Thesis (MSc)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: The genetic status of H. midae broodstock in the South African aquaculture industry reflects
that of random samples originating from undomesticated wild populations. The nature of
growth in abalone is very slow, taking between three and four years to reach a marketable size
of between 60 to 100 grams. It is therefore of paramount importance to improve this trait in
order to ensure global competitiveness and economic viability within the industry. Improving
this negative characteristic through conventional selection methods is a long-term venture and
alternative means that would yield instantaneous results had to be considered. Crossbreeding
was identified as an alternative, short-term strategy to improve growth rate.
A crossbreeding experiment was performed between two populations of the abalone,
Haliotis midae, from the East (E) and West (W) Coast of South Africa. This was done to
investigate the occurrence of heterosis for growth among the crossbred genotypes
(East x West, West x East). Fifteen males and females from both the East and the West Coast
populations were mated in a complete dialelle crossbreeding experiment to produce four
progeny groups (WW, EE, EW and WE). Progeny groups were evaluated for weight (bW) and
length gain (bL) over a specific growth period of 9 months.
The results provided no evidence of significant differences in weight (P = 0.085) or
length gain (P = 0.244) between the four progeny groups, giving no indication of significant
heterosis for weight and length gain among the crossbred progenies of these East and West
Coast populations. It is recommended that further efforts to obtain improved growth rate in
the abalone, Haliotis midae, through crossbreeding only be considered in light of clear
evidence of substantial genetic differentiation between such populations. / AFRIKAANSE OPSOMMING: Die huidige status van perlemoen, soos dit voorkom in akwakultuur bedrywighede in Suid
Afrika, weerspieël dié van ‘n ewekansige monster vanuit wilde, natuurlike populasies.
Perlemoen is inherent ‘n stadig groeiende organisme wat tussen drie en vier jaar neem om tot
‘n bemarkbare grote van 60 tot 100 gram te groei. Dit is dus uiters noodsaaklik om hierdie
eienskap te verbeter ten einde die bedryf ekonomies lewensvatbaar en mededingend op
wêreld markte te maak. Konvensionele seleksie as ‘n metode om hierdie negatiewe eienskap
te verbeter is ‘n langtermyn onderneming wat die identifisering van ‘n korttermyn metode,
wat ondmiddellike resultate lewer, noodsaak. Kruisteelt is geïdentifiseer as geskikte
korttermyn oplossing aangesien dit onmiddellike resultate lewer.
‘n Kruisteel eksperiment is uitgevoer tussen twee populasies van die perlemoen,
Haliotis midae, van die Ooskus (E = East) en die Weskus (W = West) van Suid Afrika. Dit is
gedoen om die omvang van heterose vir groeitempo in die gekruisde nageslag (East x West,
West x East) te bepaal. Fyftien mannetjies en wyfies van beide die Oos- en Weskus
populasies is met mekaar gepaar in ‘n volledige dialleel kruising om vier nageslag groepe
(WW, EE, EW en WE) te vorm. Die nageslag is geëvalueer ten opsigte van massa (bW) en
lengte (bL) toename oor ‘n spesifieke groei tydperk van 9 maande.
Die eksperimentele resultate dui daarop dat die vier nageslag groepe nie betekenisvol
van mekaar verskil het ten opsigte van massa (P = 0.085) en lengte (P = 0.244) toename nie
en dat daar dus geen aanduiding van heterose vir massa en lengte toename in die nageslag van
kruisings tussen die Ooskus en Weskus populasies bestaan nie. Daar word aanbeveel dat
kruisteling as ‘n metode van genetiese verbetering van groeitempo in Haliotis midae slegs
oorweeg word in die lig van nuwe molekulêre bewyse van genoegsame genetiese
differensiasie tussen sulke populasies.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/20900 |
| Date | 04 1900 |
| Creators | Vorster, Gysbert |
| Contributors | Brink, D., Stellenbosch University. Faculty of Agrisciences. Dept. of Genetics. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | xi, 90 leaves : ill. |
| Rights | Stellenbosch University |
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