Genetically Modified Soybean for Insect-Pests and Disease Control (2011)

Since 1996, the cultivation of genetically modified (GM) crops around the world has increased more than 80-fold.In 2009, it was registered that a total area of 134 million hectares in 25 countries were used for biotech crops, which constituted a 7 % increase from 2008.14 million farmers, of whom 90% were small producers, grew GM cultivars in 25 countries during 2009.Nowadays, GM soybean, cotton and corn correspond to 99% of all GM cultivars planted worldwide (JAMES, 2009).In the same year, with regard to the soybean crop, the planted area reached 90 million hectares worldwide, of which 69 million were GM.The world leaders of soybean production are the United States (33%), Brazil (27%) and Argentina (21%), which are also leaders in the use of GM seeds.The eight following countries also cultivate GM soybean, seven of which are developing countries: Paraguay, South Africa, Uruguay, Bolivia, Mexico, Chile and Costa Rica (JAMES, 2009).Through this use, the GM seed market contributes to an amount of US$ 10.5 billion annually to agriculture.Furthermore, GM soybean, along with corn and cotton, yielded US$ 130 million in 2008 and US$ 143 million in 2009 to the agribusiness sector, with a 10% increase projected for 2010.Each year, countries from the European Union import no less than 40 million tonnes of raw soy products, at a cost of more than U$ 15 billion, mainly from the three biggest producers.With respect to the agronomical traits used in GM crops, herbicide and insect resistance, or a combination of both traits, are the most utilised.Nevertheless, several other characteristics are being tested, such as increased nutritional quality, dry and cold tolerance, bacteria resistance, fungal and nematode resistances.Therefore, there is an expectation for future development of innovative molecular strategies in order to generate GM plants with novel features that promote reduction of costs and contamination risks for consumers, producers and the environment by decreasing the use of agrotoxic compounds.Most of the soybean-planted area is comprised of herbicide-tolerant crops (62%), distributed across 11 countries.Transgenic soybean with multiple combined traits corresponds to 21% of all biotech crops around the world (JAMES, 2009).During 2009/2010, a second generation of GM crops appeared in the market.RReady2Yield Soybean was cultivated by 15,000 www.intechopen.comSoybean -Molecular Aspects of Breeding 430 farmers distributed across 0.5 million hectares in the US and Canada, providing a higher production than traditional soybean crops.Until January of 2009, there was no GM soybean that was resistant to insect-pests or pathogens being commercialised, although the need for this trait is extremely important.However, an insect-resistant event of GM soybean, developed in China, is in the commercial and regulatory pipeline in that country (STEIN e RODRÍGUEZ-CEREZO, 2009 -Table 1).Today, there is only one commercial GM soybean event from Monsanto, which presents only herbicide-resistance as a trait.Four other GM soybean events are in the commercial pipeline (authorised but not yet commercialised), but all present herbicide resistance genes and demonstrate no resistance against pathogenic fungi, insect-pests or nematodes.In addition, three other soybean events resistant to herbicides are in the regulatory process required for worldwide marketing.Furthermore, two GM soybean events are already at late stages of development, although not yet in the regulatory process.While Monsanto is developing a soybean resistant to insect-pests, Syngenta is leading the development of a cultivar resistant to the cyst nematode (STEIN e RODRÍGUEZ-CEREZO, 2009 -Table 1). Major soybean pests and diseasesSoybean plants originate from the South Asia region, where several microorganisms and insects evolved ecological interactions.All three major soybean-producing countries in the world are located on the American continent, where more than 50% of all soybeans are harvested.This geographic distribution facilitates the spread of insect-pests and diseases.Hence, soybean can be attacked by many different organisms, ranging from viruses to nematodes and insects.These pathogens and pests can cause damage in seeds, roots, leaves, stems and pods, and usually are tissue-specific.Here, we describe some of the most important diseases that attack soybeans, as well as the major pests and pathogens, mainly found in North and South America.A list of pathogens, the diseases they cause and the infected tissues are presented in Table 2. Seedling diseasesDiseases that affect soybean seeds occur before germination or after seedling establishment.The primary reason for this is the presence of wet and/or cool soil, which enables the growth of pathogenic fungi, such as Fusarium spp, Rhizoctonia solani, Phytophthora sojae and Phythium spp.In some locations, Macrophomina spp, Coletotrichum spp and Phomopsis spp can cause this type of damage in soybean seeds.Seedling diseases can decrease seed quality, due to variation in stands, which are formed by lesions on the cotyledons, soft young stems and primary leaves.Furthermore, these diseases can retard seedling growth, causing moderate to severe losses in crop yield and, in turn, a significant increase in the use of fertilisers and herbicides (MALVICK, 2007). Leaf pests and diseasesThere are several organisms that attack soybean leaves, including viruses, bacteria, fungi and insects.Among the diseases that have already been described, the most important are soybean rust, septoria brown spot, bacterial blight, bacterial pustule, downy mildew, cercospora leaf blight, frogeye leaf spot, powdery mildew, soybean mosaic virus and bean pod mottle virus.www.intechopen.