of 30kg ha-1 of elementary sulfur did not interfere in the soil´s pH, but the efficiency of the utilization of the phosphate-fertilizers was greater with the application of sulfur.
Com o objetivo de comparar a eficiência do fosfato natural reativo (FNR) e do superfosfato triplo (SFT) associado ao enxofre elementar em pó, aplicados no sulco de plantio na cultura do milho e avaliar a influência do enxofre elementar na solubilidade do FNR instalou-se um experimento a campo no município de Toledo-PR em um Latossolo Vermelho eutroférrico. O delineamento experimental consistiu de blocos inteiramente casualizados, com duas fontes de fósforo em quatro níveis de fertilizantes fosfatados (0, 100, 200 e 300 kg ha-1 de P2O5), e 2 níveis de enxofre (0 e 30 kg ha-1 de enxofre elementar), em quatro repetições. No início do florescimento da cultura foram efetuadas coletas de tecido vegetal para determinação dos teores de fósforo e enxofre no tecido foliar. No final do cultivo foi avaliada a altura de inserção e tamanho de espiga, a massa de grãos por espiga e de 1000 grãos, número de fileiras e de grãos por espiga e a produtividade de cada parcela. Foram coletadas amostras de solo nas profundidades de 0-10cm e 10-20cm para determinação dos teores de fósforo, enxofre, potássio e pH. Foram avaliados o índice de eficiência agronômica (IEA), o equivalente em superfosfato triplo (EqSFT), o fator de utilização do P e a eficiência de utilização do fertilizante (EUF). O superfosfato triplo proporcionou maior rendimento de grãos em comparação ao fosfato de Gafsa no primeiro ano de cultivo. A eficiência agronômica do FNR foi de 43% com adição de enxofre elementar e de 33% na ausência de enxofre. O teor de fósforo no tecido foliar foi inferior com o uso do fosfato de Gafsa em função da menor disponibilidade de fósforo no solo com aplicação de FNR. A dose de 30 kg ha-1 de enxofre elementar não interferiu no pH do solo mas a eficiência de utilização da adubação fosfatada foi maior com a aplicação de enxofre

El maíz es uno de los cereales más importantes de México, no solo hablando en sentido económico y social, sino también, forma parte de la cultura e identidad. En este contexto, se realizó un análisis de los procesos de producción, de las condiciones socioeconómicas y tecnológicas, así como de las políticas gubernamentales de apoyo a la producción, todo ello para detectar las deficiencias existentes y proponer soluciones mediante las cuales los productores puedan mejorar la productividad, por tanto, sus ingresos; y así determinar la rentabilidad y ventaja comparativa del cultivo en el municipio de Texcoco, en sus diferentes tecnologías. El presente estudio se llevó a cabo en el periodo del 14 de febrero del 2017 al 04 de febrero de 2018, en donde se utilizó la Matriz de Análisis de Política (MAP) para analizar la información obtenida. Los resultados arrojaron que la tecnología de temporal no es rentable ni cuenta con ventaja comparativa, mientras que las de riego y punta de riego si; sin embargo, existe un elevado costo de insumos comerciales, una falta de asesoría técnica y subsidios adecuados al tipo de práctica y extensión del cultivo promedio en el municipio.
Recursos propios

The 12-oxo-phytodienoic acid reductases (OPRs) are enzymes of the octadecanoid pathway which converts linolenic acid to a phytohormone, jasmonic acid. Bioinformatics analysis of ESTs and genomic sequences from available private and public databases revealed that the maize genome encodes eight different OPR genes. This number of maize OPR genes has been independently confirmed by Southern blot analysis and by mapping of individual OPR genes to maize chromosomes using oat maize chromosome addition lines. Survey of massively parallel signature sequencing (MPSS) assays revealed that transcripts of each OPR gene accumulate differentially in diverse organs of maize plants. This data suggested that individual OPR genes may have a distinct function in development. Similarly, RNA blot analysis revealed that distinct OPR genes are differentially regulated in response to stress hormones, wounding or pathogen infection. ZmOPR1 and ZmOPR2 appear to have important functions in defense responses to pathogens because they are transiently induced by salicylic acid (SA), chitooligosaccharides and by infection with Cochliobolus carbonum, Bipolaris maydis and Fusarium verticillioides and not by wounding. In contrast to these two genes, ZmOPR6 and ZmOPR7/8 are highly induced by wounding and treatments with wound-associated signaling molecules jasmonic acid, ethylene and abscisic acid. ZmOPR6 and ZmOPR7/8 are not induced by SA treatments or pathogen infections suggesting their specific involvement in wound-induced defense responses. Possible functions of specific OPR genes are discussed.

In semi-arid environments, dry-land farming often exposes crops to drought stress. Although some plant species are well adapted to drought, most crops are not. Drought can reduce plant populations and limit growth and development in ways that have serious yield consequences. Planting at the beginning of the wet season, when rainfalls are often sporadic and unreliable, can expose young maize seedlings to severe drought. Through the use of plant growth regulators (PGR), maize seedlings can perhaps be altered to elicit responses that mimic drought adaptation mechanisms. A series of studies conducted in the laboratory and greenhouse looked at the response of maize seedlings (two hybrids that differed in their reported drought sensitivity) to severe drought and to PGR applications with or without drought. Results showed that drought stress altered plant morphology and key physiological parameters. Applications of three triazoles (paclobutrazol, uniconazole and tetraconazole) altered morphology and physiology in ways that might impart drought resistance. Paclobutrazol and uniconazole increased root:shoot ratio in laboratory studies and in the greenhouse. When compared to non-triazole-treated controls, uniconazole and paclobutrazol treatments caused water conservation in earlier stages of drought stress, and therefore afforded increased transpiration (and presumably less stress) at later stages. Uniconazole and tetraconazole increased photosynthesis of well-watered plants. Proline content was increased to a greater degree by these same two triazoles under drought stress conditions. It is hoped that knowledge obtained from these studies can be extended to drought-prone areas where maize dry-land farming is practiced.
Master of Science