الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 131 |  |  |
| | | from | 131 | | |
Abstract
The present work was carried out at Assiut Univ. Exp. Farm during the four summer seasons of 2008-2011. The genetic materials were two intervarietal populations of Egyptian cottons; Gossypium barbadense L. Population I (pop. I) stemmed from the cross of Giza 85/Giza 90, and population II (Pop. II) from the cross Giza 83/Giza 70. Selection started in the F2-generation at late planting (May) to develop early high yielding lines adapted to late planting. Four pedigree selection procedures were used; selection for earliness index, selection for lint yield/plant, selection for earliness index restricted by lint yield/plant, and selection for number of bolls/plant. In season 2010, the weather was very hot all over the country and the infestation of boll worms was very heavy. Hence, data were not recorded and the experiments were repeated in season 2011. Therefore, two cycles of pedigree selection were achieved.
The results could be summarized as:
1- Description of the base populations in the F2-generation; season 2008.
2- Pedigree selection for earliness index.
3- Pedigree selection for lint yield/plant.
4- Pedigree selection for earliness index restricted by lint yield/plant.
5- Pedigree selection for number of bolls/plant.
6- The merits of the four selection procedures.
1- Description of the base populations, season 2008
1.1- Seed cotton yield/plant; g.
Wide range of variation in the F2-generation in the two populations compared to narrow variability in the respective parents. In pop. I, seed cotton yield/plant in the F2-geneation ranged from 14.9 to 116.2 g with coefficient of variability (cv %) of 40.87% in pop. I, and from 10.7 to 133.50 g/plant with cv. of 43.86% in pop. II. The coefficient of variation of the four parents ranged from 0.71 to 3.74%, which resulted in very small of environmental variance, and inflation of the genetic variance. In consequence, very large and unreliable estimates of broad sense heritability of 0.99 for both populations were obtained.
1.2- Lint yield/plant; g.
The coefficient of variation (cv %) in the F2-generation was 46.39% compared to 6.84 and 8.66% for the respective parents of pop. I. In pop. II, the cv in the F2-generation was 46.35 compared to 0.39 and 3.04% for the respective parents. Broad sense heritability in the two populations was very high (0.97), hence large estimates of expected genetic advance of 79.01 and 80.60% were obtained for pop. I and II; respectively.
1.3- Lint percentage:
The cv in the F2-generation was 9.46 in pop. I and 13.48% in pop. II, compared to 5.51 and 6.26% for the parents of pop. I, and 0.42 to 2.22% for the parents of pop. II. Broad sense heritability was 0.64 in pop. I, and 0.73 in pop. II. The expected genetic advance was 10.69 in pop. I and 17.66% from the F2-mean in pop. II.
1.4- Number of bolls/plant:
Mean number of bolls/plant of pop. I was 20.89 with cv of 39.03% compared to low cv % of 5.00 for Giza 90 and 11.65% for Giza 85, and heritability of 0.93 and expected gain of 13.29% from the mean. In pop. II, mean number of bolls/plant was 22.74 with cv of 45.76%, heritability of 0.97 and expected gain of 18.13%.
1.5. Boll weight, g:
Mean boll weight of pop. I was 2.73 g compared to 2.68 g in pop. II. High estimates of coefficient of variation were obtained for the two populations. High estimates of heritability of 0.79 and 0.81, and large expected gains of 21.14 and 23.45% for popo. I and II, respectively.
1.6- Seed and lint indices:
Mean seed index was 9.34 and 9.01 g for pop. I and II, respectively. The coefficient of variation were 12.95 and 14.75%, heritability estimates were 0.93 and 0.91 and expected gains of 21.29 and 24.11% for pop. I and II, respectively.
Mean lint index was 4.70 and 5.24 g with heritability estimates of 0.59 and 0.75, and expected genetic advance relative to the of 12.67 and 28.46% for pop. I and II; respectively.
1.7- Earliness index:
High estimates of cv were obtained in the two populations and reached 18.91 and 34.75% for pop. I and II; respectively. Estimates of the expected genetic advance were 32.49 and 61.44% for pop. I and II; respectively.
1.8- Days to first flower:
Days to first flower of pop. I ranged from 51.41 to 72.36 with an average of 63.53 days, cv of 6.12%, heritability estimate of 0.72 and expected gain 7.81%. The cv, heritability and expected gain were 12.03%, 0.93 and 20.02% for pop. II.
It is of interest to indicate to the wide range of variability in the F2-generation of the two populations for all the studied characters, and very narrow variability in the four parents for all characters. This reflect the high purity of the four parents.
