Corn breeding - Native Seeds/SEARCH

Rich Pratt
Professor and Head,
Plant and Environmental Sciences
1
Diversity of Arido-American
Land Races of Maize
B.S. - U of A 1976
M.S. - U of A 1978
Ph.D. - Purdue University 1985 – Interspecific hybridization of Phaseolus
Professor – Ohio State University – Corn breeding
Special research assignment 2008-2009 with NSS
2
What type of corn will we need in the future?
What are/will be the big issues?
• Food Security - Human health and nutrition?
• Agriculture in harmony with the environment?
• Impact of climate change?
• Increasing genetic vulnerability?
3
Arido-America =
a broad, dry climatic region in
the southwestern USA and
northern Mexico
Wikipedia.org
Why work with
diverse germplasm …….from this area?
4
Lots of native corn still remains in Aridoamerica – for
how long?
Unrealized potential:
It is a useful germplasm source for:
Development of regional, sustainable, diversified
agriculture
Trait improvement in other types of corn
•highly pigmented kernels, enhanced protein quality in many
floury types? (health and nutrition)
•may be useful for stress tolerance (global warming)
5
Roughly 2000 accessions (all species) at
NS/SEARCH
Maize Collection
Tohono O'odham 60-day
Yoeme Blue
Navajo Red
Hispanic Pueblo Red
Hernandez Multi-Color
Flor del Rio
Hopi Hominy
Zea Mix
Navajo Red
San Felipe White
Onaveno ….
6
Representing
Colorado Plateau
NE Arizona
(Four Corners area)
Navajo Nation
[Hopi Nation]
Besthike.com
A few Sonoran Desert
Tohono O-odham
NW Mexico
(Copper Canyon)
Tarahumara
Rei.co
m
7
NS/SEARCH Conservation Farm near Patagonia,
Arizona – mid-altitude
8
Open-pollinated Land Race
Single-Cross Hybrid
Corn Belt Dent (B73/Mo17)
9
Materials
- 50
entries-
48
Native
Seeds
collection
-
2
entries
were
checks
(B73/Mo17
and
OhS12)
- At
two
locations
(AZ
and
OH)
across
two
seasons
2008-2009
10
Diversity!
Flor del Rio
Plateau 12-Row SW and Hopi
11
Onaveno
12
Results
13
14
15
Waller-Duncan grouping by kernel color (cont.)
Color
N
Carotenoid
range
Color
N
Anthocyanin
range
orange
11
8.48a
2.9‐14.0
blue
29
34.42a
7.4‐
73.1
yellow
67
8.36a
3.4‐18.3
purple
40
19.80ab
0.8‐111.7
mix
26
4.63b
1.6‐10.2
mix
23
14.27bc
0.8‐
33.4
purple
41
4.45bc
1.7‐11.0
red
21
5.15bc
0.8‐
24.4
brown
4
4.17bc
2.8‐
4.8
r(str)
20
1.63c
0.6‐
8.1
pink
6
3.50bcd
1.5‐
7.2
brown
4
1.16c
0.7‐
1.7
blue
29
3.29bcd 1.5‐14.8
pink
2
0.88c
0.3‐
1.4
red
22
3.21bcd
1.6‐
9.5
orange
4
0.59c
0.3‐
1.1
white
137
3.06cd
1.0‐11.3
yellow
4
0.53c
0.4‐
6.7
r(str)
20
2.70d
1.4‐
4.9
white
4
0.29c
16
0.0‐
0.4
2009 Plan: Anthocyanin
◎
Selection
high
anthocyanin
landraces
from
NSS
-
6
lines
containing
64-112mg/100g
◎
Cross
pollination
-
6
NSS
lines
x
Ohio
Blue
(Ned’s
Blue/Blue
Clarage)
-
Reciprocal
cross
◎
Objectives
-
To
introduce
high
anthocyanin
from
NSS
into
Ohio
Blue
-
To
see
the
heterotic
relationship
between
two
populations
17
Acknowledgements!
OSU-OARDC SEEDS Program
co-investigator Joe Scheerens
Native Seeds/SEARCH
collaborator Suzanne Nelson
Si Hwan Ryu
Mark Casey
Lindsay Werth
Benito Gutierrez
Chris Lowen
Andrew Burt
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Corn breeding …..
GEMS – 0002 parent line
Fusarium ear rot susceptible
Selection Works!
