الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 190 |  |  |
| | | from | 190 | | |
Abstract
The present study was carried out during, 2000, 2001 and 2002 seasons at El- Edwa, west of El- Minia Governorate, Egypt. The aimed of this investigation was to study:
A- Mean Performance and analysis of variance.
B- Nature of gene effect and genetic components.
C- Combining ability.
D- Heterosis
E- Correlation between studied traits.
Nine genetically diverse sesame genotypes were used for this study. In 2000 season all possible crosses among parents, without reciprocals, were done to make a diallel series of 36 hybrids. In 2001 season, 45 entries i.e. nine parents and 36 hybrids, were sown and the parents were crossed again to obtain more enough hybrid seeds. In 2002 seasons, the nine parents and all possible F1 and F2 hybrids were grown in Randomized Complete Block design with four replications. The experimental plot consisted of three rows, four meters long and 60 cm between rows with hills spaced 20 cm apart leaving two plants / hill.
Results obtained could be summarized as follows:
A- Performance of sesame genotype:
1-Analysis of variance revealed highly significant differences among genotypes, as well as parents and their F1 and F2 generations and the parents vs. F1 crosses and F2 populations.
2-The average of parents, F1 hybrids and F2 population were (49.14, 50.92 and 45.20 days) for number of days to 50 % flowering, (159.14 , 166.66 and 153.71 cm) for plant height, ( 26.52, 24.23 , 22.79 cm.) for the height of the first capsule, ( 133.26, 142.87 and 135.16 cm) for fruiting zone length, (26.52 , 24.22 and 22.79 cm) for number of branches, ( 158.35, 195.61 and 160.82 ) for number of capsule, ( 2.77 , 3.10 and 2.61 cm.) for capsule length, ( 26.09 , 35.10 and 29.04 gm) for seed yield/ plant, ( 3.64, 4.16 and 3.83 gm) for 1000 seed weight and (52.77 , 52.51 and 53.81 %) for oil percentage, respectively.
3-The earliest genotypes in flowering were Line 106 ( P9) , while the most promising F2 populations were ( P1x P3), ( P4x P7) and ( P8x P9) The highest parents in seed yield / plant were ( P1and P3) , while F2 populations of ( P1x P2)and (P2x P4) were the most promising . For oil percentage P4 x P5 and P9 and cross ( P7x P9) in F1 and F2 generations showed the highest oil percentage.
B- Nature of gene effect and genetic components:
1-The diallel analysis of variance revealed that the additive “a” and dominance “b” items were highly significant in the two generations for all studied traits. Moreover, highly significant mean squares were obtained for the directional dominance effect “b1” a symmetry gene distribution “b2” and specific combining ability as indicated by “b3”.
2-The additive genetic components “D” was highly significant for height of the first capsule, number of branches/ plant, number of capsules/ plant, seed yield / plant and oil percentage in both generations, plant height in F1 hybrids and (D) was in significant for capsule length in both generations. This indicate the importance of additive and non-additive gene action in the inheritance of such traits, but yet the additive gene action was the most predominant.
The dominance genetic components (H1 and H2) were highly significant for the height of the first capsule, number of capsule/ plant, capsule length, seed yield plant and oil percentage in both generations as well as for “H2” in F2 populations and significant for “H1” in F1 hybrids for number of capsules / plant and plant height, respectively. Moreover, the dominance components (H1), was higher in magnitude than (D) components in all traits, except plant height in F1, indicating that non- additive gene effect was predominant, resulting in the average degree of dominance (H1/ D)½ which was more than one for all studies traits, except plant height, number of branches / plant and 1000- seed weight, confirming over – dominance with some exceptions.
The magnitudes of H1 were larger than H2, resulting in (H2 / 4H1) which was less than 0.25 for all studies characters, except number of branches / plant and capsule length in F1 hybrids, indicating that positive and negative alleles of loci for these trait are not equally distributed between the plants, These results confirm the results of “ b2”.
The (F) components coupled with (KD/ KR), was found to be positive for most traits, indicating an excess of dominant alleles genetic constitution of parental genotypes for these traits, resulting in (KD/ KR) which was more than one with some exceptions.
High broad sense heritability values were obtained for all studies traits, while narrow sense heritability values ranged from low to moderate according to trait.
3-The differences between arrays for (Wr + Vr) values were significant or highly significant for plant height, height of the first capsule, length of fruiting zone, number of branches / plant number of capsule / plant, 1000- seed weight seed yield / plant and oil percentage in both generations, indicating the presence of non- additive genetic variation for these traits.
