1. The document discusses analyses of multiple location trials to evaluate genotype performance across environments. It describes factors to consider in determining the number and location of environments for trials and statistical analyses for multiple experiments. 2. Key analyses covered include the Bartlett test for homogeneity of error variances, analysis of variance models for sites and years, and joint regression analysis to evaluate genotype by environment interactions. 3. Joint regression analysis fits linear regressions between genotype performances in each environment and the mean performance across environments to identify which interactions are linear versus non-linear.
2. Previous Class
Why do researchers conduct experiments
over multiple locations and multiple times?
What causes genotype x environment
interactions?
What is the difference between a true
interaction and a scalar interaction?
What environments can be considered to
be controlled, partially controlled or nor
controlled.
4. Number of Environments
Availability of planting material.
Diversity of environmental conditions.
Magnitude of error variances and genetic
variances in any one year or location.
Availability of suitable cooperators
Cost of each trial ($s and time).
5. Location of Environments
Variability of environment
throughout the target region.
Proximity to research base.
Availability of good cooperators.
$$$s.
7. Points to Consider before Analyses
Normality.
Homoscalestisity
(homogeneity) of error
variance.
Additive.
Randomness.
8. Points to Consider before Analyses
Normality.
Homoscalestisity
(homogeneity) of error
variance.
Additive.
Randomness.
9. Bartlett Test
(same degrees of freedom)
M = df{nLn(S) - Ln2}
Where, S = ワ2/n
2
n-1 = M/C
C = 1 + (n+1)/3ndf
n = number of variances, df is the df
of each variance
10. Bartlett Test
(same degrees of freedom)
df 2
Ln(2
)
5 178 5.148
5 60 4.094
5 98 4.585
5 68 4.202
Total 404 18.081
S = 101.0; Ln(S) = 4.614
11. Bartlett Test
(same degrees of freedom)
df 2
Ln(2
)
5 178 5.148
5 60 4.094
5 98 4.585
5 68 4.202
Total 404 18.081
S = 100.0; Ln(S) = 4.614
M = (5)[(4)(4.614)-18.081] = 1.880, 3df
C = 1 + (5)/[(3)(4)(5)] = 1.083
12. Bartlett Test
(same degrees of freedom)
df 2
Ln(2
)
5 178 5.148
5 60 4.094
5 98 4.585
5 68 4.202
Total 404 18.081
S = 100.0; Ln(S) = 4.614
M = (5)[(4)(4.614)-18.081] = 1.880, 3df
C = 1 + (5)/[(3)(4)(5)] = 1.083
2
3df = 1.880/1.083 = 1.74 ns
13. Bartlett Test
(different degrees of freedom)
M = ( df)nLn(S) - dfLn2
Where, S = [df.2]/(df)
2
n-1 = M/C
C = 1+{(1)/[3(n-1)]}.[(1/df)-1/ (df)]
n = number of variances
16. Bartlett Test
(different degrees of freedom)
S = [df.2]/(df) = 13.79/37 = 0.3727
(df)Ln(S) = (37)(=0.9870) = -36.519
M = (df)Ln(S) - dfLn 2 = -36.519 -(54.472) = 17.96
C = 1+[1/(3)(4)](0.7080 - 0.0270) = 1.057
2
3df = 17.96/1.057 = 16.99 **, 3df
17. Heterogeneity of Error Variance
0
10
20
30
40
50
60
70
80
Mosc Gene Tens Gran Pend Colf Kalt Mocc Boze
Seed
Yield
18. Significant Bartlett Test
金What can I do where there is
significant heterogeneity of error
variances?
Transform the raw data:
Often ~
cw Binomial Distribution
where = np and = npq
Transform to square roots
19. Heterogeneity of Error Variance
0
2
4
6
8
10
Mosc Gene Tens Gran Pend Colf Kalt Mocc Boze
SQRT[Seed
Yield]
20. Significant Bartlett Test
金What else can I do where there is
significant heterogeneity of error
variances?
