الفهرس 
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Abstract
SUMMARY
Programs breeding of grain sorghum aim to develop new varieties characterized by superior economic traits as early maturity, high yield potentiality and flexibility in tolerance to unfavorable environmental conditions for growth in order to be more suitable with different environmental conditions and produce high yield under all conditions.
Therefore this research aimed to:
4. Study the genetic parameters for yield and correlated yield under drought stress.
5. Attempt to obtain genotypes of grain sorghum tolerant to drought stress.
6. Study the relationship between the ISSR-PCR, RABD-PCR and field results in an attempt to identify drought tolerant genotypes by using this technique.
The field experiments of this investigation was conducted at Giza and Shandaweel Research Stations of the Field Crops Research Institute (FCRI), Agricultural Research Center (ARC), Egypt, in the seasons from 2011 to 2013
In the first growing season (2011), crossing was made among the four parents to produce the F1 hybrid grains of the two crosses; ICSB-88005 × MR-812 (Cross I) and ICSB-37 × ICSR-93002 (Cross П).
In the second growing season (2012), F1 hybrid’s of the two crosses and the four inbred lines were sown and F1 plants of each cross were backcrossed to their respective parents to produce BC1 and BC2 grains. At the same time, some of the F1 plants for each cross were selfed to produce the F2 grains and parents were also selfed to maintain parental purity. In addition, crossing was made between the parental inbred lines again to produce additional new F1 grains for each cross.
In 2013 season, on the 26th of June, the grains of the six populations i.e. P1, P2, F1, F2, BC1 and BC2 of the two crosses were evaluated under two
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levels of watering [100 and 50% ETc] in two separate experiments at Shandaweel Research Station. Each experiment was conducted in a Randomized Complete Block Design with three replications. Each replicate comprised one row for each parent and F1 cross, four rows for each backcross and six rows for the F2 population for each cross. Data regarding backcrosses and F2,s under normal watering were not recorded due to the dissimilarity of its genetic marke-up with those under drought. The rows were 4 meters long and 60 cm apart. Plants were spaced at 20 cm apart within row. Three grains were planted in each hill and three weeks later seedlings were thinned to only two plants per hill.
Observations and measurements were recorded on individual guarded plant basis where data were recorded on 30 plants for each of P1, P2 and F1, 150 plants for each of BC1 and BC2 and 240 plants for each of F2 population from the three replications for each cross.
The following readings and observations were recorded: days to heading, plant height (cm), panicle length (cm), panicle width (cm), number of green leaves per plant, 1000-grain weight (g), grain yield per plant (g) and drought susceptibility index.
The collected data were analyzed statistically and genetically to estimate the following parameters in each cross which included: means, variances, heterosis, inbreeding depression, degree of dominance, types of gene action, heritability in broad and narrow senses, expected genetic advance from selection ,phenotypic correlation coefficients and path coefficient analysis
Inter-Simple Sequence Repeats (ISSR-PCR and RABD-PCR ) was used to analyze the genetic polymorphisms of the two tolerant grain sorghum crosses (ICSB-88005 × MR-812 and ICSB-37 × ICSR-93002), the two sensitive grain sorghum parents (ICSB-88005 and ICSB-37) and the two tolerant grain sorghum parents (MR-812 and ICSR-93002), the most two low yielding F2 groups and the most two high yielding F2 groups of the two
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crosses were used to assess molecular markers associated with drought tolerant and yield potentiality of grain sorghum.
The obtained results can be summarized as follows:
A. Analysis of variance and means performance:
1. Results of the analysis of variance showed significant differences among the six populations of each cross for the studied traits.
2. F2 populations followed by BC1 and BC2 populations gave the highest values for phenotypic variance (PV) and phenotypic coefficient of variation (PCV), while the parents and F1 populations gave the lowest values. The two traits i.e. days to heading and plant height under drought stress conditions exhibited the lowest averages of PCV, while the three traits; number of green leaves per plant, grain yield per plant and panicle width gave the highest averages. Phenotypic coefficient of variation (PCV) values were slightly higher than GCV in cases of days to heading, plant height and panicle length indicating the presence of little environmental influence on the expression of these traits. The remainder characters showed higher PCV than GCV.
B. Heterosis, inbreeding depression and potence ratio:
1. The two studied crosses exhibited significant positive heterosis percentages over the mid and better parent values for all of the traits under study, except days to heading which exhibited significant negative (desirable) heterosis values in the two crosses. The percentages of significant positive heterosis relative to the mid parent values ranged from 12.86% for panicle length in cross I to 44.64% for no. of green leaves per plant in cross I. Whereas the percentages of significant positive heterosis relative to the better parent values ranged from 6.32% for panicle length in cross I to 36.67% for grain yield per plant in cross II. On the other hand, percentages of significant negative heterosis relative to the mid-parent values ranged from -3.46 to -3.75% for days to heading in cross I and cross II, respectively, whereas percentages of significant negative
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heterosis relative to the better parent values ranged from -1.64 to -3.03% for days to heading in cross I and cross II, respectively.