4-The differences between arrays of ( Wr- Vr) values were highly significant for plant height in both generations and for number of capsules / plant in F1 hybrids as well as significant for the height of the first capsule, number of branches/ plant, number of capsules/ plant, length of capsule in F2 population and significant in both generations for oil percentage , indicating the presence of non additive genetic variation.
5-The regression line cut (Wr) axis below origin point, indicating over dominance for plant height, height of the first capsule, fruiting zone length, capsule length, seed yield / plant and oil percentage. On the hand, the regression line cut (Wr) axis above origin point, indicating partial dominance for days to 50% flowering, number of branches, number of capsules and 1000- seed weight.
The distribution of dominant and recessive genes between sesame parental genotypes varied from character to another and from parent to another.
C-Combining ability:
1- Mean squares due to both G.C.A. and S.C.A. were significant or highly significant for all studies traits, except G.C.A. for 1000- seed weight in F2 populations and S.C.A. for number of capsules / plan in F2 and 1000- seed weight in F1 generation. Moreover, the ratio of G.C.A. to S.C.A. variance was greater than one in all studies traits, except 1000- seed weight in F2 generation.
2-For general combining ability the parental genotype (P9) was considered good combiner for days to 50 % and oil percentage, (P1), (P6) and (P8) for plant height and length of fruiting zone, (P4), (P5) and (P2) for number of branches and capsules / plant, (P2) and (P6) for the first capsule height, (P7) and (P8) for capsule length, (p1) and (P7) for 1000- seed weight and (P4), (P1) and (P3) fro seed yield / plant.
3-Specific combining ability (S.C.A.) cleared that the promising combinations were (P5 X P7) and (P5 X P6) for earliness, (P7 X P9) , (P7 X P8) and (P1 X P2) for plant height and the length of fruiting zone, (P5 X P6) , (P4 X P6) and (P6 X P7) for the height of the first capsule, (P5 X P9) and (P5 X P6) for number of branches / plant, (P2 X P5) and (P1 X P3) for number of capsules/ plant, (P1 X P2) , (P2 X P4) and (P8 X P9) for capsule length, (P2 X P7) and (P2 X P5) for 1000- seed weight, (P4 X P7) and (P2 X P4) for seed yield / plant and (P2 X P6) , (P7 X P8) and (P6 X P7) for oil percentage.
D- Heterosis:
D. 1-Heterosis values as percentage for Mid- parent:
For days to 50 % flowering , crosses (P2 X P5) in F1 and (P5 X P6) in F2, for plant height (P2 X P4) in both generations, for height of eth first capsule (P5 X P6) in both generations, for fruiting zone length (P7 X P8) in F1 and (P2 X P4) in F2, branches number / plant (P2 X P6) in F1 and (P5 X P6) in F2, for capsules number / plant (P7 X P8) in F1 and (P2 X P5) in F2 , for 1000- seed weight (P1 X P7) in F1 and (P2 X P5) in F2, for seed yield / plant , (P4 X P7) in F1 and (P2 X P4) in F2 , for oil percentage (P7 X P9) in F1 and (P2 X P7) in F2 were the best for heterosis.
D. 2- Heterosis values as percentage Better parent:
For plant height (P2 X P4), for height of the first capsule (P5 X P6) , for fruiting zone length and seed yield/ plant (P5 X P6) in both F1 and F2 generations and for days to 50 % flowering (P2 X P3) in F1 and (P5 X P6) in F2, for number of branches / plant (P6 X P8) in F1 and (P7 X P8) in F2 , for number of capsules /plant (P7 X P8) in F1 and (P2 X P5) in F2, for capsule length (P2 X P3 and P4 X P6) in F1 and (P2 X P4) in F2, for 1000 seed weight (P2 X P7) for F1 and (P2 X P5) for F2 and for oil percentage (P2 X P6) in F1 and (P2 X P7) in F2 were the best for heterosis.
E-Correlation between characters:
Earliness days to 50 % flowering for genotypes was negatively associated with number of capsules/ plant, capsule length, 1000- seed weight, seed yield / plant and oil percentage.
Regarding F1, earliness was significant and negatively correlated with number of branches / plant and number of capsules/ plant, seed yield / plant and oil percentage, significant positive correlation were observed between seed yield/ plant and number of branches and capsules / plant, also this was true in F2 generation. It could be concluded that selection for seed yield could realized through selection for earliness, plant height and number of branches and capsules / plant.