Download Sweet Corn Genetics

Kevin Hosey
Choosing Sweet Corn is an art….
Growers have to balance these needs:
•Maturity – spreading out your harvest
•Ability to germinate in cold soil
•Strong vigorous plant
•Easy to pick
•Yield
•Attractive and the right size for the market
•Flavor
•Holding quality in the field and in storage
•Disease & Insect resistance
And a science…
3 MAIN TYPES
pluses
minuses
SU – standard sugary
“old-fashioned” sweet
corn
•Starchier corn is better
for soups and stews
•Loses sugar hours after
harvest
•No new breeding
SE- sugary enhanced
a gene that raises the
sugar content above SU
while retaining the
tender & creamy
texture
•Corn flavor
•Generally good texture
•Many with excellent
cold soil germination
•A gradual decline in
post-harvest quality
over a few days
Sh2- supersweet – more
sugar, and more
perceived sugar.
The sh2 gene blocks the
conversion of sugar to
starch
•Very Sweet
•Keeps in the field and
post-harvest
•Needs to be isolated
from other types of corn
by 50 – 150 feet or 14
day difference in
maturity.
•Tenderness varies
•Most are not for the
coldest soil- requires 60°
(Mirai corn was hard to
germinate)
Most new varieties of SE corn are “Synergistic”.
SE- sugary
enhanced
What it is
What it does
Se
Heterozygous
one parent has the SE
gene, the other is SU
Somewhat sweeter with extra
vigor for early seeding
Se
Homozygous
both parents have the SE
gene
Increases the sugar level over
that of SE corn while retaining
tenderness
Synergistic
One parents has the SE
gene . The other parent is
the result of a cross with
sugary & Sh2 parents.
Sweet and tender with no loss of
seed/plant vigor from the sh2
parent
Allure – nice new
synergistic variety
This would be a good time to detour into “Brands” which would be series of
varieties, grouped by the breeder, based on one or more characteristics.
Brands
Varieties
What it does
TripleSweet
Providence A unique type that uses the “Brittle Gene”
BC 0805
instead of the Sh2 gene but is otherwise similar
to synergistic.
TripleSweet Plus Primus
A double-dose of Synergistic. One parent is
Sugary/ Brittle, the other is Sugary/ Sh2
Attribute –
GE both
TripleSweet &
Sh2 types
BC 0822
BC 0805
Provides control for European Corn Borer, Corn
Earworm
Performance –
GE both SE
and Sh2 types
Temptation II
Xtra Tender –
all varieties are
Sh2
2171
2573
Vision
Provides control for European Corn Borer,
Obsession II Corn Earworm, Fall Armyworm, Western &
SV 90105A
Northern Corn Rootworm larva, Corn stalk
borer and several others. Tolerant to Roundup
Weather MAX & PowerMAX
Improved over the original Sh2 by being more
tender. The first generation Sh2 was chewy.
The tenderness is achieved using a variety of
different traditional breeding techniques.
SE corn
early maturity with good cold soil vigor
CUPPA JOE
•72 days, for your earliest seeding.
•Slightly better than Temptation in appearance,
plant height and ear height, flavor, and disease
resistance. Similar ability to germinate in cold
soil and plant vigor.
•Nice big plant 5½ - 6’ with 18” ear height
•8” ear with medium-green husk and good tip
cover
•Handles heat
•IR: Common rust, Stewart’s Wilt
TEMPTATION II
Cuppa Joe
(the person in this photo
is over 6 feet tall).
•72 days
• Performance Series – insect protection and
Roundup tolerant
•Very good cold soil germination
•Smaller ear – 7” - 7½” with dark green husk and good cover
•Plant is tall for maturity group at 6’
SE synergistic, main season maturity
ALLURE
• 75 days, with excellent seed
vigor for early seeding
• replacing Kristine – Stronger
plant
•Attractive large ear 8” – 8½” with
dark green husk and good cover
•Sturdy plant is 6½’ with a 20” ear
height
•Very good flavor, sweet
•IR: Stewart’s Wilt
KA-CHING
•78 days, grower friendly with good
flavor
•Very large 9” ear
•Husk is medium green with the excellent
cover needed later in the season.
•Tall, clean 8’ plant. And 32” ear height
•IR: Stewart’s Wilt, Rust, NCLB
Sh2 Supersweet early to main maturity
2171 Xtra Tender 71 days
• If you need to plant in cold soil
(60 degrees) this is a good choice.
•Good eating with early maturity
•Blocky ears
•Downside is longer shank and not
much flag leaf
XTH 20173 73 days
• 2573 with added rust resistance.
• Vision has set the standard for
flavor in recent years. 20173 and
2573 are the bi-color counterpart.
For those looking for the best
possible flavor.
• Only “Fair” in cool soil.
• It’s not usually a problem but this
“Vision-quality” series has plants
with “brittle roots”. They root deep,
but break easier than a really sturdy
rooted variety like Obsession.
