Breeding & Genetics

Overview

Plant breeding is the art and science of changing the traits of plants in order to produce desired characteristics. Plant breeding can be accomplished through many different techniques ranging from simply selecting plants with desirable characteristics for propagation, to more complex molecular techniques.

Plant breeding started with sedentary agriculture and particularly the domestication of the first agricultural plants, a practice which is estimated to date back 9,000 to 11,000 years. Initially early farmers simply selected food plants with particular desirable characteristics, and employed these as progenitors for subsequent generations, resulting in an accumulation of valuable traits over time. Gregor Mendel's experiments with plant hybridization led to his establishing laws of inheritance. Once this work became well known, it formed the basis of the new science of genetics, which stimulated research by many plant scientists dedicated to improving crop production through plant breeding. Modern plant breeding is applied genetics, but its scientific basis is broader, covering molecular biology, cytology, systematics, physiology, pathology, entomology, chemistry, and statistics (biometrics).

Classical Breeding

Classical plant breeding uses deliberate interbreeding (crossing) of closely or distantly related individuals to produce new crop varieties or lines with desirable properties. Plants are crossbred to introduce traits/genes from one variety or line into a new genetic background. For example, a mildew-resistant pea may be crossed with a high-yielding but susceptible pea, the goal of the cross being to introduce mildew resistance without losing the high-yield characteristics. Progeny from the cross would then be crossed with the high-yielding parent to ensure that the progeny were most like the high-yielding parent, (backcrossing). The progeny from that cross would then be tested for yield and mildew resistance and high-yielding resistant plants would be further developed. Plants may also be crossed with themselves to produce inbred varieties for breeding. Classical breeding relies largely on homologous recombination between chromosomes to generate genetic diversity. The classical plant breeder may also make use of a number of in vitro techniques such as protoplast fusion, embryo rescue or mutagenesis (see below) to generate diversity and produce hybrid plants that would not exist in nature.

Traits that breeders have tried to incorporate into crop plants in the last 100 years include:

