Thesis (MSc)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: The species Haliotis midae is the only commercially exploitable abalone
species of the six found in the South African coastal waters. This species is
under substantial pressure from both legal and illegal harvesters, to such an
extent that it could be commercially extinct within four years. Efforts to
alleviate the pressures on the natural populations of both illegal and legal
harvesting are being made. The genetic management systems for abalone
farming and ranching activities should be carefully evaluated. The loss of
genetic diversity and the risks of contaminating the gene pools of natural
populations in the vicinity of a farm should be minimized. Genetic evaluation
studies will be at great importance to acquire the necessary data needed for
genetic diversity and differentiation analysis.
The aim at this study was to develop species-specific microsatellite DNA
markers to assess the genetic diversity and differentiation within and between
the brood stock and commercial stock of the Sea Plant Products abalone farm
(Hermanus, Republic of South Africa) and natural populations related to the
brood stock. The species-specific DNA markers were also used for parentage
assignments within the tarm population (first for abalone) and preliminary OTL
(quantitative trait loci)-discovery analysis studying growth rate segregation.
Samples were taken of the farm's brood stock and commercial stock (Rows 2,
3, 4) as well as from two natural populations (Saldanha Bay and Black Rock)
related to the brood stock. Various statistical parameters and software
packages were used to assess genetic diversity and differentiation, to infer
parentage and to look for OTL's.
Eight species-specific microsatellite DNA markers were designed and used
for data analysis. Data analysis showed a loss at genetic diversity from the
brood stock to the commercial stock caused by the subdivision of the original
brood stock into rows and the differential contributions of parents to the
offspring. No genetic differentiation (Fst) was detected between the farm and natural populations, except for the offspring of Row2. levels of inbreeding
(ns) were high for all loci within the populations. Thirty-eight percent of all
studied offspring were confidently assigned to a couple. The preliminary QTldiscovery
suggested the segregation of a number of alleles and genotypes
with growth rate.
The study concluded that the commercial abalone population of the Sea Plant
Products abalone farm holds no threat to the disruption of the genetic diversity
of the natural populations. It is proposed that the farm implement a rotational
breeding program to increase the genetic diversity of the commercial
population. Any newly acquired brood stock must be profiled before their
introduction into the breeding program to assess the influence of the animals
on the current levels of genetic diversity within the farm. The accuracy and
reliability of parentage assignments and QTl-discovery need to be optimised
by adding more loci and sampling more animals or even by trying and
developing new methods. / AFRIKAANSE OPSOMMING: Van die ses perlemoen spesies wat langs die Suid-Afrikaanse kus gevind
word, is die spesie Haliotis midae die enigste een wat van kommersiële
belang is. Wettige, sowel as onwettige versameling, plaas hierdie spesie
onder sulke geweldige druk dat dit dalk binne vier jaar verlore kan wees vir
die kommersiële bedryf. Verskeie strategieë word tans geïmplimenteer om
hierdie druk te verlig. Die genetiese bestuurstrategieë binne perlemoen plase
moet deeglik ondersoek word. Die verlies aan genetiese diversiteit en die
moontlikheid vir die kontaminering van die natuurlike populasies in die
omgewing van die plaas se geenpoel, moet uitgeskakel word. Genetiese
evaluasies sal van groot belang wees om die nodige data vir genetiese
diversiteit- en differensiasie-analises te verkry.
Die doel van die studie was om spesies-spesifieke mikrosatelliet DNA
merkers te ontwikkel wat gebruik sou word om die genetiese diversiteit en
differensiasie binne en tussen die broei diere en die kommersiële diere van
Sea Plant Products se perlemoen plaas (Hermanus, Republiek van Suid-
Afrika) en die natuurlike populasies wat verwant is aan die broei diere, te
bepaal. Die spesies-spesifieke DNA merkers is ook vir ouerskap-bepalings
binne die plaas se populasie gebruik, asook vir voorlopige OTL (quantitative
trait locI) - ontdekking met betrekking tot groeitempo segregasie.
Monsters van die plaas se broei diere en kommersiële diere (Ry 2, 3, 4)
asook van twee natuurlike populasies (Saldanha Baai en Black Rock) wat
verwant is aan die broei diere, is geneem. 'n Verskeidenheid van statistiese
parameters en sagteware pakette is vir die genetiese diversiteit- en
differensiasie-analises, vir ouerskap-bepalings en vir die opspoor van OTL's
gebruik.
Agt spesies-spesifieke mikrosatelliet DNA merkers is ontwerp en toe gebruik
vir die data analises. 'n Verlies aan genetiese diversiteit vanaf die broei diere
na die kommersiële diere is deur die data analises uitgewys. Dit is veroorsaak deur die verdeling van die oorspronklike broei diere in rye en die
differensiële bydraes deur die ouers na die nageslag. Geen genetiese
differensiasie (Fst) is tussen die plaas se populasie en die natuurlike
populasies gevind nie, maar die nageslag van Ry 2 het wel differensiasie
getoon. Die vlakke van inteling (Fis) was hoog oor alle lokusse binne alle
populasies. Agt-en-dertig persent van die nageslag wat bestudeer is, was
suksesvol met 'n ouerpaartjie geassosieer. Die voorlopige OTL-ontdekking
studie toon die potesiële segregasie van 'n aantal allele en genotipes saam
met groeitempo.
Die bevindinge van die studie is dat die kommersiële populasie op die Sea
Plant Products perlemoen plaas, geen bedreiging vir die versteuring van die
natuurlike populasies se genetiese diversiteit inhou nie. Daar is voorgestel
dat die plaas 'n rotasie-basis broeiprogram moet implimenteer om sodoende
die genetiese diversiteit van die kommersiële populasie te verhoog. Enige
nuwe broei diere se genetiese profiel moet ook voor die tyd ondersoek word
om te sien wat se effek hierdie diere op die huidige genetiese diversiteit van
die kommersiële populasie sal hê. Die akkuraatheid en betroubaarheid van
die ouerskap-bepalings en OTL-ontdekking moet optimiseer word deur of
meer lokusse te bestudeer, of meer diere in analises te gebruik of selfs om
nuwe tegnieke te probeer of te ontwikkel.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/50027 |
| Date | 12 1900 |
| Creators | Slabbert, Ruhan |
| Contributors | D' Amato, M. E., Brink, D., Stellenbosch University. Faculty of Science. Dept. of Microbiology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 213 p. : ill. |
| Rights | Stellenbosch University |
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