Plant Breeding Exam 3

Front 1

2 ways to create genetic variability

Back 1

Polyploidy

Mutation

Front 2

Polyploidy

Back 2

Organisms with more than 2 sets of chromosomes in its somatic cells

Front 3

What is the value of having more than two copies of chromosomes?

Back 3

Increase the total amount of genetic Variability

Front 4

What is the highest possible number of sets of chromosomes to be found in somatic cells?

Back 4

12

most commonly found up to 8

Front 5

Euploidy

Back 5

A complete doubling or quadrupling of chromosomes

When every single chromosome is doubled

Front 6

Aneuploidy

Back 6

A single chromosome that is doubled

Multiple copies of a single chromosome (2n + 1)

incomplete sets of chromosomes; one chromosome is either missing or added

Front 7

Describe the variables of a polyploid (X, N, 2n)

Back 7

X = basic (original) chromosome number of an organism

N= Haploid (Gametic) Chromosome Number; the number of chromosomes that are present within one of the gametes (egg or pollen)

2n = Diploid (Gametic) chromosome number

Front 8

What determines the type of euploid?

Back 8

The number of complete sets of chromosomes:

Diploid = 2x

Triploid = 3x

Tetraploid = 4x

Pentaploid = 5x

Hexaploid = 6x

Septaploid = 7x

Octaploid = 8x

Front 9

Why are pentaploids rare?

Back 9

because uneven amounts of chromosomes create a genetically unstable individual when the cells divide. When an uneven number is divided into two, there is an uneven division of chromosomes between cells.

Front 10

What portion of crops are polyploids?

Back 10

1/3 to 1/2 of angiosperms are ployploid

Front 11

How must haploids be reproduced?

Back 11

Clonally

Front 12

Two different types of Euploids

Back 12

Alloploids and Autoploids

Front 13

Alloploid

Back 13

combination of genomes from two or more different species (crossing two unrelated species)

Front 14

Autoploids

Back 14

All chromosomes come from within a single species

Crossing two related species

Front 15

Chemical used to induce polyploidy?

Back 15

Colchocine

Front 16

Colchocine

Back 16

water-soluble alkaloid found in the autumn crocus, blocks or suppresses cell division by inhibiting mitosis

this causes the spindle fibers to make a failure in connection to each chromosome, causing the chromosome number to be doubled

Front 17

Value of Polyploids

Back 17

Increased variation with increasing chromosome number

taking a positive gene and doubling it will continue to double the positive effects of the gene

may increase plant size as polyploidy number increases (due to larger nuclei in cells to hold more chromosomes, the cells are in turn larger as well)

Front 18

How does colchocine effect spindle fibers?

Back 18

it breaks down spindle fibers; thus inhibiting separation of cells

Front 19

How is a triploid created?

Back 19

Creating a tetraploid (using colchicine on a diploid) then crossing the tetraploid with a diploid female. (2n=3x)

Front 20

What is the significance of a triploid watermelon?

Back 20

Seedless. the seed carries three copies of every chromosome

plant is unstable and therefore shuts down the ability to produce seed

Front 21

Microsporogenesis

Back 21

a single cell undergoes a process to make 4 haploid pollen grains

Front 22

Megasporogenesis

Back 22

a single cell undergoes a process to produce 1 egg

Front 23

True or false: All endosperms are triploids

Back 23

True

Front 24

By adding one more chromosome, what happens to the number of phenotypic classes?

Back 24

increase the number of phenotypic classes by 1 (from 3 (diploid) to 4 (triploid))

Tetraploid = 5 phenotypic classes

Front 25

What causes Aneuploidy?

Back 25

one spindle fiber does not form; one cell has two copies of one of the chromosomes and the other cell ends up with a missing chromosome

Front 26

What are the two potential aneuploids that could be created?

Back 26

Monosomic and Trisomic

Front 27

Types of Aneuploidy

Back 27

Nullisomic = 2n - 2

Monosomic = 2n - 1

Trisomic = 2n + 1

Tetrasomic = 2n + 2

Front 28

Why are Nullisomic and tetrasomic individuals very rare?

Back 28

because they are very unstable and therefore have a low likelihood for survival

Front 29

Example of chromosomal mutation

Back 29

polyploidy

Front 30

Two types of Genetic Mutation

Back 30

Recessive mutation

Dominant Mutation

Front 31

Recessive mutation

Back 31

mutating a recessive trait into its dominant form

Front 32

Dominant mutation

Back 32

Mutating a dominant trait into its recessive form

Front 33

Why was there interest in genetic mutation following WWII?

