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Plant Breeding: Final
University of Guelph MBG*4160
118
Microbiology
Undergraduate 4
12/08/2015

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Term
2n gamete
Definition
A mechanism of chromosome doubling. Mutations which result in formation of 2n gametes. Expressivity is not 100%, and expression may be related to background genetics or the environmnet. Includes ps1 and jason, osd1 and tam, and dyad and MiMe.
Term
A. squarrosa
Definition

x = 7

The D genome of wheat. Possibly crossed with T. discocoides to produce wheat.

Term
AC Colibri
Definition
A transgenic soybean variety developed at ECORC. Has germin genes from wheat, which make it resistant to Scerotinia sclerotiorum.
Term
Adult-plant reistance (APR)
Definition
Compatible wheat-rust reactions in seedlings, with relatively low disease severity in the adult.
Term
Alloploid
Definition
A polyploid that arises through crossing with other species. Generally naturally self-pollinating. Includes wheat, oats, Brassica species, and Raphanobrassica. Most arise spontaneously, but some are man-made. Multiple loci control traits, producing 15:1 ratios rather than 3:1 ratios for one locus. Although they are self-pollinating, heterozygosity is fixed due to duplicate loci: the plants show hybrid vigour.
Term
Amplified fragment length polymorphisms (AFLPs)
Definition
An approach for developing molecular genetic markers.
Term
Aneuploidy
Definition
Having extra chromosomes or chromosome fragments. There are incomplete sets. Includes trisomies.
Term
Antibiosis
Definition
A mechanism of resistance to infectious diseases. The plant harms or kills the attacking organism. The strongest type of resistance. Includes hypersensitive response.
Term
Association mapping
Definition
A biparental cross is used, followed by several generations of inbreeding to develop recombinant inbred lines. If the two parents have common alleles, those genes will not be identified. Historical recombination and natural genetic diversity are exploited. High mapping resolution.
Term
Autoploid
Definition
A polyploid that arises from multiplication of the complete chromosome set of a species. Generally cross-pollinating. Have increased cell size, especially stomata and pollen. Leaves are thicker, and the plant grows slower. Some have poor pollen production and are partially or completely sterile. In order for fertility, meiosis must be regular and produce viable gametes. High frequency of deleterious recessive alleles: inbreeding depression is more severe than in diploids. Includes autotetraploids.
Term
Autotetraploid
Definition
A type of autoploid. Four chromosomes can pair in tow configurations. Genetic analysis can be complex. Single-gene segregation can have ratios as high as 783:1. Analysis is increasingly complex when multiple loci are considered.
Term
Boom-and-bust cycle
Definition
Vertical resistance lasts long enough to support a boom of a new variety, then it ends when a new race of pathogen evolves. Pathogens often evolve faster than plants due to their biology. Occurs naturally between all host and pathogen relationships.
Term
Brassica campestris
Definition
Turnips and rapeseed.
Term
Brassica carinata
Definition

Abyssinian mustard

A cross between B. nigra and B. oleraceae.

Term
Brassica juncea
Definition

Indian mustard

A cross between B. nigra and B. rapa.

Term
Brassica napus
Definition

Rutabaga and rapeseed

A cross between B. rapa and B. oleraceae.

Term
Brassica nigra
Definition
Black mustard.
Term
Brassica oleraceae
Definition
Cabbage
Term
Breeder seed
Definition
A seed class in Canada.
Term
Breeding for disease resistance
Definition
Important to know the pathogen life cycle, distribution, and virulence. Genes are often found in wild species. Screening for resistance is done with spreader rows, artificial inoculation, and disease environments. Strategies for vertical resistance includes single resistance gene cultivars, pyramiding of race-specific genes, and multi-line varieties. Strategies for horizontal resistance are similar to strategies in other quantitative traits.
Term
Canadian Seed Growers' Association (CGSA)
Definition
Their standards for seeds were incorporated into the Seeds Act. In 1959, they were officially made the only agency responsible for prescribing standards for agricultural seeds.
Term
Certified seed
Definition
A seed class in Canada. One generation.
Term
Characterized amplified polymorphic sequences (CAPS)
Definition
An approach for developing molecular genetic markers.
Term
Colchicine
Definition
An artificial method of doubling chromosomes. Prevents formation of spindle fibres. Sister chromatids cannot be pulled apart, and cell division is halted, however chromosomes have been doubled.
Term
Compatibility reaction
Definition
The degree to whcih a disease affects a host. Depends on host and pathogen genotype.
Term
Complete resistance
Definition