2. Significant positive percentages of inbreeding depression in Table (8) ranged from 1.80% for number of green leaves per plant in cross II to 11.45% for panicle width in cross I, whereas insignificant negative percentages were detected which amounted -1.00 to -1.14% for days to heading in cross II and I, respectively.
3. Potence ratio indicated that over dominance were detected towards the earlier parent in days to heading in cross II as well as, the taller parent for plant height, the higher parent in number of green leaves per plant, the higher parent in panicle length, panicle width and 1000-grain weight, the higher parent for grain yield per plant in the two crosses.
C. Scaling test (epistasis test), F2-deviation (E1), backcrosses deviation (E2) and types of gene action:
1. The results of scaling test (A, B, C and D) indicated the presence of non-allelic interaction e.g., the presence of epistasis type of gene action in addition to the additive and dominance gene effects in the inheritance of the traits studied under drought stress condition.
2. The results showed significant deviation of F2 populations than the average of F1 performance and mean parental performance (E1), as well as significant deviation for backcross performance than the average of F1 and recurrent parent performance (E2), suggesting contribution of epistatic gene action in the inheritance of the studied traits in the two crosses.
3. The results of the nature of gene action controlling the inheritance of different traits under study using the method of generation mean analysis (six parameters model) revealed that the F2 mean effect parameter (m) was found to be highly significant for all studied traits in the two crosses under investigation, indicating that all traits were quantitavely inherited.
4. The results showed that dominance × dominance type of epistatic gene action, followed by and additive gene effects the additive × dominance type of epistatic gene action contributed with the large part of genetic
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components controlling the inheritance of the studied traits compared to dominance gene effect and the additive × additive type of epistatic gene effects.
On the other hand, the additive × additive type of epistatic gene action and additive gene effects appeared to be relatively less importance than the three above mentioned types of gene effects in the inheritance of the studied traits.
The results of generation’s variance analysis indicate the important role of the additive variance compared to dominance variance in the inheritance of the studied traits. This finding is coincidence at large extent, with the result obtained from the generation mean analysis.
D. Heritability estimates and expected genetic advance from selection:
1. The results showed high heritability estimates in the broad sense ranged from 68.95% for no. of green leaves per plant in cross I to 86.09% for day to heading in cross II. Heritability estimates in the narrow sense ranged from 19.14% for plant height to 59.21% for panicle width in cross II.
2. The expected genetic advance as percentage of the F2 mean (Δg%) for the studied traits ranged from 3.03% for days to heading to 28.72% for grain yield per plant in cross II.
3. High expected genetic advance was found to be associated with high narrow sense heritability values for panicle width and grain yield per plant in the two crosses, therefore, phenotypic selection for these characters would likely to be effective and satisfactory for successful breeding purposes. On the other hand, high genetic advance under drought condition was found to be associated with moderate narrow sense heritability values for no. of green leaves per plant, suggesting that selection for these traits would be probably effective. Furthmore, moderate expected genetic advance was found to be associated with the relatively low narrow sense heritability value for days to heading indicating slow improvement of this trait in subsequent generations.
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E. Correlation and path coefficient analysis:
1. The results of the phenotypic correlation coefficients under drought stress conditions for each cross between all possible pairs of characters including grain yield per plant, showed that grain yield showed positive significant and highly significant correlations with each of panicle length, panicle width and 1000-grain weight in the two crosses. Such positive significant associations between grain yield and these attributes means the important contributions of these components towards grain yield in grain sorghum populations by which selection for these traits would be effective in improving plant grain yield.
2. from the results of path coefficient analysis, it was found that panicle length, panicle width and 1000-grain weight in the two crosses proved to be the major grain yield contributors. Thus, the breeder should take into his consideration these traits as selection criteria for grain sorghum yield improvement especially those positively and significantly correlated with grain yield per plant and had moderate to high narrow sense heritability estimates.
F. Molecular marker results:
Six primers (A-11, B-20, C-01, HB-11, HB-12 and HB-13) showed association with drought tolerance as follows:
C. In the first cross (ICSB-88005 × MR-812):
Primer A-11 resulted in 18 bands with molecular sizes ranged from 219.6 to 2263.6 bp. Two universal bands at MW 2033.9 and 1539.9 bp were characterized the tolerant groups (the moderately tolerant parent MR-812, the most high yield group of F2 and the relatively tolerant F1). While, were absent in the sensitive groups (the sensitive parent ICSB-88005 and the most low yield group of F2). In the same time two universal bands at MW 1677.5 bp and 1444.1 bp were characterized the sensitive groups. While, were absent in the tolerant groups.
