Midterm Flashcards
In the 20th century, why the crop plants are selected for (8)?
- 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
In 3 points describe what is plant breeding
- 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
Why we need plant breeding?
- 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
What breeders do (6)?
- Recognize important traits + objectives
- Design ways to evaluate breeding material
- Find sources of genes
- Combine genes
- Compare new strains
- Release + distribute improved cultivars
What are the 3 oldest crops?
- Barley (oldest)
- Wheat
- Oat
What is the definition of domestication and evolution regarding plant breeding?
- Domestication: from wild to cultivated = genetic change
- Evolution: continued change in domesticated crops
What are the major changes from wild to domesticated crops (8)?
- 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
What are the evidence from plant about the origin, domestication, evolution and dispersal of crop plants?
- Living: morphology, genetic system, geodistribution
2. Non-living: archeology
What are the evidence from human about the origin, domestication, evolution and dispersal of crop plants?
- Living: language, techniques, nutrition
2. Non-living: history, archeology, anthropology
Who developed the center of origin of crops and what are they (8) ?
Nikolai Vavilov
- Mexico: center of America
- Andes, Brazil, Paraguay
- Mediterranean
- Ethiopia
- Fertile crescent
- India
- China
- South east Asia
How diversity might have arisen (4)?
- Spontaneous mutation
- Mixing of genes through hybridization
- Enhanced doses of different genomes through polyploidy
- Different crop species spread by transmigration of humans
What are the main differences between natural and artificial selection?
- Artificial: result from conscious decisions by human
2. Natural: when genetically heterogenous materials are cultivated.
What are the 5 levels of domestication?
- 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)
What are the 3 main factors contributing to increased food production?
- High yield variety
- Increase in crop area
- Better inputs and management practices
What is the progeny test?
- 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.
What are the goals of the progeny test?
- 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
Who has developed the progeny test?
- Louis de-Vilmorin
What is Mendel’s law of heredity?
- 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.
What is a test cross?
- a cross between an unknown and the homozygous recessive.
What is a back cross?
- is a cross between a hybrid and one of its parents
Why backcross is used by breeders?
- to incorporate a desirable gene into a variety lacking that character.
- Fast method for trait Incorporation
- Requires only observation of trait under selection
What are the 3 variation in Mendelian genetic ratios?
- Epistatic gene interaction
- Pleiotropy
- Linkage
What is Epistatic gene interaction?
- The effect of a gene mutation is dependent on the presence or absence of mutations in one or more other genes
What is pleiotropy?
- The phenomenon of a single major gene affecting more than one character
What is linkage?
- Genes often show a tendency to be Inherited together and do not show Independent segregation
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.
What is crossing-over?
- A process by which segments of chromatids of homologous chromosomes are exchanged as they synapse during meiosis.
Who is the father of the Green Revolution?
- Norman Borlaug
What Norman Borlaug developed during the Green Revolution?
- Semi dwarf wheat in 1905
What are the main characteristics of conventional breeding approach?
- It takes 10-17 years to see results
2. Problems can be caused by environmental factors = decrease efficacy of breeding method
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
What are the 3 modern plant breeding techniques?
- Tissue + cell culture + micropropagation: facilitate to make inter-specific crosses, instant homozygous, disease free.
- Molecular biology : Marker assisted selection (MAS) by developing different types of molecular markers
- Genetically modified technology: crop improvement, drought tolerant, desirable fruit ripening
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.
What are the sources of germplasm (6)?
- Domesticated cultivars
- Breeding material
- Landraces
- Plant introductions
- Genetic stocks
- Undomesticated plants
What are the germplasm materials (6)?
- New and old cultivars
- Landraces
- Selected materials from breeding programs
- Special genetic stocks (e.g., mutant lines)
- Wild populations of the crop’s species
- Related species
What is “crop gene pool”?
- Set of all genes or genetic information, in any population, usually of a particular species
What plant introduction means?
- The transport of seeds/plants from one production area to another
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.
What are the 2 agencies of Quarantine talked in class?
- CFIA: Canadian food Inspection Agency
2. APHIS: Animal and Plant Health Inspection Service
What is the definition of genetic vulnerability?
- Genetic homogeneity and uniformity of a group of plant that predisposes them to biotic/abiotic hazard.
What are the threats to plant germplasm resources (5)?
- Monoculture
- Changes production practices
- Population pressure, including urbanization
- Overgrazing
- Environmental degradation-foods, drought and wild fires
What are the main causes of genetic variation (4)?
- Natural factors
- Action of crop producers + public
- Actions of breeders
- Problems in germplasm conservation
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
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
What does “in vitro conservation of plant genetic resources” means?
- Cloned DNA representing all genes or specific targeted genes
What are the 3 main methods of maintenance of plants?
- Stored seeds
- Seedlings
- Clonal plants
What types of plants are maintained through seed storage?
- Annual, biennial and few perennials
- Maize, beet, wheat, rice
What types of plants are maintained through seedlings?
- Perennial which can be stored only as long-lived plantations
- Oil palm, coconut
What types of plants are maintained through clonal plants?
- Perennials which can be stored only as clones
- Banana, grapes, fruits
Give 2 types of storage of plant material
- Cryostorage system: seeds in liquid nitrogen
2. In vitro gene banks: sterile meristem or regenerable tissue/cell culture
What are the challenges of seedbanks (3) ?
- High number of recalcitrant species in the wild cannot be preserved in seed bank = hard to conserve
- Lack of funding and resources
- Lack of comprehensive data and limited information
What is the definition of hybridization?
- Combining 2 dissimilar genotypes via crossing
What is the definition of polyploidy?
- Assembling +2 copies of same/different genome
What is mutation?
- Sudden heritable change in a characteristic of an organism
What is genetic engineering?
- Introducing a gene from any source to another through transformation
What is artificial hybridization?
- Deliberate crossing of selected parents
- The basis for almost all modern breeding programs
What are the steps of making a hybrid cross (4)?
- 2 contrasting parents: White flowers vs Purple flower
- Emasculation: Remove petals = expose anthers. Remove anthers before any pollen is shed
- Pollination and seed development: Pollen from other plant is applied to pistil. If successful = F1 seed will develop
- Exclusion of foreign pollen: Keep pollen form other source away from flowers. Cover flowers
What are the indirect emasculation methods?
- Thermal inactivation: inflorescence in hot water
- Use of alcohol: 57% ethanol
- Chemical treatment: sodium methyl arsenate = kill anther
What are the main genetic issues in hybridization (5)?
- Expression of recessive lethal gene
- Hybrid necrosis
- Heterosis
- Transgressive segregation
- Genome-plastome incompatibility
What are the 2 methods of crossing?
- Divergent crossing: genetically divergent parents are crossed for recombination
- Convergent crossing: incorporation of a specific trait into an existing cultivar without losing any of the existing desirable one