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Abstract
The present study was carried out at Shandaweel Agricultural Research Station, Sohag, Egypt during the period of 2008-2011 summer seasons. The objective of this study was to estimate the response to selection, i.e. pedigree selection, in early and late generations as well as the effect of selection on correlation coefficients among the studied traits as revealed by path coefficient analysis in two sesame (Sesamum indicum L) populations.
The breeding material used in this study was 200 F3-families traced back to random F2 plants from two crosses i.e. (Introductions 143 x Introductions 245) as population I and (Introductions 520 x Giza 32) as population II.
Seed yield/plant, length of fruiting zone and number of capsules/plant were used as selection criteria in early and late selection in both populations.
The obtained results could be summarized as follows;
I- Description of the base population:
1- The results from the analysis of variances reflect the genetic differences among the F3-families for all studied characters in the two base populations. Hence, sufficient genetic variation is presenting in both populations and could be used for pedigree line selection.
2-The slight discrepancy between (GCV) and (PCV) resulted in high estimates of broad sense heritability for most studied traits in the two base populations. These data resulted in wide ranges and high estimates of broad sense heritability (more than 56%) for all studied characters in both base populations, except seed yield per plant (39.51%) in base population I.
3- The phenotypic correlation coefficients in the base populations between seed yield/plant and each of days to the 50 % flowering, plant height, length of fruiting zone, number of capsules/plant, and 1000-seed weight exhibited to be low to moderate values and accounted for 0.443, 0.246, 0.253, 0.466 and 0.293 in population 1 and 0.181, 0.481, 0.428, 0.543 and 0.406 in population 2, respectively. Moreover, seed yield/plant has low values with number of branches/plant (0.199) and capsule length (0.135) in population II.
2. Selection for seed yield/plant
2.1. Early pedigree selection
1- Families’ mean squares were highly significant in both populations after one and two cycles of early selection for all the studied characters.
2- The means of selected families after two cycles of early selection for seed yield/plant ranged from 31.88 g to 43.50 g with an average of 37.36g compared to 17.83g and 25.47g for P1 and P2 in population I, respectively. Likewise, these means varied from 29.33 to 39.67 with an average of compared to their respective parents P1 (19g) and P2 (29.00g) in population II.
3- The genotypic coefficients of variation (gcv) for seed yield/plant decreased from 22.94 and 37.06% in F3 to 9.88 and 8.13% after two cycles of selection in population I and II, respectively.
The phenotypic coefficients of variation (pcv) values were in line with those recorded for gcv in both populations.
4- The realized heritability estimated from the realized gain in both cycles of single trait selection in the two studied populations decreased from C1 to C2 for the selection criterion of seed yield per plant and all correlated traits.
5- The observed realized response after two cycles of pedigree selection for seed yield/plant were 46.70 and 60.11% in population I and 17.36 and 13.44% in population II as measured from the best parent and bulk sample, respectively. Moreover, the highest values of correlated response were recorded for number of capsules/ plant i.e. 51.89 and 38.35 in population I and 31.47 and 27.75 in population II, followed by length of fruiting zone which revealed 33.50 and 15.38 in population I and 27.92 and 25.58 in population II as a deviation from the best parent and bulk, respectively.
It is clear that the direct and correlated response values of selection were larger in population I than population II in most studied traits. This result exhibited the different genetic make-up of the two current populations.
6- The selected families in both populations surpassed significantly the respective parents and bulk, except two families (no. 21 and no, 116) in population II. Same view of trend could be found in correlated traits .i.e. plant height, length of fruiting zone and number of capsules / plant in both populations.
In population 1, the superior family No.153 yielded the highest seed yield/plant (43.50g) and surpassed highly significantly the respective parents P1 (17.83g), P2 (25.47g) and the bulk sample (23.33g) by 144, 70.8 and 86.5%, respectively. Also, this family (No.153) exceeded significantly the respective parents and the bulk sample in plant height, capsule length, number of branches /plant, number of capsule /plant and 1000-seed weight indicating the importance of those traits on seed yield/plant.
In population II, the superior family No. 47 after two cycles of selection out yielded 39.67g and surpassed significantly the respective parents P1 19g, P2 29.00g and bulk sample 30.00g by 108.08, 36.8 and 32.2%, respectively. This family (No 47) exceeded significantly the respective parents and bulk sample for plant height, Fruiting zone, capsule length, number of capsules/plant and 1000-seed weight explaining the effeteness of those traits on seed yield/plant as also recorded in superior family No.153 of population 1.