Breeding cross-pollinated crops
• Breeders seek to increase the frequency of desirable
alleles in a population (also need to maintain genetic
diversity in the population – allows further improvement)
• Population improvement
-- intra-population -- e.g. in a maize open pollinated
population (recurrent mass selection for multiple cycles)
-- interpopulation – reciprocal recurrent selection,
evaluate crosses between populations, exploits
inerpopulation heterosis
Unit of selection may be plants or lines (e.g. “selfed”, fullsib (sibling) crosses)
20
OPPs
•
Many OPPs in wind-pollinated species
have been replaced with hybrids
conduct inbred line development then make
hybrids with inbred parents
e.g. maize
21
OPPs
• Essentially all maize opps were replaced
by hybrids in the U.S. by the early 1950s
• Still important where farmers save seed
22
OPPs
Recurrent selection – heterozygous and heterogeneous,
improve a general population e.g. Cash RS (‘Cash’ was
“good local corn” – a farmer variety in SW Ohio)
Synthetic cultivars – heterozygous and heterogeneous,
produced by planned matings of selected genotypes -can be many but often e.g. 8 -12
Breeding population – “pull” parents from a synthetic
population or breeding population
Tend to have a broad genetic base
Composite is a mixture of genotypes maintained in a bulk –
often a “balanced” composite (equal no. of seed)
23
Controlled pollinations are an important part of
maize breeding programs
• Self-pollination must be controlled
• Self-pollination results in inbreeding
depression
• Self-fertilization reveals desirable gene
combinations – as well as undesirable
recessive alleles
24
Linearity of inbreeding
depression with F
Inbreeding depression
in Maize
Mean Inbred
Outbred
1
Height
.6
Yield
.2
0
.2
.4
.6
.8
1.0
F
25
Pollination and its control:
An example of a monecious
species: maize
(Wikipedia.com)
CORN POLLINATION BIOLOGY
26
Maize Pollen
The pollen grain is the male gametophyte
• About 25 million grains
per plant are produced
in the anthers
• Maize pollen is large (90
to 100 microns dia.) and
heavy (.25 µg!)
• Viable for 2 to 4 hours,
longer under favorable
conditions
27
Pollination
• Monoecy (male and
female floral parts on
same plant)
• Anthers dehisce windborne pollen
• Pollen lands on silks,
(stigmatic surface),
germinate and pollen
tubes reach egg cells
• Pollen effects fertilization
of the egg to give rise to
embryo
28
A silk with stained grains of pollen
• A well developed ear
shoot should have 750
to 1,000 ovules each
producing a silk
• Silks are covered with
fine, sticky hairs which
serve to catch and
anchor pollen grains
• Average of approx. 12
pollen grains per silk
observed (poss. 5-6k)
29
Distance Traveled?
• Most pollen falls within about 5-6 meters
(Hutchcroft, 1958)
• Pollen can travel 20 miles on a strong wind
current? (hearsay)
• Most of the pollen cloud produced by a plant
misses the parent plant (5 to 10% “hits”)
• It all depends on the wind and the weather
30
Corn breeding “swapping bags”
Glassine ear shoot bag – silks
emerge but are protected
Tassel bag – pollen is shed but
it is contained in the bag
31
Corn pollination
• Effective pollination is necessary for normal yield
(pollen and silk are heat and stress susceptible)
• Effective pollination control is necessary for hybrid
seed production
• Pollination source can influence grain appearance
(pigmentation) and chemical compositional values
(e.g. oil) xenia effect
Pollen dispersal may result in GMO corn traits
winding up where they are not wanted
Controlled pollinations are an important part of
breeding programs
32
Isolation Requirements
(AOSCA Study 2001)
• Seed producer’s point of view – pure seed
production (95 - 98% purity)
• Distance from nearby fields, border rows,
empirically derived over time
e.g. 290 ft. + 6 border rows for field <20A
• New era – GMO detection
• Hybrid grain production fields were an issue
e.g. Star-link maize
33
Effects of stress on pollination
• Pollen becomes sterile at high temperatures
(e.g. in excess of 95 degrees F) especially when
accompanied by low relative humidity (the outer
membrane of a pollen grain is very thin)
• Silk growth slows down and it may even stop
entirely (or does it “dessicate”?)
• Asynchrony of flowering results -- increasing the
anther-silk interval (ASI)
• What are the implications in nature, breeding,
hybrid production?
