Midterm Flashcards
(151 cards)
1
Q
In the 20th century, why the crop plants are selected for (8)?
A
- High yield and production under stress
- High nutritional and food quality
- Efficient use of nutrients and H2O
- Resistance (pests + pathogens)
- Better architecture (growth + harvest)
- Chemical + fertilizer revolution
- Increase yield
- Good $$ value
2
Q
In 3 points describe what is plant breeding
A
- Art and science of developing new varieties
- It consists of the principles + methods for favorably changing the genetic constitution of plants
- Modern: genetic improvement in plants
3
Q
Why we need plant breeding?
A
- Increase of world population = source of food for people
- For developed countries: Maintain product, Increase quality, Develop economical/ecological food, Food for specific needs (allergies etc)
- For developing countries: Higher quantity of major food grains, Nutritionally enhanced food grains
4
Q
What breeders do (6)?
A
- Recognize important traits + objectives
- Design ways to evaluate breeding material
- Find sources of genes
- Combine genes
- Compare new strains
- Release + distribute improved cultivars
5
Q
What are the 3 oldest crops?
A
- Barley (oldest)
- Wheat
- Oat
6
Q
What is the definition of domestication and evolution regarding plant breeding?
A
- Domestication: from wild to cultivated = genetic change
- Evolution: continued change in domesticated crops
7
Q
What are the major changes from wild to domesticated crops (8)?
A
- Loss of dispersal
- Loss of dormancy
- Loss of fruit/seed production
- Removal of toxins
- Perennial to annual
- Disease + pest resistance
- Increase size of fruit/seeds/storage organs.
- Vernalization requirement
8
Q
What are the evidence from plant about the origin, domestication, evolution and dispersal of crop plants?
A
- Living: morphology, genetic system, geodistribution
2. Non-living: archeology
9
Q
What are the evidence from human about the origin, domestication, evolution and dispersal of crop plants?
A
- Living: language, techniques, nutrition
2. Non-living: history, archeology, anthropology
10
Q
Who developed the center of origin of crops and what are they (8) ?
A
Nikolai Vavilov
- Mexico: center of America
- Andes, Brazil, Paraguay
- Mediterranean
- Ethiopia
- Fertile crescent
- India
- China
- South east Asia
11
Q
How diversity might have arisen (4)?
A
- Spontaneous mutation
- Mixing of genes through hybridization
- Enhanced doses of different genomes through polyploidy
- Different crop species spread by transmigration of humans
12
Q
What are the main differences between natural and artificial selection?
A
- Artificial: result from conscious decisions by human
2. Natural: when genetically heterogenous materials are cultivated.
13
Q
What are the 5 levels of domestication?
A
- Unconscious selection for desirable traits (9000BC)
- Conscious cultivation with desirable traits (7000-5000BC)
- Deliberate breeding to improve traits (1700)
- Scientific breeding: genetic mechanism known and exploited (1900)
- Direct genetic manipulation (2000)
14
Q
What are the 3 main factors contributing to increased food production?
A
- High yield variety
- Increase in crop area
- Better inputs and management practices
15
Q
What is the progeny test?
A
- It is a test that focus on the value of a single plant by the performance of its progeny to improve sugar content of beet root.
16
Q
What are the goals of the progeny test?
A
- To determine the genotype of plants (Aa, AA, aa)
- To find out whether the character for which the plant is selected is heritable i.e. due to genotypes.
- -If all plants look like F2 = uniform and will not segregate further
- -If all plant fail to produce uniformity = F2 is not pure
17
Q
Who has developed the progeny test?
A
- Louis de-Vilmorin
18
Q
What is Mendel’s law of heredity?
A
- Each inherited trait is defined by a gene pair. Parental genes are randomly separated to the sex cells so that sex cells contain only one gene of the pair. Offspring therefore inherit one genetic allele from each parent when sex cells unite in fertilization.
19
Q
What is a test cross?
