Transcript Slide 1

Breeding Vegetables for
Optimum Levels of
Phytochemicals
Kevin Crosby
Texas A&M University
Plant Breeding
• Application of genetic theory, including
molecular biology to develop improved
plant cultivars
• Vegetables are high priority crops in Texas
and USA- numerous cultivars from diverse
breeding programs; $15 billion in USA
Definitions
A. ANY HUMAN HANDLING OF PLANTS WHICH GENETICALLY
ADAPTS THEM TO THE SERVICE OF MEN.
B. THE ART OF SELECTION BASED UPON THE SCIENCE OF
GENETICS.
C. EVOLUTION DIRECTED BY THE WILL OF MAN. (Vavilov, 1935)
Wild Types vs. Improved
Foods for Health
• Elevated levels of flavonoids, carotenoids,
ascorbic acid, minerals, pectins
• Traditional plant breeding- exploitation of
naturally occurring genes in the germplasm
• Gene mapping and genetic transformationincreased Ca, vitamin C, β-carotene
Pepper Phytochemicals
• Peppers are good source of important human
health related compounds
• Carotenoids, flavonoids, ascorbic acid,
capsaicin
• Great genetic variation within pepper
germplasm & at different maturity stages
Dietary Fiber in ½ cup Serving
Green Peppers- raw
2.4
Hot Red Peppers19.2
raw
Hot Red Peppers57.6
dried
Pinto Beans- cooked 9.4
Prunes- dried
3.8
Tomatoes- raw
1.4
Spinach- cooked
7.0
Squash- cooked
3.0
a
15
8
36
lla
Variety
Se
rra
no
SS
87
0
88
0
es
i
SS
M
Ja
la
pe
no
Ja
lo
ro
Pa
pr
ik
B
mg/100 g
Pepper Vitamin C
700
600
500
400
300
200
100
0
S
Screening Germplasm
• Planted 60 diverse pepper lines at
Weslaco and Uvalde
• Harvested green and red mature fruit
• Analyzed Vit C by HPLC for replicated
samples
High Vitamin C
• Peproncinis- high at all locations, 557
ppm (green) to 2377 ppm (red)
• Pasilla, Anaheim, Marconi and Ancho
also very high at red stage- 1900-2280
ppm
• TAM B36- Tropic Bell, highest at green
stage: 600 ppm= 60 mg/100g
TAM Pasilla VR
Cultivar: B 36 (GR-RD)
Vitamin C: 1758-2082 ppm
Flavonoid: 6-13 ppm
High β-carotene
• Highest in red chile/paprika- C127
(2330 µg/100g) 38% RDA, Fidel
orange chile (2366)
• Almost none in many wax and hot types
• TMJ2 (1242 µg/100g) > Grande (850)
Cultivar: C 127
Vitamin C: 1721 ppm
Flavonoid: 45 ppm
Beta-Carotene: 23.3 ppm
Habanero β-carotene
TAM Mild- 760 µg/100g
Yucatan- 20 µg/100g
Fresh fruit vitamin C and beta-carotene contents of melons from Weslaco
Cultivar/line
Vitamin C
(mg·100g-1)x
-carotene
(µg·g-1)x
Fruit type
TAM Perlita 45
21.7 az
62.2 az
Western shipper- size 15y
TAM Uvalde
15.2 b
57.5 ab
Western shipper- size 18
Explorer
12.4 bc
45.0
cde
Western shipper- size 15
Cruiser
12.1 bc
36.3
e
Western shipper- size 12
Mission
11.9 bc
40.3
de
Western shipper- size 15
Green Ice
11.8 bc
4.70
f
Honeydew- size 15
TAM Mayan
11.2 bcd
11.5
f
Casaba- size 12
Gold Mark
10.8 bcd
41.4
TXC 2015
10.0 bcd
49.8
HMX 9583
9.4
cd
46.0
cd
Western shipper- size 12
Valley Gold
9.3
cd
48.5
bcd
Western shipper- size 12
Mainpak
9.2
cd
43.5
cde
Western shipper- size 12
Pronto
8.0
cd
43.0
cde
Western shipper- size 12
TAM Dew Impr.