It is clear from the obtained results that all families after two cycles of pedigree line selection were late in flowering comparing of their respective parents and bulk in both populations, except the family No. 143 in population II was significantly earlier than its second parent (P 2) and was early flowering comparing to its first parent (P 1) and bulk. Moreover, this family surpassed significantly its parents and bulk in seed yield/plant (34.83 g), plant height (251.0 cm), length fruiting zone (163.0 cm), capsule length (5.12 cm), number of branches/plant (4.53), number of capsules/plant (147.5) and 1000-seed weight (5.10 g). The obtained results indicated that the pedigree line selection was most efficient procedure for improving seed yield and other companied traits.
7- After the cycles of selection, the coefficients of phenotypic correlation between seed yield and each of plant height, fruiting zone, capsule length, number of capsule /plant, 1000-seed weight and seed oil percentage were 0.626, 0.685, 0.863, 0.803, 0.745 and – 0.634 in population I and to 0.731, 0.805, 0.827, 0.729, 0.627 and – 0.550 in population II, respectively.
2.2. Late pedigree selection for seed yield/plant in the F5 generation
1- The mean squares revealed to be highly significant for seed yield/ plant and all correlated traits, indicating the genetic differences among the selected families in both populations.
2- The average of seed yield/plant overall selected families of 41.24 and 42.37g in late selection surpassed the averages from selected families of 37.36 and 34.03 g after two cycles of early selection by 10.38 and 24.51% for population I and II, respectively. Same trend of observation could be found for number of branches and capsules/ plant in both populations and for plant height and fruiting zone in population I as well as 1000-seed weight and oil % in population II.
3- The overall mean of selected families in late selection was slightly earlier than those of early selection after two cycles of selection by 2.87 to 1.34 days in populations I and II, respectively. Moreover, the overall mean of seed yield/plant for selected families in late selection surpassed their respective parents and bulk sample by 131.30, 61.92 and 76.77 % in population I and 122.84,89 and 41.23% in population II, respectively.
4- The estimates of PCV, GCV and heritability in broad sense for seed yield/plant were low and accounted 6.54, 5.93 and 82.37 % and 5.25, 4.71 and 80.53 % after one cycle of late selection comparing to 10.62, 9.88 and 86.66%, and 8.85, 8.13 and 84.26 % after two cycles of early selection in populations I and II, respectively.
5- The selection response to one cycle of late selection for seed yield/plant was large comparing to their values after two cycles of early selection in both populations. The values accounted 61.94 and 76.74 % in population I and 46.11 and 41.24 % in population II with late selection comparing to 46.70 and 60.11 % in population I and 17.36 and 13.44 % in population II as a deviation from the best parent and bulk, respectively.
6- In population I, the selected families No. 122 and 153 exceeded significantly the best parent and bulk sample in all studied traits, except oil%. Moreover, the selected family no 111 surpassed the best parent and bulk in all studied traits, except number of branches/ plant. It is importance to mention that those families were matched also the selections of two cycles of early selection in current population.
In population II, the highest family No. 82 in seed yield/plant surpassed significantly the best parent and bulk for all studied traits, except oil %. Same picture of view could be nearly found for selected families No. 13 and 98. Furthermore, the highest selected families for oil % No. 5, 25 and 109 exceeded significantly the best parent and bulk in oil %, seed yield/ plant, number of capsules/ plant and 1000-seed weight, as well as length fruiting zone for the former two families (No. 5 and 25).
It is important remark that selected family No. 98 exceed significantly its best parent and bulk for seed yield / plant, number of capsules/ plant, capsule length, length fruiting zone, plant height and 1000-seed weight. In addition to, it was earlier than its parents and bulk sample.
7- High positive correlations coefficient with values ranged from 0.55 to 0.72 were found between seed yield / plant and each of length fruiting zone, capsule length, number of capsules / plant and 1000-seed weight in both populations.
