Citrullus lanatus (Thunb.) Matsum. & Nakai - Cucurbit Breeding ...

Lande's method III:
Mather's method:
Wright's method:
[ ( ) ] 2
µ ( P ) ! µ P b
a
8 " # 2 ( BC P ) + # 1 a
2 ( BC P ) ! # 1 a
2
2
# ( P ) + # a
{ [ ( F ) 1 ] } ! 2 [ ( P ) b ]
2
[ ( ) ] 2
µ ( P ) ! µ P b
a
2
2 " # 2 [ ( F ) 2 ] ! # 2 ( BC P ) + # 1 a
2
[ ( ) ] 2
[ ( BC P ) 1 a ]
µ ( P ) ! µ P " 1.5 ! 2 " b
a
µ F ( ) ! µ ( P )
1
a
µ ( P ) ! µ ( P ) b
a
" 1 ! µ F / )
# ( ) ! µ P 1
a
0 +
$
%
1 *
µ ( P ) ! µ P b
a
8 " 5 2
2
5 ( P ) + 5 a ( F ) ! 2
2 ( P ) + 2 " 5 b
2
/
[ ( F ) 1 ] 2
0
4
The possible gain from selection per cycle was predicted as h n
1
2
! " 2
3
4
( )
( )
& , 2
'
( . 3
-4
( P)
multiplied by the selection
differential in standard deviation units k for selection intensities of 5%, 10%, or 20% (Hallauer and Miranda,
1988). The statistical analysis was performed using the SAS-STAT statistical package (SAS Institute, Cary,
North Carolina).
Results and Discussion
In our experiments, watermelon fruit weight was a quantitative trait, with normal distribution of the F 2
data for all the families tested (data not shown). Due to the large and continuous variation of the data, it was not
possible to generate classes of weight and analyze the data according to a Mendelian model.
The field at Clinton had fewer problems with standing water during fruit development than at Kinston,
providing a better environment for growth for those families. Overall, the crop at Clinton appeared more
vigorous and uniform than at Kinston, even though cultural practices were similar, and there was no problem
with biotic or abiotic diseases at either location. The overall mean weights were higher at Clinton than at
Kinston (12.2 vs. 8.7 kg, respectively). Furthermore, the fruit weight of the parental inbred lines were closer to
the expected weights at Clinton. Nevertheless, we were interested in variance estimates and not in mean
performance across environments. Thus, we presented the data from both locations. The measured variances
were not homogeneous across locations and families, based on Bartlett's test (Ostle and Malone, 1988; Steel et
al., 1997). Therefore, the data were analyzed separately by location and family.
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