Transform the raw data:
Homogeneity of error variance can always
be achieved by transforming each sites data
to the Standardized Normal Distribution
[xi-]/
21. Significant Bartlett Test
金What can I do where there is
significant heterogeneity of error
variances?
Transform the raw data
Use non-parametric statistics
23. Model ~ Multiple sites
Yijk = + gi + ej + geij + Eijk
i gi = j ej = ij geij
Environments and Replicate blocks are usually
considered to be Random effects. Genotypes are
usually considered to be Fixed effects.
24. Analysis of Variance over sites
Source d.f. EMSq
Sites (s)
Rep w Sites (r)
Genotypes (g)
Geno x Site
Replicate error
25. Source d.f. EMSq
Sites (s) s-1
Rep w Sites (r) s(1-r)
Genotypes (g) g-1
Geno x Site (g-1)(s-1)
Replicate error s(r-1)(g-1)
Analysis of Variance over sites
26. Source d.f. EMSq
Sites (s) s-1 2
e + g2
rws + rg2
s
Rep w Sites (r) s(1-r) 2
e + g2
rws
Genotypes (g) g-1 2
e + r2
gs+ rs2
g
Geno x Site (g-1)(s-1) 2
e + r2
gs
Replicate error s(r-1)(g-1) 2
e
Analysis of Variance over sites
28. Analysis of Variance
Source d.f. EMSq
Years (y) y-1 2
e+gy2
rwswy+rg2
swy+rgs2
y
Sites w Years (s) y(s-1) 2
e + g2
rwswy + rg2
swy
Rep w Sites w year (r) ys(1-r) 2
e + g2
rwswy
Genotypes (g) g-1 2
e + r2
gswy + rs2
gy + rl2
g
Geno x year (y-1)(g-1) 2
e + r2
gswy + rs2
gy
Geno x Site w Year y(g-1)(s-1) 2
e + r2
gswy
Replicate error ys(r-1)(g-1) 2
e
30. Interpretation
Look at data: diagrams and graphs
Joint regression analysis
Variance comparison analyze
Probability analysis
Multivariate transformation of residuals:
Additive Main Effects and Multiplicative
Interactions (AMMI)
31. Multiple Experiment Interpretation
Visual Inspection
Inter-plant competition study
Four crop species: Pea, Lentil,
Canola, Mustard
Record plant height (cm) every week
after planting
Significant species x time interaction
32. Plant Biomas x Time after Planting
0
20
40
60
80
100
120
140
1 2 3 4 5 6 7 8 9 17
Weeks
Height
(cm)
33. Plant Biomas x Time after Planting
0
20
40
60
80
100
120
140
1 2 3 4 5 6 7 8 9 17
Weeks
Height
(cm)
Pea Lentil
Mustard
Canola
34. Plant Biomas x Time after Planting
0
20
40
60
80
100
120
140
1 2 3 4 5 6 7 8 9 17
Weeks
Height
(cm)
Legume
Brassica
36. Regression Revision
Glasshouse study, relationship
between time and plant biomass.
Two species: B. napus and S.
alba.
Distructive sampled each week
up to 14 weeks.
Dry weight recorded.
