Stephen J. Molnar and Nicholas A. Tinker, Eastern Cereal and Oilseed Research Centre, Agriculture and Agri-Food Canada, Ottawa, Ontario, Canada; Heidi F. Kaeppler, Department of Agronomy, University of Wisconsin, Madison, Wisconsin, U.S.A.; Howard W. Rines, USDA-ARS and Department of Agronomy and Plant Genetics, University of Minnesota, St. Paul, Minnesota, U.S.A.
Authors Stephen J. Molnar and Nicholas A. Tinker are employees of the Department of Agriculture and Agri-Food, Government of Canada. ©Her Majesty the Queen in Right of Canada, as represented by the Minister of Agriculture and Agri-Food Canada.
OATS: Chemistry and Technology, Second Edition
Pages 51-75
DOI: https://doi.org/10.1094/9781891127649.004
ISBN: 978-1-891127-64-9
Abstract
Quality, like beauty, is in the eye of the beholder. Various end-users define oat quality differently, and their ideal profiles often evolve over time. It can be challenging for the oat breeder to hit such diverse and moving targets. The components of oat quality are addressed individually and in detail in the other chapters of this monograph. Most are controlled by the interplay of genetic and environmental factors affecting the oat plant (Peterson et al 2005). For example, there is strong genetic control of various chemical seed composition traits. Genetics also plays a role in stabilizing quality by mitigating fluctuations due to environmental effects, for example through genetic mechanisms of disease and stress resistance. Understanding the genetics of oat quality components opens opportunities to manipulate these traits more efficiently to achieve the quality profile desired by each end-user.
Classical genetics has demonstrated that one or more genes control most traits and that these genes are located along the DNA threads that constitute the chromosomes in the nucleus of each plant cell. Recently, there has been an explosion of molecular genetic techniques that dramatically extend our genetic knowledge of oats (Rines et al 2006). Recombination mapping and physical mapping are showing us the chromosomal locations of genes. Quantitative trait locus (QTL) analysis using these maps identifies which chromosomal regions have significant genetic effects on particular traits. Comparative mapping allows us to make inferences in oats based on gene, QTL, or genomic map information acquired in related plant species.
Numerous types of molecular markers exist, but all of them identify differences, or polymorphisms, in the DNA between two individuals. Molecular markers are stable, exhibit Mendelian inheritance, and usually have no effect on phenotype. In addition, molecular markers are numerous and distributed throughout the plant's genome. Taken together, these attributes make molecular markers ideal for mapping and QTL analysis. Furthermore, when a breeder wishes to select for a particular QTL or gene, one or more linked molecular markers can be used as diagnostic indicators. These molecular marker “tags” can be easier or faster to assess in a large number of plants than a biological or phenotypic assay. This concept forms the foundation of molecular-marker-assisted selection or breeding.
Cultivated oats is a hexaploid species (Avena sativa), with 21 pairs of chromosomes, originating from two or three ancestral diploid genomes. In theory, a trait that is controlled by a single gene in a diploid could be controlled by three homoeologous genes in a hexaploid. In reality, this is not always the case due to factors such as mutation and gene silencing. In addition to this genetic complexity, most traits of interest in oats are quantitative traits, controlled by multiple genes. Fortunately, QTL analysis and other techniques are able to partition this genetic complexity into more manageable portions. Another simplifying strategy is the use of doubled haploids, which are plants that are homozygous at all loci. Doubled haploids are genetically stabilized, and therefore many “identical twin” plants can be produced to compare results across years, environments, or experiments.
In addition to cultivated hexaploid oats, there are related wild diploid, tetraploid, and hexaploid species of oats, and these are a valuable source of additional genetic variation. This variation can be introduced into cultivated oats through a combination of wide sexual crossing, tissue culture, and molecular assays. The opportunity also exists to introduce genes from an even wider field by genetic transformation strategies, thereby expanding the genetic repertoire of cultivated oats.
The goal of this chapter is to highlight these recent advances in oat molecular genetics, genomics, and biotechnology and to illustrate how they contribute both genetic knowledge and molecular tools to assist the plant breeder to continuously improve the quality of oats.