A
- a cross between an unknown and the homozygous recessive.
20
Q
What is a back cross?
A
- is a cross between a hybrid and one of its parents
21
Q
Why backcross is used by breeders?
A
- to incorporate a desirable gene into a variety lacking that character.
- Fast method for trait Incorporation
- Requires only observation of trait under selection
22
Q
What are the 3 variation in Mendelian genetic ratios?
A
- Epistatic gene interaction
- Pleiotropy
- Linkage
23
Q
What is Epistatic gene interaction?
A
- The effect of a gene mutation is dependent on the presence or absence of mutations in one or more other genes
24
Q
What is pleiotropy?
A
- The phenomenon of a single major gene affecting more than one character
25
What is linkage?
- Genes often show a tendency to be Inherited together and do not show Independent segregation
26
What is multiple allelism?
- Existence of many alleles for a single gene. Within the allelic series, each member can show any Type of dominance to another member.
27
What is crossing-over?
- A process by which segments of chromatids of homologous chromosomes are exchanged as they synapse during meiosis.
28
Who is the father of the Green Revolution?
- Norman Borlaug
29
What Norman Borlaug developed during the Green Revolution?
- Semi dwarf wheat in 1905
30
What are the main characteristics of conventional breeding approach?
1. It takes 10-17 years to see results
| 2. Problems can be caused by environmental factors = decrease efficacy of breeding method
31
What are the 6 steps of conventional breeding approach ?
a. Crossing
b. Breeding method
c. Selection process (6-10 yrs)
d. Replicate trial (2-4 yrs)
e. Seed increase (2-3 yrs)
f. Release of new variety
32
What are the 3 modern plant breeding techniques?
1. Tissue + cell culture + micropropagation: facilitate to make inter-specific crosses, instant homozygous, disease free.
2. Molecular biology : Marker assisted selection (MAS) by developing different types of molecular markers
3. Genetically modified technology: crop improvement, drought tolerant, desirable fruit ripening
33
What is the definition of germplasm?
- Living genetic resources such as seeds or tissues that are maintained for the purpose of animal and plant breeding, preservation, and other research uses.
34
What are the sources of germplasm (6)?
1. Domesticated cultivars
2. Breeding material
3. Landraces
4. Plant introductions
5. Genetic stocks
6. Undomesticated plants
35
What are the germplasm materials (6)?
1. New and old cultivars
2. Landraces
3. Selected materials from breeding programs
4. Special genetic stocks (e.g., mutant lines)
5. Wild populations of the crop’s species
6. Related species
36
What is “crop gene pool”?
- Set of all genes or genetic information, in any population, usually of a particular species
37
What plant introduction means?
- The transport of seeds/plants from one production area to another
38
What are the important observations regarding plant introduction?
- Similarity in climate between the region of origin and the new area of production helps introduction to better adapt in new region.
- An introduced crop was most successful if it possessed a considerable amount of variation for adaptation traits, allowing some selection in the new area.
39
What are the 2 agencies of Quarantine talked in class?
1. CFIA: Canadian food Inspection Agency
| 2. APHIS: Animal and Plant Health Inspection Service
40
What is the definition of genetic vulnerability?
- Genetic homogeneity and uniformity of a group of plant that predisposes them to biotic/abiotic hazard.
41
What are the threats to plant germplasm resources (5)?
1. Monoculture
2. Changes production practices
3. Population pressure, including urbanization
4. Overgrazing
5. Environmental degradation-foods, drought and wild fires
42
What are the main causes of genetic variation (4)?
1. Natural factors
2. Action of crop producers + public
3. Actions of breeders
4. Problems in germplasm conservation
43
What does “in situ conservation of plant genetic resources” means?
- The plants are growing in their native habitat
| - It is the most appropriate way of conserving biodiversity
44
What does “ex situ conservation of plant genetic resources” means?