Total resistance

Immunity

Ability of the host plant to prevent multiplication of the pathogen. Reactions are hypersensitive; the plant uses its own defence mechanisms to excrete toxins. The plant displays no disease.

Term
Control of plant pathogens
Definition
Plant pathogens are controlled culturally, biologically, chemically, or genetically. Biological control includes endophytes. Genetic control is environmentally and health friendly because it leads to use of less pesticides.
Term
Differential lines
Definition
Pure lines with known resistance genes, used for differentiating races of pathogens.
Term
Diploid
Definition

2n = 2x

Organisms with two sets of chromosomes. Most common.

Term
Diploid sporophyte
Definition
n = x
Term
Dr. Daina Simmonds and Dr. E. Cober
Definition
AAFC scientists who coordinated field tests of near-isogenic lines for Sclerotinia sclerotiorum resistance in Southern Ontario and Quebec in 1998.
Term
dyad and MiMe
Definition
Mutations which cause 2n gamete formation. Causes the mother cell to undergo mitosis rather than meiosis.
Term
Eastern Cereal and Oilseed research centre (ECORC)
Definition
An AAFC centre in Ottawa. Developed AC Colibri by inserting germin genes from wheat.
Term
Endophytes
Definition
A form of biological control of plant pathogens. Beneficial plants or fungi living within the plant. Can slow disease progression.
Term
Flor
Definition
Developed the gene-for-gene hypothesis. Studied diseases of flax.
Term
Foundation seed
Definition
A seed class in Canada. One generation.
Term
Gene-for-gene hypothesis
Definition
Devloped by Flor. Host and pathogen genes occur in matched pairs. Genes for resistance are usually pathotype specific, and pathotypes are host-specific.
Term
Genotype by sequencing (GBS)
Definition
A method of detecting SNPs. Newer and cheaper than Illumina Golden Gate assay. The current standard. Molecular markers loci are directly sequenced by sequencing the genotype. Usually only areas of interest are sequenced, not the entire genome. The DNA is first digested by enzymes into fragments, with different overhang ends depending on the enzyme. Adaptors are ligated to ends of the fragments, and they are sequenced. DNA from multiple plants can be sequenced in the same sample using adaptors for enzymes with sample ID tags, such as blue, yellow, or purple. Sequencing errors are possible, so several readings are necessary to deveop a consensus sequence.
Term
germin
Definition
A gene in wheat which codes for oxalate oxidase (OXO), which breaks down oxalate, the main toxin secreted by Sclerotinia sclerotiorum. It was transferred from wheat into soybeans to produce AC Colibri, which have resistance to Sclerotinia sclerotiorum.
Term
Hexaploid
Definition
2n = 6x
Term
Hexaploid sporophyte
Definition
n = 3x
Term
Horizontal resistance (HR)
Definition

Field resistance

Resistance to all races of a pathogen. Controlled by polygenes; not based on gene-for-gene relationships, based on compatibility reactons: expression is quantitative. Decelerates infection after it has already taken place, preventing epidemics; long-term resistance. Natural selection favours horizontal resistance, and may appear in cultivars even when breeders are not selecting for it. Not hypersensitive. Less easy to breed for. Includes resistances which reduce yield due to sugar sink-loss.

