El uso repetido del mismo herbicida, puede provocar poblaciones de malezas que consisten de biotipos susceptibles (S) que son controlados y biotipos resistentes (R), que escapan al control para producir y retornar semilla con la característica de resistencia, al banco de semillas del suelo. Esta lección se enfocará en la dinámica poblacional de una población de malezas mezclada con biotipos S y R. Se comparará y contrastará la tasa a la que aparecen malezas resistentes en una población bajo diversas presiones de selección. ****** Esta lección se enfocará en la dinámica poblacional de una población mezclada (biotipos susceptibles y resistentes a un herbicida), y comparar y contrastar la tasa a la cual aparece resistencia al herbicida, en una población de malezas mezclada, bajo diversas presiones de selección.
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Esta lección se focaliza en el impacto de las características de la planta y el herbicida, importantes para determinar el desempeño del herbicida. Se usarán imágenes visuales para ilustrar varios principios, incluyendo el sitio de absorción del herbicida en la planta, transporte, el sitio de acción sensible, y efectos del ambiente sobre el desempeño del herbicida. Esta información provee la base para maximizar la utilidad del uso de los herbicidas.
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Through the repeated use of the same herbicide, weed populations can consist of susceptible (S)-biotypes that are controlled and herbicide resistant (R)-biotypes that are left behind to produce and return seed with the resistance characteristic back into the soil. This lesson will highlight the population dynamics of a mixed weed population, containing S- and R-biotypes, and compare and contrast the rate at which herbicide resistant weeds appear in a population under a diversity of selection pressures. ****** This lesson will highlight the population dynamics of a mixed (herbicide susceptible and resistant biotype) weed population, and compare and contrast the rate of appearance of herbicide resistance in a mixed population under a diversity of selection pressures.
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This lesson will discuss the corn rootworm complex, which consists of
the northern, western, and southern corn rootworm, focusing on the
northern and western species. The information in this lesson will focus
on the biology of corn rootworms in the north central Corn Belt,
including Iowa and Nebraska. Crop producers, crop scouts, students, and
the general public may find the information in this lesson helpful for
identifying corn rootworm, other corn pests, and the feeding damage
caused by each insect.
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This lesson will discuss economic thresholds and management options
related to the corn rootworm complex consisting of the northern,
western, and southern corn rootworm, with emphasis on the northern and
western species. The information in this lesson will focus on the north
central Corn Belt, including Iowa and Nebraska. Crop producers,
crop scouts, students, and the general public may find this lesson
helpful for obtaining information about developing a management plan to
control corn rootworm.
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This lesson discusses what DNA is and how it relates to genes and chromosomes. How and why DNA is extracted in the genetic engineering process is also covered.
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This lesson contains information about the history, life cycle, and host plants of the European corn borer and information relating to the history and biology of Bacillus thuringiensis.
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This lesson describes the three gene regions and their roles in gene expression. It also discusses how the regions of a gene can be altered to obtain desired trait expression.
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This lesson builds upon the gene region lesson discussing the gene construct of currently used hybrids and explaining how these combinations result in a particular gene expression.
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En esta lección se examinarán los herbicidas que afectan los procesos celulares relacionados con la utilización de la luz, causando así daños a las plantas. Existen cuatro mecanismos básicos que serán estudiados: herbicidas que obstruyen la síntesis de protoporfirina IX; herbicidas que inhiben la síntesis de carotenoides; herbicidas que obstruyen la transferencia de electrones en el fotosistema II; y herbicidas que substraen electrones del fotosistema I. Todos ellos comparten la misma habilidad de causar daños celulares en presencia de luz.
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This lesson focuses on the process of eutrophication; the relationship between land application of manure and soil phosphorus (P) dynamics on P delivery to surface waters; and on the P dynamics in water bodies that result in increased P available to aquatic vegetation.
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This lesson describes how source factors, including soil characteristics and management practices, affect phosphorus (P) delivery to surface waters; and also discusses how crop producers can control these factors through their management practices.
