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Current breeding technology with the challenge of food insecurityqrcode

Oct. 13, 2016

Favorites Print Oct. 13, 2016
张静松-AgroPages Jason Zhang
Jason Zhang

Jason Zhang, Editor of AgroPages. Email: jason@agropages.com

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Seeds are the delivery systems for agricultural biotechnology. High quality seed leads to excellent seedling performance in the field, which is the basis of high yield crop production.

At present, the most important driver for innovations in plant breeding and the seed sector are the challenges we face with respect to food insecurity, as a consequence of the growing world population and climate change. A report from the Food and Agricultural Organization of the United Nations predicts that feeding a world population of 9.1 billion people in 2050 would require raising overall food production by some 70% between 2005-07 and 2050.

As a result, there’s a strong call for advanced breeding technologies to generate crops with salt tolerant traits, diseases and plague resistant traits, and high yield traits, which are the most important and, yet, most complex trait in crops. In recent years, companies, institutes and universities invested significant resources in developing advanced breeding technologies, which include conventional breeding technology, transgenic breeding technology and new breeding technology. The objective of this article is to discuss some representative technologies developed in the past few years.

Conventional Breeding Technology

Conventional breeding essentially consists of the repeated selection of the best individuals of a plant population over time. It ranges radically in sophistication from the inadvertent selection of genotypes that grow best in a given cultivated environment, to massive multi-year statistical studies on large pedigreed families grown in multi-location trials.

Modern conventional breeding uses a combination of hybridization and prominent laboratory techniques, including induced polyploidy, tissue cultures, embryo rescue, and mutagenesis. One example of successful mutagenesis discovered in 2009 is Advanta Seeds imidazolinone (IMI) technology. It is a plant resistance trait based on a sorghum mutation that allows the plants to tolerate IMI based herbicides. This technology allows to manage broad leaf and grass weed in sorghum fields through residual activity of the IMI herbicide trait.

Additionally, some companies developed conventional breeding technologies with seed enhancement techniques, including priming, steeping, hardening, pregermination, and others. For example, a Dutch company, Bejo, recently introduced B-Mox seed enhancing formula, which is a combination of priming and conventional breeding technology, in combination with a recipe of natural seed enhancing ingredients that bring more energy to the seedling and improve the vigour of the plant. And Monsanto’s subsidiary company, Seminis, combined conventional breeding with Post Priming Treatment (PPT) to extend the life of primed seeds.

Conventional plant breeding resulting in open pollinated varieties or hybrid varieties has had a tremendous impact on agricultural productivity in past decades. Although it takes a lot of time and has many limitations, such as breeding only can be performed between two plants that can sexually mate with each other, and when plants are crossed, many traits are transferred along with the trait/s of interest—including those traits that have undesirable effects on yield potential, the concerns of genetically modified organisms (GMOs) and rapid growth of the organic food market make it increasingly important.

Transgenic Breeding Technology

Transgenic breeding technology brings desired foreign genes into the host plant genome, and the inserted gene sequence could come from another unrelated plant, or from a completely different species. The beauty of this breeding technology is that it can transfer the cloned gene, regardless of the source or recipient of the genes, which breaks plants’ normal gene acquiring pollination method. Plants containing transgenes are often called GM crops, or GMO crops.

GM crops are used to express proteins, such as the cry toxins from Bacillus thuringiensis (Bt), herbicide resistant genes, antibodies and antigens for vaccinations. During the last 20 years, companies like Monsanto, DuPont and Syngenta introduced many GM crops into the market, especially Monsanto, with its Bt crop and Roundup Ready crop becoming one of the most successful GM crops in the world. GM crops are considered to have become the fastest adopted crop technology in the history of modern agriculture. Since its first commercialization, the planting area has increased a remarkable 100-fold, from 1.7 million hectares in 1996 to 179.7 million hectares in 2015.

In recent years, the trends of transgenic breeding are to progress from simple, single-gene traits, such as herbicide and insect resistance, towards more complex agronomic traits. These complex agronomic traits include photosynthetic enhancement, yield increases, modification of seed compositions, alteration in senescence, sugar and starch metabolism, and improvements in response to abiotic and biotic stresses. For example, Monsanto launched Roundup Ready 2 Xtend technology last year, which contains the traits of dicamba and glyphosate herbicide resistance. Also, this technology is stacked with the Genuity® Roundup Ready 2 Yield® soybean trait technology, which offers farmers the highest yield opportunities. And another multinational corporation, Bayer CropScience, launched its third generation technology for cotton seeds in 2014, which is the stacked technology of GlyTol®-LibertyLink®-TwinLink® (GLT). GLT contains glyphosate and glufosinate resistance, and two BT genes (Cry1Ab and Cry2Ae) for the control of lepidopteran caterpillars. Also, it offers cotton increased fiber yields.