2.3. Path coefficient analysis in base, early and late selection for seed yield /plant
1- The direct effect of number of capsules /plant exhibited superiority on seed yield/ plant for selection especially in late selection comparing to their base in both populations. That direct effect of number of capsules on seed yield/plant was 0.4330 and 0.4056 in base increased to 0.5611 and 0.4429 in early and to 0.9083 and 0.7558 in late selection for population I and II, respectively. Likewise, its indirect effect on seed yield/ plant via length fruiting zone were 0.0234 in base increased to 0.2873 in early and to 0.7639 in late selection as well as via 1000-seed weight were 0.0597 in base increased to 0.3138 in early and to 0.8720 in late selection for population.
2- The increasing of the direct effect of length fruiting zone on seed yield/ plant in population II which recorded 0.2375 in base increased to 0.7702 in early and to 0.6773 in late selection.
3- It is clear that the effect of residual factor was decreased from 0.8396 and 0.7852 in base to 0.4825 and 0.4856 early and to 0.709 and 0.4289 in late selection in population I and II, respectively.
3. Selection for length of fruiting zone
3.1. Early pedigree selection
1- Families’ mean squares were highly significant in both populations after one and two cycles of early selection for all the studied characters.
2- After two cycles of early selection for length of fruiting zone in population I, the means of selected families ranged from 147.50 to 192.50 cm with an average of 171.15 compared to 116.67 and 121cm for P1 and P2, respectively (Table 28). Likewise, these means varied from 129 to 181 with an average of 162.47 cm compared to their respective parents P1 (116cm) and P2 (121.67) in population II.
3- The genotypic coefficient of variation (gcv) for length of fruiting zone decreased from 16.98 and 22.87% in F3 to 11.21 and 9.37% after one cycle and to 8.37 and 9.52% after two cycles of selection in population I and II, respectively. Same view was found for phenotypic coefficient of variation (pcv) which recorded 22.52 and 28.20 % in F3 decreased to 12.33 and 11.57 % after one cycle and to 8.95 and 10.11% after two cycles of selection in population I and II, respectively. Same view could be found for correlated traits.
4- The realized heritability estimated from the realized gain in both cycles of single trait selection in the two studied populations decreased from C1 to C2 for the selection criterion of length of fruiting zone and all correlated traits.
5- The observed realized response after two cycles of pedigree line selection for length of fruiting zone were 41.45 and 22.25% in population I and 33.53 and 34.13 % in population II as measured from the best parent and bulk sample, respectively. Moreover, the highest values of correlated response were recorded for plant height (32.22 %) and seed yield/plant (33.63%) in population I and 1000-seed weight (21.07 %) and seed yield/plant (47.63 %) in population II, as a deviation from the best parent and bulk, respectively.
It is clear that the direct and correlated response values of selection in population I were larger than population II in most studied traits.
6- The overall mean of the 10 superior selections after two cycles of pedigree line selection for length of fruiting zone were exceeded significantly the respective parents and bulk sample in both populations. It is clear that the all selected families in both populations surpassed significantly the respective parents and bulk, except two family no. 86 in population I and no. 1 in population II. Same view of superiorly for general mean of selected families could be found in correlated traits .i.e. plant height, seed yield / plant and 1000-seed weight in both populations.
In population 1, the superior family no.111 as longest fruiting zone (192.50cm) and surpassed highly significantly the respective parents P1 (116.67cm), P2 (121cm) and bulk sample (140cm) by 65, 59 and 37.5 %, respectively. Moreover, it was the highest in number of capsules and seed yield / plant
In population II, the superior family no. 98 after two cycles of selection (181 cm) and surpassed significantly the respective parents P1 (116cm), P2 (121.67cm) and bulk sample (121.13) by 56.03, 48.76 and 49.42%, respectively. Also, this family (no. 98) yielded the highest seed yield/plant (43.0 g).
7- After one cycle of selection, the coefficients of phenotypic correlation between length of fruiting zone and each of plant height, capsule length, seed yield /plant and 1000-seed weight were 0.801, 0.545, 0.472, and 0.461 increased to 0.909, 0.732, 0.717, and 0.787 in population I after two cycles of selection, respectively.
In population II the coefficients of phenotypic correlation after one cycle of selection between length of fruiting zone and each of plant height, capsule length, number of capsules / plant seed yield /plant and 1000-seed weight were 0.555, 0.446, -0.027, 0.341 and 0.164 increased to 0.727, 0.750, 0.789, 0.788 and 0.824 after two cycles of selection, respectively.