Term
Hypersensitive response
Definition
A form of antibiosis. Localized programmed cell death arount points of infection. The infection is localized and growth is prevented.
Term
Illumina Golden Gate assay
Definition
A method of detecting SNPs. Allows multiple marker genotypes to be determined simultaneously. Used to be expensive and was used only in major crops. For many crops, pre-made chips are available. Maps large numbers of SNPs in populations of a selected species. DNA is immobilized and made single-stranded. Primers fo 1A1A, 1A1B, and 1B1B are added, each with a specific binding sequence, and sequences for PCR recognition. The primers have specific fluorescent colours, such as blue and yellow. The samples are hybridized into beads and a computer can read thosands of loci at a time.
Term
Incomplete resistance
Definition

Partial resistance

Has characteristic individual disease lesions. A relatievly small area of the leaf has the diseaes. Includes slow rusting in wheat.

Term
Infectious disease
Definition
A plant disease caused by a pathogen. Pathogens in plants are often fungi, bacteria, and viruses. Co-exist with the plants for survival; natural selection does not favour exceedingly aggressive or virulent pathogens.
Term
Kennebec
Definition
A potato variety with resistance gene R1, ensuring vertical resistance to races (0), (2), (4), (2,3), (2,4), (3,4), and (2,3,4). Infection onset is faster than in Maritta.
Term
Leaf brown rust
Definition

Puccinia triticina

A rust disease in wheat.

Term
Linkage analysis
Definition
Only a few opportunities for recombination occur within families and pedigrees of known ancestry. Low mapping resolution.
Term
Linkage map
Definition

A map of the chromosome. Map distances are found by calculating the frequency of recombinant gametes. Not a precise measurement because the value does not count double-crossovers.

p = f(AB) + f(ab)

Term
Loegering
Definition
Considered the host-pathogen association to be a third entity in the agro-ecosystem.
Term
Mapping function
Definition
A mathematical formula used by Maximum Likelihood to produce linkage maps.
Term
Maritta
Definition
A potato variety with resitance gene R1, ensuring vertical resitance to races (0), (2), (4), (2,3), (2,4), and (2,3,4). Infection onset is slower than in Kennebec.
Term
Marker assisted selection
Definition
Molecular markers are 100% heritable, so no error is made when selecting plants this way. Molecular markers adjacent to genes of interest allow breeders to select for alleles directly. Frequency of errors is proportional to the map distance between markers and the gene of interest.
Term
Maximum Likelihood
Definition
A computer program that maps markers. Can handle large sets of genetic data. Uses all segregation data, not just those for homozygous receissive markers. Generates a linkage map using SNPs and recombination frequencies, using mapping function.
Term
Molecular markers
Definition
Heritability is 100%. Used to select for linked genes. Includes phenotypic traits, or SNPs.
Term
Monogenic resistance
Definition
A type of vertical resistance, controlled by a single gene.
Term
Monoploid
Definition
2n = x
Term
Multi-line varieties
Definition
A strategy for breeding for vertical resistance. Not suitable for cross-pollinated crops. The genes are introduced to a population through backcrossing, producing near-isogenic lines. The variety released is a mixture of near-isolenic lines. If there is a disease outbreak, only a few lines will be attacked. More adaptive to environmental changes than pure lines. Need to be updated as races evolved, and are costly. If a new race evolves, all lines in the variety may be attacked.
Term
n
Definition
The gametophytic chromosome number.
Term
Nattosan
Definition
A soybean variety highly susceptible to Sclerotinia sclerotiorum.
Term
Non-infectious disease
Definition
A plant disease caused by unfavourable growing conditions, such as exreme temperature, moisture, oxygen levels, toxic substances, or excess or deficiency of essential nutrients.
Term
Non-preference
Definition

Avoidance

A mechanism of resistance to infectious diseases. Physiological characterstics make the plant unattractive to the patogen. Temporal or physical separation. Includes wax coatings.

Term
OAC Salem
Definition
A soybean variety highly tolerant of Sclerotinia sclerotiorum.
Term
Oligogenic resistance
Definition
A type of vertical resistance, controlled by several major genes.
Term
osd1 and tam
Definition
Mutations which cause 2n gamete formation. Causes premature cytokinesis. Sister homologs do not split into separate genes.
Term
Pathogens
Definition
Includes fungi, bacteria, mycoplasma, viruses, viroids, nematodes, and parasitic plants. Have their own inheritance and development biology, and interact separately in the environment. In most cases it occurs on the leaf surface, reducing photosynthesis. Pathogens can never fully be eliminated, only controlled to an economically tolerable level.
Term
Pentaploid
Definition

2n = 5x

Sterile.