40. B. napus
Mean x = 7.5; Mean y = 0.936
SS(x)=227.5; SS(y)=61.66; SP(x,y)=114.30
Ln(Growth) = 0.5024 x Weeks - 2.8328
se(b)= 0.039361
41. B. napus
Mean x = 7.5; Mean y = 0.936
SS(x)=227.5; SS(y)=61.66; SP(x,y)=114.30
Ln(Growth) = 0.5024 x Weeks - 2.8328
se(b)= 0.039361
Source df SS MS
Regression 1 57.43 57.43 ***
Residual 12 4.23 0.35
42. S. alba
Mean x = 7.5; Mean y = 1.435
SS(x)=227.5; SS(y)=61.03; SP(x,y)=112.10
Ln(Growth) = 0.4828 x Weeks - 2.2608
se(b)= 0.046068
43. S. alba
Mean x = 7.5; Mean y = 1.435
SS(x)=227.5; SS(y)=61.03; SP(x,y)=112.10
Ln(Growth) = 0.4828 x Weeks - 2.2608
se(b)= 0.046068
Source df SS MS
Regression 1 55.24 55.24 ***
Residual 12 5.79 0.48
44. Comparison of Regression Slopes
t - Test
[b1 - b2]
[se(b1) + se(b2)/2]
0.4928 - 0.5024
[(0.0460 + 0.0394)/2]
0.0096
0.0427145
= 0.22 ns
48. Joint Regression Example
Class notes, Table15, Page 229.
20 canola (Brassica napus)
cultivars.
Nine locations, Seed yield.
49. Joint Regression Example
Source df SSq MSq F
Sites 8 1125.2 140.6 8.2 **
Reps w Sites 27 462.5 17.1 11.4 ***
Cultivars 19 358.8 20.3 6.7 *
S x C 152 459.4 3.0 2.0 *
Rep Error 513 771.3 1.5
50. Joint Regression Example
Mo Ge Te Gr Pe Co Ka Mc Bo
Westar 22.0 48.9 28.7 11.1 14.2 54.5 44.3 22.1 25.0
Mean 19.5 52.0 32.0 13.1 15.6 56.1 47.2 21.2 25.7
Source df SSq MSq
Regression 1 1899 1899 ***
Residual 7 22 3.2
Westar = 0.94 x Mean + 0.58
51. Joint Regression Example
Mo Ge Te Gr Pe Co Ka Mc Bo
Bounty 17.2 54.8 32.8 15.4 19.6 60.0 47.6 22.7 28.9
Mean 19.5 52.0 32.0 13.1 15.6 56.1 47.2 21.2 25.7
Source df SSq MSq
Regression 1 2247 2247 ***
Residual 7 31 4.0
Bounty = 1.12 x Mean + 1.12
52. Joint Regression Example
Source df SSq MSq F
Sites 8 1125.2 140.6 8.2 **
Reps w Sites 27 462.5 17.1 11.4 ***
Cultivars 19 358.8 20.3 6.7 *
S x C 152 459.4 3.0 2.0 *
Heter of Reg 19 208.9 11.0 5.8 ***
Residual 133 250.5 1.9 1.2 ns
Rep Error 513 771.3 1.5
53. Joint Regression ~ Example #2
Genotype Site 1 Site 2 Site 3 Site 4 Site 5 Site 6
A 9.9 12.1 15.0 17.7 18.2 22.6
B 12.3 13.7 14.9 16.5 17.1 17.4
C 8.4 12.0 15.7 19.5 19.9 27.2
Mean 10.2 12.6 15.2 17.9 18.4 22.4
55. Problems with Joint Regression
Non-independence - regression of
genotype values onto site means, which
are derived including the site values.
The x-axis values (site means) are
subject to errors, against the basic
regression assumption.
Sensitivity (-values) correlated with
genotype mean.
56. Problems with Joint Regression
Non-independence - regression of
genotype values onto site means, which
are derived including the site values.
Do not include genotype value in mean
for that regression.
Do regression onto other values other
than site means (i.e. control values).
57. Joint Regression ~ Example #2
Genotype Site 1 Site 2 Site 3 Site 4 Site 5 Site 6
A 9.9 12.1 15.0 17.7 18.2 22.6
B 12.3 13.7 14.9 16.5 17.1 17.4
C 8.4 12.0 15.7 19.5 19.9 27.2
Mean for
A
10.3 12.8 15.3 18.0 18.5 22.3
58. Joint Regression ~ Example #2
Genotype Site 1 Site 2 Site 3 Site 4 Site 5 Site 6
A 9.9 12.1 15.0 17.7 18.2 22.6
B 12.3 13.7 14.9 16.5 17.1 17.4
C 8.4 12.0 15.7 19.5 19.9 27.2
Control 11.0 13.4 16.3 19.0 20.5 24.3
59. Problems with Joint Regression
The x-axis values (site means) are
subject to errors, against the basic
regression assumption.
