plant breeding revised
TRANSCRIPT
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8/6/2019 Plant Breeding Revised
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Plant Breeding
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Reproduction
Definition
Sequence of events involved in themultiplication & perpetuation of cells and
organisms. Types
Sexual - the increase of plants through seedformed from the union of male and female
gametesAsexual - the increase of plants through ordinary
cell division and differentiation
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Genetics
Basics of heredity
Gregor Mendel
1860s: traits
controlled by genes Qualtitative traits
single gene
Quantative traits
multiple genes Genome
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8/6/2019 Plant Breeding Revised
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Genetics
Basics of heredity
Chromosome - structural units in the nucleuswhich carry the genes in linear order Made of DNA - deoxyribonucleic acid
Gene - the unit of inheritance determines the sequence of a given protein
Protein made by reading RNA - ribonucleic acid
messenger - mRNA
transfer - tRNA
ribosomal - rRNA
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8/6/2019 Plant Breeding Revised
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8/6/2019 Plant Breeding Revised
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Genetics
Definitions
Allele alternate form of gene
Homozygous Alleles for trait are identical
Heterozygous Alleles for trait are not
identical
Genotype Organisms genetic
constitution Phenotype - Outward expression of the
genotype
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8/6/2019 Plant Breeding Revised
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Genetics
Definitions
Dominant gene - When genes areheterozygous for a certain trait, one isexpressed
Recessive gene - When genes areheterozygous for a certain trait, one is notexpressed
Complete dominance: the dominant gene isthe only one expressed
Incomplete dominance: both genes play intothe phenotype, intermediate phenotype
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8/6/2019 Plant Breeding Revised
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8/6/2019 Plant Breeding Revised
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Given: A= Red flowers; a= White flowers
Complete Dominance
Parents: AA x aa
Genotypic
Ratio
Aa- All
Phenotypic Ratio
Red- All
Parents: Aa x Aa
Genotypic RatioAA- 1
Aa- 2
aa- 1
PhenotypicR
atioRed- 3
White- 1
Parents: Aa x aa
Genotypic
Ratio
Aa- 2= 1
aa- 2= 1
Phenotypic Ratio
Red- 1
White- 1
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8/6/2019 Plant Breeding Revised
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Given: AA= Red flowers; Aa= Pink flowers; aa= White flowers
Incomplete Dominance
Parents: AA x aa
Genotypic Ratio
Aa- All
Phenotypic Ratio
Pink- All
Parents: Aa x Aa
Genotypic
Ratio
AA- 1
Aa- 2
aa- 1
Phenotypic Ratio
Red- 1
Pink- 2
White- 1
Parents: Aa x aa
Genotypic Ratio
Aa- 2= 1
aa- 2= 1
Phenotypic Ratio
Pink- 1
White- 1
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8/6/2019 Plant Breeding Revised
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Types of cell division
Mitosis
One cell divides into two cells and those two
daughter cells will each have bothchromosomes
Meiosis
One cell divides into two cells that both have
the full set. Then, each daughter cell willsplit into two cells, which will only have half
of the chromosome pair.
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8/6/2019 Plant Breeding Revised
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Definitions
Gamete - Sex cell or nuclei (egg cell or sperm nuclei)produced during meiosis
Self pollination - Transfer of pollen from the male
structure to the female structure of a flower on the
same plant Cross pollination - Transfer of pollen between flowers
on different plants (plants must differ genetically)
Fertilization - The actual union of male and female
gametes Hybrid - The first generation offspring of a cross
between two individuals differing on one or more
genes
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Crop Improvement: Objective
To improve a certain trait in a species or toincorporate into or delete from a species acertain trait Increased productivity
Increased quality Ability to improve crop based on two
assumptions: Genetic variations exists
Adapted cultivars, breeder stock, wild plants,mutations, previously crossed plants, andintroductions from other parts of the world
Techniques exist for getting a favorablecombination of genes
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8/6/2019 Plant Breeding Revised
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Methods with self-pollinating crops
Crops
Cotton, barley, sorghum, soybean, and
peanut
Crossing followed by selection
Pedigree Selection
Mass Selection
Backcross Method
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8/6/2019 Plant Breeding Revised
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Methods with cross-pollinating crops
Crops
Alfalfa, corn, and fescue
Crossing followed by selection Pedigree selection
Mass selection
Backcross method Hybrid breeding
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8/6/2019 Plant Breeding Revised
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Hybrid Production
Production of heterozygous populations
from the crossing of homozygous lines
Mostly used for cross-pollinated crops The hybrid seed must be reproduced each
year
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8/6/2019 Plant Breeding Revised
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Hybrid Production
Steps involved
Produce inbred lines
Cross the inbred lines
Single cross hybrid
Harvest the female rows because they have the hybrid
seed
Double cross hybrid
Three way cross hybrid
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8/6/2019 Plant Breeding Revised
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Weaknesses
Many years to provide a commercially
marketable seed.
Crossing can only occur within the same
species, and often selection is inefficientbecause it depends primarily on phenotypes.
Finding the desirable trait takes large numbers
of crosses so space can be a premium.