Doctoral theses
Current Record: 277 of 336
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| Identifier |
uch.biology.phd//1999batarias |
| Title |
Γενετική της τσιπούρας (Sparus aurata). Μελέτη των μικροδορυφορικών αλληλουχιών και χρήση τους στην εκτίμηση γενετικών παραμέτρων της αύξησης και άλλων ποσοτικών χαρακτήρων |
| Alternative Title |
Genetics of seabream (Sparus aurata). Study of microsatellites and their use for the estimation of genetic parameters of growth and other quantitative characters |
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Author
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Μπαταργιάς, Κωνσταντίνος
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Thesis advisor
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Ζούρος, Ε.
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| Abstract |
In the present study, we have developed suitable microsatellite markers in order to use them for parenthood identification of a given number of offspring. After the identification of the families, we estimated the genetic parameters of several quantitative characters of the species. The brood population was consisted of 32 wild individuals. The spawning took place under natural conditions of temperature and photoperiod. The brooders were mass spawned for two different reproductive periods. During the first reproductive period, the weight of 150 progeny was recorded for the ages of 6 and 10 months old. During the second reproductive period 33 quantitative characters were recorded (the weight and several morphometric, hormonal, biochemical, reproductive and physiological characters) for 600 progeny (22 months old). Genetic parameters were estimated using the animal model. A DFREML algorithm was used for the estimation of the variance and covariance components. The models were checked for their significance using the Maximum Likelihood ratio. For the development of the microsatellite loci, a partial genomic library was constructed digesting a given amount of total DNA with 3 enzymes. Given the number of positive clones of the library, the mean distance of 2 microsatellite (GT)n loci was estimated at 16 Kbp. Imperfect microsatellites were dominated of the perfect ones. Among the 50 clones sequenced, adjacent microsatellites were detected in 26% of the clones. Primers were developed for 5 of the sequenced clones and they were checked for their polymorphism. The levels of heterozygosity of the 5 microsatellite loci in the broodstock were extremely high ranging from 87.5% to 100%. The mean heterozygosity was 95%. Two loci were physically linked in a distance of 75 bp. The analysis of the crosses revealed some linkage for 2 other loci in a distance of about 12 cM. The above in conjunction with the adjacent microsatellites leads us to the hypothesis of cluster formation of microsatellites in the genome of gilthead seabream. The contribution of the brooders during the 2 reproductive periods was highly uneven. During the 1st reproductive period 13 males and 9 females (sex ratio 1 :1.4 ) contributed to the next generation. During the 2nd period the males that contributed to the next generation were 5 and the females were 10(sex ratio 2 :1 ). 4 out of 13 males of the 1st period changed their sex and acted as females at the 2nd reproductive period. The contribution of the males that changed sex, during the 1st period, was medium to low. The uneven contribution and the change of the sex ratio resulted in a severe reduction of the effective population size. The rate of inbreeding was estimated to 4.2% for the 1st period and 5.5% for the second one. The use of microsatellites could play a major role in the monitoring of the broodstocks and in the study of the reproductive behaviour of the species. The estimates of heritability for the weights of 3 different ages were high. The heritability estimate for the weight at the age of 6 months old was 0.44 ± 0.20. Some paternal effects were detected at this age. The heritability estimates for the weight at the ages of 10 and 22 months old were 0.52 ± 0.22 and 0.55 ± 0.18, respectively. Non additive effects were statistically zero at these ages. The genetic correlations of the weights at the three ages were medium (~50%). The genetic parameters for the rest of the characters refer to 22 months old individuals. The heritability of the gutted body weight was high (0.51) whilst the estimate of dressing was lower (0.31). The heritability estimates of the morphometric characters displayed a wide range. The estimates for the lengths ranged from 0.11 to 0.36. The heritabilities of the hights and width were higher and ranged from 0.32 to 0.54. The genetic correlations among them and with the weight were very high. Thyroid hormones showed low heritabilities along with plasma glucose and total proteins. On the contrary, the estimates of the plasma lipids were very high. The genetic correlations among the hormones and the metabolites were low to medium except those among the lipids which were high. The additive component of the "sex change" character represents the 31% of the total phenotypic variance while that of gonadosomatic index was 54%. Hepatosomatic, fat and visceral indices showed very high heritabilities. The estimate for the condition factor was low (0.23). The genetic correlations among the weight, the hormones and the metabolites were low to medium except the genetic correlation with the plasma total proteins which was high (0.66). The genetic correlations with the sex change was very high (0.90). The genetic correlations among weight and the physiological indices were high. The results regarding the microsatellites are discussed in respect to their use in the study of the reproductive behaviour of gilthead seabream. The genetic correlations of the sex change and other characters stimulated a discussion of the nature of this phenomenon. Final, the genetic parameter estimates are discussed in respect to their use in deciding an effective selection program. The expected response of the weight is very encouraging for the application of such a program.
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| Language |
Greek |
| Subject |
Γενετικές παράμετροι; Γενετική βελτίωση; Μικροδορυφορικά |
| Issue date |
1999-03-31 |
| Collection
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School/Department--School of Sciences and Engineering--Department of Biology--Doctoral theses
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Type of Work--Doctoral theses
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| Permanent Link |
https://elocus.lib.uoc.gr//dlib/0/c/b/metadata-dlib-1999batarias.tkl
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| Views |
253 |
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