Back 33

discovered that plants introduced to levels of radiation would change, altering their phenotypic state

this became known as mutation breeding

Front 34

Mutation breeding

Back 34

change in state of one gene (goal is to change only one gene)

Front 35

T/F: All mutations have a recognizable phenotype

Back 35

False; not all mutations have a recognizable phenotype

Front 36

Two guidelines to mutation breeding

Back 36

1) choose a qualitative trait controlled by one gene

2) trait that is chosen must be easily screened (ie. color)

Front 37

Mutation breeding requires methods to

Back 37

1) induce radiation

2) screen for advantageous mutations

Front 38

Two methods of inducing mutations

Back 38

1) Ionizing radiation: Xray, neutrons, UV radiation, GAmma Rays, Beta Radiation

2) Chemical mutagens (most common): Ethyl methane sulfonate (EMS); ENH, MNH, ENV, DES, EI

Front 39

EMS

Back 39

Ethyl methanesulfanate - Mutagen used in mutation breeding

Front 40

Two facilities used for Radiation breeding

Back 40

Gamma field

Gamma Room

Front 41

Gamma Field

Back 41

100m circular field with an 88.8 TBq60Co source at the center

Front 42

Gamma Room

Back 42

7m octagonal greenhouse with a 44.4TBq60Co source

Front 43

Mutant variety database

Back 43

joint group between FAO and IAEA

Front 44

What departments inspect GMO crop safety?

Back 44

USDA, EPA, FDA (only crops that use radiation)

Front 45

T/F: Mutation breeding requires testing and inspection

Back 45

False; mutation breeding falls under conventional breeding. Inspection is only necessary when radiation is being used

Front 46

Why don't more people use mutation breeding?

Back 46

Expensive and time consuming

but a great way for creating genetic variability.

Front 47

V.A.S.T. Labs

Back 47

Variation and Abiotic Stress Tolerance Labs

basically G x E experimentation; alters things like water, light, PGR, etc.

only evaluates one specific trait

Front 48

Why are chemical mutagen agents preferred over radiation

Back 48

simpler to apply

produce less damaging and durastic effects

fewer chromosomal disruptions

Front 49

Two methods (location) of evaluating breeding material

Back 49

Greenhouse or growth chamber

Field

Front 50

Goals of line evaluation

Back 50

Performance: measure performance of each plant so to compare amongst them (environmental variation)

Whole plant evaluation - come up with a way to evaluate all of the genetic variability in order to figure out which plant grows better than everything else (interest in other traits)

Comparison - checks

Front 51

Perfect environment

Back 51

environment where environmental variation does not change throughout the field

Front 52

Why are replicates so important

Back 52

because no environment is different; therefore it is necessary to develop a system that allows a measure of the differences across a single field

Front 53

Which experimental design is preferred?

Back 53

randomized block design; want to evaluate each individual plant in a perfect environment

Front 54

Goal of proper experimental design?

Back 54

reduce experimental error

Front 55

Experimental error

Back 55

error that cannot be defined

Front 56

Considerations of selecting a growing location

Back 56

Soils and media heterogeneity

growing environment

cropping history

chemical residues

cultural practices

Front 57

Why is a uniform (or perfect) environment so desired?

Back 57

in a uniform environment, any change in phenotype is due to genetic variability

Front 58

T/F: The more uniform the environment, the less variation can be explained

Back 58

FALSE: the more uniform the environment, the MORE variation can be explained

Front 59

What are some important factors of statistics and experimental design when breeding plants?

Back 59

Data collection

use of specialized equipment (some crops)

Need for proper design

Front 60

How is replication achieved in breeding experiments?

Back 60

Grow the same entry in multiple plots

Provide sufficient number of replicates

Front 61

Why must breeders provide replicates in multiple plots?

Back 61

reduces the effect of random variation by averaging over plots

allows for the measurement of random variation

Front 62

How many replicates is sufficient?

Back 62

Depends: two, four or more are common

Front 63

What are the possible types of replication

Back 63

Within plot

Within year

Between year

Front 64

As homyzygosity is increased through generations of inbreeding rice, what happens to the number of plants grown?

Back 64

As homozygosity is increased, the number of plants grown in each clump is also increased; but reducing the amount of variation (selecting for best clumps)

Front 65

What is the overall goal of the rice evaluation center?

Back 65

to evaluate each plant in different environments to determine if any one plant is equal or better than the current commercial standard

Front 66

Why do we try to spread out to multiple environments when experimenting with plant breeding?

Back 66

by spreading out to multiple environments, you get more environmental variability and you can therefore determine overall environemntal stability of the plant

Front 67

What must be done before increasing the number of environments in an experiment?

Back 67

A certain level of homozygosity must first be reached

Front 68

How long does it take for evaluations of perennials, shrubs, and vines at the Chicago botanic Garden?

Back 68

Perennials - 4 years

Shrubs and vines - 6 years

Front 69

What did Clematis do that was significant for plant breeding?

