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
2009
A set of 1107 legume cross species orthologous sequences (COS) were amplified from Lens culinaris (CDC Redberry and Eston) and L. ervoides (L01-827a and IG 72815). Sequences were aligned and SNPs identified. A subset of 110 KASP assays were designed for use in L. culinaris. An Illumina GoldenGate array of 768 SNPs was designed for use in L. ervoides or interspecies hybrid populations between Lc and Le.
2008 to 2009
Mixture of eight cultivars with varying seed phenotypes: Indian Head, Commando, CDC LeMay, CDC Robin, and breeding lines 1899T-50 and 1788-4 (CDC, Univ. Saskatchewan, Saskatoon, Canada) All developmental stages of seeds and very young fertilized pods were harvested from mature plants, and divided into the following lots: very young fertilized ovaries, young ovules, enlarging seeds, cotyledons of fully filled seed, seed coats of fully filled seeds. cDNA library was made from a mixture of equal amounts of mRNA extracted from each of the above tissues.
2009
<p>Preparation of EST data: Sequences were extracted from dbEST and were subjected to quality control screening (vector, E. coli, polyA, T, or CT removal, minimum length = 100 bp, &lt; 3% N). Preparation of transcript (ET) database: All sequences from the appropriate divisions of GenBank (including RefSeq) were extracted. Non-coding sequences were discarded and cDNAs and coding sequences from genomic entries were saved. Sequences and related information (e.g. PubMed links) are stored in the qcGene database (qcGene). Assembly: Cleaned EST sequences and non-redundant transcript (ET) sequences were combined. Using the Paracel Transcript Assembler Program, sequences were assembled into contigs. TCs are consensus sequences based on two or more ESTs (and possibly an ET) that overlap for at least 40 bases with at least 94% sequence identity. These strict criteria help minimize the creation of chimeric contigs. These contigs are assigned a TC (Tentative Consensus) number. TCs may comprise ESTs derived from different tissues. The best hits for TC's were assigned by searching the TC set against a non-redundant amino acid database(nraa) using BLAT. The top five hits based on score were selected and displayed for each TC. Caveats: TCs are only as good as the ESTs underlying them; there may be unspliced or chimeric ESTs and thus TCs. There is still redundancy in the TC set because sequences must match end to end and at a certain percent identity to be combined. Directionality of the TCs should not be assumed. Not all TCs contain protein-coding regions.</p>
2009
Ninety-six Pea Association mapping panel (PAM) lines were run on the Ps1536 Pea Illumina Golden Gate assay.
2009
Lentil has been grown commercially in western Canada since 1970. Ascochyta lentis, the causal agent of ascochyta blight of lentil is established as one of the most economically important diseases of lentil in Western Canada. To deal with this problem, the widely acceptable genetic improvement strategy is to pyramid resistance genes. Developing closely linked single nucleotide polymorphism (SNP) markers for resistance genes is prerequisite for pyramiding resistance genes. To develop SNP markers, a series of selected recombinant inbred line (RIL) populations derived from resistant sources will be phenotyped under greenhouse conditions (pathogenicity tests) followed by screening available SNP markers across the entire set of RIL populations.

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