  • Increased quality and yield of the crop
  • Increased tolerance of environmental pressures (salinity, extreme temperature, drought)
  • Resistance to viruses, fungi and bacteria
  • Increased tolerance to insect pests
  • Increased tolerance of herbicides
Projects
2015 to 2019
<p>Development of improved lentil cultivars well-adapted to the local environment is an on-going process in the breeding program and is critical for long-term genetic gain. Recent climate instability adds another layer of complexity to breeding efforts. Continued genetic improvement of lentil will, therefore, involve the introduction of new alleles that extend beyond the existing adapted pool of germplasm. Our goal in AGILE is to enhance the productivity and quality of Canadian lentils by expediting the expansion of genetic diversity of the Canadian lentil germplasm base with the use of genomic technologies.</p>
2018
<p>Lentil breeders sometimes use exotic germplasm to broaden the genetic base and introduce desirable traits to elite cultivars. However, offsprings from these wide crosses often adapt poorly in the short growing season of western Canada. Identifying regions in the lentil genome that influences traits such as flowering time and maturity will help develop markers for breeders to effectively predict the adaption characteristics without trialing the plants in the field.&nbsp; To achieve this objective, we are phenotyping and genotyping several RILs that are developed from crosses of adapted and exotic germplasm.</p>
2018
<p>Lentils are known as low-fat, nutrient-dense foods with many health benefits. Part of these beneficial properties have been attributed to their colorful content, namely carotenoids, anthocyanins and other flavonoid pigments. Carotenoids are responsible for red, orange and yellow colors in plants, and they are of major importance in human diet as precursors of vitamin A, antioxidants, and for their anticancer properties. In lentils, differences in carotenoid concentration may explain the differences in cotyledon colors, which can be red, yellow or green. Anthocyanins are responsible for orange, red, and purple colors in plants, and have also been shown to reduce the risks of cardiovascular diseases and cancer. Lentil seed coat colors can be green, brown, tan or black, with or without patterns. These differences might be explained by differences in anthocyanin, pro-anthocyanidin and carotenoid concentrations. We are working on characterizing the effects of the environment on these pigments in both the cotyledon and the seed coat, and the genetics underlying color determination. We are also interested in developing automated solutions to precisely and efficiently determine color variation and diversity in lentil cotyledon and seed coat.&nbsp;</p>
2018
<p>Growth habit, seed size and shattering are some of the most significant agronomic traits involved in the domestication process. Wild lentils tend to be prostrate while cultivated ones need to be upright, especially for disease avoidance and mechanical harvesting. Wild lentil seeds are tiny while cultivated ones tend to be slightly to significantly larger, depending on market class.&nbsp; Shattering is an effective method of seed dispersal in the wild but leads to terrible yields under crop conditions!</p><p>We are phenotyping and genotyping several interspecific RIL populations with a view to tagging regions of the lentil genome associated with the shift from a wild phenotype to a more farmer-friendly one. For phenotyping purposes, we are developing an imaging system (Nielsen, K et al, manuscript in preparation) to characterize more accurately and automatically traits such as leaf surface area and biomass.</p>
2017 to 2018
<p>Today, superior Canadian lentil cultivars are expected to grow well in our northern growing conditions while being resilient to various abiotic and biotic stresses.&nbsp; &nbsp;The breeders achieve this by using diverse materials in their crosses, but need to ensure that offspring from these crosses can flower and mature at the right time in Saskatchewan. If we could predict flowering and maturity traits in lentil effectively using genetic markers, we will then be able to devote more valuable resources to evaluating other important traits such as yield, disease resistance and seed quality.</p><p>To develop genetic markers, we are studying a RIL population from a cross between a South Asian line and a Canadian line.&nbsp; Under Saskatchewan field conditions, this population segregates for days to flowering and other traits related to plant development and maturity. The population has been genotyped and we will identify genetic regions influencing flowering time and maturity traits and turn over markers for these traits to lentil&nbsp; breeders.</p>
2017
<p>Nitrogen fixation is a symbiotic relation between legumes and Rhizobium that allows the bacteria to convert atmospheric nitrogen to other molecules (like ammonia) for the plant, and the plant to provide the bacteria with carbohydrates in exchange.&nbsp; We now know that this process provides many great benefits to the health of our soil and crops.</p><p>The effectiveness/intensity of the nitrogen fixation process is dependent on both the bacteria and the legume plant under specific environment.&nbsp; Wild species have contributed to the lentil crop with tolerance and resistance to biotic and abiotic stresses. We believe that our modern lentil varieties are "lazy fixer" as compared to their wild relatives, as they are bred under high fertility conditions and there is no need for them to establish relations with the rhizosphere.</p><p>To test this hypothesis, we are exploring 6 wild lentil species as well as a group of cultivated lentils to characterize their nitrogen fixing ability. The purpose is to identify specific genotypes with higher ability and to better understand potential contributions of wild plants to the domesticated lentil.</p>
2015 to 2017
Stone seeds, which are seeds that do not absorb water, are considered a negative seed quality characteristic because they need to be removed before commercial processing. A high physical dormancy at the end of seed development is found to be the cause of this issue, but it is not known how or when it develops. This project will focus on attempting to determine when the seeds begin to develop physical dormancy, and also how to avoid hard seededness through harvest times.
2017
<p>For farmers, crops that quickly cover the ground soon after seeding ("ground-cover") generally mean fewer weeds and reduced need for in-crop herbicide applications. Plants that grow faster early in the growing season and larger as the season goes on also tend to produce higher seed yields. These traits, however, have generally been very difficult and time-consuming to quantify. Biomass, in particular, is rarely measured due to associated time, costs, and killing the entire plants early.</p><p>The goal of this project is to quantify ground-cover and plant volume using overhead imagery captured from unmanned aerial vehicles (UAV's) and handheld cameras. Image analysis is performed on 2-dimensional stitched images to determine ground-cover and on 3-dimensional point clouds to measure parameters of plant volume, which are then compared with actual above-ground biomass. These imaging can be done quickly and economically.&nbsp; No plant killing is needed so&nbsp; it is possible to collect data at multiple times throughout the growing season.</p><p>Ultimately, these imaging methods may be used to quickly and efficiently obtain plant growth and architecture information in breeding programs.</p>
2017
An Illumina Golden Gate array was developed using SNPs identified as part of the Common Bean 454 Sequencing & Genotyping Project.
2014 to 2017
This is an international project funded by the Global Crop Diversity Trust aimed at evaluating cultivated x wild lentil introgression lines for multiple traits in multiple environments.

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