الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 154 |  |  |
| | | from | 154 | | |
Abstract
This study investigated the extent of heterosis, combining
ability and their interactions with three nitrogen fertilizer levels (as
three different environmental conditions) for some agronomic characters.
Path coefficient analysis for grain yield, regression analysis, and the
predictionof possible double crosses yield were also included. Two
sets of diallel crosses were used in this study. The first diallel set
involved eight inbred lines i,e, Moshtohor 28 (M.28), M.33, M.41, M.44,
M.50, M.70c, M.103 and Giza 307-A. The second diallel set involved
seven inbred lines i.e. Moshtohor 50 (M.50), M.54, M.lDl, M.103, M.104,
Giza 102 and Giza 307-A, representing wide range of variability in
most of the studied traits. In 1989 growing season, these lines for
each diallel set were sown and were crossed in all possible cross combination
without reciprocals to obtain grains of 28 FI straight crosses
(first diallel set) and 21 F 1 straight crosses (second diallel set) at
the Agricultural Research and Experiment Center of Faculty of Agriculture,
Moshtohor, Kalubia Governorate. In 1990 season, three adjacent
experiments for each diallel set were conducted at the Experimental
Station of the National Research Center, at Shalakan, Kalubia Governorate.
The three experiments were fertilized by 40, 80 and 120 Kg
N/fed. The first diallel set included 28 FI Ihybrids and D.C. 204 (check
variety). While, the second set of diallel included 21 FI hybrids and
D.C. 204. The experimental design used a randomized complete blocks
with three replications In each experiment. Data of the following
traits were recorded on ten individual plants chosen at random from
each plot, except silking and tasseling dates where the plot mean
basis was used.
Data recorded on :
A. Agronomic characters:
1. Tasseling date
3. Ear height
5. Leaf area
2. Silking date
4. Plant height
6. Ear husk
B. Yield and yield components:
I. Number of ears/plant.
3. Ear diameter
5. Number of rows/ear
7. Grain yield/plant.
2. Ear length
4. Number of kernels/row
6. IDO-kernel of weight
An ordinary analysis of variance was first performed for
each experiment and then a combined analysis was carried out whenever
homogenity of error variances was realized. Heterosis was computed
as the percentage deviation of F I mean performance from check variety
D.C. 204 average value for individual crosses. General and specific
combining ability estimates were obtained by employing Griffing’s
(1956) diallel cross analysis designated as method 4 model I. The obtained
results can be summarized as follows :-
I. Nitrogen levels mean squares were highly significant for all studied
traits except number of ears/plant for both diallel set. Most traits
were significantly increased as the level of nitrogen increased.
2. Genotype mean squares were highly significant for all the studied
traits except number of ears/plant at 40, 80 and 120 Kg N/fed.
and combined analysis in the first and second diallel sets, ear
length at 110and 120 Kg N/fed. and ear diameter at 110,80 and
120 Kg N/fed. and combined analysis in the second diallel set.
3. For grain yield/plant, the hybrid (3xll) gave the highest value
followed by cross (lIx5) and- then by cross (5x6) in the first diallel
set. While, the cross (Jx3), (lIx5) and (lIx5) expressed the highest
grain yield/plant at 110,80 and 120 kg N/fed., respectively.
II. The interactions between nitrogen fertilizer levels and hybrids
mean squares were significant for all the studied traits except
number of ears/ plant, ear length and number of kernels/ row in
the first diallel set, and for ear height, leaf area, ear husk, 100-
kernel weight and grain yield/plant in the second diallel set.
5. Heterosis estimates percentages revealed that the first diallel
cross, the five crosses; (3xll), (lIx5), (5x6), (7x8) and (Jx2) outyielded
the D.C. 2011 by 311.11, 26.90, 18.87, 17.117and 13.56 %,
respectively over the three nitrogen levels. In the second diallel
set, the four F I hybrids (lIx6), (3x6), (2x6) and (2xll) significantly
out-yielded the check variety by 12.16 to 20.79 % with a mean
value 15.82 % over the three nitrogen fertilizer levels.
6. General combining ability mean squares reached the significant
level of probability for all agronomic traits, yield and yield components
except number of ears/plant in the first diallel set. While
in the second diallel set, g.c.a. mean squares were significant
for agronomic attributes, number of rows/ear, 1DO-kernel weight
and grain yield/plant in the three nitrogen levels as well as at
the combined data, and ear diameter at 120 Kg N/fed. and the
combined analysis.
