الفهرس 
CONTENTS
Recurrent selection methods and gain from selectionOnly 14 pages are availabe for public view
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Abstract
This study was carried out during the period from 2007 to 2010 at Mallawy and Sakha Agricultural Research Stations, A.R.C., Egypt. One cycle of S1 family selection and half–sib reciprocal recurrent selection (NC Design-1) methods were applied in two maize populations. The two selection methods were practiced in two yellow maize populations pop (A) and pop (B).
The main objectives of this study were to:
1- Evaluate two methods of selection (half–sib and S1 line), for improving grain yield and earliness of two different maize populations.
2- Estimate the genetic components of variance and heritability.
3- Calculate the expected and observed gain from selection after one cycle of reciprocal recurrent and S1 line per se selection methods.
Two exotic maize populations i.e., Tuxpeno Corn Belt and Puerto Rico were used in the present study. The two populations were planted in the summer season of 2007 at Mallawy Agricultural Research Station. from each population, approximately 200 plants were selected and selfed and used as male parents to pollinate randomly five plants from the other population which used as females.
At harvest, three ears for each male which had sufficient seed for evaluation were selected. Eighty-one male groups (half-sib families) or total of 243 full-sib families were developed from each population. Each ear from the female plants represents a full-sib family, while the ears having a common male parent introduced half-sib families. In 2008 season these materials were evaluated in four experiments at two locations. In 2009 season ten S1 lines were selected based on two selection criteria, i.e, grain yield and earliness of silking from each trial to form the first cycle seed.
In 2010 season, the first cycle of selection (C1); S1 per se and H.S for each population were evaluated against the original populations to measure the actual gain from selection at Mallawy and Sakha Agric. Res. Stations, A.R.C. Randomized complete block design with 4 replications was used in the two locations. Data recorded were days to 50% silking, plant and ear height, ear length, ear diameter, no. of rows/ear, no. of kernels/row, 100-kernel weight and grain yield /plot.
1- Evaluation of S1 lines:
1-1. Analysis of variance
Combined data showed that mean squares due to locations for all studied traits of both populations were highly significant differences. Mean squares due to S1 lines of both populations were significant or highly significant for all studied traits. On the other hand, mean squares due to S1 x locations were significant or highly significant for all the studied traits of the two populations, except ear length for Pop. A, no. of kernels/row and 100-kernel weight of Pop. B and ear diameter for both populations.
1-2. Variance components and heritability:
Results showed that genetic variance for all studied traits were less than phenotypic variance. Genetic and phenotypic variances of plant height, ear height, ear diameter, no. of kernels/row and 100-kernel weight for S1 lines derived from Pop. A at both locations were higher than those of S1 lines derived from Pop. B, indicating the presence of more variability in the base Pop. A for these traits. On the other side, genetic and phenotypic variance values of Pop. B were more than those obtained for Pop. A for days to 50% silking and grain yield/plot, indicating that more variability were existed in the base Pop. B for these traits.
Genetic variance for S1 lines across the two locations for all studied traits were less than phenotypic variance. Genotypic variances for plant height, ear height, ear length and ear diameter of Pop. A were higher than those of Pop. B. While genotypic variances for days to 50% silking, no. of rows/ear, no. of kernels/row, 100-kernel weight and grain yield of Pop. B were higher than those of Pop. A.
Genotypic x locations interaction variances for plant height, ear height, no. of rows/ear, no. of kernels/row and 100-kernel weight of Pop. A were higher than those of Pop. B, while the opposite was true for days to 50% silking, ear length and grain yield. Phenotypic variances for plant height, ear height, ear length, ear diameter, no. of rows/ear and no. of kernels/row for S1 lines of Pop A. were higher than those of Pop. B. The opposite was true for days to 50% silking, 100-kernel weight and grain yield for S1 lines of Pop. B were higher than those of Pop. A.
For combined data broad sense heritability for S1 lines of Pop. A was high for days to 50% silking, (69.40%), ear height (68.91%), ear length (71.27%) and plant height (82.26%); moderate for ear diameter (47.37%), and grain yield (44.74%); and low for no of kernels/row (32.00%), 100-kernel weight (37.87%) and no. of rows/ear (18.94%). For S1 lines of Pop.B broad sense heritability was high for plant height (76.82%), ear height (69.18%), no. of rows/ear (63.10%), grain yield (68.00%) and days to 50% silking (80.25%); moderate for ear length (47.56%), 100-kernel weight (51.46%), and no. of kernels/row (44.65%) and low for ear diameter (23.81%).
