Agriculture Reference
In-Depth Information
Step 4: Calculation of Indirect Effects
The indirect effects of different factors are
calculated with the help of the following formula:
r
1
y
¼ p
y
1
þ p
y
2
r
12
þ p
y
3
r
13
¼
0
:
225134
þð
0
:
51855
0
:
773
Þþ ð
ð
0
:
2146
Þð
0
:
2
Þ
Þ
¼
0
:
225134
þ
0
:
4008
þ
0.04292,
r
2
y
¼ p
y
1
r
12
þ p
y
2
þ p
y
3
r
23
¼
:
:
þ
:
þð
:
Þð
:
Þ
0
225134
0
773
0
51855
0
2146
0
221
0.0474,
r
3
y
¼ p
y
1
r
13
þ p
y
2
r
23
þ p
y
3
¼
0
:
225134
ð
0
:
2
Þþ
0
:
51855
ð
0
:
221
Þ
0
:
2146
¼
¼
0
:
174
þ
0
:
51855
þ
0
:
045
0
:
11459
0
:
2146
:
Thus
; r
1
y
¼
0
:
225134
þ
0
:
4008
þ
0.04292,
where 0.4008 and 0.04292 are the indirect effects
of
Multi-situational/multilocational/multi-seasonal
(environments) trials are conducted to oversee
the stability in the performance of the varieties
or the genotypes. When the interaction effects
between the treatments and the environment is
nonsignificant it implies the consistency of the
treatment concerned over varied range of
environments. But when this interaction becomes
significant, then measuring the stability comes
into mind, to find out the environment suitable
for specific treatments.
Measuring the stability, mostly related to
genotypic stabilities, has been worked out taking
the environmental indices as the indicator and
using the regression technique. Several measures
are in literature; among these, Eberhart and
Russell (
1966
) model is mostly used. But the
methods of Yates and Cochran (1938), Comstock
and Robinson (1952), Wricke (1962), Perkins
and Jinks (1968), Freeman and Perkins (1971),
etc., are also found to have been used. For details
of these studies, readers may consult
X
3
, respectively. Similarly, the
indirect effects of other variables can also be
worked out.
X
1
via
X
2
, and
Step 5: Calculation of Residual
Residual value is calculated using the above
path and correlation coefficients that we have
already
calculated
using
the
following
relationship:
h
2
2
y
1
2
y
2
2
y
3
R
¼
1
p
þ p
þ p
þ
2
r
12
p
y
1
p
y
2
r
23
p
y
2
p
y
3
i
þ
2
r
13
p
y
1
p
y
3
þ
2
¼
0
:
385
:
The procedure for the calculation of path anal-
ysis at the phenotypic and genotypic levels using
SPAR1 has been presented in Example 2.
11.4
Stability Analysis
Agriculture
and Applied Statistics II
by Sahu and Das (2009).
However, here we shall discuss Eberhart and
Russell (
1966
) model.
One of the major tasks before releasing a
genotype, or a variety for cultivation, or a tech-
nology at a farmers field is to judge its perfor-
mance under varied situations. Multi-situational,
multilocational, or multi-seasonal or all trials are
conducted to understand the adaptability and
the performance of the genotypes, the varieties,
or
11.4.1 Eberhart and Russell Model
the technology under different situations.
According to this method,