Term
Phtophthora infestans
Definition
Blight in potatoes.
Term
Plant Breeders' Rights (PBR)
Definition

Bill C-1 5

Became a law on June 19, 1990. Establishes the rights of plant breeders to varieties they have developed. Increases investments into plant breeding, protection of varieties, beter access to germplasm, and better and more diverse varieties. Holders of PBRs have exclusive rights to sell and produce their material, use the material to produce more varieties, or authorise its use by other parties.

Term
Plant disease
Definition
When a plant is continuously disturbed by a causal agent that results in abnormal physiological processes. Disrupts the plant's normal structure, growth, or function, eliciting characteristic pathological conditions or symptoms. May be infectious or non-infectious.
Term
Polygenes
Definition
A number of minor genes, each contributing a small but cumulative effect on phenotype.
Term
Polyploidy
Definition
Having more than two sets of chromosomes. Plants with oddly numbered sets of chromosomes are sterile.
Term
Procedures for the Registration of Crop Varieties in Canada
Definition
Explains the details of how varieties are registered in Canada.
Term
ps1 and jason
Definition
Mutations which cause 2n gamete formation. Causes production of parallel spindle fibres rather than perpendicular, producing two cells from meiosis rather than four.
Term
Puccinia graminis tritici
Definition
Rust in wheat.
Term
Puccinia sorghi
Definition
Rust in maize.
Term
Pyramiding of race-specific genes
Definition
A strategy for breeding for vertical resistance.
Term
Qualitative traits
Definition
Marker assisted selection is used if phenotying is expensive or unreliable, such as for disease resistance.
Term
Quantitative traits
Definition
Controlled by many genes and have low heritability. Alleles differ in their effect on phenotype. Molecular markers may be found for several genes controlling the trait. Selection is performed in segregating generations based on genotype, and not environmental effects. Recombinant inbred lines may be produced and grouped based on the parental SNP allele and their yields are compared to establish linkage between SNPs and genes of interest.
Term
Random amplified polymorphic DNA (RAPD)
Definition
An approach for developing molecular genetic markers.
Term
Raphanobrassica
Definition
An alloploid species created by crossing cabbage (Brassica oleraceae) and radish (Raphanus sativus), both diploids 2n = 2x = 18. The chromosomes did not pair properly in the F1 progeny, so it was sterile. It was treated with colchicine to produce a fertile allotetraploid plant.
Term
Recombinant inbred lines (RILs)
Definition
Produced when selecting for quantitative traits in an association mapping method. Stable and homozygous.
Term
Registered seed
Definition
A seed class in Canada. One generation unless otherwise specified by the breeder.
Term
Resistance
Definition
Less disease, on the susceptibility scale.
Term
Restriction fragment length polymorphism (RFLPs)
Definition
An approach for developing molecular genetic markers.
Term
Sclerotinia sclerotiorum
Definition

Sclerotinia stem rot

White mould

A disease in soybeans. AC Colibri is resistant to it, due to its transgenic genes germin.

Term
Score
Definition
Based on the difference in yield betwen alleles.
Term
The Seeds Act
Definition
Federal legislation governing the testing, inspection, quality, and sale of seeds in Canada. Enacted in 1905, and amended in 1911 and 1926 to establish more definite requirements. Seed standards of the CSGA were incorporated into the act.
Term
Seed Regulations
Definition
Enforces grade standard, variety, marketing, units of measurement, sampling, seed testing, and importation of seeds.
Term
Select seed
Definition
A seed class in Canada. Five generations unless otherwise specified by the breeder.
Term
Short sequence repeats (SSR)
Definition
An approach for developing molecular genetic markers.
Term
Simple sequence length polymorphisms (SSLPs)
Definition
An approach for developing molecular genetic markers.
Term
Single nucleotide polymorphisms (SNPs)
Definition
An approach for developing molecular genetic markers. The primary marker of choice. A molecular marker where a single nucleotide difference can be detected between alleles at a locus. Has co-dominacne: can be identified in a heterozygous individual. Methods include Illumina Golden Gate assay and genotyping by sequencing.
Term
Single resistance gene cultivars
Definition
A strategy for breeding for vertical resistance.
Term
Slow rusting
Definition
Incomplete resistance in wheat-rust interactions. Infection process is slowed down, although the host-pathogen interaction is still compatible.
Term
Somatic doubling
Definition

