WELCOME Agenda Introductions & brief overview of the objectives Maize physiologist’s understanding of phenology Maize modeling – descriptions of phenology.

WELCOME

Agenda•Introductions & brief overview of the objectives

•Maize physiologist’s understanding of phenology

•Maize modeling – descriptions of phenology routines

1. To discuss the current ‘state-of-the-art’ knowledge on the physiological mechanisms controlling maize phenology.

2. To identify how various maize models quantify these mechanisms, and discuss their consistency with the physiological understanding identified above,

and possible rationale for inconsistencies.

3. To test different methodologies used to simulate phenology across a range of environmental conditions

Objectives of our meeting

(Presentations by Thijs and Greg)

(Presentations by modeling groups)

(Will be discussed)

Objective 1To discuss the current ‘state-of-the-art’ knowledge on the physiological mechanisms controlling maize

phenology.

Phenology

Phenology constitutes the framework within which all

processes that are simulated in a crop model are

operating.

Consequently, simulation of all crop processes are

directly dependent on an accurate estimation of

phenology .

planting silking maturity

Phenology

Tollenaar et al. (1979)

Lehenbauer, 1914 (seedling elongation)

Blacklaw, 1972 (radicle elongation)

Parent et al., 2010 (leaf expansion, cell division)

Tollenaar et al., 1979

4th tip

5th tip

6th tip

Relationship between leaf tips (x-axis) and leaf collars (y-

axis) [Muldoon et al., 1984]

www.biochemsoctrans.org Biochem. Soc. Trans. (2005) 33, 1502-1506

Apex

J. Colasanti, U

niv. of Guelph

Tassel Initiation - TI

Leaf tip stage

Lejeune and Bernier, 1996

Leaf primordia (Y=1.95+1.84 × X) vs. leaf-tip stage

Anthesis

Anthesis

Silking

Half Milk Line

Physiological maturity – Black Layer

Modeling Phenology

• Temperature effects on duration of total life cycle and component phases

• Photoperiod effects on duration of total life cycle and component phases

• Genotypic effects on duration total life cycle and component phases

CERES-Maize, IXIM, and Hybrid-Maize[GDD(34,8)]

0 5 10 15 20 25 30 35 40 45 500

5

10

15

20

25

30

Mean daily temperature (oC)

Deg

ree

day

s

MAIS [Pre-silking phase]

Beta function (Yan and Hunt , 1999)

GTI vs. GDD(30,10) [Pre-silking phase]

GDD(30,10)

GTI

(Stew

art et al., 1998)

GTI

GDD(30,10)

GTI vs. GDD(30,10) [Post-silking phase](S

tewart et al., 1998)

Modeling Phenology

• Temperature effects on duration of total life cycle and component phases

• Photoperiod effects on duration of total life cycle and component phases

• Genotypic effects on duration total life cycle and component phases

Leaf primordia (Y=1.95+1.84 × X) vs. leaf-tip stage

Leaf tip stage

Photoperiod effect on leaf number

Photoperiod-sensitive phase for leaf number

Tollenaar and Hunter, 1983

Photoperiod-sensitive phase for leaf number

Tollenaar and Hunter, 1983

Reciprocal transfer experiments Summary

• End of juvenile phase: 4-leaftip stage• End of photoperiod /temperature sensitive period for

leaf number: TI• TI: ~ 0.5 * Final Leaf no.

Issues in photoperiod response in maize

• How can we quickly characterize photoperiod sensitivity of maize hybrids?

• Is maize influenced by photoperiod during ‘other’ phases of development (e.g., grain-filling period), and if so, how?

Modeling Phenology

• Temperature effects on duration of total life cycle and component phases

• Photoperiod effects on duration of total life cycle and component phases

• Genotypic effects on duration total life cycle and component phases

Relationship between Relative Maturity and Accumulated Thermal Units using Different Methodologies

Phase GDD 30, 10 TLU GTI

--------------------- R2 -------------------

Planting to Anthesis 0.55 0.65 0.72

Planting to Black layer 0.26 0.39 0.78

Anthesis to Black layer 0.10 0.16 0.58

Hybrids (>1,100) representing Relative Maturities ranging from RM 75- RM125 grown at a single location in two years (approx. 550 hybrids tested each year)

Tollenaar and Kumudini, unpublished

Temperature and Photoperiod Responses in Tropical Maize Germplasm

Greg EdmeadesJune 5, 2012

Tropical environment, tropical adaptation

Between 30 oN or S of the equator Adaptation zones are

Lowland tropical (LT) (< 1000 masl) Mid-altitude tropical (MAT) (1000-1800 masl) Highland tropical (HT) (> 1800 masl) Temperate (>30oN or S or equator, 0-1500 masl) Differentiation on disease pressures (LT, MAT)

vs. temperature adaptation (HT vs. the others) Natural daylengths vary from 12.3 hrs to

14.3 hours. Tropical maize has evolved with daylength

variation at TI from 13-14.5 hours, over a range of altitudes (temperatures).