- Samples of seeds/plants are conserved in controlled conditions
- Can be used to regenerate the plants
45
What does “in vitro conservation of plant genetic resources” means?
- Cloned DNA representing all genes or specific targeted genes
46
What are the 3 main methods of maintenance of plants?
1. Stored seeds
2. Seedlings
3. Clonal plants
47
What types of plants are maintained through seed storage?
- Annual, biennial and few perennials
| - Maize, beet, wheat, rice
48
What types of plants are maintained through seedlings?
- Perennial which can be stored only as long-lived plantations
- Oil palm, coconut
49
What types of plants are maintained through clonal plants?
- Perennials which can be stored only as clones
| - Banana, grapes, fruits
50
Give 2 types of storage of plant material
1. Cryostorage system: seeds in liquid nitrogen
| 2. In vitro gene banks: sterile meristem or regenerable tissue/cell culture
51
What are the challenges of seedbanks (3) ?
1. High number of recalcitrant species in the wild cannot be preserved in seed bank = hard to conserve
2. Lack of funding and resources
3. Lack of comprehensive data and limited information
52
What is the definition of hybridization?
- Combining 2 dissimilar genotypes via crossing
53
What is the definition of polyploidy?
- Assembling +2 copies of same/different genome
54
What is mutation?
- Sudden heritable change in a characteristic of an organism
55
What is genetic engineering?
- Introducing a gene from any source to another through transformation
56
What is artificial hybridization?
- Deliberate crossing of selected parents
| - The basis for almost all modern breeding programs
57
What are the steps of making a hybrid cross (4)?
1. 2 contrasting parents: White flowers vs Purple flower
2. Emasculation: Remove petals = expose anthers. Remove anthers before any pollen is shed
3. Pollination and seed development: Pollen from other plant is applied to pistil. If successful = F1 seed will develop
4. Exclusion of foreign pollen: Keep pollen form other source away from flowers. Cover flowers
58
What are the indirect emasculation methods?
1. Thermal inactivation: inflorescence in hot water
2. Use of alcohol: 57% ethanol
3. Chemical treatment: sodium methyl arsenate = kill anther
59
What are the main genetic issues in hybridization (5)?
1. Expression of recessive lethal gene
2. Hybrid necrosis
3. Heterosis
4. Transgressive segregation
5. Genome-plastome incompatibility
60
What are the 2 methods of crossing?
1. Divergent crossing: genetically divergent parents are crossed for recombination
2. Convergent crossing: incorporation of a specific trait into an existing cultivar without losing any of the existing desirable one
61
What is the definition of wide hybridization?
- Making crosses between species
62
What are the 5 objectives of wide crosses?
1. Alien introgression: generate material for breeding and genomic research
2. Introgression of alien genes fro economic production
3. Cloning of alien genes/QTLs
4. Creastion of new allopolyploids
5. Curiosity
63
What are the external barriers to interspecific hybridization?
1. Spatial isolation (geographical distance)
| 2. Prefeertilization reproductive barrier (isolation and incompatibility)
64
What are the internal barriers to interspecific hybridization?
1. Prevent hybrid zygotes to form: incompatibility in crosses
2. Hybrid plants is invivable, weak or sterile: due to genomic disharmony (nuclear-nuclear, nuclear-cytoplasmic…)
3. Hybrid breakdown in F2 or later: F1 good but F2 not.
65
How is it possible to overcome the barriers to interspecific hybridization (8 ways) ?
1. Sample the parental population: some plant more compatible
2. Make cross in both direction
3. Double chromosome #: in 1 or 2 parents or in a sterile plant
4. Use “bridging crosses”: to allow gene transfer between species that cannot be crossed
5. Use special emasculation/pollination techniques
6. Embryo culture on medium
7. Graft hybrid seedlings onto normal rootstock
8. Polyploidy: allopolyploid overcomes sterility by providing a pairing partner during meiosis
66
What is the main difference between hybridization and polyploidy?
