الفهرس 
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Abstract
The present work was designed to study the inheritance
of earliness character using different measurements in
the following two crosses
* Cross I Bah tim lll (G. barbadense L.) X 8763i (G. barb adense
L. ).
* Cross II Bah tim Ill (Q:_. barbadense L.) x Mesilla Valley
(~. hirsutum L. ).
The earliness measurements used were; node number
of the first fruiting branch, days to first flower, days
to first boll opening and earliness index.
The study of each entry included :
1- Degree of homozygosity.
2- Type of inheritance.
3- Degree of dominance.
4- Nature of gene action.
5- Transgressive segregation.
6- Heritability estimate.in the narrow sense.
7- Expected advance upon selection.
8- Heterosis and inbreeding depression.
As mentioned in tne results section of this thesis
it was found that in most measurements studied the coeffici e: :”of variation valuc”S of the non sec”egatin;;c populatiolls
(parents and F1 ) were in general lower than those estimated
for the segregating populations (F2 and backcrossec),
indicating parental homozygosity.
Results indicates that :
l- Node number of the first fruiting branch :
1- The character found to be quantitatively inherited.
2- Low node number was partially dominant over high
node number in cross I, whereas overdominance of
low node number was found.
3- Nature of gene action could not be determined in
the two crosses except from the F1 data in cross I
which showed more multiplicative than additive gene
action.
4- No transgressive segregation was detected in
cross I, whereas in cross II F2 data as well as
backcross to both parents data sho”ved transgressi v’.
segregation towards the earlier parent.
5- Heritability values in narrow sense were 68.29%
and 78.13% for cross I and cross II, respectively.
6- The ex-pected genetic advance upon selecting the best5 % of indiViduals being X’.09 % in cross L and
48.58 in cross II.
7- Highly significant negative heterosis was observed
in each of the two eros ses. No inbreeding depress.i..oL
was found in cross I, whereas significant neg,ative
inbreeding depression was obtained for cross II.
2- Days to first flower :
1- The character inherited in a quantitative manner.
2- Partial dominance of the latter parent was found
in cross I, while partial dominance of the earlier
parent was revealed for cross II.
3- Nature of gene action could not be determined from
either F1 o~ F2 in both crosses.
4- Cross I showed transgressive segregation towards
the latter parent. In cross II transgressive segregation
was detected in both directions.
5- The narrow sense heritabtlity values were 43.36 %
and 57.33% for cross I and cross II, respectively,
6- The expected genetic advance was calculated to be
4.30 % for cross I and 9. 20 % for cross II upon
selecting the earlier 5 % of the plants,?- 1- highly sir:s.n.ficant posl t._vr; he rr,~_-i(; c;ffect
was found in cross 1, while a highly s:cgnificant
negative heterotic effect was found in cross II.
Highly significant positive 1nbreeding de-pression
was found in cross I, whereas highly significant
negative inbreed~ng depression was found in
cross II.
3- Days to first boll opening :
1- The character found to be quantitatively inherited,
2- Partial dominance of the latter parent found in
both eros ses.
3- No conclusion could be reached with regard to
gene action in either cross I or cross II.
4- Transgressive segregation was not detected in
either crosses.
5- The narrow sense heritability values were 59.54 %
and 32.13 % for cross I and Gross II, respectively.
6- The expected advance was calculated to be 5.15%
in cross I and 4.02 % in cross II when the best
5 % of individuals were saved.7- Highly sie;nificant positive hetr’:cosis in the two
crosses were observed. Highly significant -positive
inbreeding depression was reported in cross I whe rcc·
as cross II showed small but highly significant
negative inbreeding depression.
4- Earliness index :
Earliness index was studied only in the intervarietal
cross (Bahtim lll x 8?63i) where the interspecific
cross was excluded because of sterility occurred in F2 population
of that cross.
1- The character inherited in a quantitative manner.
2- Partial dominance of the earlier parent was found.
3;... No conclusion for the nature of gene action could
be reached either from F1 or F2 •
4- Transgressive segregation was observed with respect
to earliness index character in both directions.
5- The narrow sense heritability value was determined
as being 59. 28 %.
6- The expected genetic advance would be 30.82 ?o ur.on
selecting the best 5 % of bhe individual plants.
7- Earliness index character showed highly significar
positive heterotic effects. No significant inbr<e ~d
depression was found for this trait.Correlations betvNen characters :
--~·~ --
between each pair ct.’ the ·:.fcarach’•rs, ’lode number ot the
first fruiting bra,’1Ch, days to first flower, days to first
boll opening earliness index and yield.