الفهرس 
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Abstract
The aim of this investigation was to detennine the extent of
heterosis and combining ability and their interaction with seasons
(environments) for growth and yield characteristics i.e. tasseling and
silking dates, ear and plant heights, leaf area, leaf angle, ear husk, stem
diameter, number of ears per plant, ear length, ear diameter, number of
rows per ear, number of kernels per row, 100- kernel weight, shelling
percentage and grain yield per plant.
To achieve this target Fl and F2 of the half dialle cross between
eight inbred lines namely Moshtohor 101H,M 105g,M 110M,M 72,
M 27, M 70B, M 106i andM 36 representing wide range of variability
in most of the studied traits.
In 1994 season, crossing was made with all possible
combinations among the eight parental inbred lines without the
reciprocals and evaluated in 1995 season with three check varieties
(including single cross 10, three way cross 310 and Giza 2) in a
randomized complete block design with three replications. In 1996
season, two adjacent experiments were conducted the first involved
the parental inbred lines and their twenty eight possible crosses and
three check varieties, and the second included the parents and the F2
crosses.
Data were recorded on F1 using 10- plant per plot. However,
on F2 a 40- plant samplel plot was used. The data obtained for each
trait were analysed on individual plant mean bases. The ordinary
analysis of variance was firstly performed. Heterosis was computed as
the percentage deviation of F1 mean performance from the mid- parent,
better parent and check variety average values for individual crosses.
General and specific combining ability estimates were obtained by
employing Griffing’s (1956) diallel cross analysis designed as
method 2 model 1. The obtained results can be summarized as
follows :
A- F) generation:
1- Season mean squares were significant for all traits.
2- Significant genotypes mean squares were detected for all traits in
separate season as well as the combined analysis except for ear
diameter in the second season. Significant genotypes by season
interaction mean squares were detected for all traits except
number of rows/ ear.
3- Significant inbred lines mean squares were showed in all traits
except number of eats per plant, and 100- kernel weight in both
seasons as well as the combined analysis, number of kernels per
row, shelling percentage, leaf angle and ear husk in the first
”season, ear height, tasseling date and stem diameter in the second
season. Insignificant mean squares of interaction between
parental inbred lines and seasons were detected for all traits
except silking date, stem diameter and ear husk.
4- The parental inbred line 27 and lOIH behaved as the earliest
inbreds in both seasons as well as the combined analysis.
5- The parental inbred lines 70B gave the lowest mean values for
ear and plant height in both seasons. However, the parental
inbred line 1108 had the highest mean values for both traits. The . .•.
parental inbred line 101H had the highest mean value for leaf
area.
6- The parental inbred lines 110B, 72 and 36 recorded heavier 100-
kernel weight. While the parental inbred lines 1lOB, 27 and I05g
gave the highest shelling percentage. The parental inbred lines
II0b was the first in gain yield per plant, while the inbred line
101H was the second one for this trait.
7- Crosses mean squares were significant for all cases except
number of rows per ear in the second season and the combined
analysis, number of kernels per row, ear length, ear diameter,
stem diameter and tasseling date in the combined analysis.
8- Significant interaction between FI hybrids and seasons were
detected for all traits except number of rows/ ear.
9- The crosses 10IH x 72, 72 x 27 and 27 x 10IH had the earliness,
while the crosses 11OBx 105g and 105g x 106i exhibited short
plant. Also, the crosses 1lOB x 70 B , I lOB x 101H, IIOB x 36
and 105g x I06i gave the lowest mean values of ear height. The
highest values for leaf area were recorded by crosses 110B x 72,
lIOB x 70B, 1108 x 106i, 72 x 70B, 72 x 106i, 27 x 101H, 27 x
70B, 27 x 36,101 Hx 70B, 101 Hx 105g and l05g x 106i in the
combined analysis The best crosses for leaf angle were 27 x 36
, and 36 x 106i.
10- For grain yield per plant, six hybrids lOIH x 106i, 10lH x 105g,
27 x 105gm 110B x 105g, IIOB x 10lH and 110B x 27 had
significant superiority over the check varieties in the first
season. None of the hybrids had significant superiority over the
check varieties in the second season. In the combined analysis,
the two crosses (110B x 101H) and 10lH x 106i had significant
superiority over the check varieties.
11- Mean squares for parents vs crosses were significant for all traits
except 100- kernel weight in both seasons as well as the
combined analysis, and stem diameter and shelling percentage in
the second and first season, respectively.
12- Insignificant interaction mean squares between parents vs crosses
and season were detected for all traits except for ear diameter ,
tasseling date, silking date, ear husk and grain yield per plant.
For grain yield per plant, all crosses significantly exceeded out of
respective mid- parent or better parent in each season as well as
the combined analysis.
13- The three crosses 110B x 101H, IOIH xl05g and IOIH x 106i
out yielded the check variety S.C. 10 by 14.34% in the combined
analysis. It could be concluded that these crosses offer possibility
for improving grain yield of maize.