- In polyploidy, we are playing with chromosome # and segments of chromosomes while in hybrids, the # of chromosomes stays the same.
67
What is the definition of BASIC chromosome number?
- Letter X
| - It is the haploid chromosome # (n)/ number of genome
68
What is the definition of HAPLOID chromosome number?
- Letter n
| - It is the total # of chromosomes/2 =n
69
What is the relationship between basic and haploid chromosome number in diploid species?
- x=n
- each somatic cell has 2n=2x chromosomes
- each gamete has n=x chromosomes
70
How do we call polyploids of 3X, 4X, 5X, 6X, 7X and 8X?
- 3X: triploid
- 4X: tetraploid
- 5X: pentaploid
- 6X: hexaploidy
- 7X: septaploid
- 8X: octoploid
71
If the polyploid has an uneven number of genome we say that the plant is…
- Sterile because the chromosomes cannot pair.
72
What is autopolyploid?
- Created by duplicating chromosomes of diploid species
- The same genome increase 3 times, 4 times, 5 times…
- Ex: AAA, AAAA, AAAAA
73
What is allopolyploid?
- Derived by combining chromosome set of 2 different diploid species.
- Doubling chromosomes of 2 species
- Ex: wheat and rye= triticale (AA + BB= AABB) **triploid not possible)
74
What are the 2 types of natural induction of polyploids?
1. Fusion of unreduced gametes: when chromosomes # is not reduced during meiosis. Gametes will have 2n chromosomes
a. Unred. F + red. M= 2n +n
b. Red. F + unred. M= n +2n
c. Unred M and F = 2n + 2n
2. Spontaneous chromosome doubling: rare
75
How artificial induction of polyploids can be made (2)?
1. Environmental shock
| 2. Chemical that disrupt chromosome division
76
What are the typical characteristics of autoploids?
1. More vegetative growth (Gigas): larger cells, thicker leaves, bigger flowers, larger plants.
2. Less seed production
77
What are the best candidates for artificial autoploidy?
- Crop harvested for their vegetative parts (forage, root, vegetable, flowers)
- Diploid with low chromosome numbers
- Cross-pollinated species (more opportunities for recombination)
78
What is the definition of amphidiploid?
- Polyploid made up of different genomes but act like diploid (A,a= 3 possible genotype: AA, Aa, aa)
79
What is the definition of autotetraploid?
- Contain 2 alleles (A, a) but 5 possible genotypes
- AAAA: quadruplex
- AAAa: triplex
- AAaa: duplex
- Aaaa: simplex
- Aaaa: nulliplex
80
What is the difference between homologous pairing and homeologous?
- Homo: with same genome AA, BB. One come from male and other female
- Homoeo: similar but not identical copies. Come from different genome. A, B, D.
81
What is the definition of haploidy in plants?
- A plant in which the somatic cells contain n chromosomes (the number that is normally found in the gametes).
82
What are the 2 methods to produce haploids?
1. Interspecific crosses: chromosome elimination
| 2. In vitro culture: anther + microspores culture, ovule culture
83
What is the difference between haploid and monoploid?
- Haploid: somatic cells with n chromosomes
- Monoploid: somatic cells with ONE set of chromosomes
- Haploid of a diploid = monoploid
- Haploid of a polyploid is NOT a monoploid
84
What is a polyhaploid?
- Haploid of a polyploid
85
What is a dihaploid?
- Haploid of a tetraploid
86
Why haploidy is of interest?
1. Reduce length of breeding program
2. Improve the selection efficiency
3. Genetic analysis
87
What is the difference between euploid and aneuploid?
- Euploid: has an exact multiple of the basic chromosome # (1x, 2x,3x…)
- Aneuploid: missing/extra chromosomes = gamete imbalance
88
What are the 4 types of aneuploid?