No G*temperature interaction for CER

Maize carbon exchange rate asaffected by adaptation and

environment

Lowland Subtropical Highland0

10

20

30

40

50AdaptationLSD0.05 ns * ns

Environment

CE

R (

um

olC

O2 m

-2 s

-1)

Source: Lafitte & Edmeades (1997) Field Crops Res. 49:231-247

G*temperature interaction for partitioning

Harvest indices of two highlandand two lowland tropical maizevarieties vs. mean temperature

15.0 17.5 20.0 22.5 25.0 27.5 30.00.0

0.1

0.2

0.3

0.4

0.5Lowland tropicalHighland

Temperature (deg C)

Har

vest

ind

ex (

g g

-1)

Source: Lafitte & Edmeades (1997) Field Crops Res. 49:231-247

Allelic contribution to thermal adaptation

Correlation between proportionof highland alleles in a (HL xLT) cross and biomass, vs.

temperature

15 20 25

-0.6

-0.4

-0.2

0.0

0.2

0.4

Source: Jiang et al. (1999) Theor. Appl. Genet. 99:1106-1119

Temperature (deg C)

Co

rrel

atio

n

Thermal adaptation and biomass production in the tropics

Highland (left) vs. temperate (right) sown same date in Toluca

2,650 masl, mean temperature during the growing season 13 oC

Variation for developmental response to temperature

Rate of development to TI vs.temperature in highland,

temperate and lowland maize

10 15 20 25 30 35 400.00

0.25

0.50

0.75LowlandHighlandTemperate

Temperature (deg C)

Rat

e o

f p

rog

ress

to

tas

sel i

nit

iati

on

(1/

d x

10)

Source: Ellis et al. (1992) Crop Sci 32: 1225-1232

Generalized response of leaf number to photoperiod in maize

Response of leaf number tophotoperiod around tassel

initiation

10 12 14 16 18 2015

20

25

30LowlandHighlandTemperate

Pc

Pmax

a/b = sensitivitya

b

Adaptation

Source: Edmeades et al. (1994) Agron Abstr. 86

Photoperiod (hrs)

To

tal l

eaf

nu

mb

er

Photoperiod sensitivity in landrace Pepitilla

Photoperiods

(from left)

• 13 hr

• 14.5 hr

• 16 hr

• 17.5 hr

Photoperiod sensitivity reduces grain yield significantly

Grain yield vs. photoperiod forfour hybrids differing in

adaptation

10.0 12.5 15.0 17.5 20.00.0

2.5

5.0

7.5

10.0LowlandMidaltitudeHighlandTemperate

Adaptation

Source: Edmeades 1995 (unpublished data: TL95A-1665)Photoperiod, Hybrid and Photoperiod x Hybrid effects sig (P< 0.01)

Photoperiod (hrs)

Gra

in y

ield

(to

n/h

a)

Photoperiod sensitivity varies with adaptation

Photoperiod sensitivity(summer) of maize vs.

adaptation class

LT MAT HL TE0

1

2

3LowlandMid-altitudeHighlandTemperate

Adaptation

N=15 N=11

N=7

N=7

Sen

siti

vity

(le

aves

hr-1

)

Genetics of photoperiod sensitivity

Cross between a highly sensitive lowland tropical Tuxpeño inbred CML9 and a virtually insensitive temperate line A632Ht from Minnesota

Advanced to 236 RILs by selfing to F7 Evaluated under natural daylengths (13.5 hrs

summer, 11.7 hrs winter) and extended daylengths (17 hrs, both seasons) in Tlaltizapán, Mexico (940 masl; 19oN)

Measures of sensitivity: final leaf number; change in flowering date; anthesis-silking interval

Typical climate during the growing season

Season Tmax Tmin PP at TI

Summer 33 oC 20 oC 13.4 hr

Winter 32 oC 12 oC 11.7 hr

Photoperiod sensitivity varies with adaptation and with temperature

regime

Photoperiod sensitivity extends beyond TI

Photoperiod sensitivity affects ASI

How important are these responses?

For production impact importance relatively small: Highland tropics account for 2% global

production mid-altitude tropics 8%, lowland tropics 10% but temperate around 80%.

Introgression of temperate germplasm into tropical backgrounds is occurring quite rapidly, bring photoperiod insensitivity alleles.

For effective mining of alleles adequate phenotyping is essential CIMMYT’s maize Germplasm Bank has

25,000 accessions; 22% highland; 43% midaltitude; 35% lowland tropical

Model Name Institute/company

CERES MAIZEBoote, Ken Univ. of Florida, Gainesville, FL.Lizaso, Jon Univ. of Madrid, Madrid, Spain

HYBRID MAIZE Yang, Haishun Monsanto Co., St. Louis, MO

EPIC Kiniry, Jim USDA-ARS, Temple, TX

APSIM Hammer, Graeme Univ. of Queensland, Brisbane, Australia.

CropSyst Stöckle, Claudio Washington State Univ, Pullman, WA.

MONICA Nendel, Claas Leibniz, Germanny

MAIZESIM Timlin, Dennis USDA-ARS, Beltsville, MD

Objective 2To identify how various maize models quantify these mechanisms, and discuss their consistency with the physiological understanding identified above, and possible rationale for inconsistencies.

Objective 3To test different methodologies used to simulate phenology across a range of environmental conditions.

1. Why? Ultimately, the usefulness of a specific methodology is indicated by how well it reflects observed outcomes. How well do the current methodologies perform and how can we improve them?

Objective 3We need a number of datasets to evaluate the methodologies, specifically, datasets that capture phenology in terms of (1) thermal, (2) photoperiod, and (3) genotype effects.

For instance:• Different thermal regimes for same genotype(s) and

photoperiod.• Different photoperiods for same thermal regime and

genotype(s).• Different genotypes for (a) same thermal regime and

photoperiod, and (b) different thermal regimes and different photoperiods (i.e., G x T x P).

Objective 3

2. Identify Data Sets for testing:

• What minimum data to include (e.g. ,daily Max/Min temperature, planting date, latitude, anthesis/silking date), and what format?

• Who can contribute data - 6 sets identified so far.• When available?• How data will be shared?

Objective 3

3. Outcomes:

• Next meeting, discuss results• Writing paper(s) on outcomes for thermal,

photoperiod and genotype responses