3.2. Late pedigree selection for length of fruiting zone in the F5 generation
1- The means squares revealed to be highly significant for length of fruiting zone and all correlated traits, indicating the genetic differences among the selected families in both populations.
2- These average overall selected families of 189.77 and 177.75 in late selection surpassed the averages from selected families of 171.15 and 162.47 after two cycles of early selection by 10.9 and 9.4 % for population I and II, respectively. Moreover, the overall mean of length of fruiting zone for selected families in late selection surpassed their respective parents and bulk sample by 62.7, 56.8 and 35.6 % in population I and 53.2, 46.1 and 46.7 % in population II, respectively.
3- Also, the estimates of PCV, GCV and heritability in broad sense for length of fruiting zone were low and accounted 4.66, 4.24 and 82.88 % and 2.49, 2.17 and 76.24 % after one cycle of late selection comparing to 8.95, 8.37 and 87.39%, and 10.11, 9.52 and 90.22 % after two cycles of early selection in population I and II, respectively.
4- The selection response after one cycle of late selection for length of fruiting zone was large comparing to their values after two cycles of early selection in both populations. The values accounted 56.83 and 35.55 % in population I and 46.10 and 46.74 % population II with late selection comparing to 41.45 and 22.25 % in population I and 33.53 and 34.13 % in population II after two cycles of early selection as a deviation from the best parent and bulk, respectively.
5- In populations I, the selected families’ no. 109 and 111 exceeded significantly the best parent and bulk sample in all studied traits, except number of branches/ plant. It is importance to mention that the family no. 111 was matched also the selections of early selection for fruiting zone as will as early and late selection for seed yield /plant criterion.
In population II, the highest family no. 3 and 98 in length of fruiting zone surpassed significantly the best parent and bulk for all studied traits, except number of branches/ plant in both families and oil % in family no. 98. The family no. 98 matched the selections in early selection for fruiting zone and late one for seed yield /plant.
6- It is remark result that all selections output through one cycle of late selection surpassed significantly their respective parents and bulk sample in seed yield /plant in population I. This result could be extending to most of all selection in population II. Consequently, the effeteness of fruiting zone on seed yield of sesame.
7- High positive correlations coefficients with values ranged from 0.53 to 0.81 were found between length of fruiting zone and each of plant height, capsule length, number of capsules/ plant and seed yield / plant in both populations. Also, seed yield /plant has positive correlation with each of plant height, number of capsules/plant and 1000 seed weight in both populations
3.3. Path coefficient analysis in base, early and late selection for length of fruiting zone
1- The direct effect of number of capsule /plant exhibited to be superiority on seed yield/plant for selections in early and late selection comparing to their base in both populations. That direct effect of number of capsules on seed yield/plant was 0.4330 and 0.4056 in base increased to 0.7313 and 0.9173 after two cycles of early and to 0.5599 and 0.7822 after one cycle of late selection in population I and II, respectively
2- Moreover, its indirect effects on seed yield/ plant via length fruiting zone were 0.0234 in base increased to 0.2998 in early and to 0.5470 in late selection as well as via 1000-seed weight were 0.0597 in base increased to 0.4073 in early and to 0.6828 in late selection for population I; 0.1314 in base increased to 0.7238 in early and to 0.4451 in late selection, and via 1000-seed weight recorded 0.1618 in base increased to 0.8109 in early and to 0.4701 in late selection in population II.
3- It is obvious result that the effect of residual factors were decreased from 0.8396 and 0.7852 in base to 0.3051 and 0.4482 after two cycles of early selection and to 0.2729 and 0.4912 after one cycle of late selection in population I and II, respectively.
4. Selection for number of capsule /plant
4.1. Early pedigree line selection for number of capsule /plant
1- Families’ mean squares were highly significant in both populations after one and two cycles of early selection for all the studied characters, reflecting the genetic difference among those studied families.
2- After two cycles of early selection for number of capsules/plant, the means of selected families ranged from 140.04 to 168.40 with an average of 152.58 compared to 83.67 and 95.33 for P1 and P2 in population I, respectively. Likewise, these means varied from 132.17 to 168.33 with an average of 153 compared to their respective parents P1 (93) and P2 (103) in population II.