1. Nullisomic: 2n-2
2. Monosomic: 2n-1
3. Trisomic: 2n+1
4. Tetrasomic: 2n +2
89
What is mutation?
- Any changes that has an effect on a genotype which is hereditable
90
What is point mutation?
- It is a type of gene mutation. It is a change in one base of a gene
91
What is genomic mutation?
- It is an error in cell division (polyploidy and aneuploidy)
92
What is chromosomal mutation?
- A loss, duplication or rearrangement of chromosome segments
93
What are the 3 types of gene mutations?
1. DNA substitution mutation
2. Tautomeric shift
3. Single base addition/deletion
94
What is DNA substitution?
- Gene mutation which involve the exchange of 2 base pairs
- 2 types
o Transition: interchange of purines with purines or pyrimidine with pyrimidine
o Transversion: substitution of a purine by a pyrimidine and vice versa
95
What is tautomeric shift?
- It is a gene mutation that involve electron shift in base pair
- Change of an amino for an imino (A with A’)
96
What are the characteristics of recessive mutation?
- It is a mutation from dominant allele to recessive one.
- The individual must be homozygous recessive (aa) for the mutant allele to show the mutant phenotype.
- AA will have no mutation
- Aa will not be homogenous recessive = no mutation
- It is difficult to screen because the F1 does not have any indication of mutation
- More common than dominant
97
What are the characteristics of dominant mutation?
- It is a mutation from recessive allele to dominant one.
- A heterozygous individual carrying one mutant and one normal allele
- 3 Scenarios possible in M1 generation
o No mutation: aa
o Chimeric mutation: Aa (part is mutated and part not
o Non-chimeric mutation: Aa (can see change to dominant but only one pair is changed.
98
What are mutagens?
- Methods or product used to induced mutations
99
Give 2 types of mutagens
1. Ionizing radiation
| 2. Chemical mutagens
100
What direct the choice of mutagen (4)?
1. Type of tissue
2. Type of mutation desired
3. Availability of the mutagen
4. Safety consideration.
101
What are the changes that occurs when using ionizing radiation (6)?
1. Structural change within the gene
2. Deletion of gene or sequence
3. Chromosomal rearrangement
4. Increase/decrease in frequency of chiasmata
5. Missdivision of centromere
6. -/+ of chromosomes
102
What are the 4 types of ionizing radiation?
1. Gamma rays: cause less damages. Used in whole plants.
2. X-rays: precise control of dose. Good tissue penetration
3. Neutron: cause high rate of chromosomal aberration. Used with seeds
4. UV light: low penetration power. Used with pollen + in vitro
103
What are the advantages of chemical mutagens (3)?
1. Simple to apply
2. Less damaging than radiation
3. Produce more gene mutations and fewer chromosome disruption
104
What are the disadvantages of chemical mutagens (4)?
1. Uncertain penetration to target
2. Poor reproducibility
3. Can persist in tissue
4. Dangerous to handle
105
What are the possible changes done by induced mutation (6)?
1. New architecture of the plant
2. Earlier/later flowering time
3. Different flower/fruit color/shape
4. Resistance to pathogen/pests
5. Change in chemical composition (oil content, FA, AA, starch, proteins)
6. Reproductive characteristics (male sterility, self-incompatibility, seedlessness)
106
Expand the acronym TILLING?
- Targeting Induced Local Lesion IN Genome
107
What does TILLING involve?
- Combining chemical mutagenesis with sensitive mutation detection methods
108
What is the typical TILLING strategy (6)?
1. Soak seed in chemical
2. Have M1 and M2 plants
3. De replicated
4. Pool the DNA with PCR and primers
5. With PCR if mutation happen both strands will be different
6. Really $$$$
109
What is the new TILLING strategy (4)?
1. Do the same steps as the typical until PCR
2. Then do PCR heat-cool
3. When it cools, where there is a mutation, there will be a loop because of a nucleotide difference = cannot bind
4. The loop = Cell1
110
What are the advantages of TILLING (5)?