Primer B-20 indicated the amplification of 24 bands with molecular weight ranged from 305.9 to 2346.9 bp. Five universal bands at MW 962.1,
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784.9, 488.2, 419.4 and 305.9 bp were characterized the tolerant groups while, were absent in the sensitive groups. In the same time two universal bands at MW 500.1 and 436.6 bp were distinguished the sensitive groups.
Primer C-01 resulted in 21 bands with molecular weight ranged from 224.7 to 1298.6 bp. Two universal bands at MW 669.6 and 398.8 bp were characterized the tolerant groups (the moderately tolerant parent MR-812, the most high yield group of F2 and the relatively tolerant F1). In the same time three universal bands at MW 766.3, 661.4 and 296.4 bp were distinguished the sensitive groups (the sensitive parent ICSB-88005 and the most low yield group of F2).
Primer HB-11 indicated the amplification of 33 bands with molecular weight ranged from 422.7 to 2030.9 bp. Three universal bands at MW 1162.5, 811.8 and 467.7 bp were characterized the tolerant groups while, were absent in the sensitive groups. In the same time five universal bands at MW 1447.3, 1215.6, 1111.4, 814.8 and 422.6 bp were characterized the sensitive groups (the sensitive parent ICSB-88005 and the most low yield group of F2).
Primer HB-12 resulted in 25 bands with molecular weight ranged from 187.2 to 1625.2 bp. Two universal bands at MW 1189.3 and 750.1 bp were characterized the sensitive groups while, were absent in the tolerant groups. In the same time two universal bands at MW 634.5 and 524.9 bp were distinguished the tolerant parent and the most high yield of F2 groups.
Primer HB-13 resulted in 27 bands with molecular weight ranged from 337.7 to 880.4 bp. Two universal bands at MW 747.3 and 477.6 bp were characterized the tolerant groups while, were absent in the sensitive groups.
D. In the second cross (ICSB-37 × ICSR-93002):
Primer A-11 resulted in 18 bands with molecular sizes ranged from 224.3 to 1741.2 bp. Two universal bands at MW 1741.2 and 1284.4 bp were characterized the tolerant groups (the moderately tolerant parent ICSR-93002, the most high yield group of F2 and the relatively tolerant F1). While, were absent in the sensitive groups (the sensitive parent ICSB-37 and the most low yield group of F2). In the same time two universal bands at MW
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Heba M. Hafez (2016), Ph. D. Fac. Agric., Ain Shams Univ.
1491.3 and 1165.9 bp were characterized the sensitive groups while, were absent in the tolerant groups.
Primer B-20 indicated the amplification of 22 bands with molecular weight ranged from 286.4 to 1101.9 bp. Two universal bands at MW 604.2 and 388.7 bp were characterized the tolerant parent ICSR-93002 and the most high yield group of F2 while, was absent in the sensitive groups. In the same time one universal band at MW 758.7 bp was distinguished the sensitive groups.
Primer C-01 resulted in 28 bands with molecular weight ranged from 221.9 to 1267.1 bp. Six bands at MW 1191.7, 1016.1, 804.8, 729.6, 614.5 and 486.7 bp were characterized the most high yield group of F2 while, were absent in the sensitive groups. In the same time one universal band at MW 691.1 bp was distinguished the sensitive groups.
Primer HB-11 indicated the amplification of 28 bands with molecular weight ranged from 369.4 to 1802.0 bp. Three universal bands at MW 1724.0, 1401.7 and 859.9 bp were characterized the tolerant groups while, was absent in the sensitive groups. In the same time one universal band at MW 655.44 bp was characterized the sensitive groups (the sensitive parent ICSB-88005 and the most low yield group of F2).
Primer HB-12 resulted in 17 bands with molecular weight ranged from 524.9 to 1557.4 bp. Two universal bands at MW 1557.4 and 597.3 bp were characterized the tolerant groups (the moderately tolerant parent ICSR-93002, the most high yield group of F2 and the relatively tolerant F1) while, were absent in the sensitive groups (the sensitive parent ICSB-88005 and the most low yield group of F2).
Primer HB-13 resulted in 32 bands with molecular weight ranged from 379.8 to 1155.5 bp. Two universal bands at MW 509.6 and 429.6 bp were characterized the tolerant groups (the tolerant parent ICSR-93002, the most high yield group of F2 and the tolerant F1) while, were absent in the sensitive groups. While, were absent in the sensitive groups. In the same time one universal band at MW 1155.5 bp, was characterized the sensitive groups while, was absent in the tolerant grou