الفهرس 
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Abstract
SUMMARY
The present studies included heterosis, combining
abilities over environments and genetic behaviour of
some characters in cucumber (Cucumis sativus L.) were
conducted at Kaha Experimental station, Hart. Res.
Institute, Agricultural Research Center, Giza, during
the years 1987-1990.
The experimental material consisted of six crosses
and four inbred Lines. The parental lines were 1909,
Marbosan, Beit alpha and Chinese Long and data were
obtained on the parents, F1, Fz’ BCl and BCz populations.
Data were recorded on, number of days to open the first
female flower, the nodal pasition to open first female
flower on the main stem, number of pistillate flower per
plant, number of fruits per plant, number of nodes per
plant on the main stem and plant height in open field
summer and Nili seasons 1989 and under fiberglass house
in winter 1989-1990. Results were summarized as follows:
Genetic differences among the genotypes
significant for all the character studied.
Female flowering time:
Potence ratio exhibited partial dominance for early
flowering in all crosses studied except two [(1909 x
Marbosan) and (Marbosan x Chinese Long)].
were
Heterosis compared with
insignificant negative values in
except two (1909 x Marbosan) and
Long) .
mid-parent
all crosses
(Marbosan x
showed
studied
Chinese
Inbreeding depression percentage showed
insignificant positive values in the cross (1909 x
Marbosan), (Marbosan x Beit alpha) and (Marbosan x
Chinese long) which may be due to heterozygosity in the
F2 generation. While, the significant negative values in
the other three crosses, indicating, heterozygosity in
most factors influencing date to female flowering.
Narrow sense heritability gave values more than 62%
in the crosses (1909 x Beit alpha), (1909 x Chinese
long) and (Marbosan x Beit alpha) indicating, selection
would be effective for early flowering time in these
crosses. Broad sense heritability in all crosses showed
values above 73% suggesting that the total genetic
components were larger than the environmental
components.
The results for testing the goodness of fit of the
additive and dominance model showed that the model was
not adequate to interpret gene effects. Meanwhile,
estimates of gene action parameters using method of
Gamble showed that the additive x dominance gene effect
was the most important part in one cross only (1909 x
Chinese long).
2. The nodal position of the first pistillate flower:
The result of potence ratio indicates absence of
dominance in the cross Marbosan x Beit alpha, partial
dominance in the cross (Beit alpha x Chinese long),
complete dominance in the cross (Marbosan x Chinese
long) and over dominance in the other three crosses i.e.
(1909 x Marbosan), (1909 x Beit alpha) and (1909 x
Chinese long).
The mid-parent heterotic values were significant and
negative in the crosses (1909 x Beit alpha) and (1909 x
Chinese long), Better parent heterosis showed also
significant negative value in the cross (1909 x
Marbosan) , indicating that these crosses were lower on
nodal position in producing female flower on the main
stem than parents and better-parent, respectively.
Narrow sense heritability was high in the cross
(1909 x Beit alpha). Broad sense heritability gave
values above 52% in all crosses studied.
The additive-dominant model was not adequate to
assume that genes which control this character acted
only dominantly and/or additivelY· However, the
estimates of gene action parameters using method of
Gamble (1962) showed that insignificant values for all
parameters of gene effects in all crosses studied.
3. Number of females flowers per plant:
The results of potence ratio showed over-dominance
of high over low number of female flowers per plant in
the crosses (1909 x Marbosan), (Marbosan x Beit alpha)
and (Beit alpha x Chinese long) which means, the
breeding plan should turn toward inbreeding with the
objective of producing hybrids.
The mid-parent heterosis values were significant and
positive in all crosses studied except one and the
inbreeding depression was less than heterosis,
indicating, the F1 crosses produced higher number of
female flowers per plant than their parents and the
importance of additive x additive gene action in
heterosis. The Fl mean did not differ significantly than
mid-parent in the crosS (1909 x Chinese long) which
confirms that approximately all the genetic variance is
due to additive component. Meanwhile better-parent
heterotic values were significant and positive and
values of inbreeding depression were less than that of
heterosis in the crosses (1909 x Marbosan) and Beit
alpha x Chinese long).