14- The results showed that the best productions of double crosses
were (110B x 10IH)(l06i x 105g), (110B x 70B)(l01H x 10,5g),
(lOIH x 110B)(105g x 106i), (lOIH x 110B)(106i x 105g), (70B
x 10IH)(l05g x 110B), (lOlH x 110B)(70B x 106i), (lOIH x
101B)(106i x 27), (110B x 101H)(27 x 105g), (27 x 70B)(l05g x
110B) and (119B x 36)(105g x lOIH) . These double crosses
exhibited high performance and out yielded the check varieties.
2- Combining ability:
1- The mean squares associated with general combining ability
(GCA) were significant for all traits except ear length in the
second season, number of ears per plant, leaf angle and ear husk
in the first season, and number of ears per plant, number of
kernels per row and ear diameter in the combined analysis.
2- Specific combining ability (SeA) variances were found to be
significant for all characters under study.
3- Non additive type of gene action was more important part of the
total genetic variability for ear length in the second season, .
number or ears per plant, leaf angle and ear husk in the first
season, and number of ears per plant, number ’or kernels per row
and ear diameter in the combined analysis.
4- Low GCAl SeA ratios of less than unity were detected for grain
yield per plant in number .of rows per ear, ear length in both
seasons as well as the combined analysis. Plant height, ear
height, leaf area and number of kernels per row in both seasons,
number of ears per plant, leaf angle and ear husk in the second
season, ear length, ear diameter, tasseling date, silking date in
the first season, and ear length, tasseling date and ear husk in the
combined analysis. However, high GCA/ SeA ratios which
exceeded the unity were detected for 100- kernel weigh in both
seasons and the combined analysis, shelling percentage in both
seasons, silking date in the second season as well as the
combined analysis, stem diameter in the first season as well as
the combined analysis. And tasseling date in the second season.
5- Mean squares of interaction between season and general
combining ability were significant for ear diameter, silking date
and grain yield per plant. However, significant mean squares of
interaction between SCA and season were detected for all traits
under study except stem diameter, number of rows per ear,
number ofkemels per row and 100- kernel weight.
6- The best combiners parental inbred lines were Moshtohor 106i,
and 27 for earliness, parental inbred lines M 72, M 70B, and M
I06i for plant height and parental inbred lines IOlH and Il0B
for grain yield and some of its attributes.
7- The two crosses 110B x l06i and 10IH x 36 expressed
significant negative Sij effects for silking and tasseling dates.
Also, ten crosses: 1l0B x 27, llOB x 101H, 72 x 27, 27 x 70B,
10lH x 70B, 101 H x 105g, 10lH x 106i, 70B x 105g, 105 g x 36
and 36 x I06i appeared to be the promising crosses for breeding
towards high yielding potentiality.
- 117-
B- F2 generation:
1- Mean squares for genotypes were significant for al the studied
traits except number of ears per plant. Meanwhile, parents mean
squares were significant for all traits except 100- kernel weight
and ear diameter. Also, hybrid mean squares were significant
for all traits except number of rows per ear and number of
kernels per row.
2- Non of the F1 hybrids surpassed the better check variety for all
hybrids except 100- kernel weight, plant and ear heights.
3- Nineteen, twenty two, twenty seven, twenty six, twenty three,
twenty three, twenty ,thirteen, nine and twenty seven hybrids
exhibited significant positive inbreeding depression percentage
for stem diameter, ear diameter, ear length, ear husk, number of
rowsl ear, number of kernels per row, 100 kernel weigh, shelling
percentage and grain yield, respectively.
4- General and specific combining ability mean squares were
significant for all traits except GCA for 100 kernel weight and
<.
seA for tasseling date. The similar trend was obtained form F2
data with the analysis of FI data.
5- The results obtained from F2 data for general an specific
combining ability effects were coincided with that already
reached from combining ability effects derived from FI
generation, for most cases.
Association study :
1- Significant positive phenotypic correlation coefficients values
were detected between grain yield and each of number of ears
per plant, number of rows per ear, number ofkemels per row and
plant height in both seasons as well as the combined analysis.
Also, significant positive phenotypic correlation values were
detected between grain yield and leaf area in the first season and
the combined analysis.
2- Number of rows per ear had a high and positive direct effect on
yield by a value of 0.40, 0.412, and 0.0153 in the first, second
seasons and the combined analysis, respectively. Also, its
indirect effects are important through number of kernels per row
in the first season and the combined analysis. While, other
indirect effect was not important.
3- In the first season, the direct effect of the four traits; number of
rows per ear, number of kernels per row, leaf area and plant
height accounted for approximately 61.54%. While, the direct
effect for number of rows per ear and plant height accounted for
approximately 35.41% in the second season. Moreover, the
direct effect of number of ears per plant, number ofkemels per
row and leaf area accounted for approximately 33.01% in the
combined analysis.