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This lesson addresses transport factors that may contribute to phosphorus (P) delivery to surface waters. Erosion, runoff, subsurface flow, drainage, and distance to surface water are the main factors. In some places, wind erosion may also be important. The effects of management practices on P transport are discussed, and water-related P transport processes are described in detail.
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Lesson one is a general description of the overall process of genetic engineering. A basic explanation of the five steps for genetically engineering a crop is provided. Details for each step are given in later lessons of this course. The five steps are:
- Locating an organism with a specific trait and extracting its DNA
- Cloning a gene that controls the trait
- Designing a gene to express in a specific way
- Transformation, inserting the gene into the cells of a crop plant
- Plant breeding to get the transgene into an elite background
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The polymerase chain reaction laboratory technique is used in a variety of applications to make copies of a specific DNA sequence. This lesson describes how a PCR reaction works, what it accomplishes and its basic requirements for success. Examples of interpreting results are given. PCR's strengths, weaknesses and applications to plant biotechnology are explained.
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This lesson will focus on the impact of herbicide and plant characteristics important in determining herbicide performance. Visual images will be used to illustrate several principles including herbicide site of uptake, translocation, site of action sensitivity, and environmental effects on herbicide performance. This information provides a basis for maximizing herbicide performance.
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This lesson will focus on molecular principles involved in the detection of biotechnology derived proteins in crops, using the lateral flow ELISA.
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Real time PCR is a laboratory technique that can perform relatively accurate, reliable and reproducible measurements, to quantitatively determine the presence of specific gene sequences. Its value is being recognized in a variety of applications, including transgenic (GMO) detection. It is becoming increasingly important to know what percentage of a particular transgene is present in an export shipment, for example. Real time PCR can also be used to support more traditional plant breeding techniques, making the process of distinguishing allelic variations more efficient. This lesson explains the principles of real time PCR and its' application, with examples in plant breeding and GMO detection.
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Soils - Part 9 addressed how soil testing works and the proper method of taking soil samples. The purpose of soil testing is to provide a rational basis for making fertilizer recommendations. The impact of not having the optimum crop nutrition can be yield loss, economic expense and environmental contamination. For many years, it has been widely known that fertilizer recommendations for a given crop often vary widely, depending on who is making the recommendation. With the development of site- specific nutrient management, more emphasis is being placed on soil sampling as a basis for predicting response to applied fertilizer. This lesson will explain several approaches to making fertilizer recommendations and will discuss why recommendations may vary widely when different approaches are used to interpret soil tests.
[This lesson, as well as the other nine lessons in the Soils series, is taken from the "Soils Home Study Course," published in 1999 by the University of Nebraska Cooperative Extension.]
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Soil means different things to different people. To some, soil is something that must be swept away; to others it is just a material that sticks to your shoes. In both instances, soil is associated with unpleasantness. To the engineer, soil is something to be moved, manipulated or built upon. To the farmer and rancher, soil is the source of nutrients which crops use to produce the grain and with it the livestock needed to produce a profit on the farm and in agribusiness. For some of us, soils provide recreation through the development of landscapes or vegetable gardens. For all of us, soils are the medium that provides the food production that has been so successful in feeding our population.
[This lesson, as well as the other nine lessons in the Soils series, is taken from the "Soils Home Study Course," published in 1999 by the University of Nebraska Cooperative Extension.]
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Soil may look simple; however, it is an extremely complex system. It is most often described by its physical, chemical and biological properties and processes. Soil is organic or inorganic; inert or active; living or non-living. Soil contains many organisms: bacteria, nematodes, fungi, earthworms, and small animals. From a physical perspective the soil constitutes the building blocks upon which we walk, construct buildings, grow crops and filter natural and manmade compounds. Soil’s physical, chemical and biological properties and processes interact to enhance its value as a natural resource.
[This lesson, as well as the other nine lessons in the Soils series, is taken from the "Soils Home Study Course," published in 1999 by the University of Nebraska Cooperative Extension.]
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To most gardeners, organic matter is like Husker football—everybody is a fan, but not everybody understands the details of the game. Anyone who uses a soil should have an interest in its organic matter content because so much about the soil is influenced by its organic matter content. In this lesson, we will increase our knowledge about soil organic matter to be able to understand its importance.
