question

2n gamete

answer

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.

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A. squarrosa

answer

x = 7
The D genome of wheat. Possibly crossed with T. discocoides to produce wheat.

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AC Colibri

answer

A transgenic soybean variety developed at ECORC. Has germin genes from wheat, which make it resistant to Scerotinia sclerotiorum.

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Adult-plant reistance (APR)

answer

Compatible wheat-rust reactions in seedlings, with relatively low disease severity in the adult.

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Alloploid

answer

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.

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Amplified fragment length polymorphisms (AFLPs)

answer

An approach for developing molecular genetic markers.

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Aneuploidy

answer

Having extra chromosomes or chromosome fragments. There are incomplete sets. Includes trisomies.

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Antibiosis

answer

A mechanism of resistance to infectious diseases. The plant harms or kills the attacking organism. The strongest type of resistance. Includes hypersensitive response.

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Association mapping

answer

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.

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Autoploid

answer

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.

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Autotetraploid

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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.

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Boom-and-bust cycle

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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.

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Brassica campestris

answer

Turnips and rapeseed.

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Brassica carinata

answer

Abyssinian mustard
A cross between B. nigra and B. oleraceae.

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Brassica juncea

answer

Indian mustard
A cross between B. nigra and B. rapa.

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Brassica napus

answer

Rutabaga and rapeseed
A cross between B. rapa and B. oleraceae.

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Brassica nigra

answer

Black mustard.

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Brassica oleraceae

answer

Cabbage

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Breeder seed

answer

A seed class in Canada.

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Breeding for disease resistance

answer

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.

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Canadian Seed Growers' Association (CGSA)

answer

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.

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Certified seed

answer

A seed class in Canada. One generation.

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Characterized amplified polymorphic sequences (CAPS)

answer

An approach for developing molecular genetic markers.

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Colchicine

answer

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.

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Compatibility reaction

answer

The degree to whcih a disease affects a host. Depends on host and pathogen genotype.

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Complete resistance

answer

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.

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Control of plant pathogens

answer

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.

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Differential lines

answer

Pure lines with known resistance genes, used for differentiating races of pathogens.

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Diploid

answer

2n = 2x
Organisms with two sets of chromosomes. Most common.

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Diploid sporophyte

answer

n = x

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Dr. Daina Simmonds and Dr. E. Cober

answer

AAFC scientists who coordinated field tests of near-isogenic lines for Sclerotinia sclerotiorum resistance in Southern Ontario and Quebec in 1998.

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dyad and MiMe

answer

Mutations which cause 2n gamete formation. Causes the mother cell to undergo mitosis rather than meiosis.

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Eastern Cereal and Oilseed research centre (ECORC)

answer

An AAFC centre in Ottawa. Developed AC Colibri by inserting germin genes from wheat.

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Endophytes

answer

A form of biological control of plant pathogens. Beneficial plants or fungi living within the plant. Can slow disease progression.

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Flor

answer

Developed the gene-for-gene hypothesis. Studied diseases of flax.

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Foundation seed

answer

A seed class in Canada. One generation.

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Gene-for-gene hypothesis

answer

Devloped by Flor. Host and pathogen genes occur in matched pairs. Genes for resistance are usually pathotype specific, and pathotypes are host-specific.

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Genotype by sequencing (GBS)

answer

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.

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germin

answer

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.

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Hexaploid

answer

2n = 6x

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Hexaploid sporophyte

answer

n = 3x

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Horizontal resistance (HR)

answer

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.

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Hypersensitive response

answer

A form of antibiosis. Localized programmed cell death arount points of infection. The infection is localized and growth is prevented.

question

Illumina Golden Gate assay

answer

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 1^A1^A, 1^A1^B, and 1^B1^B 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.

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Incomplete resistance

answer

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

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Infectious disease

answer

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.

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Kennebec

answer

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.

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Leaf brown rust

answer

Puccinia triticina
A rust disease in wheat.

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Linkage analysis

answer

Only a few opportunities for recombination occur within families and pedigrees of known ancestry. Low mapping resolution.

question

Linkage map

answer

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)

question

Loegering

answer

Considered the host-pathogen association to be a third entity in the agro-ecosystem.

question

Mapping function

answer

A mathematical formula used by Maximum Likelihood to produce linkage maps.

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Maritta

answer

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.

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Marker assisted selection

answer

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.

question

Maximum Likelihood

answer

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.

question

Molecular markers

answer

Heritability is 100%. Used to select for linked genes. Includes phenotypic traits, or SNPs.

question

Monogenic resistance

answer

A type of vertical resistance, controlled by a single gene.

question

Monoploid

answer

2n = x

question

Multi-line varieties

answer

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.

question

n

answer

The gametophytic chromosome number.

question

Nattosan

answer

A soybean variety highly susceptible to Sclerotinia sclerotiorum.