2- Pedigree selection for earliness index:
2.1- Mean squares of the earliness index and all the studied traits in the two populations were significant (P<0.01) after two cycles of selection. The retained genetic coefficient of variability was sufficient for further cycles of selection and reached 16.20 and 11.32% for pop. I and II; respectively. Unreliable estimates of broad sense heritability were obtained for all traits. However, the realized heritability estimates were 0.3524 and 0.4214, and the heritability estimates in narrow sense as calculated from offspring on parent regression were 0.1699 and 0.1610 for cycle 1 and cycle 2; respectively in population I. Likewise realized heritability estimates of earliness index were 0.2315 and 0.3649, and narrow sense heritability estimates were 0.1851 and 0.1372 in pop. II for cycle 1 and cycle 2; respectively.
2.2- After two cycles of selection for earliness index in pop. I, 17 out of the 20 selected families showed significant (P<0.01) observed gain from the better parent which ranged from 2.74 to 29.36%. In pop. II, eight families showed significant (P<0.05 – P<0.01) observed gain in earliness index ranged from 3.13 to 17.48% from the better parent.
2.3- The best three superior families in pop. I were families No. 56, No. 1 and No. 234. Family No. 56 showed direct and correlated genetic gains of 26.52 and 28.68% for earliness index, 43.45 and 53.17% for seed cotton yield/plant, 55.70 and 70.28% for lint yield/plant, 8.51 and 11.13% for lint percentage, 29.59 and 37.85% for boll weight, 10.69 and 5.45% for lint index and -10.04 and -17.72% for days to first flower from the bulk sample and the better parent; respectively.
2.4- In pop. II, two families; No. 130 and No. 174 showed significant (P<0.01) direct gains in earliness index and correlated gains in the other traits.
3- Pedigree selection for lint yield/plant:
3.1- The families mean squares of the selection criterion and the other traits were significant (P<0.01) in both populations. Sufficient genotypic coefficient of variability were found in lint yield/plant of 17.55% in pop. I, and 25.20% in pop. II. High estimates of broad sense heritability were obtained for all traits. However, the realized heritability estimates for lint yield/plant were 0.2543 and 0.5509 in pop. I, and 0.2114 and 0.3016 in pop. II for cycle 1 and 2; respectively, compared to parent offspring regression estimates of 0.7402 and 0.2606 in pop. I, and 0.1587 and 0.3388 in pop. II for cycle 1 and 2; respectively.
3.2- The average direct observed gain in lint yield/plant ranged from 4.82 to 70.28% from the better parent in pop. I. The most superior families were families No. 1, No. 56, No. 234 and No. 298. In pop. II, 14 families showed significant (P<0.01) direct gain, which ranged from 7.08 to 67.54% from the better parent.
3.3- In pop. I, the correlated gain from the better parent was significant (P<0.01) for seed cotton yield/plant (19.79%), number of bolls/plant (13.38%), seed index (7.71%), lint index (9.70%), earliness index (5.30%) and days to first flower (-3.62%).
3.4- Eight selected families in pop. II were superior and showed significant or highly significant correlated gains for seed cotton yield/plant, earliness index and most of the other traits.
4- Pedigree selection for earliness index restricted by lint yield/plant:
4.1- Families mean squares was significant (P<0.01) for all the studied traits of the two populations. Sufficient phenotypic coefficient of variability for further cycles of selection was found for earliness index and lint yield/plant in the two populations. It reached 11.16 and 11.86% for earliness index, and 21.96 and 25.73% for lint yield/plant in pop. I and II; respectively. The broad sense heritability as calculated from the mean squares was very high for all traits.
4.2- Mean direct observed gains were 9.08 and 12.89% in pop. I, and -0.99 and 16.82% from the better parent for earliness index and lint yield/plant; respectively. Several families showed significant (P<0.01) observed gains in both populations for the two criteria of selection.
4.3- In pop. I, three superior families; No. 56, No. 1 and No. 298 showed significant correlated gains from the better parent for most traits. Family No. 56 showed significant direct and correlated gains of 43.45 and 53.17% for seed cotton yield/plant, 55.70 and 70.28% for lint yield/plant, 8.51 and 11.13% for lint percentage, 29.59 and 37.85% for boll weight, 10.69 and 5.45% for number of bolls/plant, 10.58 and 10.10% for seed index, 25.68 and 29.74% for lint index, 26.52 and 28.68% for earliness index and -9.91 and -17.72% for days to first flower from the bulk sample and better parent; respectively.
4.4- In pop. II; five superior families (No. 58, No. 130, No. 149, No. 167 and No. 174) showed significant (P<0.05 to P<0.01) observed direct and correlated gains from both of the bulk sample and the better parent.
5 – Pedigree selection for number of bolls/plant:
5.1- The selected families mean squares for all traits in both population were significant (P<0.01). After two cycles of pedigree selection for number of bolls/plant, the gcv was 18.93 and 21.37% for pop. I and II; respectively, indicating sufficient variability for further cycles of selection. Estimates of broad sense heritability were very high and unreliable for all traits. However, the realized heritability estimates were low; 0.2056 and 0.3890 in pop. I; and 0.1723 and 0.3946 in pop. II for cycle 1 and 2; respectively. Furthermore, estimates of narrow sense heritability as calculated from parent. Offspring regression were very low; 0.1465 and 0.0886 in pop. I, and 0.1949 and 0.1271 in pop. II for cycle 1 and 2; respectively.
