MAS is not used in all plant-breeding programs, but its use might soon become universal as more genetic information is made available and screening costs are reduced.Īs in all other disciplines of biology, plant breeding is now in the genomics era, in which paradigm-changing methods are being incorporated to accelerate and improve the efficiency of breeding. MAS does not require knowledge of the specific genes that confer a trait it only requires markers that are tightly associated with a trait, which may or may not be within the gene controlling the trait (see, for example, Box 7-1). However, molecular markers associated with self-compatibility (in which fertilization does not require outside donor pollen) and fruit size have recently been used to eliminate seedlings that lack alleles favorable for these two critical market traits in a sweet cherry ( Prunus avium) breeding program, resulting in substantial savings ( Ru et al., 2015). For example, before MAS, each tree in a fruit-tree breeding program had to be grown for years before it would produce fruit that could be phenotyped. MAS allows the identification and elimination of an individual plant from a population on the basis of its genetic composition and, as a consequence, reduces the costs associated with both continued propagation and downstream phenotyping ( Ru et al., 2015). MAS reduced plant sample sizes needed to select desirable individual plants and has been used in many crops to reduce costs and increase efficiency. The entry of molecular biology into breeding programs in the 1980s enabled knowledge of genetic determinants of phenotypes and marker-assisted selection (MAS) in which DNA-based molecular markers are used to screen germplasm for individual plants that have desired forms of genes, known as alleles. All plants of potential interest would be grown, phenotyped, and harvested, all of which are time-intensive and resource-intensive. Breeding used to be entirely phenotype-based that is, plants were selected solely on the basis of features such as yield, without knowledge of the genetic composition of the plants. The committee concludes that advances in genetic engineering and -omics technologies have great potential to enhance crop improvement in the 21st century, especially when coupled with advanced conventional-breeding methods.Ĭonventional plant-breeding approaches rely on the selection of plant germplasm with desirable agronomic and product characteristics (that is, phenotypes) from among individual plants created by using crosses and mutagenesis. The expected applications of genome editing and the technologies available for assessing associated nontarget effects are discussed in more detail.įinally, “-omics” (genomics, transcriptomics, proteomics, metabolomics, and epigenomics) approaches are reviewed to evaluate their potential to assess intended and unintended effects of genetic engineering and conventional plant breeding. Next, it scans the horizon for emerging genetic-engineering technologies, including synthetic biology and genome editing, and speculates about how they might shape the future of crops. It then discusses commonly used genetic-engineering technologies, examining the breadth and depth of current use and current limitations. To provide a context for genetic engineering in overall crop improvement, the chapter first provides a description of plant-breeding methods and of genomics approaches that enable rapid advances in basic knowledge related to crop genetics and plant breeding. That includes speculation about future genetic-engineering technologies. The purpose of the present chapter is to consider the “prospects,” that is, how genetic engineering might be used in the future in agricultural crops. This report has focused thus far on the “experiences” aspect of the committee’s statement of task.
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