• HR: Rs, RpGDJ IR: Bm Pst
Sh2 Supersweet main season maturity
AWESOME XR
•
•
•
•
•
•
74 days
Our top selling Awesome with
added rust resistance.
Very good flavor and tenderness,
but not so tender that it can’t be
used for shipping.
Dark green husk with tight cover.
The rust resistance makes for a
slightly more vigorous plant.
Very easy snap.
HR: Ps, RpGDJ IR: Pst
XTH 2674 74 days
• Rust resistant version of 274A
limited seed available in 2013
• Improved plant vigor
• Large, 8.5” ears
• Improved tip fill
• Tip cover may not be as good as
274A
• HR: Ps, RPGDJ
Sh2 Supersweet main & late season maturity
Stellar 76 days.
•Awesome tastes very good but Stellar can
be even better and has a bigger ear
•Ear cover is better than Obsession and
husk less likely to burn up.
•Strong plant
•If not planted densely, shanks can be big.
•HR: Pst IR: Ps
OBSESSION II 78 day.
• Performance Series version of popular
• Obsession – great plant, very good flavor
and appearance and disease resistance
• Grower comment “I was the envy of my
Hollow” with no weeds
• Nice big ears and easy to pick
(Obsession is easy to pick, but even
easier without the weeds)
• Great yields
• R: PS IR: ET, Pst
Sh2 Supersweet late season maturity
SV 90105A
•
•
•
•
80 day,
Performance Series version of
“7143” (EX08767143)
Resembles Obsession with
added rust resistance – this
makes it a good choice to
wrap up your season when
insect & rust pressure is high
Vigorous plant handles stress
well
IR: Bm, Et, Ps-Rp1-d, Ps-RpG
7143 in photo
A note on Rust Resistance – there are many strains of rust and each
strain can have its own gene conveying resistance. When a race is
specified the resistance is linked to a given gene. Polygenic rust
resistance means that several genes are working together, providing
a broader resistance, but not necessarily as complete a resistance to
a named strain. This is often described as “good field tolerance”.
Synergy, a synergistic corn, is an example of polygenic resistance.
Sh2 seed on left– note the
shrunken-ness
Synergistic
seed on right
The evolution toward tender sh2 corn that also germinates well.
The first supersweet, Florida Staysweet, was bred in the 1970’s. The
original breeding was for shipping. As you can imagine, for corn that
would be consumed a week after harvest, even a tough pericarp
(skin) would be better than a week old “Butter & Sugar”.
Crookham & IFS shared in the original inbreds. The early supersweets had
inherently poor germination and vigor. 50% stands were to be expected.
Although a tender pericarp was achieved by different paths in
traditional breeding, all genes link back to the same modifier genes
that have made SE corn tender for a few generations. What this means
is that sugary x shrunken parents were used in breeding for tenderness.
By the early 2000’s this resulted in very good eating quality, with the
Mirai series as an example. Cold soil germination and plant vigor for
sh2 corn went from bad to worse as eating quality improved.
277A introduced around 2001 was the first variety that combined good
growing characteristics with very good flavor and tenderness.
Since then, with Awesome as a good example, supersweets now combine
good cool soil germination and vigor with exceptional eating quality.
SE program
pluses
considerations
alternatives
First Seeding
Cold soil
Cuppa
Joe
72 days
Great in cold soil
Good flavor
Good plant
Better than other early
corn in flavor but still not
great
Tried & True: Temptation
Roundup-Ready, insect
protected: Temptation II
Early Main
Season from
early seeding
Allure
75 days
Very good in cold soil
Very good flavor
Large attractive ear
Occasional hard snap
SC 1102 great flavor,
excellent plant: clean w/
high ear placement.
Main Season late
Ka-Ching
78 days
Grower friendly
Good flavor
Very large ear
Not as widely adapted
as →
Tried & True: Montauk,
Providence or (insect
protected) BC-0805
Sh2 program
pluses
considerations
alternatives
First Seeding
Cold soil
2171 Extra
Tender
71 days
Great in cold soil
Vigorous clean plant
Best eating of first early class
Generally good tip fill
Low ear placement
Awesome (but later
maturing)
Early Main
Season from
early seeding
Awesome
XR
74 days
Very good in cold soil
Very good flavor/ tenderness
Great yield & easy pick
Stress tolerant
Improved rust resistance
Can be “shanky” in
lower plant
populations
XTH 2674
Main Season
XTH 20173
73 days
Best flavor “Vision quality” now
with rust resistance
Increased plant vigor
Great for freezing
Not a strong plant
Not easy to pick
2573 or 2673 (similar
varieties but without rust
resistance)
Main Season
late
Stellar
76 days
Great flavor
Easy to pick
Strong, lodge-resistant plant.
Needs high plant
population to keep
shank size down
Round Up Ready & Insect
protected: Obsession II
Late Season
EX 7143
80 days
Obsession quality and yield
potential with improved Rust
resistance
Flavor / tenderness
is a slight step down
from earlier varieties
Round Up Ready & Insect
protected: 90105A (with
improved rust resistance)