1-3. Means, genotypic and phenotypic coefficient of variability:
Combined data over the two locations showed that mean values for days to 50% silking, plant height, ear height, ear length, ear diameter, no.
of rows/ear, no. of kernels/row, 100-kernel weight and grain yield of Pop. A were 62.86, 222.80, 136.40, 15.60, 4.63, 15.74, 32.73, 26.57 and 1.54, respectively. The corresponding means of S1 lines of Pop.B were 61.22, 222.18, 132.50, 15.89, 4.35, 13.56, 31.93, 28.90 and 1.56, respectively.
For combined data, phenotypic coefficient of variability (PCV%) for plant height, ear height, ear length, ear diameter, no. of kernels/row and 100-kernel weight of S1 lines derived from Pop. A were higher than their corresponding values of S1 lines of Pop. B. On the other hand, the opposite was true for days to 50% silking, no of rows/ear and grain yield.
Genotypic coefficient of variability for plant height, ear height, ear length and ear diameter for S1 lines of Pop. A were 7.12, 8.04, 7.67 and 4.85% and higher than those from S1 lines from Pop. B with values of 6.19, 6.87, 5.10 and 2.57% for the same traits, respectively. On the other hand the opposite was true for days to 50% silking, no of rows/ear, no of kernels/row, 100-kernel weight and grain yield.
2-Half-sib families selection:
2-1. Analysis of variance:
Analysis of variance for the combined data across locations showed that male variances were significant or highly significant for all traits, however females/males were significant or highly significant for all traits at half-sib for two populations. The interaction mean squares of males x locations in Pop. A and Pop. B were highly significant for all traits except ear length, ear diameter in Pop. A, no. of rows/ear, no. of kernels/row and 100-kernel weight, while ear diameter in Pop. B were significant.
The interaction mean squares of females/males x locations were significant or highly significant for plant height, ear height and grain yield in the two populations, in addition to days to 50% silking of Pop. B.
2-2. Means, variance components, average degree of dominance and heritability:
Combined data showed that, mean values of Pop. A. for days to 50% silking, plant height, ear height, ear length, ear diameter, no. of rows/ear, no. of kernel/row, 100-kernel weight and grain yield were 58.69, 284.92, 179.31, 18.49, 4.82, 15.07, 37.63, 32.92 and 2.85, respectively. The corresponding mean values of Pop. B. were 58.83, 280.61, 175.10, 18.29, 4.92 15.34, 37.39, 32.66 and 2.74, respectively.
Combined data revealed that genetic variance for all studied traits were less than the phenotypic variance. The genetic variance for plant height, ear length, no. of rows/ear, no. of kernels/row, 100-kernel weight and grain yield for half-sib of Pop. A were higher than those of half-sib of Pop. B. On the other hand, days to 50% silking, ear height and ear diameter for half-sib of Pop. B were higher than those of half- sib of Pop. A.
Phenotypic variance of half- sib of Pop. A for plant height, ear length, ear diameter, no. of rows/ear, no. of kernels/row, 100- kernels weight and grain yield were higher than those of half-sib of Pop. B. On the other hand, days to 50% silking and ear height for half- sib of pop. B were higher than those of half- sib of Pop A.
Variance due to male (σ2m) of half-sib of Pop. B for days to 50% silking, ear length, no. of rows/ear, no. of kernels/row and 100-kernels weight were higher than those of half-sib of Pop. A. On the other hand, plant height, ear height, ear diameter and grain yield for half- sib of pop. A were higher than those of half- sib of Pop. B.
Variance due to females (σ2f) of half-sib of Pop. A for days to 50% silking, ear height, ear length, no. of rows/ear, no. of kernels/row, 100- kernel weight and grain yield were higher than those of half-sib of Pop. B. On the other hand, plant height and ear diameter for half-sib of Pop. B were higher than those of half-sib of Pop. A.
