الفهرس 
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Abstract
This investigation was carried out at the Research Farm of Rice
Research and Training Center (RRTC), Sakha, Kafr El-Sheikh, Egypt
during growing seasons 2009 and 2010 and Tissue Culture and Molecular
Plant Biotechnology Labs, Genetic Engineering and Biotechnology
Research Institute (GEBRI), Sadat City, Sadat City University, Egypt
during 2011 and 2012. Seven rice (Oryza sativa L.) genotypes, i.e., Giza
177, Giza 178, Sakha 101 and Sakha 102 as local genotypes from
Agriculture Research Center (ARC), Giza, Egypt and three exotic
varieties namely i.e., Suweon 349, IET1444 and Gaori, were used to
establish the experimental materials for this investigation. The seeds of
the seven parents and all possible 21 crosses were sown in 2010 under
two different conditions; i.e., control condition (cont.) and post anthesis
drought stress (PADS) in two adjacent experiments. The experiments
were arranged in a randomized complete block design (RCBD), with
three replicates for each stress condition. Each replicate consisted of
single row, 5 meters long, with 20 cm between rows and comprised 25
hills each of single plant. The data were recorded on an individual plant
basis for parents and F1 generation. At maturity, ten guarded plants were
selected at random for subsequent measurements; i.e., Days to 50 %
heading (days), plant height (cm), sterility (%), number of panicles per
plant, panicle length (cm), panicle weight (g), 100-grain weight (g), grain
yield per plant (g), hulling percentage, milling percentage, head rice
percentage, grain length and grain shape
One media protocol with three replicates for each genotype was used
in this study. The culture medium contained the inorganic salt of
Murashige and Skoog (MS 1962), supplemented with (2.5 mg/L and free
hormones medium) 2, 4 dichlorophenoxy acetic acid (2, 4-D), 0.5 mg/L thiamin- HCL, 150 mg/L asparagines, 30g/L sucrose and 7 g/L agar and
their callus fresh weights evaluated by using different concentrations of
polyethylene glycol in two periods is (30, 45 days). Eleven rice
microsatellite markers were selected from the rice genome data base
(http://www.gramene.org/markers/microsat/all-ssr.html*) for genotyping
on the basis of their known chromosomal location to give a uniform
coverage all rice genome.
Seven rice (Oryza sativa L.) genotypes were used in a diallel cross to
study: (i) The potentiality of heterosis expression of agronomic, yield, its
component traits, grain quality traits under two different conditions and
in vitro traits, (ii) the magnitude of both general and specific combining
abilities and their interaction with two different conditions, their
combined data and stress tolerance index (iii) the importance of using
tissue culture as rapid procedure for early predicting combining ability
and heterosis in rice hybrid breeding programs, (iv) the genetic diversity
based on SSRs markers among rice genotypes, (v) the relationship
between genetic distance based on SSRs markers with SCA and heterosis
effects of all traits studied and (vi) the importance should given to these
materials in a breeding program by evaluating the seven rice genotypes
according to their general and specific combining ability effects.
The obtained results could be summarized as follows:
I. Agronomic, yield and its components traits
1- The mean squares of stress conditions were detected to be highly
significant for plant height, sterility %, number of panicles per plant,
panicle length, panicle weight, 100-grain weight, 100 grain weight and
grain yield per plant.
2- The mean squares of genotypes, parents and the resultant crosses were
found to be highly significant for days to 50 % heading, plant height, sterility %, number of panicles per plant, panicle length, panicle weight,
100 grain weight and grain yield per plant at the two different
conditions, their combined data and the stress tolerance index except
stress tolerance index for plant height.
3- The mean squares of parents vs. crosses were found to be highly
significant for all agronomic, yield and its components studied traits at
the two different conditions, and their combined data; however the
stress tolerance index showed no significant except number of panicles
per plant.
4- The interactions of genotypes, parents and crosses at the two different
conditions, based on combined data were detected to be highly
significant for all agronomic, yield and its components studied traits
except plant height.
5- The interaction of parents vs. crosses at the two different conditions,
based on combined data, was found to be highly significant for sterility.
6- The most desirable useful heterosis for grain yield per plant was
detected in eight hybrids under study, which ranged from 5.19 % to
58.22% over the respective better-parents.
7- The four hybrid combinations; i.e., Giza 177 x IET 1444, Giza 178 x
Sakha 102, Sakha 102 x IET1 444 and Suweon 349 x IET 1444 would
be of practical importance in abrading program for producing hybrid
rice because of their superiority in number of panicles per plant, panicle
length, panicle weight, 100-grain weight and grain yield per plant.
8- Both GCA and SCA variances were found to be highly significant for
all agronomic, yield and its components studied traits under two
different conditions, their combined data and the stress tolerance index. 9- The GCA / SCA ratios were found to be greater than unity for all
agronomic, yield and its components studied traits.
10- The interactions GCA and SCA at the two different conditions,
based on combined data were detected to be highly significant for all
agronomic, yield and its components studied traits.
11- The two rice genotypes, Giza 178 and IET 1444 which proved to be
excellent combiners for grain yield per plant, could be of practical
interest in a rice breeding program towards developing high yielding
genotypes.
II. Grain Quality traits
1. The mean squares of stress conditions were detected to be highly
significant for hulling percentage, milling percentage, head rice
percentage, grain length and grain shape.
2. The mean squares of genotypes and resultant crosses were found to be
highly significant for hulling percentage, milling percentage, head rice
percentage and grain length under the two different conditions, their
combined data and the stress tolerance index except stress tolerance
index for grain shape.
3. The parents were found to be highly significant for all grain quality
studied traits under the two different conditions, their combined data
and their stress tolerance index except combined data and stress
tolerance index for grain shape.
4. The mean squares of parents vs. crosses were found to be highly
significant for all grain quality studied traits at the two different
conditions and their combined data except post-anthesis drought stress conditions and their combined data for hulling percentage; however
only hulling and milling percentage showed highly significant at the
stress tolerance index.
5. The interactions of genotypes, parents and crosses with two conditions
based on combined parents with stress conditions and crosses with
stress conditions were found to be highly significant for all grain
quality studied traits.
6. The interaction of parents vs. crosses with two stress conditions based
on combined data were found to be highly significant for hulling
percentage and milling percentage.
7. Both GCA and SCA variances were found to be highly significant for
all grain quality studied traits at the two different conditions and their
combined data except GCA under control condition for grain shape.
However stress tolerance index were found to be highly significant
except GCA for milling percentage and (GCA, SCA) for grain shape.
8. The GCA / SCA ratios were found to be high than unity for all grain
quality studied traits, indicating that additive type of gene action was
greater importance in the inheritance of all grain quality studied traits.
9. The interactions of stress conditions with both types of combining
ability were found to be highly significant for all grain quality studied traits except GCA for milling percentage and (GCA, SCA) for grain
shape.