Development of AFLP markers for Haliotis midae for linkage mapping

Badenhorst, Daleen (2008-12)

Thesis (MSc)--Stellenbosch University, 2008.

Thesis

ENGLISH ABSTRACT: Haliotis midae, is the only commercially important species of the six abalone species found in South African coastal waters and has become a lucrative commercial commodity. Wild stocks of H. midae are, however, no longer commercially sustainable due to a combination of environmental factors and poaching. The solution to the crisis is artificial production systems in the form of abalone farms. An abalone enhancement programme was initiated in South Africa in 2006, funded by industry and government. This programme focuses on the elucidation of the abalone genome and genetic factors contributing to increased productivity, thereby aiding the commercial production of abalone. The aims of this study, the first of its kind concerning H. midae, were to develop AFLPbased markers (specifically fluorescent AFLP analysis); to monitor the segregation of these markers in a single full-sib family and to use the markers and additional microsatellite markers to generate the first preliminary linkage map for H. midae. Genomic DNA of sufficient quality and purity for fluorescent AFLP analysis was obtained from 3.5-month-old H. midae juveniles. Preliminary linkage maps were constructed using AFLP and microsatellite markers segregating in an F1 family following a pseudo-testcross mapping strategy. Twelve AFLP primer combinations, producing 573 segregating peaks, and 10 microsatellite markers were genotyped in the parents and 108 progeny of the mapping family. Of the 573 segregating AFLP peaks genotyped, 241 segregated in a 1:1 ratio and 332 in a 3:1 ratio. Of these AFLP markers, 90 segregated according to the expected 1:1 Mendelian ratio and 164 segregated according to the expected 3:1 Mendelian ratio at the P = 0.05 level and were used for linkage analysis. Of the 10 microsatellite markers genotyped, nine were informative for linkage mapping analysis. Preliminary male and female genetic linkage maps were developed using markers segregating in the female or male parent. A total of 12 and 10 linkage groups were detected for the female and male maps respectively. The female map covered 1473.5cM and consisted of 56 markers, and the male map covered 738.9cM consisting of 30 markers. Markers with segregation distortion were observed as previously reported in other abalone species and potential homology between one of the linkage groups of the male map and two of the linkage groups of the female map were identified using the 3:1 segregating AFLP markers. In conclusion, the genetic linkage map presented here, despite the fact that it has relatively low genome coverage and low marker density, forms an ideal starting point for more detailed study of the H. midae genome and will provide a scaffold for basic and applied studies in abalone. A high-density linkage map of H. midae should in future be developed with additional co-dominant molecular markers, such as microsatellites, to improve the transferability of the linkage map between different laboratories and among populations. A high-density linkage map will facilitate the mapping of QTL of commercially important traits (i.e. growth) and future MAS breeding programmes.

AFRIKAANSE OPSOMMING: Perlemoenspesie, Haliotis midae, is die enigste spesie van kommersiële belang van die ses wat in die kuswater van Suid-Afrika aangetref word en het ‘n winsgewende handelskommoditeit in Suid-Afrika geword. Die ontginning van natuurlike H. midae populasies is egter, as gevolg van ‘n kombinasie van omgewingsfaktore en stropery nie meer kommersieel volhoubaar nie. Die perlemoenkrisis kan die hoof gebied word deur kunsmatige produksiesisteme op perlemoenplase tot stand te bring. ‘n Perlemoen verbeteringsprogram is in 2006 in Suid-Afrika geïnisieer en word deur die industrie en regering befonds. Die program focus op die ontrafeling van die perlemoen genoom en die genetiese faktore wat bydrae tot verhoogde produksie. Sodanige inligting kan gebruik word om kommersiële perlemoenproduksie te bevorder. Die doel van hierdie studie, die eerste met H. midae, is om AFLP-gebaseerde merkers (spesifiek fluoresserende AFLP analise) te ontwikkel; die segregasie van hierdie merkers te monitor in ‘n enkel volledige verwante familie en die merkers en addisionele mikrosatelliet merkers te gebruik om die eerste voorlopige koppelingskaart vir H. midae te genereer. Genomiese DNS van genoegsame kwaliteit en suiwerheid vir fluoresserende AFLP analise is ge-ekstraeer uit 3.5-maand-oue H. midae individue. Voorlopige koppelingskaart is gekonstrueer deur van segregerende AFLP en mikrosatelliet merkers in ‘n F1 familie gebruik te maak deur ‘n pseudo-kruistoets karteringstrategie te volg. Twaalf AFLP inleier kombinasies, wat 573 segregerende fragmente geproduseer het, en 10 mikrosatelliet merkers is gegenotipeer in die ouers en 108 individue van die nageslag van die karteringsfamilie. Van die 573 segregerende AFLP merkers wat gegenotipeer is, het 241 in ‘n 1:1 verhouding en 332 in ‘n 3:1 verhouding gesegregeer. Van hierdie AFLP merkers, het 90 volgens die verwagte 1:1 Mendeliese verhouding en 164 volgens die 3:1 Mendeliese verhouding by die P = 0.05 gesegregeer vlak en is vir die koppelingsanalise gebruik. Van die 10 mikrosatelliet merkers gegenotipeer, was 9 informatief vir koppeling karteringsanalise. Voorlopige manlike en vroulike genetiese koppelingskaarte is ontwikkel met gebruik te maak van merkers wat in die manlike of vroulike ouer segregeer het. ‘n Totaal van 12 en 10 koppelingsgroepe is onderskeidelik in die vroulike en manlike karate gegenereer. Die vroulike kaart dek 1473.5cM and bestaan uit 56 merkers, terwyl die manlike kaart 738.9cM beslaan het met 30 merkers. Merkers wat segregasie distorsie toon is waargeneem soos voorheen in ander perlemoenspesies gerapporteer. Potensiële ooreenstemming tussen een van die koppelingsgroepe van die manlike kaart en twee van die koppelingsgroepe van die vroulike kaart is aangetoon deur van die 3:1 segregerende AFLP merkers gebruik te maak. Die genetiese koppelingskaarte verskaf wel ‘n relatiewe lae genoomdekking en ‘n lae merkerdigtheid, maar is ‘n ideale vertrekpunt vir meer gedetailleerde studie van die H. midae genoom en dien as ‘n raamwerk vir toekomstige basiese en toegepaste studies in perlemoennavorsing. ‘n Hoëdigtheid koppelingskaart van H. midae moet in die toekoms ontwikkel word met gebruik van bykomstige ko-dominante molekulêre merkers, soos mikrosatelliete. Dit sal die oordraagbaarheid van die koppelingskaart tussen verskillende laboratoria asook tussen populasies verbeter. ‘n Hoëdigtheid koppelingskaart sal die kartering van kwantitatiewe kenmerk loki (KKL) vir kommersieel belangrike kenmerke (onder andere groeikrag) en toekomstige merker bemiddelde seleksie (MBS) teelprogramme moontlik maak.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/21525
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