الفهرس 
Material and methodsOnly 14 pages are availabe for public view
 |  | from | 77 |  |  |
| | | from | 77 | | |
Abstract
SUMMARY
This work was undertaken at the Experimental and Research Center
Faculty of Agriculture, Moshtohor, during two successive seasons 1992
and 1993. The main objective of this study was to estimate genetic
variance components and their interaction with planting date as well as
some other genetic parameters in the synthetic variety ”Cairo 1”. In 1992
season, 100 rows of the variety ”Cairo I” were planted and one plant was
randomly chosen as a male parent from each row and crossed into seven
random plants used as female plants. At harvest seeds were taken from
the first four females per each male which had sufficient seeds for
evaluation. Twenty eight out of 100 planted rows were selected and
represented 28 male groups (half- sib families) each had four females (fullsib
families). Consequently, the total number of the full- sib families were
112. The twenty eight male groups each with four full sib families were
randomly divided into four sets. Each set consisted of seven males each
with four full- sib families.
In 1993 season, the four sets were evaluated in two different
planting dates representing two different experiments. The experimental
design was CRBD with three replications. The full- sib families from each
set were randomized within each replication. The two planting dates were
May 30 and July 10 for the early and late planting, respectively. Data
were recorded on a plot basis in each planting date for grain yield g1plant,
ear length, ear diameter, number of rows/ear, kernel row number, plant
.height, ear height, and silking date.
The analysis of variance for Design 1 mating scheme was applied as
suggested by Comstock and Robinson (1948) to estimate the genetic
components in each planting date as well as the combined data. Some
61
statistical and genetical parameters were computed .i.e., mean (x),
experimental error (o2e), coefficient of variability (C.V.%), genetic
variance components (additive and dominance variances) and their
interaction with planting dates, heritability in narrow sense, phenotypic
and genotypic correlation coefficient, and expected genetic gain from six
methods of selection.
The obtained results could be summarizedas follows:
1- The mean values of the early planting were higher than those of late
planting for all studied traits except for silking date. The error variance
(o2e) was higher for late planting than the early planting for ~ll traits
except for grain yield/plant and kernel row number. Also, the
coefficient of variability was much higher in late planting than early
planting for all studied traits.
2- Mean squares due to planting dates were significant for all traits.
Significant entries and entries x planting date interaction was obtained
for all studied characters.
3- Male variances were significant for ear diameter, kernel row number,
plant height, and silking date in the first planting date; for all traits
except grain yield/plant in the second planting date; and for number of
rows/ear, kernel row number, plant height, ear height, and silking date
in the combined analysis. Female/male variances, significant differences
were detected for all traits except for kernel row number in the early
planting; and ear diameter and ear height in the second planting date.
4- The interaction effect of male variance x planting date was significant
for ear diameter and kernel row number. The interaction effects of
female x planting date were significant for all traits except for ear
length and ear diameter.
62
5- The additive genetic variance was the predominant component in the
inheritance of most studied traits.
6- Dominance genetic variance was negative and significant for most
traits in both planting dates and their combined data.
7- The degree of dominance indicated that no to partial dominance was
the major type of gene action prevailing for the loci controlling most of
traits under study.
8- The additive genetic variance x planting date interaction was significant
only for kernel row number, whereas the interaction between . dominance genetic variance x planting date was significant for ear
diameter, number of rows/ear, and plant height.
9- Low to moderate heritability values in narrow sense were obtained for
grain yield/plant, ear length and ear height in the two planting dates and
their combined analysis. Whereas, high estimates of h2 were obtained
for plant height, silking date in the three studied cases. For the other
studied traits, high heritability values were obtained in both planting
dates and their combined analysis.
10- Positive and significant phenotypic correlation coefficient was
obtained between grain yield/plant and each of ear length, kernel row
number, and silking date. The highest magnitude of genetic correlation
was detected between grain yield /plant and kernel row number.
11- The expected genetic gain from selection was 8.60, 17.21, 5.72,
14.28, 21.94, 22.71, and 27.74 g/cycle for mass selection one sex
and two sexes, modified ear- to- row, half- sib family selection, fullsib
family selection, test cross selection, and Sl selection, respectively.
The S1 selection was the best method to improve the variety ”Cairo 1u
followed by test cross and full- sib family selection.