3- The genotypic coefficients of variation (gcv) for number of capsules/plant decreased from 40.03 and 27.96 % in F3 (base) to 14.24 and 14.27 % after one cycle and to 5.93 and 8.45 % after two cycles of selection in population I and II, respectively. Same view was found for phenotypic coefficient of variation (pcv) which recorded 47.49 and 34.26 % in F3 decreased to 15.86 and 17.41 % after one cycle and to 6.57 and 9.21 % after two cycles of selection in population I and II, respectively.
Also, gcv decreased from 18.85, 13.62, 16.98, 17.87, 30.92, 22.94, 16.28 and 11.23% in base F3 to 7.62, 4.31, 6.86, 8.68, 16.09, 7.03, 9.09 and 7.61 % after two cycles of selection for correlated traits of days 50% flowering, plant height, fruiting zone, capsule length, number of branches /plant, seed yield /plant, 1000-seed weight and seed oil percentage in population I. In population II, gcv values were decreased from 17.90, 15.21, 22.87, 28.08, 53.19, 37.06, 21.72 and 11.50% in base F3 families to 9.38, 5.65, 4.16, 9.42, 17.85, 9.81, 7.36 and 4.87 % after two cycles of selection for the respective correlated traits. The pcv values were in line with those recorded for gcv in both populations.
4- The realized heritability estimated from the realized gain in both cycles of single trait selection in the two studied populations decreased from C1 to C2 for the selection criterion of number of capsules/plant and all correlated traits.
5- The observed realized response after two cycles of pedigree line selection for number of capsules/plant were 60.06 and 56.23% in population I and 48.54 and 29.69 % in population II as measured from the best parent and bulk sample, respectively. Moreover, the highest values of correlated response were recorded for seed yield /plant i.e. 43.99 and 103.71% in population I and 26.55 and 50.82% in population II, as a deviation from the best parent and bulk, respectively.
6- The overall mean of the 10 superior selections after two cycles of pedigree line selection for number of capsules/plant were exceeded significantly the respective parents and bulk sample in both populations. It is clear that the all selected families in both populations surpassed significantly the respective parents and bulk.
In population 1, the superior family no.35 has the highest number of capsules/plant (168.40) and surpassed highly significantly the respective parents P1, P2 and bulk sample by 82.4, 60.1 and 56.2 %, respectively.
Also, it exceeded significantly the respective parents and bulk sample in plant height, length of fruiting zone, capsule length, number of branches /plant, seed yield/plant and 1000-seed weight. Otherwise, the family no. 52 yielded the highest seed yield / plant (43.0 g). It is clear that the family no. 31 matched also the selections obtained with early selection for fruiting zone, as well as the family no. 48 matched the selections of early selection for seed yield / plant for population I.
In population II, the superior family no. 12 after two cycles of selection has the highest number of capsules/plant (168.83) and surpassed significantly the respective parents P1, P2 and bulk sample by 64.5, 48.5 and 29.7 %, respectively. It exceeded significantly the respective parents and bulk sample for plant height, fruiting zone, capsule length, number of branches/plant, seed yield /plant and 1000-seed weight. It is obvious result that the family no.12 was the highest in seed yield / plant (43.0 g). The family no. 10 matched also the selections with early selection for fruiting zone, as well as the families no 21 and 47 matched the early selection for seed yield / plant.
It is clear from the obtained results that all families after two cycles of pedigree line selection for number of capsules/plant were late in flowering comparing of their respective parents and bulk in both populations, except the family no 72 in population I and no. 10, 21 and no.70 in population II was significantly earlier than its best parent and bulk. Moreover, these families surpassed significantly their parents and bulk in number of capsules/plant and seed yield/plant.
7- After one cycle of selection, the coefficients of phenotypic correlation coefficients between number of capsule /plant and other traits were low in population I. The only correlation increased between number of capsule /plant and each of number of branches /plant (0.473) and seed yield/ plant (0.682) after two cycles of selection for current criterion. In population II, the correlation values between number of capsules /plant and each of plant height, fruiting zone, number of branches /plant, seed yield/ plant and 1000-seed weight were 0.334, 346, 0.377, 0.488 and 0.172 and increased to 0.439, 0.802, 0.536, 0.590 and 0.317 after two cycles of selection, respectively.