Back 69

Tested 108 varieites in a uniform environment; but instead of growing in optimal conditions, he chose a screening technique that would select for plants that would be best suited for a home grower environment (poor nutrient and water care)

Oranamental qualities, ease of growth, hardiness, disease and pest resistance

Front 70

Criteria for Randomization of an experiment

Back 70

1) plots in different orders in different replications

2) Competition between two entries must be "eliminated"

3) Cannot eliminate competition, must account for it

4) Every replication must have different randomization

Front 71

Different types of design plots

Back 71

Single-plants

multiple plant plots

single row plots - (headrows)

Multiple row plots

Front 72

What happens to experimental error as interplot competition plays a roll?

Back 72

Experimental error increases whenever interplot competition causes performance of a genotype in one plot to be altered by performance of another plot

In other words, experimental error increases if one plot has an effect on a different plot

Front 73

What is the point of selection scheme, and how is this achieved?

Back 73

Selection schemes are designed to fix genetic variability over time; this is done by fixing genes

Front 74

Oldest method of selection

Back 74

mass selection

Front 75

Mass selection

Back 75

based on phenotypic selection in a heterogeneous population

Front 76

How mass selection works

Back 76

plant a large field with many different varieties, select for a desirable trait and replant all of those seeds. Continue to do this until quantitative trait has been sufficiently reached

Front 77

Problem with mass selection

Back 77

1) in some cases, we are Selecting for individuals due to location; environmental variation is not accounted for

2) selecting plants on the edge will effect results due to less competition

Front 78

When does mass selection work best?

Back 78

Mass selection works well when heritability for the trait of interest is very high; this is because high heritability means environment doesn't play as much of a role

Front 79

Four techniques that are used for inbreeding while reducing plant number

Back 79

1) bulk population

2) pedigree selection

3) single-seed descent (SSD)

4) recurrent selection

Front 80

T/F: Most selection techniques begin with parent plants

Back 80

False; most selection techniques begin with plants in the F1

Front 81

Inbreeding techniques that rapidly increase inbreeding (increased homozygosity) while fixing both qualitative and quantitative characteristics

Back 81

Bulk population, pedigree selection, single-seed descent

Front 82

T/F: Recurrent selection is the fastest method of inbreeding

Back 82

False; recurrent selection will inbreed at a slower pace, but if done correctly, we will continue to improve quantitative characteristics

Front 83

How long does it take for quantitative characteristics to balance out?

Back 83

depends on how many genes effect the trait

Front 84

In annual plants, how long does each step take?

Back 84

one year

Front 85

Bulk population

Back 85

procedure for inbreeding a segregating population; used mostly in self pollinators

procedure continues until an inbreeding level is attained

may take advantage of natural selection

Front 86

Methodology of Bulk population

Back 86

plant 1000 seeds, select for 100 plants; take 10 seeds from each 100 plants and grow them together

this increases the homozygeity of the plants (but back at 1000 plants again)

adding a selective pressure each generation of inbreeding and allowing for natural selection to take place in fields and select for plants that survive

Front 87

Who first described bulk population

Back 87

Nilsson-Ehle (1908) - Natural selection vs. Competition

Winter Hardy Wheat

Front 88

Thermal photography

Back 88

decrease of water decreases transpirtaion which increases reflective temperatures. The cooler the plants during drought conditions, the more water that is withheld within the plant

Increases the ease of observing a large number of plants

Front 89

Pedigree selection

Back 89

Useful in handling segregating generations following initial cross

Front 90

Explain the selection process for pedigree selection

Back 90

Selection in F2, F3, or F4

Plants are reselected each generation

Pedigree of each selection is maintained by numbering system so that a line can be traced back to an individual F2 plant in any subsequent generation

As selfing continues, each generation becomes unique individual; each generation has its own value that can be recreated at any point

Front 91

T/F: The further along in the selfing process you go, the easier it is to recreate it

Back 91

True; the further along in the selfing process, the higher percent homozygosity

Front 92

How is environment accounted for in Pedigree selection?

Back 92

each generation of pedigree selection requires you to select the plant in the environment in which it will be grown

Front 93

Disadvantage of pedigree selection method

Back 93

relatively slow process: one generation per year; 5 years to get to F6 generation

Front 94

When is single-seed descent most commonly used?

Back 94

Self fertilized crops

Front 95

Two functions of Single-seed descent

Back 95

progress toward homozygosity by selfing

selection of superior lines from segregating populations

Front 96

T/F: Single seed descent is faster to reach high % homozygosity than pedigree method

Back 96

True

Front 97

How does Single-Seed Descent work?

