Welcome to our website featuring the controversial topic of Herbicidal Crop Tolerance! Here you will find all the necessary information you will need for research on Herbicidal Tolerance on crops. 

Crops: Resistance is Key gives you the know-how on Herbicide Tolerant Crops!

I. Introduction

Crop management is an essential tool in modern agriculture. Herbicidal Experts in Canada have determined a process that kills the weeds growing along with the plants in a controlled manner. HTCs (Herbicide Tolerant Crops) enhance weed control options and greatly expand market demand for certain herbicides. (Knezevic, and Cassman)

Herbicide resistance is the inherited ability of a plant to survive and reproduce following exposure to a dose of herbicide that would normally be lethal to the crop type. (Prather, Ditomaso, and Holt)

Recent research efforts have been directed at breeding herbicide resistance into crops. For minor-use crops it may be more economical to breed herbicide resistance into a crop than to develop new selective herbicides for current crop varieties. For major-use crops such as corn, soybeans, and wheat, herbicide resistant crops may be useful where difficult to control weeds or environmental conditions dictate the use of specific herbicides to which the crop is normally susceptible. (Gunsolus)

It must also be noted that herbicide-resistant crops (HRCs) were first produced by methods of traditional breeding, whereas the major current HRCs have been produced by genetic engineering, the technology which has unintentionally placed these crops in a fierce debate between those in favor, and those against, the introduction and commercial use of genetically modified (GM) crops (fao.org).

Roundup-Ready Crops 

 

When and where?

Herbicide Resistant weeds were first found in a Washington tree nursery in 1970 where the first strain of herbicide resistant weeds was found; Senecio vulgaris, which was resistant to herbicides in the triazine chemical class. Since then, multiple other weeds became resistant. (Prather, Ditomaso, and Holt)

Why?

We need to develop more ways to create H.T. crops because we must protect our food development from the harmful weeds that occur, which complicate cultivation, contaminate crops, and enhance gene transfer to weedy relatives. (badseed.info) It must also be noted that herbicide-resistant crops (HRCs) were first produced by methods of traditional breeding, whereas the major current HRCs have been produced by genetic engineering, the technology which has unintentionally placed these crops in a fierce debate between those in favor, and those against, the introduction and commercial use of genetically modified (GM) crops (fao.org).


How?

By using chemicals which target key enzymes in the plant metabolic pathway, like Glyphosate-tolerant crops (which block the EPSPS enzyme involved in the biosynthesis of amino acids) and Glufosinate-tolerant crops (which contain Phosphinothricin which blocks the enzyme responsible for nitrogen metabolism and detoxifying ammonia), and the traditional crop rotation technique, we can get rid of those pesky weeds (isaaa.org).

The traditional method to get rid of herbicide resistant weeds was crop rotation, and through Roundup. Crop rotation is the practice of growing a series of dissimilar types of crops in the same area in sequential seasons (www.en.wikipedia). Roundup is a herbicide which contains Glyphosate, the most common herbicide used in America.

Currently, two herbicide resistant cropping systems are common for soybean, maize, rapeseed, and cotton: Roundup Ready (active agent: glyphosate) and Liberty Link (active agent: glufosinate) (www.gmo-compass.org).

Problems with herbicides.

Before 1996, weeds were not observed to have evolved resistance to Glyphosate in the field, but since then, the introduction of transgenic Glyphosate tolerant crops has led to evolution of a number of resistant weeds as the result of the greatly increased use of the herbicide particularly during the post-emergent growth of the crops (badseed.info) Also, traditional methods such as hand labor and cultivation continue to thrive.

A major environmental concern associated with herbicide-tolerant crops is their potential to create new weeds through out crossing with wild relatives or simply by persisting in the wild themselves (isaaa.org). A universal challenge scientists face is trying to create substances which weeds will not be resistant to. However, history has shown that over a certain amount of time, plants will become resistant to any substance.This application of biotechnology is still under development, and scientists hope to achieve methods that remove 100% of the weeds caused by herbicide resistant weeds, and to create herbicide tolerant crops which will inevitably deter the creation of weds in the first place. Herbicide-tolerant (HT) crops also offer farmers a vital tool in fighting weeds and are compatible with no-till methods, which help preserve topsoil. They give farmers the flexibility to apply herbicides only when needed, to control total input of herbicides and to use herbicides with preferred environmental characteristics (isaaa.org).  

 Roundup Ready Crops

Advantages of Herbicide Tolerant Crops

  • Excellent weed control and hence higher crop yields;

  • Flexibility – possible to control weeds later in the plant’s growth;

  • Reduced numbers of sprays in a season;

  • Reduced fuel use (because of less spraying);

  • Reduced soil compaction (because of less need to go on the land to spray);

  • Use of low toxicity compounds which do not remain active in the soil; and

  • The ability to use no-till or conservation-till systems, with consequent benefits to soil structure and organisms (Felsot, 2000).

Disadvantages of Herbicide-Tolerant Crops

Excessive Herbicide Use

  • One possible disadvantage of herbicide-resistant crops is that it can potentially lead to farmers using excessive amounts of herbicides in order to attack weeds. Because there is no risk of killing the crops with the herbicides, farmers might not feel the need to be judicious about how they distribute the herbicide. An increased use of herbicides carries environmental risks, possibly leading to increased pollution. Possible effects include contamination of groundwater, carrying risks for human health.

New Weeds

  • In the case of certain crops, the use of herbicide-resistant crops might trigger the evolution of new species of weeds in the fields, according to the Food and Agriculture Organization of the United Nations. These weeds would be resistant to the herbicides in use and new herbicides would need to be developed and used on affected crops in order to manage the herbicide-tolerant weeds. In addition, volunteer crops resistant to herbicides could emerge as nuisances.

    Biodiversity Impact

    • Another potential disadvantage of herbicide-resistant crops is that they are suspected of sometimes harming the biodiversity on the farms where they are used, affecting the ecology of farms in a broader way than is intended. In particular, there are concerns of affecting the diversity of the plant species that are present on farmland where herbicide-resistant crops are planted. However, the risks are low that nearby plant species that are not actually located where the land is cultivated will be affected, according to the Food and Agriculture Organization of the United Nations.

    Gene Flow

    • The use of herbicide-resistant crops could potentially affect other crops on the farm that are not herbicide-resistant, leading to a danger of transferring genes to a crop that a farmer wants to keep non-herbicide-resistant, according to the Food and Agriculture Organization of the United Nations. Not only could this potentially occur within a farm but from one farm to an adjacent farm, according to the FAO (Gresham).

 
 

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