4.2. Late pedigree selection for number of capsules /plant in the F5 generation
1- The mean squares revealed to be highly significant for number of capsules/plant and all correlated traits, indicating the genetic differences among the selected families in both populations.
2- The average overall selected families of 174.65 and 172.98 in late selection surpassed the averages from selected families of 152.58 and 153 after two cycles of early selection by 14.46 and 13.05 % for population I and II, respectively. Same trend of observation could be found for capsule length and oil % in both populations, and number of branches and seed yield/ plant in population II. Moreover, the overall mean of number of capsules/plant for selected families in late selection surpassed their respective parents and bulk sample by 108.73, 83.2 and 78.81 % in population I and 86, 67.94 and 46.63 % in population II, respectively. Also, the seed yield/plant for selected families in late selection exceed their respective parents and bulk by 105.1, 43.58 and 103.17 % in population I, and 109.95, 37.55 and 63.95 in population II, respectively.
3- The estimates of PCV, GCV and heritability in broad sense for number of capsules/plant were low and accounted 6.01, 5.53 and 84.76 % and 4.62, 3.96 and 73.55 % after one cycle of late selection comparing to 6.57, 5.93 and 81.38%, and 9.21, 8.45 and 84.12 % after two cycles of early selection for number of capsules/plant in population I and II, respectively.
4- The selection response to one cycle of late selection for number of capsules/plant was large comparing to their values after two cycles of early selection in both populations. The values accounted 83.20 and 78.82 % in population I and 67.94 and 46.63 % in population II with late selection comparing to 60.05 and 56.23 % in population I and 48.54 and 29.69 % in population II after two cycles of early selection as a deviation from the best parent and bulk, respectively.
5- In population I, the selected family No. 73 exceeded significantly the best parent and bulk sample in all studied traits, except oil%. Moreover, the selected family No 86 surpassed the best parent and bulk in all studied traits, except plant height and oil %. It is importance to mention that the family No. 35 was matched also the selections of early selection in current criterion of selection. Also, the families No 21 and 86 matched selections obtained with early selection with fruiting zone.
In population II, the highest family No. 82 in number of capsules /plant surpassed significantly the best parent and bulk for all studied traits, except oil % and it has matched the selections in late selection for fruiting zone. It is important remark that selected families no 29 and 64 exceed significantly its best parent and bulk for seed yield / plant, number of capsules/ plant, and plant height. In addition to, they were significantly earlier than their parent and bulk sample. Moreover, the selected families nos. 5, 13, 45, 109 and 136 were matched the obtained selections from late selection for seed yield/plant.
6- High positive correlation coefficients with values ranged from 0.46 to 0.81 were found between number of capsules /plant and each of days to 50 % flowering, length fruiting zone, number of branches/plant seed yield /plant and 1000-seed weight in both populations.
4.3. Path coefficient analysis in base, early and late selection for number of capsule /plant
1- The direct effect of no of capsules /plant on seed yield/ plant increased from 0.4330 and 0.4056 in the base to 0.5699 and 0.5773 after two cycles of early selection in the populations I and II, respectively. Moreover, its indirect effect increased from 0.0091 in the base to 0.1600 with early and to 0.4763 with late selection via fruiting zone in population I, and from 0.0605 in base to 0.5099 with late selection via 1000 seed weight in population II.
2- The direct effect of fruiting zone on seed yield/ plant increased from 0.1677 in base to 0.5695 with early and to 0.8100 with late selection in population I. The indirect effect of fruiting zone on seed yield/ plant via number of capsules/plant increased from 0.0234 in base to 0.1601 with early selection in population I, and from 0.1314 in base to 0.4630 with early and to 0.2864 with late selection in population II. Also, it indirect effect increased from 0.0591 in base to 0.6111 in late selection via 1000-seed weight in population II.
It is clear that the direct effect of 1000-seed weight on seed yield/ plant increased from 0.1516 in base to 0.8159 with late selection in population II. Meanwhile, its indirect effect via fruiting zone increased from 0.0599 in base to 0.3542 with early and to 0.3807 with late selection in population I.
3- It is obvious and remark result that the effect of residual factors were decreased from 0.8396 in base to 0.2881 with early and to 0.3502 with late selection in population I, and decreased from 0.7852 in base to 0.3595 with late selection from population I.