**1. Introduction**

Soybean (Glycine max L.) is a leguminous species, native to Northeast Asia, and is one of the most important sources of oil and protein for livestock and the human diet. The crop is also being used to make diesel biofuel from the oil extracted from the seed. Today, the world's top producers of soybean are the United States (90 million ton), Brazil (68 million tons), Argentina (52 million tons), China (15 million tons) and India. These countries' production represents more than 90% of global soybean production. In the 2009/2010 harvest the world produced 261.57 million tons of soybean grain on 102.38 million hectares define this by [1]. Also, according to [1], over a period of 50 years, soybean production area increased 330%, rising from 23.81 million in 1961 to the current production area.

Currently with a world population of 7.0 billion people, which is projected to increase to more than 9.0 billion by 2050 and 10 billion by 2100 [2], there is a concern to maintain food. To achieve a gradual increase in world production of soybeans, two alternatives are possible: increased production area and/or increased productivity. Because planted area has increased 37% between 2000 to 2011 [1] and productivity has increased only 17.8%, the second solution looks to be the better option

Among all the factors inherent in agricultural production, the climate are the most difficult to control and it exercises greater limiting action in the maximum yield. It worsens according to the difficult to predict occurrences of adverse weather, the main risk factors in the exploration of major crops. Stress non biotic such as drought, excessive rain, extreme temperatures and low light can significantly reduce yields of crops and restrict the locations, times and soils, where the species most important commercially, can or not be cultivated.

© 2013 Avila et al.; licensee InTech. This is an open access article 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. © 2013 Avila et al.; licensee InTech. This is a paper 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.
