Thesis (MSc)--University of Stellenbosch, 2007. / ENGLISH ABSTRACT: The indigenous abalone Haliotis midae is one of the most remarkable and highly exploited species
of marine molluscs in South Africa. It is the only species of southern African Haliotidae to be
commercially reared and has been successfully cultured for almost two decades. Its short history of
domestication along with market demands and the need to develop efficiency in the production
process has resulted in an increased interest in the possible genetic improvement of this species.
The unhurried growth rate associated with H. midae is a cause of particular concern to the industry,
predominantly with regards to profitability and competitiveness in the market place. A modest
amount of work has so far been directed at establishing a means of enhancement for selective
breeding on the commercial level. Genetics plays a key role in the establishment of successful
improvement programmes in various aquaculture species. The aim of this study was to develop
species-specific microsatellite markers for the abalone and subsequently perform parentage
assignment on farm produced animals entered into a growth performance recording scheme.
Animals were obtained from the hatcheries of three commercial abalone farms situated in the
Walker Bay region in the Western Cape.
Microsatellites were isolated using the enrichment-based FIASCO method, and characterised into
perfect, imperfect and compound repeats according to the structural nature of their repetitive units.
From the partial gDNA libraries obtained and 365 screened colonies, a total of 54 loci were located.
PCR primers were designed for 36 markers and the 15 primer pairs that displayed loci with the
highest level of polymorphism were subsequently chosen for fluorescent labelling. The markers
were tested on a subset of 32 wild H. midae individuals to determine their usefulness and efficiency
in genotyping. Five markers, along with five others that were previously designed, were chosen for
assigning parentage to the animals submitted to the performance recording scheme. Three thousand
offspring from each of the three participating farms were equally divided and reared at five different
locations. From each location 20 fast growing and 20 slow growing juveniles, as well as the
broodstocks, were sampled and genotyped using the ten chosen microsatellite loci. Two farms had
60% of offspring unambiguously assigned to a single parental couple. Assignments showed
patterns of dominant male and female brooders, but no trend in brooders specifically contributing to
fast or slow growing offspring. Parentage assignment for the third farm was, however, unsuccessful
due to lack of broodstock data. In future, screening of all available broodstock will ensure
acquisition of relevant pedigree information. The results obtained in this study are an initial step in
the development of a genetic improvement programme for commercial Haliotis midae. / AFRIKAANSE OPSOMMING: Die inheemse skulpvis Haliotis midae is een van die mees merkwaardige en hoogs oorbenutte
mariene slakspesies in Suid-Afrika. Dit is die enigste suidelike Afrika Haliotidae spesie wat
kommersieel benut word en dit word al meer as twee dekades suksesvol geteel. Die spesie se kort
domestiseringsgeskiedenis, toenemende mark aanvraag en die behoefte om meer effektiewe
produksie daar te stel, het gelei tot toenemende belangstelling in die moontlike genetiese
verbetering van die spesie. Die stadige groeitempo geassosieer met H. midae is veral ‘n punt van
kommer vir die industrie, veral in terme van winsgewendheid en kompetering in die markplek.
Minimale werk is sover gedoen in die daarstelling van verbetering deur selektiewe teling op ‘n
kommersiële skaal. Genetika speel ’n sleutelrol in die daarstelling van suksesvolle
verbeteringsprogramme van verskeie akwakultuur spesies. Die doel van hierdie studie was om
spesie-spesifieke mikrosatelliet merkers vir perlemoen te ontwikkel en vervolgens
ouerskapsbepaling van kommersiële diere, wat deelneem aan ‘n groeiprestasie aantekenstelsel, uit
te voer. Diere is voorsien deur die teelstasies van drie kommersiële perlemoenplase geleë in die
Walker Bay omgewing in die Wes-Kaap.
Mikrosatelliete is geïsoleer deur die verrykings-gebaseerde FIASCO metode, en gekarakteriseer as
perfekte, onderbroke of saamgestelde herhalings gebaseer op die strukturele aard van die herhalings
eenhede. Vanaf die gedeeltelik gDNA biblioteke wat bekom is en 365 gesifte kolonies, is ‘n totaal
van 54 loki opgespoor. PKR inleiers is ontwerp vir 36 merkers en die 15 inleierpare, wat loki met
die hoogste polimorfisme geamplifiseer het, is vervolgens geselekteer vir fluoreserende merking.
Die merkers is getoets op ’n kleiner groep van 32 natuurlike H. midae individue om hulle
bruikbaarheid en genotiperingseffektiwiteit te bepaal. Vyf merkers is saam met vyf reeds
ontwikkelde merkers gekies vir ouerskapsbepaling van die diere in die prestasie aantekenstelsel.
Drieduisend nageslag diere vanaf elkeen van die drie deelnemde plase is gelykop verdeel en
grootgemaak op die vyf verskillende lokaliteite. ‘n Monster van 20 vinnig groeiende en 20 stadig
groeiende jong perlemoen, sowel as broeidiere, is vanaf elke lokaliteit geneem en gegenotipeer deur
middel van die 10 geselekteerde mikrosatelliet loki. Sestig persent van twee van die plase se
nageslag is onteenseglik toegesê aan ‘n enkele ouerpaar. Ouerskapstoekenning het patrone van
dominante vroulike en manlike broeidiere getoon, maar geen tendens in terme van bydrae tot vinnig
en stadig groeiende nageslag kon gevind word nie. Ouerskapstoekenning vir die derde plaas was
onsuksesvol as gevolg van ’n gebrek aan data vir die broeidiere. In die toekoms sal genotipering
van alle beskikbare broeidiere die daarstelling van relevante stamboominligting verseker. Die
resultate verkry in hierdie studie verteenwoordig ‘n eerste stap in die ontwikkeling van ’n genetiese
verbeteringsprogram vir kommersiële Haliotis midae.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/21755 |
| Date | 12 1900 |
| Creators | Ruivo, Nicola Ribeiro |
| Contributors | Roodt-Wilding, R., 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 | viii, 120 leaves : ill. |
| Rights | Stellenbosch University |
Page generated in 0.0031 seconds