Additive genetic variances (σ2A) for all traits for half-sib families of Pop. B was higher than those of half- sib Pop. A. On the other hand, additive genetic variances (σ2A) for plant height, ear height, ear diameter and grain yield of Pop. A were higher than those of half- sib Pop. B.
Variances due to dominance in half-sib Pop. A were positive for all traits except plant height were negative value. Variances due to dominance in half- sib Pop. B were positive for plant height, ear height, ear diameter, 100-kernels weight and grain yield, while variances due to dominance were negative for days to 50% silking, ear length, no. of rows/ear and no. of kernels/row.
The average degree of dominance (ā) as obtained from the two populations for all studied traits, indicated that the presence of over-dominance in Pop. A for ear height, ear length, ear diameter, 100-kernel weight and grain yield and partial dominance for no. of rows/ear. In Pop. B was over-dominance for plant height and grain yield and partial dominance for 100- kernel weight.
Variance due to male x locations interaction of half- sib of Pop. B for all studied traits were higher than those of half- sib of Pop. A, except days to 50% silking, plant height, ear length and no. of kernels/row. However, estimates of females x locations interaction of half- sib of Pop. A for all studied traits were higher than those of half-sib of Pop. B, except days to 50% silking, ear height, ear length and no. of kernels/row.
Variance due to male x locations of Pop. A were positive for all traits, except no. of rows/ear and 100-kernels weight. Variance due to male x locations of Pop. B were positive for all traits, except no. of rows/ear, no. of kernels/row and 100- kernels weight. Also variance due to females x locations interaction of Pop. A were positive for all traits, except days to 50% silking, ear length and no. of kernels/row. Variance due to females x locations interaction of Pop. B were positive for all traits, except ear diameter.
Additive x location interactions for all traits for half- sib families of Pop. B were higher than those of half- sib Pop. A, except days to 50% silking, plant height, ear length and no. of kernels/row. Additive x location interactions variances in half-sib of Pop. A were positive for all traits, except no. of rows/ear and 100-kernel weight were negative value. Additive x location interactions variances in half-sib of Pop. B were positive for all traits, except no. of rows/ear, no. of kernels/row and 100-kernel weight.
All of the dominance x location interactions variances in half-sib of the two populations were positive for all the studied characters, except for days to 50% silking, ear length and no. of kernels/row, except for plant height, ear diameter and grain yield/plot for Pop B.
Genotypic x location interaction variances (σ2GL) in Pop. A was negative for days to 50% silking, ear length and no. of kernels/row. Genotypic x location interaction variances (σ2GL) in Pop. B was negative for ear diameter. The genotypic x location interaction variances (σ2GL) in Pop. A were higher than those of half- sib of Pop. B for all studied traits,
except days to 50% silking, ear height, ear length and no. of kernels/row.
The combined data showed the heritability in broad sense for Pop. A for days to 50% silking (84.04%), ear length (83.85%), no. of rows/ear (86.50%), no. of kernels/row (93.67%) and grain yield (64.54%) were high, but for plant height (29.31%) and ear height (19.62%) were low. On the other hand, moderate estimates were obtained for ear diameter (50.00%), 100-kernel weight (54.74%).
For Pop. B, heritability in broad sense were high for days to 50% silking (79.28%), ear diameter (85.71%), no. of rows/ear (86.91%), ear length (61.48%) and grain yield (64.28%), but it were low for plant height (25.20%), ear height (25.04%), moderate for 100-kernel weight (55.92%) and no. of kernels/row (43.44%). Generally, heritability estimates in broad sense in Pop A were higher than those for Pop. B for all traits, except ear height, ear diameter, no. of rows/ear and grain yield.
Heritability estimates in the narrow sense in Pop. A for days to 50% silking (80.27%) and no. of rows/ear (61.15%) were high, but were low for plant height (29.31%), ear height (10.21%), ear length (38.94%), ear diameter (20.00%), 100-kernel weight (2.55%) and grain yield (15.37%).
Heritability estimates in the narrow sense in Pop. B were high for days to 50% silking (79.28%), ear length (61.48%) and no. of rows/ear (86.91%), but were low for plant height (2.70%)., and grain yield (8.21%), moderate for no. of kernels/row (43.44%) and 100-kernel weight (43.68%).
