**1. Introduction**

Humans have travelled a long way reaching the agriculutre that is there today. In the initial days, weed control has been a major concern in crop production and different approaches have been tested to manage weeds. Some approaches have been retired after several years and others still being adopted. Herbicide application is one of the approaches that still remain durable and efficient. Similarly, for every Human-made strategy, herbicide application has both positive and negative effects. Herbicides have increased agricultural productivity effectively, but on the other hand, has caused a serious problem by promoting the evolution of herbicide-resistant weeds. Successive applications of some herbicides of the same group or some herbicides with the same mode of action in a field will contribute resistance to herbicides in

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

one or several weed species. In spite of some concerns about weed resistance to herbicides, only a logical approach integrates all common strategies to inhabit herbicide resistance in weeds because the Human population is ever increasing.

Although development of resistance in weeds is an undesirable phenomenon, herbicide tolerance in crops is favorable. If the principle crop is not always tolerant to the herbicide, the herbicide will either decrease the productiveness of the primary crop or kill it. If the herbicide is not strong enough, it could allow the proliferation of weeds within the crop field thus affecting the productiveness of the primary crop. It is therefore desirable to produce crops that are tolerant to herbicides. The important objectives of this chapter are to clearly explain the important biochemical and molecular reasons of herbicide resistance in weeds, and and at the same time investigate the methods for the production of HR crops.