- Generate a wide range of mutant alleles
- Applicable to any organisms that can be chemically mutagenized
- Fast
- Automatable
- No tissue culture or transformation needed
111
What are the limitations of TILLING?
- Background noise
| - Ascertaining the resulting phenotype requires further work
112
What are transposons?
- Transposable elements
- Mobile element jumps from introduced DNA: Ac in maize, P in Drosophila
- Mobilize by introducing active element: Ac/Ds elements in plant
113
What is genome editing
- Altering the sequence of DNA in its natural environment
| - Leave no transgene footprint
114
Expand the acronym CRISPR
- Clustered Regularly Interspaced Short Palindromic Repeats
115
Why we need to understand how plant reproduce?
- Manipulation of reproduction
- Understand the inheritance of the trait and develop appropriate breeding method
- Cultivar developed will need to be propagated
116
What are the 2 modes of reproduction?
1. Sexual
a. Monoecious: M + F on same plant
b. Dioecious: M + F on separate plant
c. Hermaphroditic: M + F on same flower
2. Asexual: does not involve fusion of F + M gametes
117
What are the flower parts (4)?
1. Sepals: petal leaf
2. Petals
3. Stamen: anther and filament
4. Pistils: stigma, style, ovary, ovule
118
What describe a perfect flower?
- Stamen and pistils are in the same floral structure (bisexual)
- Ex: wheat
119
What describe imperfect flowers?
- Stamen and pistil are not in the same floral structure (unisexual)
- Ex: corn
120
What are the 2 major phenomenon that happen during sexual reproduction
- Segregation: new ALLELE combination
| - Recombination: new GENE combination
121
What are the 2 types of pollinated plant?
1. Self-pollinated
| 2. Cross-pollinated
122
What issues can happen in self-pollinated plants (4)?
1. Cleistogamy: flower may not open
2. Chasmogamy: pollen grain shed before flower opening
3. Stigma + stamen may be hidden by floral organs
4. Stigma may elongate through a staminal column after the anther open
123
What issues can happen in cross-pollinated plants (4)?
1. Mechanical obstruction to self-pollination
2. Different period of maturity of pollen and stigma
3. Self-sterility or self-incompatibility
4. Presence of imperfect flowers / dioecious flowers
124
What are the 3 types of asexual reproduction (cloning)?
1. Vegetative propagation
2. Tissue culture
3. Apomixis: Result in embryo development from an unfertilized egg. No gamete fusion. Due to a short circuit during sexual reproduction
125
What are the 2 types of fertility regulating mechanisms?
1. Self-incompatibility: plant with functional gametes unable to produce zygote after self-pollination
2. Male sterility: pollen absent or nonfunctional
126
What is the definition of self-incompatibility?
- Have all required sexual part but not able to produce zygote after self-pollination
127
What is heteromorphic self-incompatibility?
- Perfect flower but morphologically different
| - Visible difference in flower morphology
128
What is heterostyly?
- A type of heteromorphic self-incompatibility
| - Stamens and pistils vary in length
129
What are the 2 types of flower in heterostyly?
1. Thrum: long stamen + short pistils (long male, short female)
2. Pin: long pistil + short stamen (long female, short male)
130
What control heterostyly?
A gene with 3 major components
o Style length
o Pollen size
o Anther position
131
What is the difference between heteromorphic SI and homomorphic SI?
- Hetero: flowers are perfect but morphologically different.
- Homo: flowers have exactly the same structure. Avoidance of self-fertilization depends on genetic/biochemical mechanisms.
132
What is sporophytic self-incompatibility?
- A type of homomorphic SI
- Depend on the genotype of the plant producing the pollen
- Reaction controlled by S loci
- Highly polymorphic
- S1 dominate over S2 which dominate over S3…
- Need 2 completely different pollen structure to recognize and germinate. Ex: S1 and S2 on S3 and S4
- Less common tan gametophytic SI
133
What is gametophytic SI?
