Biotechnological approach: an option for integrated weed management in crop production

Crops made resistant to herbicides by biotechnology are being widely adopted in various parts of the world. From the genesis of commercialization in 1996 to 2011, herbicide tolerance has consistently been the dominant trait. Those containing transgenes that impart resistance to post-emergence, non-selective herbicides such as glyphosate and glufosinate will have the major impact. These products allow the farmer to more effectively use reduced or no-tillage cultural practices, eliminate use of some of the more environmentally suspect herbicides and use fewer herbicides to manage nearly the entire spectrum of weed species. In some cases, non-selective herbicides used with herbicide resistant crops reduce plant pathogen problems because of the chemicals’ toxicity to certain microbes. Herbicide tolerant crops can be produced by either insertion of a “foreign” gene (transgene) from another organism into a crop, or by regenerating herbicide tolerant mutants from existing crop germplasm.Biotech crops reached 160 million hectares, up 12 million hectares on 8% growth, from 2010 and 94 fold increase in hectarage from 1.7 million hectares in 1996 to 160 million hectares in 2011, makes biotech crops the fastest adopted crop technology in the history of modern agriculture. The inclusion of several transgenes in a single hybrid or variety commonly referred as stacked genes or stacked traits. For example, some corn and cotton hybrids have been genetically engineered to contain two transgenes, one for insect tolerance and another for herbicide tolerance (e.g., Bt/glyphosate, or Bt/glufosinate). Furthermore, some corn hybrids have three traits, two for herbicide tolerance and one for insect tolerance (e.g., Liberty, Clearfield, and Bt). Stacked traits occupied ~25% of the global 160 million hectares. From the genesis of commercialization in 1996 to 2011, herbicide tolerance has consistently been the dominant trait. In 2011, herbicide tolerance deployed in soybean, maize, canola, cotton, sugar beet and alfalfa, occupied 59% or 93.9 million hectares of the global biotech area of 160 million hectares. In 2011, the stacked double and triple traits occupied a larger area (42.2 million hectares, or 26% of global biotech crop area) than insect resistant varieties (23.9 million hectares) at 15%. The stacked genes were the fastest growing trait group between 2010 and 2011 at 31% growth, compared with 5% for herbicide tolerance and 10% for insect resistance. Over the past few years, several herbicide resistant crops (HRCs), both transgenic and non-transgenic, have become available in many countries for commercial cultivation. But in India, the technology of herbicide tolerant crops is in initial stage of field evaluation. Efforts have been made to evaluate and consolidate the agronomic management and advantages of herbicide tolerant transgenic crops.