Sensitivity (-values) correlated
with genotype mean.
60. Addressing the Problems
Use genotype variance over sites
to indicate sensitivity rather than
regression coefficients.
61. Genotype Yield over Sites
0
10
20
30
40
50
60
Mosc Gene Tens Gran Pend Colf Kalt Mocc Boze
Seed
Yield
Ark Royal
62. Genotype Yield over Sites
0
10
20
30
40
50
60
Mosc Gene Tens Gran Pend Colf Kalt Mocc Boze
Seed
Yield
Golden Promise
63. Over Site Variance
Genotype Mean 2
g
A 20.0 (3) 24.13 (2)
B 22.0 (1) 8.11 (4)
C 21.5 (2) 19.24 (3)
D 18.0 (4) 26.05 (1)
69. Use of Normal Distribution
Function Tables
|T m|
g
to predict values greater than
the target (T)
|m T|
g
to predict values less than
the target (T)
70. The mean (m) and environmental variance (g
2) of a
genotype is 12.0 t/ha and 16.02, respectively (so =
4).
What is the probability that the yield of that given
genotype will exceed 14 t/ha when grown at any site
in the region chosen at random from all possible
sites.
Use of Normal Distribution
Function Tables
71. T m
g
=
14 12
4
=
Use of Normal Distribution
Function Tables
= 0.5
Using normal dist. tables we have the probability
from - to T is 0.6915. Actual answer is 1 0.6916 =
30.85 (or 38.85% of all sites in the region).
72. Use of Normal Distribution
Function Tables
The mean (m) and environmental variance (g
2) of a
genotype is 12.0 t/ha and 16.02, respectively (so =
4).
What is the probability that the yield of that given
genotype will exceed 11 t/ha when grown at any site
in the region chosen at random from all possible
sites.
73. T m
g
=
11 12
4
=
Use of Normal Distribution
Function Tables
= -0.25
Using normal dist. tables we have (0.25) = 0.5987,
but because is negative our answer is 1 (1
0.5987) = 0.5987 or 60% of all sites in the region.
74. Exceed the target; and (T-m)/ positive,
then probability = 1 table value.
Exceed the target; and (T-m)/ negative,
then probability = table value.
Less than the target; and (m-T)/ positive,
then probability = table value.
Less than target; and (m-T)/ negative, then
probability = 1 table value.
Use of Normal Distribution
Function Tables
76. Univariate Probability
Genotype Mean 2
g g T=21
A 20.0
(3)
24.13 4.91 0.43
(3)
B 22.0
(1)
8.11 2.85 0.64
(1)
C 21.5
(2)
19.24 4.38 0.54
(2)
D 18.0
(4)
26.05 5.10 0.28
(4)
77. Univariate Probability
Genotype Mean 2
g g T=21 T=24 T=26
A 20.0
(3)
24.13 4.91 0.43
(3)
0.21
(3)
0.11
(2)
B 22.0
(1)
8.11 2.85 0.64
(1)
0.24
(2)
0.08
(3)
C 21.5
(2)
19.24 4.38 0.54
(2)
0.28
(1)
0.15
(1)
D 18.0
(4)
26.05 5.10 0.28
(4)
0.12
(4)
0.06
(4)
79. Problems with Probability Technique
Setting suitable/appropriate target
values:
Control performance
Industry (or other) standard
Past experience
Experimental averages
81. Additive Main Effects and
Multiplicative Interactions
AMMI
AMMI analysis partitions the residual
interaction effects using principal
components.
Inspection of scatter plot of first two
eigen values (PC1 and PC2) or first eigen
value onto the mean.