Back 97

During off seasons, selected seeds are sent to a different location with similar environment (ie Brazil, greenhouse) to be grown into the next generation

Selection does not take place at the alternate site, but simply increases level of homozygosity quicker

Front 98

T/F: F6 generation can be achieved in 2/3 years in SSD

Back 98

True

Front 99

Value of SSD

Back 99

speeed; decreases time to go to market

Front 100

Problems with SSD

Back 100

loss of ability to look for selection in a large number of environments (cuts the number of environments in half)

Front 101

objective of Recurrent selection

Back 101

improve the performance of populations for one or more trait

Front 102

What is Recurrent Selection

Back 102

a system of cyclical improvement

a systematic selection of desirable individuals from a population

recombination of the selected individuals to form a new population

used extensively and effectively in cross-fertilized crops

taking every selected individual and crossing them with one another

Front 103

T/F: Recurrent selection is best utilized for qualitative traits

Back 103

False; recurrent selection is best utilized for selecting quantitative traits

only method of increasing quantitative characteristics within a population

Front 104

objective of Early Generation Testing

Back 104

eliminate inferior lines or populations that do not merit further evaluation or selection

Front 105

How to: Early generation testing

Back 105

Take F2 (and subsequent generations) and evaluate as though it is the most elite line

evaluate for everything; yield, disease resistance, etc.

Front 106

what type of crops is early generation testing most commonly used in?

Back 106

self and cross pollinated species

Front 107

What is the overall point of early generation testing?

Back 107

estimate the genetic potential of an individual or population at an early stage of breeding to get a generalized idea of how well a plant will grow

Front 108

Benefits of early generation testing

Back 108

minimize population at an early stage

Front 109

Problems with early generation testing

Back 109

Minimizes the number of locations viewed

Each location brings value, if not done in enough locations, there may be a miss in an important phenotypic factor--this may be missed and never recreated

Front 110

Selection index

Back 110

method of selecting for multiple traits simultaneously

Traits are ranked in order of importance; and plants are selected based on this rank

Narrows the focus of what is most important in the desired crop (ie. taste, texture, aesthetics, etc.)

Front 111

Backcross Breeding

Back 111

essentially a method for improving an established variety that is deficient in only one or a few characteristics

Front 112

What type of reproductive plants is backcross breeding most useful in?

Back 112

both self and cross pollinated species

Front 113

What type of traits is backcross breeding most used for?

Back 113

Qualitative traits; backcrossing for quantitative traits is out of the question

Front 114

Harlan and Pope

Back 114

Bred for the smooth awned : white seeded wheat variety

Front 115

Recurrent parent

Back 115

plant that has everything that is desired, besides for one trait

Front 116

Donor Parent

Back 116

plant that has nothing that is desired, besides for one trait

Front 117

Basic methodology behind backcrossing

Back 117

cross recurrent parent with donor parent to get F1; cross F1 with recurrent parent to get BC1, continue to cross BC generations back to recurrent parent

Front 118

T/F: Harlen and pope found the smooth awned trait in the first generation of backcrossing

Back 118

True! 75% of Recurrent parent, 25% of Donor Parent traits

Front 119

Definition of backcrossing

Back 119

the repeated crossing of hybrid progeny bak to a single parent

Front 120

At what point is 99% homozygosity reached while backcrossing?

Back 120

BC6

Front 121

Two things to watch while backcrossing

Back 121

1) simply inherited (qualitative) traits

2) everything else: trying to reconstitute the original recurring parent while incorporating the desirable trait from the donor plant

Front 122

Mathematical equation for the recovery of the recurrent parent

Back 122

1 - (0.5)^m

m= number of generations of backcrossing

Front 123

Describe the progression of % recurrent parent through multiple generations (up to BC4)

Back 123

F1 - 50%

BC1 - 75%

BC2 - 87.5%

BC3 - 93.75%

BC4 - 96.87%

Front 124

How does backcrossing a recessive trait differ from backcrossing a dominant trait?

Back 124

It becomes much more difficult because at the BC1, the qualitative trait cannot be selected via natural selection. It requires one of two different methods in order to show the recessive traits

Front 125

What are two methods for determining the BC1 of a backcrossed parent whose desired trait is recessive?

Back 125

Testing: Selfing each plant in the BC1 and selecting for those that have the desired trait

Blind: Backcrossing every single individual back to the Recurrent parent

Front 126

Which is most efficient, Test or Blind method for determining genetics of a BC1 individual derived from a recessive parent

Back 126

Test method takes longer due to the need for a full year to self plants

Blind method can be faster, but requires a lot of space and labor, which costs more money

Front 127

Why is selfing a BC generation dangerous?

Back 127

Because while selfing a BC1 fixes the desired gene, it can also fix other genes from the donor plant that have not been accounted for (undesirable genes from donor plant)