34
Types of selection
• Mass selection – the easiest and most
inexpensive; select based on phenotype to
improve average performance of
population
General clean up – keeping a variety true to
type
Directed breeding from a base population
35
Synthetics
cultivars/improved populations
• Synthetics can be improved for production
(cultivars) and they may also be produced
for use as a breeding resource or base
population
• “Synthesizing” a population by combining
many parents – e.g. BSSS – comprised of
20+ maize inbreds
36
Iowa Stiff Stalk Synthetic (BSSS)
Elite inbred lines can be derived from
the population for production of hybrids
>> cycles of recurrent selection >>
produced inbreds B14, B37, B73, B84
suitable for use as parents in hybrids
37
End products
• An improved population or synthetic
cultivar
• Elite inbred lines can be derived from the
improved population for production of
hybrids
• Developing mixed genotype cultivars –
(but uniform for phenotypic traits of the
cultivar)
38
Types of recurrent selection
1) Phenotypic recurrent selection – mass,
family
2) Recurrent selection for GCA (broad
based tester)
3) Recurrent selection for SCA (inbred
tester)
4) Reciprocal recurrent selection
39
Advantages and disadvantages of different
recurrent selection schemes
Mass selection
Advantages: relatively easy and inexpensive
Disadvantages: mass selection does not
work so well for quantitative traits, no
pollen control (no idea what the worth of
male parent plants is)
Save selected seed and replant the
following season….completes one cycle
40
Family selection methods
1) Creation of a family structure (e.g. S, FS, HS)
2) Evaluation of families and selection of superior
ones – advantage … can be replicated, save
remnant seed
3) Recombination of selected families
(intermating) – plant remnant seed of superior
families during next season
41
Reciprocal recurrent selection
• Pops A and B
• Pollen from one plant X several plants
from the other population e.g. A1 pollen X
B-a, B-b, B-c, B-d …
average A1 X (B-abcd)
• Determines GCA of the population with
multiple lines, given SCA match of two
parents can give rise to new hybrids?
42
Reciprocal recurrent selection
Plants from one population are testers for plants of
another population; can also self the lines and use them
for making next cycle
Cycles should build up combining ability for the other
population ..establish or reinforces heterotic patterns
43
Optimizing gain through selection in
population improvement
• Genetic variance, start with it and try to
keep it
• Selection intensity – limit to the best
performers
• Generations per cycle, how rapidly can a
cycle be completed?
• Field plot technique
44
HYBs
Hybrids (HYB) - heterozygous,
homogeneous
Single cross….two uniform inbred
parents (homozygous and
homogeneous)
Make new hybrid from parents with best
specific combing ability (SCA
combinations)
45
Use of testers
Selection of SCA and GCA permits selection for genetic
variance other than additive variance - e.g. dominance,
overdominance etc.
Increasing selection intensity increases response to
selection unless it results in genetic drift or loss of
desirable genetic variation
46
Implications of HYB
• The cultivars are more productive (and
easier to manage) but they are more
vulnerable.
• Enhanced uniformity brings with it
associated problems such as increased
vulnerability e.g. to disease.
47
Current Breeding Effort
An estimated 85% of the corn grown in the US
today is genetically modified, and most seed
companies continue to phase out non-GMO
corn seed varieties.
Thirty-two percent of conventional farmers wish
their seed company offered more non-GMO options,
according to a 2010 survey.
Where are improved non-GMO corn hybrids
available? Can farmers obtain them to plant on
their farms?
48
A different model:
UNTN
US Testing Network: Cooperators launched the US
Testing Network in 2009 to rebuild the dwindling
selection of non-GMO corn seed. PFI acts to coordinate
and as the fiscal agent today.
The US Testing Network (USTN) is a group of
independent seed companies, public corn breeders and
private corn breeders who work to test non-GMO corn
hybrids across the US.
The goal is to improve the quality and quantity of nonGMO corn hybrids available in the marketplace.
49
Develop new non-GMO corn hybrids
Some of the companies involved in the network include
Albert Lea Seed House, American Organic Seed, Blue
River Hybrids, Brownseed Genetics, Doeblers Hybrids*,
and Organic Valley. University members include Cornell,
and Ohio/New Mexico State.
The Michael Fields Institute is involved, as are public corn
breeders from the USDA’s Agricultural Research Service
at Iowa State University.
50
Growing network
USTN members tested corn at 36 locations stretching
from New England south to North Carolina, west to
Ohio, Illinois, Wisconsin, Iowa, Minnesota, and North
Dakota and New Mexico.
USTN is analyzing data from the tests, which will lead to
the development of new corn hybrids for both
conventional, non-GMO and organic production.
51
NIFA OREI Grant just started –
Strengthening Public Corn Breeding to Ensure that Organic
Farmers have Access to Elite Cultivars: Breeding for the Eastern
and Southwest USA”
Agreement No.
Cooperator: New Mexico State University
Objective:
1) Contribute populations to and provide testing sites/evaluations for a
joint experiment to catalog germplasm for organic production, 2)
cooperate in an inter-regional breeding effort concentrating on the
eastern Corn Belt and Southwestern USA, 3) take the lead in
breeding/evaluation for biotic and abiotic stresses and enhanced grain
quality 4) participate in USTN trials and pre-trials and 5) cooperate in onfarm evaluations and stress nurseries.
52
Tempis fugit
“Time flies like an arrow; fruit flies like a banana." Groucho Marx
53