Transgenic technology has achieved great success in supplementing crop breeding in the past 20 years, and has considerable commercial value. However, this technology faces some technical challenges. For instance, there are many economically important plant species, or elite varieties of particular species, that remain highly recalcitrant to genetic transformation and regeneration. Further, transgenic technology has faced increasing opposition in recent years because of the likely unpredictable risks to the environment and food safety, even though many of these claims are baseless.

New Breeding Technology

New breeding technologies (NBTs) are actually not that new, as many of them have been available for years. In 2007, with the request of the National Competent Authorities, the European Commission set up a New Techniques working group to assess whether a number of new breeding techniques might fall within the scope of the GMO legislation. The NBTs under review include gene-editing techniques, such as zinc finger nucleases (ZFN), TALENs, CRISPR-Cas, meganucleases and oligonucleotide-directed mutagenesis (ODM); cisgenesis and intragenesis; RNA-dependent DNA methylation (RdDM); grafting (on GM rootstock); reverse breeding and agro-infiltration (encompassing agro-infiltration ‘sensu stricto’, agro-infection and floral dip).

Compared to “older” technologies, NBTs display technical advantages. For example, gene-editing techniques allow site-specific and targeted changes in the genome. And except for the cis/intragenesis and ZFN-3 technique, NBTs do not introduce new DNA fragments. The genetic information coding for the desired trait is only transiently present in the plants, or stably integrated only in intermediate plants. Therefore, the commercialized crop will not contain an inserted transgene and cannot be distinguished from conventionally bred crops. In addition, the use of NBTs bring economic advantages, as it speeds the breeding process, which lowers production costs. For instance, breeders may need only one year to breed a new potato variety with NBTs, though it normally takes more than 10 years.

In recent years, many companies engaged in developing NBTs, including multinational corporations such as Dupont and Monsanto, and many biotechnology companies, including KeyGene, Arcadia Bioscience, Evogene, and others. Among these new breeding technologies, gene-editing techniques gain the most attention, especially CRISPR-Cas, the latest gene-editing technique, which is judged to be most promising by many stakeholders. The US company Cibus, a leader in non-transgenic breeding and precision gene editing, has developed a patented RTDS™ (Rapid Trait Development System) technology, which contains ODM, CRISPRs and other gene editing techniques. Based on this technology, Cibus developed SU Canola™ (sulfonylurea tolerant), the first approved and commercialized non-transgenic gene-edited product. SU Canola is now being grown in the US in a 4,000 hectare planting area, and will be introduced in Canada next year as a non-GMO product. And in April this year, DuPont Pioneer announced waxy corn hybrids as its first commercial agricultural product using the CRISPR-Cas breeding technology, which is expected to be available within five years.

Although gene-editing and other NBTs can offer several advantages, researchers say there is still the chance of creating so-called off-target effects during the slicing and splicing. With that in mind, GMO critics argue that there is no reason to view gene-edited crops any differently than transgenic crops. Until now, the US and Canadian authorities have evaluated crops grown using gene editing on a case-by-case basis but, so far, they have not treated them as GMOs. Argentina has taken a similar approach, while it is reported that China is in the process of determining how to regulate this technology.

For the European Union, Cibus has approached national authorities in at least six EU countries asking for confirmation that its product is not a GMO and can be released in field trials. However, in June 2015 the EU Commission asked all national authorities “to await, as much as possible, the outcome of the Commission’s legal interpretation before authorising a deliberate release of organisms obtained with new plant breeding techniques”. Initially, the Commission’s opinion was due by the end of 2015, but the procedure was postponed. And at the end of March this year, the Commission further delayed the decision on NBTs.

In the next few years, many regulatory jurisdictions around the world will make decisions on the governance of new plant breeding techniques, which will have implications for technology adoption, but also for the global agricultural supply chain. If crops derived by NBTs are classified as non-GMOs, it would be the most significant news for the seed industry and will speed up the innovation of breeding technologies. Otherwise, the risk assessment and registration process will lead to potentially high costs, as seen in GMOs.

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