7. Specific combining ability mean squares were significant for all
agronomic attributes in two diallel set except plant height at
£f0 Kg N/fed. in the second diallel set. In the first diallel set,
s.c.a, mean squares were significant for yield and yield components
except number of ears/plant. While, in the second diallel set,
s.c.a, variances were significant for 100-kernel weight, grain yield/
plant, in the three nitrogen levels and the combined analysis,
ear length at 80 Kg N/fed. and the combined data, ear diameter
at 120 Kg N/fed., number of rows/ear at 120 Kg N/fed. and the
combined analysis and number of kernels/row at £f0 Kg N/fed.
8. High g.c.e.l s.c.e, ratios which largely exceed the unity were obtained
for all cases except, (ear height at 80 Kg N/fed. in the second
diallel set), 100-kernel weight at the three nitrogen levels and
the combined analysis, grain yield/plant at £f0 and 80 Kg N/fed.
and the combined analysis, and ear length at £f0and 120 Kg N/fed.
in the first diallel set, and ear length at 80 Kg N/fed. and number
of kernels/row at £f0 Kg N/fed. in the second diallel set. While,
ear length at 80 Kg N/fed. and the combined analysis and grain
yield/plant at 120 Kg N/fed. had g.c.a./s.c.a. ratio was equal
to unity.
9. In both diallel sets, the mean squares of interaction between the
three nitrogen fertilizer levels and both types of combining ability
were significant for all the studied traits, indicating that the
magnitude of g.c.a. and s.c.a. varied from nitrogen fertilizer
level to another.
10. The best combiners were: Parental inbred line Moshtohor 50 for
earlines and leaf area, parental inbred line Moshtohor 44 for height
of plant and ear in the first diallel set, parental inbred line Moshtohor
28 for earliness and height of plant and ear, parental inbred
line Moshtohor 103 for leaf area in second diallel set, and parental
inbred line Moshtohor 103 for yield and most of yield components
in two diallel set.
I J. The three combinations; (3x4), (4x5) and (5x6) in the first diallel
set and (4x6), (3x6) and (2x6) in the second diallel set appeared
to be the most promising crosses for breeding towards high yielding
potentiality. Also, the four crosses (2x4), (3x6), (Jx2) and (2x7)
would be promising for; earliness, short plant and ear height,
leaf area and ear husk in the first diallel set, and, cross (2x6)
earliness, short plant and ear height and cross (lx2) for leaf area
and ear husk in the second diallel set.
12. Significant positive phenotypic correlation values were obtained
between grain yield/plant and number of kernels at 120 Kg N/fed.
and 100-kernels weight at 40 and 120 Kg N/fed. in the first diallel
set. Also, it were significant between grain yield/plant and each
of its components at 120 Kg N/fed. and each of number of rows/ear
and 100-kernel weight at 80 Kg N/fed. and 100-kernel weight
at 40 Kg N/fed. in the second diallel set.
13. Based on multiple linear regression analysis, three characters
could be arranged in their relative contributions in grain yield
as 100-kernel weight, number of rows/ear and number of kernels/
row in two diallel set.
14. Based on path coefficient· analysis, the most important sources
of variation in plant yield were: the direct effect of 100-kernel
weight, number of rows/ear and number of kernels/row at the
three nitrogen levels in the first and second diallel set.
15. Predictions of the yield for the possible 210, 105 double crosses
in the first and second diallel set, respectively were estimated.
The predictions of double crosses: (lx3) (2x4), (lx3) (4x6), (lx5)
(2x4), (lx5) (4x6), (2x4) (3x5), (3x5) (4x6), (3x5) (4x7), (3x5) (4x8),
(3x7) (4x8), (4x6) (5x7) and (4x8) (5x7) at 40, 80 and 120 Kg N/fed.
as well as at the combined data in the first diallel set, and double
crosses : (lx4) (2x6), (lx6) (3x4), (Lxs) (2x3), (2x3) (4x6), (2x6)
(3x4), (3x4) (6x7) and (3x7) (4x6) in the second diallel set over
the three nitrogen levels would exhibited high performance and
out-yielded the check variety D.C. 204. It could be concluded
that these double crosses offer a possibility for increasing grain
yield of maize especially at 80 Kg N/fed.