Endomitosis

A mechanism of chromosome doubling. May occur in a meristematic cell undergoing mitosis. Sister chromatids separate before metaphase. The metaphase plate does not form; cell division does not occur, however, chromosomes have been doubled.

Term
Stem black rust
Definition

Erysyphe gramninis

Powdery mildew in wheat. A rust disease in wheat.

Term
Stripe yellow rust
Definition

Puccinia stritiformis

A rust disease in wheat. Appeared in Australia in the 1980s.

Term
Susceptibility
Definition
Disease resistance is manifested on a scale, in relation to the most susceptible standard variety. Scales must be adjusted for different populations.
Term
T. discocoides
Definition

AABB

2x = 4x = 28

An allotetraploid formed from a cross between T. monococcum and T. searsii.

Term
T. monococcum
Definition

x = 7

The A genome contributing to wheat.

Term
T. searsii
Definition

x = 7

The B genome contributing to wheat.

Term
T. taushii
Definition

x = 7

The D genome contributing to wheat. Possibly crossed with T. discocoides to produce wheat.

Term
Tetraploid
Definition
2n = 4x
Term
Tetraploid sporophyte
Definition
n = 2n
Term
Tolerance
Definition
The plant develops the disease, but yield reduction is insignificant. Calculated from the ratio between yields in an uninfected field and an infected field.
Term
Triangle of U
Definition
A diagram of the relationships between natural allopolyploids in the Brassica family.
Term
Triploid
Definition

2n = 3x

Result from crossing tetraploid and diploid genotypes. Often sterile and produces seedless fruit. Form unviable gametes. Example: limes, bananas.

Term
Union for the Protection of New Varieties of Plants (UPOV)
Definition
A legal document which recognizes the importance of protecting plant varieties. There are 21 countries in the union. The office of UPOV is in Geneva, Switzerland. Canada became a member in 1991.
Term
Unviable gametes
Definition
In tetraploids, gametes with 1 trivalent + 1 univalent.
Term
Van der Plank
Definition
Studied Phytophthora infestans. Resistance in potatoes. Defined vertical restiances in 1963.
Term
Variety Registration Office of the CFIA
Definition
Documents related to plant breeding can be found on their website.
Term
Vertical resistance (VR)
Definition

Race-specific resistance

Resistance to some pathogenic races, but not susceptibility to other races of the same pathogen. Expressed when the pathogen does not possess corresponding genes for virulence; expression is qualitative. Based on gene-for-gene relationships. Postpone epidemics by reducing initial inoculum. Unless genetic diversitin the plant population is high, an epidemic can occur when resistance is broken by a mutation; short-term resistance. Controlled by major genes. Often hypersensitive. Easy to breed for. Ineffective resistance to mobile air pathogens unless critically deployed. Effective resistance to localized immobile pathogen such as soil pathogens. Includes monogenic and oligogenic resistance.

Term
Viable gametes
Definition
Gametes with either bivalent or univalent of all chromosomes: complete sets of chromosomes. The chances of viable gametes forming in an oddly-numbered polyploid are very low, and the likelihood decreases with increased number of chromosomes.
Term
Virulent
Definition
A pathotype which can attack genotypes bearing a specific resistance.
Term
Wheat
Definition

AABBDD

2n = 6x = 42

An allohexaploid with chromosomes from three different species. The allotetraploid. T. discocoides crossed with T. tauscii or A. squarrosa, producing a sterile ABD plant which then had chromosome doubling to form an allohexaploid.

Term
x
Definition
The basic chromosome number of a species.
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