الفهرس 
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Abstract
Summary
The present investigation was conducted to develop
molecular genetic fingerprints for nine local rice cultivars, to
elucidate relationships among these cultivars and to investigate the
molecular basis of salt tolerance in nine rice cultivars.
Identification of nine rice cultivars
Identification based on SDS-PAGE protein electrophoresis
Data of SDS-PAGE for total protein in leaves revealed that bands
with different molecular weights (MW) were detected and ranging
from about 9.9 KDa to 166 KDa. The total number of bands among
genotypes ranged from 27 in Sakha101 to 29 in Sakha104,
Sakha103 and Giza178. The level of polymorphism was 38.5%
among the studied cultivars.
Identification based on RAPD
Analysis of ten RAPD primers successfully produced multiple
band profiles with a polymorphism percentage ranged from 30% to
81.82%. Primers produced band numbers ranging from 11 (primer
OP- E19) to 23 (primer OP-A16) across cultivars the total number
of reproducible fragments amplified by the ten primers reached 157
from which 74 were polymorphic fragments. This represented a
level of polymorphism of 47.13% among the studied lines.
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Identification based on SSR
Data of the amplified fragments using five SSR primers for
the nine rice cultivars revealed that all primers succeeded in
amplifying DNA fragments. Number of alleles in all tested primers
is one allele per locus. The overall size of amplified products ranged
from 137 bp (RM246) to 338 bp (RM166). There is no unique
alleles were observed at all of the 5 tested SSR loci. The frequency
of all alleles was 100% while the polymorphism was zero.
Phylogenetic Relationships
The phylogenetic dendrogram based on the overall markers (SDSPAGE,
RAPD and SSR- PCR) indicated two main groups: The first
main group was subdivided into two subgroups. The first subgroup
includes Sakha102 and each of Sakha105, Sakha103 and Sakha101.
The second subgroup group was includes AgamiM5 and Sakha104.
The second main group included Giza 178 and each of Giza 177 and
Nabatat asmar. The similarity coefficient reached a highest value of
1.0 between Sakha102 and Sakha103, and reached a minimum value
0.0 between Giza 178 and Sakha105.
After conducting a series of laboratory experiments,
greenhouse pot and application under saline field
experiments so as to assess the role of exogenously applied
validamycin A in inducing salt tolerance in two rice cultivars
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through enhancing the accumulation of trehalose, following
conclusions can be drawn:
1- Salt stress-induced reduction in growth of rice plants was
alleviated by exogenously applied validamycin A.
2- Improvement in growth of salt stressed plants of both rice
cultivars was associated with increased photosynthetic
rate.
3- Improvement in photosynthetic efficiency was partially
associated with amount of photosynthetic pigments,
probably due to osmo-protective effects of trehalose on
chloroplast (thylakoid membranes).
4- Salinity stress decreased starch and total soluble protein
contents concomitantly with increasing total soluble
sugars, sucrose, trehalose, proline and free amino acids in
both cultivars. Raising trehalose level in the plant tissues
treated with validamycin A was accompanied by increase
in the starch and protein content and appearance of new
protein pattern of both cultivars.
5- Trehalose accumulation can enhance tolerance of both rice
seedlings to salt stress by decreasing the concentration of
MDA and H2O2 and increasing the transcript levels and
activities of SOD, APX, CAT, GR, POD and PPO, and the
contents of cartenoids, ascorbic acid, flavonoids, and
tocopherols which, in turn, enhance the antioxidant ability
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and protect rice seedlings against oxidative stress induced
by salt stress.
6- Production of antioxidants and membrane protecting
compounds help plants accumulated trehalose to withstand
salt exposure. It is reasonable to believe that specific
membrane lipid classes and sustainable transport proteins
are constitutive or induced under saline conditions which
might contribute to salt tolerance acquired by trehalose
accumulation.
7- Exogenous application of validamycin A caused high
accumulation of K+, N and P and lowering the content of Na+ in
both cultivars under salt stress conditions.
Further investigations are needed to validate the effectiveness of this
antibiotic manipulation under field conditions and to establish the
effective doses based on different salt stress levels.
1- Salt stress-induced reduction in number of seeds, grain yield per
plant, 1000-grain weight and filled-grain percentage for both rice
cultivars was alleviated by exogenous application of validamycin
A as pre-sowing seed treatment under saline field conditions
2- Exogenous application of validamycin A was found to be most
effective at AgamiM5 cultivar as compared to the other cultivar
Skha103.
At the molecular level, alterations in protein pattern of the
treated rice tissues revealed that validamycin A treatments induced
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the appearance of new set of protein bands concomitant with the
disappearance of others. Moreover increment in TPS gene
expression of both rice cultivars tissues over those untreated tissues
was recorded.