Generally, heritability estimates in the narrow sense in Pop. A were higher than those for Pop. B for all traits, except ear length, no. of rows/ear, no. of kernels/row and 100- kernel weight. This attributed to that breeding value for Pop. A was higher than that for Pop. B.
3- Evaluation of the first cycle of selection (C1)
3-1. Analysis of variance:
Significant differences were detected between the two locations for all the studied traits, except no. of rows/ear and no. of kernels/row. This is may be due to the differences in the environmental conditions from location to another. Mean squares of populations were significant or highly significant for all studied traits, indicating the presence of variations among populations. Mean squares due to populations x locations interaction were highly significant for grain yield.
3-2. Mean performance:
Average days to 50% silking for the two selection criterion of Pop. A. were (59.13 & 57.25) and (59.75 & 57.25) for S1 per se and HS method, respectively compared to 57.00 of the original Pop. A. The difference between the two methods of selection and the difference between the S1 cycle, HS and original population was insignificant. For Pop. B average days to 50% silking of the two selection criterion were (56.88 & 56.13) and (57.50 & 55.75) for S1 per se and HS method, respectively, compared to 56.88 of the original Pop. B., the difference between the two methods of selection was insignificant.
The difference between S1 cycle, HS method and the original population for the first criterion was insignificant. The first cycle of HS method for the second criterion (earliness) was significantly earlier than the original Pop. B, indicating that the HS selection method was better than S1 method for improving earliness.
For Pop. A average grain yield for the two selection criterion were (8.48 & 7.82) and (7.54 & 7.55 kg/plot) for S1 per se and HS method, respectively, compared to 7.24 kg/plot of the original Pop. A. Significant difference was detected between the two methods. The improved cycl-1 (C1) S1 per se, which formed for grain yield outyielded the original pop. A.
For Pop. B average grain yield for the two selection criterion were (8.18 & 6.41) and (7.91 & 6.94 kg/plot) for S1 per se and HS method, respectively, compared to 7.57 kg/plot of the original Pop. B. The differences between the methods and the original Pop. B was insignificant. Generally, the yield of the first cycle-1 of Pop. A was more than that of Pop. B, this due to the variability of Pop. A was more than the Pop. B. The method of selection of S1 per se was more effective than HS method because it depends upon the general combining ability and utilized more additive than non-additive genetic variance but HS method selection depend upon the specific combining ability and utilizes more non-additive variance
3-3. Expected (Ex.) and actual gain from selection (Ac.):
Expected gain for grain yield (kg/plot) were 23.58 and 22.07% and actual gain was 17.12 and 4.14% for the two methods S1 per se and HS, respectively for Pop. A. Respecting Pop. B. The expected gain from selection were 31.87 and 20.70% for the two methods S1 per se and HS method, respectively and their actual gain were 8.06 and 4.49%.
Expected gain for both methods in the two populations was higher than the actual gain from selection because the expected gain were calculated from genetic variance which included both of additive and non-additive components
Generally, the expected gain from the reciprocal recurrent selection for improvement interpopulations A and B was 42.77 and actual gain was 8.63%, and the expected gain from S1 per se method were 23.58 and 31.87% and actual gain were 17.12 and 8.06 for Pop. A and B, respectively, indicating that the two methods of S1 per se and reciprocal recurrent selection can be used to intrapopulation and interpopulations improvement.
Expected gain for days to 50% silking was 4.03 and 3.75% in Pop. A and 5.09 and 3.94% in Pop. B. for S1 per se and HS method, respectively. On the other hand, the actual gain from selection of improved Pop. A was 0.40 and 0.40%, while, was -1.30 and -2.30% for improved Pop. B for S1 per se and HS method, respectively. However expected gain from S1 per se and HS method selection in Pop B. was higher than those of Pop. A.
Also the actual gain from selection in improved Pop. A was better than those in Pop. B for the two selection methods. These results could be attributed to the presence of more additive genetic variance in Pop. A than in Pop. B.
from this study we can be noticed that yield improvement of Pop. A was more suitable than the Pop. B for S1 per se causing the more variability of Pop. A. Also the S1 per se selection method was more effective in population improvement. For earliness improvement, Pop. B was more suitable than Pop. A for both methods of selection. Indicating that Pop. B was more variability than Pop. A for this trait. Selection for earliness was not effective this maybe due to the similarity in flowering date for both populations.