All crosses had values above 80% and 66% of narrow
and broad sense heritabilities, respectively, indicating
that the greater part of phenotypic variance was due to
genetic variance components.
However, the results for testing the goodness of fit
of the additive and dominance model confirmed the model
was not adequate and there was beyond additive and
dominance gene effects in all crosses studied except
one. The calculated X 7. in the croSS (1909 x Marbosan)
was insignificant, which indicated the adequacy of the
model.
The estimates of gene action parameters using method
of Gamble in all crosses studied indicated insignificant
values for all parameters of gene effects.
4. Number of parthenocarpic fruits per plant:
The value of potence ratio indicated over-dominance
of high over low number of parthenocarpic fruits per
plant in all crosses, indicating, the breeding plan
should turn toward inbreeding with the objective of
producing hybrids. However, the high values in the
crosses (1909 x Marbosan) and (Marbosan x Chinese long)
could be biased by both linkage disequilibrium and
epistasis.
The mid-parent heterotic values were highly
significant and positive. Inbreeding depression values
were less than heterosis values in all crosses
indicating that variation was mostly due to dominance
and the importance of additive x additive gene action in
heterosis. Butter parent heterosis showed the same trend
in all crosses except three.
Inbreeding depression gave highly significant
positive values in all crosses studied. This seems to be
caused by segregation of genes influencing this
characters during selfing of Fl generation.
Narrow sense heritability estimate was
cross (Beit alpha x Chinese long).
heritability gave values above 60% in
studied.
high in the
Broad sense
all crosses
The values of X2 for testing the goodness of fit of
the additive-dominance model were highly significant in
all crosses, indicating the model was not adequate and
there was beyond additive and dominance gene effects.
The estimation of gene effects using methods of
Gamble showed that dominance and additive x dominance
effects were the most important parameters in the
inheritance of number of parthenocarpic fruits per plant
in the crosS (1909 x Marbosan) and (Beit alpha x Chinese
long), respectively.
5. Number of nodes on the main stem:
The value of potence ratio indicated over-dominance
in two crosses and partial dominance in another two
crosses toward the high number of nodes per the main
stem. The highest value in the cross (1909 x Chinese
long) (12.06%) could be biased by both linkage
disequilibrium and epistasis.
The F1 mean did not differ significantly from both
mid- and better-parent in all crosses except two, which
confirmed that approximately all the genetic variance
was due to additive component.
The inbreeding depression showed insignificant
positive or negative values in all crosses except two,
which may be due to heterozygosity in the F2
generations.
Narrow sense heritability gave values more than 57%
in all crosses except one, indicating, selection would
be effective for this character. Broad sense
heritability gave values above 47% in all crosses
studied.
The values of Xl for testing the goodness of fit of
the additive-dominance model were significant in all
crosses. These results confirmed the model was not
adequate and there was beyond additive and dominance
effects. However, the estimates of gene action
parameters using method of Gamble in all crosses showed
insignificant values for all parameters of gene effects.
6. Main stem length:
Values of potence ratio indicated over-dominance in
all crosses except one in direction of increase main
stem length. The highest value of the cross (1909 x
Chinese long) could be biased
disequilibrium and epistasis.
by both linkage
The mid-parent and better-parent heterosis were
significant with positive values and values of
inbreeding depression were less than those of heterosis
in all crosses except one, indicating that variation was
mostly due to dominance and the importance of additive x
additive gene action in heterosis.
Inbreeding depression gave highly significant
positive values in all crosses. This seems to be caused
by segregation of genes influencing plant height during
selfing of Fl generation.
Narrow sense heritability gave values above 67% in
all crosses except three. Broad sense heritability gave
values above 73% in all crosses.
The number of genes controlling this character
ranged from one to two pair of genes.
Moreover, the values of X2 for testing the goodness
of fit of the adequacy of additive and dominance model
was significant in all crosses indicating, the model was
not adequate and there was beyond additive and dominance
effects.