[This lesson, as well as the other nine lessons in the Soils series, is taken from the "Soils Home Study Course," published in 1999 by the University of Nebraska Cooperative Extension.]
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Soil pH is one of the most important chemical characteristics of the soil. For example, soil pH can affect availability of plant nutrients. In addition, the soil pH can affect the performance of preemergence herbicides, activity of microorganisms, the need for lime, soil bacteria activity, the best crop to be grown, and other characteristics.
[This lesson, as well as the other nine lessons in the Soils series, is taken from the "Soils Home Study Course," published in 1999 by the University of Nebraska Cooperative Extension.]
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Phosphorus fertilizers are second only to nitrogen in importance for growing crops in Nebraska; however, the principles affecting efficient phosphorus use are totally different. Nitrogen is a mobile nutrient, both in the plant and in the soil, while phosphorus moves very little in the soil. Additionally, total plant requirements are much lower for phosphorus than for nitrogen. For example, leaves commonly contain 10 times more nitrogen than phosphorus. However, phosphorus is concentrated in the grain so that only about 2.5 times more nitrogen is removed in harvested grain compared to phosphorus.
Potassium (K) is an essential plant nutrient. Next to nitrogen, crops absorb potassium in greater amounts than any other nutrient. It is a vital component of numerous plant functions including nutrient absorption, respiration, transpiration, and enzyme activity. Potassium is unique because it does not become part of plant compounds, but remains in ionic form in the plant. Potassium remaining in plant residues after harvest and in manure are quickly returned to the soil when water leaches through the plant residue.
[This lesson, as well as the other nine lessons in the Soils series, is taken from the "Soils Home Study Course," published in 1999 by the University of Nebraska Cooperative Extension.]
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Sixteen elements are known to be essential for plant growth. These are divided into two groups: macronutrients — those elements used in relatively large quantities and micronutrients — those needed in very small amounts.
Macronutrients | ||
Carbon (C) | Nitrogen (N) | Calcium (Ca) |
Hydrogen (H) | Phosphorus (P) | Magnesium (Mg) |
Sulfur (S) | Potassium (K) | Oxygen (O) |
Micronutrients | ||
Zinc (Zn) | Copper (Cu) | Boron (B) |
Iron (Fe) | Manganese (Mn) | Molybdenum (Mo) |
Chlorine (Cl) |
|
|
[This lesson, as well as the other nine lessons in the Soils series, is taken from the "Soils Home Study Course," published in 1999 by the University of Nebraska Cooperative Extension.]
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During the first seven lessons, we have discussed a variety of topics related to soils, ranging from their formation to how nitrogen reacts in the soil. In Soils - Part 8, we are going to shift gears and discuss some common fertilizers and their characteristics. These will include the common nitrogen and phosphorus fertilizers, as well as many fertilizers that provide micronutrients to the soil. In this chapter, no attempt is made to judge the value of each type of fertilizer.
[This lesson, as well as the other nine lessons in the Soils series, is taken from the "Soils Home Study Course," published in 1999 by the University of Nebraska Cooperative Extension.]
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Soil tests are part of a four-step process of determining and providing nutrients to agronomic crops. The four steps are:
1) soil sampling,
2) soil analysis,
3) result interpretation and decision making, and
4) fertilizer application.
This chapter will focus on Steps 1 and 3 — soil sampling and result interpretation and decision making. It will not examine specific laboratory procedures or address fertilizer application issues. Until very recently, soil testing was conducted on a field basis. Site-specific management and the associated technologies of fertilizer application and yield monitoring are enabling agriculture management to reduce the area associated with each soil test to the subfield level. The article, "Soil Testing and Nutrient Recommendations," from Nutrient Management for Agronomic Crops in Nebraska, includes further information on soil testing.
[This lesson, as well as the other nine lessons in the Soils series, is taken from the "Soils Home Study Course," published in 1999 by the University of Nebraska Cooperative Extension.]
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