7.2
cd
4.70
Primo
7.0
cd
56.7 ab
zMean
cde
Western shipper- size 12
bc
Western shipper- size 12
f
Honeydew- size 12
Western shipper- size 12
separations by LSD, P ≤ 0.05. Values followed by the same letter are not significantly different.
based on number of fruit which fit into a standard melon packing box.
xBased on fresh weight.
ySizes
Selection Process
• Choose the best parents for target traits
• Controlled pollinations to create new families
• Selection for traits by combined quality
analyses- field and lab
• Backcrossing or inbreeding to fix key genes
Controlled Pollination
Developing a New Melon
• Industry wants larger cantaloupes with
good flavor and disease resistance
• We had excellent flavor, disease
resistance, Vit C, carotene in TAM Uvalde
• So we crossed it with ‘Cruiser’ (very large,
high yield but poor flavor, carotenoids)
‘Chujuc’ Muskmelon
• Large, round fruit, Sz
9-12
• High yield and
resistant to PM
• High in beta-carotene
Vitamin C, sugars
Genetic Linkage Mapping
• Develop population which segregates for
gene(s) of interest
• Carefully measure phenotype of trait for
each plant and parents
• Screen DNA for molecular markers which
are linked to the trait (gene)
DNA Marker Linkage
1
2
3
4
5
-1500 bp
OAC09.900
-600 bp
RAPD marker OAC09.900 expressing polymorphism between
two DNA bulks from high and low beta-carotene F2 plants. 1 =
Sunrise (low parent), 2 = TAM Uvalde (high parent), 3 = DNA bulk
from low beta-carotene F2 plants, 4 = DNA bulk from high betacarotene F2 plants, and 5 = a 100-bp DNA marker ladder.
1
2 3
4 5
-1500bp
OAU02.600
-600bp
-300bp
Figure 5. RAPD marker OAU02.600 expressing polymorphism between two
DNA bulks from high and low ascorbic acid F2 plants, and between ‘Dulce’
and TGR1551. 1=’Dulce’, 2=TGR1551, 3=DNA bulk from high ascorbic
acid F2 plants, 4=DNA bulk from low ascorbic acid F2 plants, and
5=molecular size marker.
Molecular Markers in Pepper
• Family of high flavonoid CA377 x high
vitamin C B22
• F2 progeny, F1 progeny, Parents grown in
two environments for mature fruit
• Screening with RAPD markers in bulks
and genotyping each F2 progeny
• Constructing genetic linkage map
High Antioxidant Parents
TAES B22
CA 377
F1 Hybrid
1
OL07.2050
OL07.1700
OL07.1500
2
3 4 5
6 7
8 9 10 11 12 13 14 15 16 17 18 19 20 M
-2072bp
-1500bp
OL07.1100
OL07.800
OL07.520
OL07.480
-600bp
-300bp
Fig. 1. Segregation of seven RAPD markers in an F2 population derived
from the pepper cross of CA 377 x B 22. 1 to 20=F2 plants of the CA 377 x
B 22 cross and M=a 100-bp DNA marker ladder.
Current Progress
Flavor is Crucial
• Many people complain about tomatoes
• Long shelf life and green harvested fruit
just do not taste very good
• Enhancing fresh market consumption and
profitability for growers requires change
New Breeding Priorities
• Screen germplasm for best tasting tomato
cultivars, lines, landraces
• Cross with TAMU heat-tolerant, disease
resistant, high yielding breeding lines
• Developed better tasting, adapted cultivars
Improved Heirloom Types
Introgressed virus, fusarium and
heat resistance genes; developed
more compact plants adapted to
staked culture
Flavor Trumps Appearance
Why Vegetable Genetics?
• Vegetables are excellent source of key
human health related phytochemicals
• $15 billion component of US agriculture
• Not all cultivars are equal- flavor and
appearance are also crucial