This document discusses the use of genetic markers for peach breeding. It outlines using markers to characterize parent plants, validate pedigrees, and assist in seedling selection. Specific markers are available for traits like fruit shape, acidity, and flesh color. The workflow involves determining if markers exist for a target trait, developing new markers if needed, and validating markers before using them in marker-assisted selection. An example is given of a peach breeding program that demonstrated the accuracy of markers for fruit shape and acidity, and now uses markers to select 66% of seedlings.

1. MARKERS FOR
PEACH BREEDING
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2. 1. PARENT CHARACTERIZATION AND SELECTION
•
•
•
Relationships between parents
Cross planning
 Genetic distances
 Heterozygosity
Breeder’s rights enforcement
2. SEEDLING MARKER-ASSISTED SELECTION
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3. MARKER (SSR) FINGERPRINTING FOR
BREEDER’S RIGHTS PROTECTION
251
261
280
280
246
280
251
246
261
261
189 196
139
139
189 196
189 196
196
189 196
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135
148
148
148
139
135 139
148

4. PEDIGREE VALIDATION
167
P1
P2
141
178
183
147
189
178 183
141
H-A
178
H-B
189
125
141
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147
147
129
131
125 131
125
131

5. SELECTING PARENTS FOR A CROSS: GENETIC DISTANCE
The DENDROGRAM
Clusters group genetically
similar parents
Do my pedigree data fit?
Do I need more variability?
Do I want to have a fixed
background where only a few
traits segregate?

6. SELECTING PARENTS FOR A CROSS: HETEROZYGOSITY
% Heterozygosity
0
10
20
30
40
50
60
More heterozygosity in the parents  More segregation in their progeny

7. MARKER-ASSISTED SELECTION
G
M1
M2
APPROPRIATE USE OF MARKERS REQUIRES DETAILED
KNOWLEDGE OF THE PARENTS OF EACH BREEDING PROGRAM
0-5 cM
LINKED MARKERS: Require validation in a progeny (phase
knowledge)
DIAGNOSTIC MARKERS: Presence of certain alleles predict
corresponding phenotypes
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8. a
t
D
h
ncia
ell
H
RINE
g
PEACH MAJOR GENES used for Marker-
Assisted Selection (MAS)
Male sterility
Acidity
Peach/Nectarine
Pubescencia
de la pell
MELTING
NECTARINE
Color de la
polpa
Consistencia
de la polpa
PEACH
Flesh color
NON-MELTING
WHITE
YELLOW
G/g
Y/y
Forma
del fruit
Flesh texture
Consistencia
de la polpa
M/m
Fruit shape
Pubescencia
de la pell
Consistencia
de la polpa
Forma
del fruit
PEACH
MELTING
ROUND
NECTARINE
Color de la
polpa
NON-MELTING
Color de
polpa
MD
MELTING
ROUND
WHITE
WHITE
Maturity date
NON-MELTING
NON-MELTING
M/m
F/f
FLAT
Sh/sh
YELLOW
Y/y
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G/g
M/m
FLAT
Sh/sh
YELLOW
Y/y

9. Marker Assisted Breeding (MAB) workflow
- ARE THERE MARKERS AVAILABLE FOR THE TRAIT?
YES
NO
(Ex: acidity, flat shape…)
(Ex: pistilar closing…)
Use the marker or saturate the region in a
segregating population to find a better marker
Find or develop a segregating population
and construct a genetic map and look for
the position of MAJOR GENES or QTLs
Prunus reference map (Dirlewanger et al. 2004, PNAs 101(26):9891-9896)
validate markers in germplasm collection
Peach genome
(www.rosaceae.org)
MAS
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10. INTRODUCTION of MAB in the IRTA
BREEDING PROGRAM
1st STEP: DEMONSTRATION: plants in the field phenotype known
or that could be determined
# plants analyzed by fruit
shape
# plants analyzed by acidity
Years
1,311
1,349
2010-2012
Less than 5 % of errors in phenotype predictions
with either marker
2nd STEP: SEEDLING SELECTION: selection in the greenhouse
# plants
analyzed by fruit shape
# plants
analyzed by acidity
Years
1,245
1,502
2012-2013
66% of the seedlings of the program in 2013 were selected with markers:
All except small progenies and fixed progenies
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11. THANK YOU
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