The estimates of generation parameters using method
of Gamble showed the additive x dominance gene effect
was the most important part of gene interactions in the
cross (Beit alpha x Chinese long).
Correlation:
The phenotypic and genotypic correlation coefficient
were higher than the environmental correlation
coefficient among the studied characters except between
female flowering time and number of female flowers per
plant and between number of female flowers per plant and
number of nodes on the main stem, indicating most of the
studied characters had not been appreciably affected by
environmental factors. Also, values of genotypic
correlation were higher than that of phenotypic
correlation among all characters studied except between
female flowering time with each of number of female
flowers per plant and with number of nodes on the main
stem, nodal position of first female flower with each of
number of nodes on the main stem and with plant height,
No. of female flowers per plant and with No. of nodes on
the main stem, No. of fruits per plant and with No. of
nodes on the main stem, and between No. of nodes on the
main stem and with plant height, indicating magnitude of
rG as compared to rp was high for these characters.
Values of genotypic and phenotypic correlation were
approximately equal among all other characters,
indicating magnitude of rG was compared to rp was equal
for these characters.
The environmental correlation values were high
between flowering time and No. of female flowers, No. of
female flowers per plant and No. of nodes on the main
stem and between No. of fruits per plant and No. of
nodes on the main stem, indicating, the expression of
these characters had been appreciably affected by
environmental factors.
The correlation between flowering time and No. of
nodes on the main stem, nodal position of first female
flower and plant height, and between No. of nodes on the
main stem and plant height were significant and rp value
was higher than rG value, indicating that rp was high in
magnitude than rG and the genetic association between
these characters were attributed to non genetic linkage.
Combining ability
1. The general and specific combining abilities were
significant at all seasons for all the studies traits.
Combined analysis over planting seasons showed the
same trend of significance. This indicated that both
the additive and non-additive type of gene action were
important and involved in the inheritance of these
traits. The ratio of GCA to SCA mean squares was
greater than one for each of the traits in single
season analysis as well as in combined analysis except
that for main stem length in open field nili season
and number of fruits per plant over three planting
seasons. This indicated the presence of genotypeenvironmental
interactions for these studied traits.
Therefore, one should bUy attention to diminish
environmental effects when practicing selection.
Moreover, significant genotypes-environment interactions
for all characters studied, indicated that
more than one environment are required to obtain
reliable information. The significance of GCAtreatment
interactions showed that GCA effects of the
parents (additive effects) were more sensitive by the
changes of the treatments (planting seasons) for all
traits except female flowering time. Furthermore, the
significance of sCA-treatments interactions showed
that SCA effects of the crosses for all characters
were inconsistent over planting seasons.
2. The results revealed that Line 1909 was the best
combiner for early female flowering and number of
female flowers per plant in single sea~on as well as
over three planting seasons. The line Chinese long was
the best combiner in open field for number of fruits
per plant and plant height. While Line 1909 was the
best combiner under green house as well as in pooled
over three planting seasons for number of fruits per
plant and plant height under green house condition.
3. Among all crosses and under open field summer season,
the cross (Marbosan x Chinese long) was the most
promising one for early female flowering time and
higher number of fruits per plant. Meanwhile, the
cross (1909 x Chinese long) was the most promising one
for higher number of female flowers per plant and
plant height. Under open field nili season, the cross
(1909 x Beit alpha) was the most promis ing one for
early female flowering, higher number of female
flowers per plant and plant height. While cross
(Marbosan x Chinese long) was the most promising one
for higher number of fruits per plant. Meanwhile, the
cross (Beit alpha x Chinese long) was the most
promising one for early female flowering and (Marbosan
x Beit alpha) was the most promising cross for the
other three characters under the greenhouse
conditions. Combining abilities pooled over three
planting seasons, the cross (Marbosan x Chinese long)
was the most promising one for early flowering time.
Meanwhile, the cross (Marbosan x Beit alpha) was the
most promising one for higher number of female flowers
per plant, number of fruits per plant and plant
height.