- A type of homomorphic SI
- Depend on the genotype of the pollen
- Reaction controlled by S loci
- Highly polymorphic
- Need one different pollen to germinate. Ex: S1+S3 on S1+S2= S3 will germinate
134
What are the 5 techniques to overcome SI?
1. Bud pollination: pollination before the stigma develops incompatibility barriers
2. Rupture of the stigma surface
3. Temperature, irradiation, electric shock, increased CO2
4. Double/mix pollination
5. Self-fertility alleles
135
What is male sterility?
- The pollen is sterile
| - Can say that the pollen is aborted
136
What are the 3 basic kinds of male sterility?
1. True male sterility: unisex flower lack male organ or bisexual flower with abnormal/non-functional microspores
2. Functional male sterility: anther fail to release their contents even if pollen is fertile
3. Induced male sterility: chemical used by plant breeders
137
What are the 2 main characteristics of flowers on male-sterile plants?
1. Cannot be self-pollinated
| 2. Can be cross-pollinated using pollen from a male-fertile plant
138
What are the use of male sterility?
- Making crosses without emasculation
- Increasing natural cross-pollination in self-pollinated crops
- Producing seed of hybrid varieties
139
Genetic male sterility is the result of
- Govern by nuclear genes under monogenic recessive gene control
140
Male-sterility caused by nuclear genes is often dominant or recessive and why?
- Recessive
| - Sometimes dominant
141
To be male sterile, recessive male-sterility alleles should be
- ms ms
| - recessive homogeneous
142
To be male sterile, dominant male-sterility alleles should be
- Ms ms
| - Dominant heterogenous
143
How breeder maintain a recessive nuclear male-sterile line in self-pollinated species (4)?
1. Pollinate the male-sterile source with pollen from a normal male-fertile plant.
2. In each generation, grow male-sterile + male-fertile progeny together, allowing the male-sterile plants to be pollinated by pollen from male-fertile progeny.
3. Harvest seed from the male-sterile plants only.
4. If the male-sterility is recessive, the ratio of sterile: fertile plants will stablilize to 1:1 after several generations. If the male-sterility is dominant, the ratio will immediately stabilize to 1:1
144
What is cytoplasmic male-sterility (Cms)?
- Govern by genes present in mitochondrial genome
145
What are the disadvantages of cytoplasmic male-sterility (4)?
1. Unstable male sterility
2. Difficulties in restoration system
3. Difficulties with seed production
4. Undesirable pleitropic effect
146
What are the 2 types of cytoplasmic male-sterility?
1. Autoplasmic: has arisen within a species as a result of spontaneous mutation in cytoplasm
2. Alloplasmic: has arisen from intergenic, interspecific or intraspecific crosses
147
What is cytoplasmic genetic male sterility (CGMS)?
- Govern by interaction between male sterility inducing cytoplasm and nuclear fertility restorer gene
148
What is the utilization of cytoplasmic genetic male sterility (CGMS)?
```
Provide a possible mechanism of pollination control = easy production of commercial quantities of hybrid seeds
Consist of
o A line: male sterile line
o B line: isogenic maintainer line
o R line: restore line (if necessary)
```
149
What are the 3 origin of male sterile cytoplasm?
1. Spontaneous: MSC arise spontaneoudly in low frequencies
2. Interspecific hybridization: transfer of the full somatic chromosome of a crop through repeated backcrossing into cytoplasm
3. Induced through ethidium bromide
150
What are the limitations of CGMS (4)?
1. Undesirable effect of cytoplasm
2. Unsatisfactory pollination + incomplete fertility restoration
3. Effect of environment
4. Contribution of cytoplasm by male parent
151
What are the chemical ways of producing male sterile plants (3)?
1. Feminizing hormones
2. Inhibitors of anther/pollen development
3. Inhibitors of pollen fertility