5.2- Mean observed direct gain from the better parent for number of bolls/plant was 7.80 and 7.56% (P<0.01) in pop. I and II; respectively.
5.3- Two cycles of selection for number of bolls/plant in pop. I resulted in three promising families No. 1, No. 56 and No. 234. Family No. 56 showed significant correlated gains for all traits from the bulk sample and the better parent. Family No. 1 showed significant (P<0.01) correlated gains of 45.70, 49.50, 3.58, 14.20 and -11.43% for the better parent for seed cotton yield/plant, lint yield/plant, seed index, lint index and days to first flower; respectively.
5.4- In pop. II, two cycles of selection for number of bolls/plant resulted in four superior families; No. 58, No. 130, No. 145 and No. 174, which showed significant sizeable direct and correlated gains for most traits.
6- The efficiency of the four selection procedures
6.1- The relative of the four selection procedures in improving earliness index:
Average observed gain in pop. I in earliness index in percentage of the better parent was significant (P<0.01) and reached 14.17, 5.30 and 9.08%, when selection practiced for earliness index, lint yield/plant and earliness index restricted by lint yield/plant; respectively. However, it was not significant (0.66%) when selection practiced for number of bolls/plant. selection for earliness index in pop. I resulted in 17 individual families, which showed significant (P<0.01) direct observed gain, ranged from 2.74 to 29.36%. Nine of these families showed significant correlated gain in lint yield/plant. selection for lint yield/plant, for earliness index restricted by lint yield/plant and for number of bolls/plant resulted in 11, 15 and 10 individual families which showed significant correlated gain in earliness index from the better parent; respectively. The four superior families in earliness index common in the four selection procedures were families No. 1, No. 56, No. 193 and No. 234. It could be concluded that in pop. I, the best procedure to increase earliness index, was selection for earliness index itself.
In pop. II, based on the superiority of selected families in both of earliness index and lint yield/plant, four superior families were obtained. Three of them i.e., family No. 130, No. 174 and No. 191 were selected by the four selection procedures, and showed significant observed gain from the better parent of 6.70 and 67.54%, 11.60 and 52.53%, 11.68% and 8.36% for earliness index and lint yield/plant; respectively. The fourth family No. 58 showed significant observed gain of 17.77 and 48.30 for earliness index and lint yield/plant; respectively. This family was selected by three procedures; selection for lint yield/plant, selection for earliness index restricted by lint yield/plant, and selection for number of bolls/plant. It should be indicate that, pop. I was more responsive to selection for earliness index than pop. II.
6.2- The merits of selection procedures in improving lint yield/plant:
In pop. I, the average observed gain in lint yield/plant after two cycles of selection was significant (P<0.01) and reached 4.54, 21.15 and 12.89% as a result of selection for earliness index, lint yield/plant, and earliness index restricted by lint yield/plant. However, the average correlated gain in lint yield/plant was not significant (2.26%) when selection practiced for number of bolls/plant. Therefore, it could be concluded that the best procedures to increase lint yield/plant in pop. I, was selection for lint yield per se.
The selected families showed significant (P<0.01) correlated gains in lint yield/plant ranged from 6.56 for family No. 299 to 70.28% for family No. 56 after two cycles of selection for earliness index, while selection for lint yield/plant gave 17 families showed significant (P<0.01) direct observed gain in lint yield/plant, which ranged from 4.82 for family No. 227 to 70.28% for family No. 56. Also, eleven and ten families showed significant gain in lint yield/plant, when selection practiced for earliness index restricted by lint yield/plant and number of bolls/plant; respectively. Based on both of earliness index and lint yield/plant in combined, it could be concluded that the best superior families in both traits selected in the four selection procedures were family No. 56, No. 1 and No. 234, which showed 28.68 and 70.28, 14.20 and 49.50 and 29.36 and 37.48% for earliness index and lint yield/plant; respectively.
In pop. II, the average observed gain in lint yield/plant in pop. II was significant (P<0.01) and accounted for 9.51, 18.20, 16.82 and 14.02% from the better parent after two cycles of selection earliness index, lint yield/plant, earliness index restricted by lint yield/plant and number of bolls/plant; respectively, and 10, 13, 14 and 15 families showed significant genetic gain in lint yield/plant in the four respective selection procedures.
Based on the earliness index and lint yield/plant in combined; several selected families showed superiority in genetic gain. Families No. 130, No. 174 and No. 191 were selected by the four procedures. Furthermore, families No. 58, No. 190 and No. 198, No. 58 and No. 190, No. 58 and No.1 45 were selected by selection for lint yield/plant, earliness index restricted by lint yield/plant and number of bolls/plant; respectively.