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Non-infectious disease

answer

A plant disease caused by unfavourable growing conditions, such as exreme temperature, moisture, oxygen levels, toxic substances, or excess or deficiency of essential nutrients.

question

Non-preference

answer

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

question

OAC Salem

answer

A soybean variety highly tolerant of Sclerotinia sclerotiorum.

question

Oligogenic resistance

answer

A type of vertical resistance, controlled by several major genes.

question

osd1 and tam

answer

Mutations which cause 2n gamete formation. Causes premature cytokinesis. Sister homologs do not split into separate genes.

question

Pathogens

answer

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.

question

Pentaploid

answer

2n = 5x
Sterile.

question

Phtophthora infestans

answer

Blight in potatoes.

question

Plant Breeders' Rights (PBR)

answer

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.

question

Plant disease

answer

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.

question

Polygenes

answer

A number of minor genes, each contributing a small but cumulative effect on phenotype.

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Polyploidy

answer

Having more than two sets of chromosomes. Plants with oddly numbered sets of chromosomes are sterile.

question

Procedures for the Registration of Crop Varieties in Canada

answer

Explains the details of how varieties are registered in Canada.

question

ps1 and jason

answer

Mutations which cause 2n gamete formation. Causes production of parallel spindle fibres rather than perpendicular, producing two cells from meiosis rather than four.

question

Puccinia graminis tritici

answer

Rust in wheat.

question

Puccinia sorghi

answer

Rust in maize.

question

Pyramiding of race-specific genes

answer

A strategy for breeding for vertical resistance.

question

Qualitative traits

answer

Marker assisted selection is used if phenotying is expensive or unreliable, such as for disease resistance.

question

Quantitative traits

answer

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.

question

Random amplified polymorphic DNA (RAPD)

answer

An approach for developing molecular genetic markers.

question

Raphanobrassica

answer

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.

question

Recombinant inbred lines (RILs)

answer

Produced when selecting for quantitative traits in an association mapping method. Stable and homozygous.

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Registered seed

answer

A seed class in Canada. One generation unless otherwise specified by the breeder.

question

Resistance

answer

Less disease, on the susceptibility scale.

question

Restriction fragment length polymorphism (RFLPs)

answer

An approach for developing molecular genetic markers.

question

Sclerotinia sclerotiorum

answer

Sclerotinia stem rot
White mould
A disease in soybeans. AC Colibri is resistant to it, due to its transgenic genes germin.

question

Score

answer

Based on the difference in yield betwen alleles.

question

The Seeds Act

answer

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.

question

Seed Regulations

answer

Enforces grade standard, variety, marketing, units of measurement, sampling, seed testing, and importation of seeds.

question

Select seed

answer

A seed class in Canada. Five generations unless otherwise specified by the breeder.

question

Short sequence repeats (SSR)

answer

An approach for developing molecular genetic markers.

question

Simple sequence length polymorphisms (SSLPs)

answer

An approach for developing molecular genetic markers.

question

Single nucleotide polymorphisms (SNPs)

answer

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.

question

Single resistance gene cultivars

answer

A strategy for breeding for vertical resistance.

question

Slow rusting

answer

Incomplete resistance in wheat-rust interactions. Infection process is slowed down, although the host-pathogen interaction is still compatible.

question

Somatic doubling

answer

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.

question

Stem black rust

answer

Erysyphe gramninis
Powdery mildew in wheat. A rust disease in wheat.

question

Stripe yellow rust

answer

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

question

Susceptibility

answer

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

question

T. discocoides

answer

AABB
2x = 4x = 28
An allotetraploid formed from a cross between T. monococcum and T. searsii.

question

T. monococcum

answer

x = 7
The A genome contributing to wheat.

question

T. searsii

answer

x = 7
The B genome contributing to wheat.

question

T. taushii

answer

x = 7
The D genome contributing to wheat. Possibly crossed with T. discocoides to produce wheat.

question

Tetraploid

answer

2n = 4x

question

Tetraploid sporophyte

answer

n = 2n

question

Tolerance

answer

The plant develops the disease, but yield reduction is insignificant. Calculated from the ratio between yields in an uninfected field and an infected field.

question

Triangle of U

answer

A diagram of the relationships between natural allopolyploids in the Brassica family.

question

Triploid

answer

2n = 3x
Result from crossing tetraploid and diploid genotypes. Often sterile and produces seedless fruit. Form unviable gametes. Example: limes, bananas.

question

Union for the Protection of New Varieties of Plants (UPOV)

answer

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.

question

Unviable gametes

answer

In tetraploids, gametes with 1 trivalent + 1 univalent.

question

Van der Plank

answer

Studied Phytophthora infestans. Resistance in potatoes. Defined vertical restiances in 1963.

question

Variety Registration Office of the CFIA

answer

Documents related to plant breeding can be found on their website.

question

Vertical resistance (VR)

answer

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.

question

Viable gametes

answer

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.

question

Virulent

answer

A pathotype which can attack genotypes bearing a specific resistance.

question

Wheat

answer

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.

question

x

answer

The basic chromosome number of a species.

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