From out of old fields comes all this new corn:

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Plant breeding and genetics
Floral Biology
Stigma Ovary Nectaries Anthers Petals
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Mendelian Heredity

• Mendels first law- segregation- is a direct
  result of separation of homologues into opposite
  cells during the first meiotic division
• Mendels second law- independent assortment-
  results from the independent behavior of separate
  pairs of homologous chromosomes

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Mendelian Heredity
B
A
PAIRING SEGREGATION INDEPENDENT
ASSORTMENT
b
a
B
A
b
a
b

B
A
A
B
a
a
b
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What is genotype of F1? How will it segregate in
the F2 generation?
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X
Green, round yy RR
Yellow, wrinkled YY rr
What are the genotypes and phenotypes of the F1
and F2 generations?
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Mendelian Heredity

• Results from pea crosses where parents differ for
  1 character
• First law segregation
• Parent phenotype F1 F2 F2 Ratio
• Round/wrinkled round 54741850 2.961
• Yellow/green yellow 6022-2001 3.011
• Purple/white purple 705224 3.151
• Inflated/pinched inflated 882299 2.951
• Axial/terminal axial 651207 3.141
• Long/short long 787277 2.841

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Inbreeding

• Inbreeding is due to mating of individuals that
  are more closely related through common ancestry
  than are individuals taken at random from the
  population.
• The extreme expression of this is selfing

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Outcrossing

• Random mating promotes diversity
• Heterozygosity
• Extreme example is F1 hybrids (Aa)

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Self-Incompatibility
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• Found in many species, including Brassica spp.
• Multiallelic S locus (gt 60 alleles!)
• All pollen from a plant has same incompatible
  reaction

S1S3
S1S3
S1S3
NO
NO
S2S4
S1S2
S2S3
Incompatible Incompatible
Compatible
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Male Sterility Systems

• Genic
• Nuclear gene conditions sterility
• Sterility usually recessive, often msms
• Cytoplasmic
• Non-nuclear genes responsible for sterility
• Pollen parent has no influence on fertility or
  sterility
• Not useful for seed crops
• Cytoplasmic-Genic
• Non-nuclear genes cause sterility, nuclear
  restores fertility
• Two-gene system required for sterility /
  fertility
• Useful for seed-propagated crops

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Inheritance of Male Sterility
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• Genic
• msms sterile
• msms X MsMs
• Msms X Msms
• msms X Msms
• Cytoplasmic
• S X F
• Cytoplasmic-Genic
• Smsms sterile
• NMSMS fertile
• Nmsms fertile
• SMsms fertile

All Msms 100 fertile 31 segregation 25
sterile 11 segregation 50 fertile
All progeny sterile due to maternal inheritance
Only Smsms conditions sterility Fertility with
either N cytoplasm or dominant Alleles at nuclear
restorer locus (Ms)
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Use of Genic Male Sterility
Fertile parent MsMs msms x MsMs Msms
Segregate 31, 25 sterile PROBLEM IS - HOW DO
YOU IDENTIFY and maintain msms steriles ?
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Use of Cytoplasmic Male Sterility

• Must use sterile as female parent,
• all progeny are sterile
• S X F
• S

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Use of Cytoplasmic-Genic Sterility

• Inheritance of CMS system
• Smsms x Nmsms Smsms only, all
  sterile
• Smsms x NMsMs SMsms only, all
  fertile
• SMsms x NMsms 1 Smsms sterile
• 2 SMsms fertile
• 1 SMsMs fertile

msms
msms
S
F
S
N
F
Ms-
Ms-
F
S
N
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Variation in ploidy

• General concepts
• Genome is basic unit of chromosomal makeup
• Chromosomes of a genome inherited together in a
  normal meiosis and mitosis
• Chromosome number of the gametophyte is n
• Chromosome number of the sporophyte is 2n
• Base number of chromosomes (one of each pair)
  is x
• If 2n2x22, gametes are nx11 (diploid)
• If 2n4x44, gametes are n2x22 (autotetraploid)
• In a monoploid, 2nx11
• In a triploid, 2n3x33

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Ploidy Configuration
Haploid 1x
Diploid 2x
Tetraploid 4x
Triploid 3x
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Autoploidy

• Monoploid A
• Diploid AA
• Triploid AAA
• Tetraploid AAAA
• Pentaploid AAAAA
• Hexaploid AAAAAA
• Duplication 2n2x...........2n4x

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Genetics of Autoploidy

• Autotetraploid 5 different genotypes
• Gametes are 2x
• Nulliplex aaaa
• Simplex Aaaa
• Duplex AAaa
• Triplex AAAa
• Quadriplex AAAA

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Banana

• Banana typically autotriploid and sterile
• Low fertility is desired to make a seedless
  banana
• Fruit is produced parthenocarpically

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Allopolyploidy

• Typical diploid inheritance patterns because of
  lack of pairing of chromosome sets
• Possibility of multiple alleles in different
  genomes
• Can result in unique nuclear-cytoplasmic
  interactions
• Case of cotton demonstrates value of D genome to
  cultivated types despite poor performance of D
  genome per se
• Dihaploid AB
• Allotriploid ABC, AAB, ABB
• Allotetraploid AABB
• Allopentaploid AABBC
• Allohexaploid AABBCC

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allopolyploidy
A B D
Separate genomes come together, but each Genome
has normal diploid pairing and segregation
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Triangle of U
B. rapa n10 AA
B. juncea n18 AABB
B. napus n19 AACC
B. oleracea n9 CC
B. nigra n8 BB
B. carinata n17 BBCC
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Brassciaoleracea and rapa
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Quantitative inheritance
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• Quantitative traits
• Continuos variation (normal distributions)
• Often characterized as being affected by many
  genes expression of which is modified by the
  environment
• Qualitative traits
• Often single gene Mendelian traits
• Segregate into discrete classes

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Distribution of Quantitative trait(s)
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Mean Variance covariance
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Pedigree selectionHow to do it
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• Pedigree, as the name implies, provides a record
  of the lines of descent of all individuals in
  each generation.
• The accumulation of information is important when
  decisions need to be made regarding keeping or
  eliminating a line.

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Yellow butternut
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Requirements
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Pedigree selection

• Two parents
• Choice of parents is critical, as you invest a
  lot of time and resources in each pedigree popn
• Complementary in strengths and weaknesses
• AAbb x aaBB

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Implementation
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Pedigree selection

• P1 AAbb x P2 aaBB
• F1 AaBb
• F2 (9 genotypic classes) 3n
• A_B_ AAB_ A_BB aabb
• F? (4 genotypic classes) 2n
• AABB AAbb aaBB aabb

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Implementation
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Pedigree selection

• Self pollinate each F2 plant, and grow out F3
  families. Self pollinate selected plants.
• Select among and within families in early
  generations

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F2 plants 1/4 1/2 1/4
BB Bb bb
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Pedigree selection
Individuals

• BB BB BB bb
• BB Bb Bb bb
• BB Bb Bb bb
• BB bb bb bb

F3 Families
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Pedigree selection
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Outline
F1
Select among
F2 individuals
F3 Families
Select among and within
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Features of Pedigree selection
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• After inbreeding and testing lines can be bulked
  and released as cultivars.
• Its fun and flexible
• When a superior family is identified, you can
  trace back in the pedigree and select in earlier
  generations

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Negative features
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• Maximum productivity is established in F2
  generations.
• From AaBbCcdd cannot select AABBCCDD
• Minimum recombination
• No opportunities to cross
• aabbCCDD x AABBccdd