| Summary: | Thesis (MScAgric)--Stellenbosch University, 2011. === ENGLISH ABSTRACT: Research into markers for the detection of genetic diversity and cultivar identification has
become an important component of the genetic improvement of crops. However, the incorporation
of marker assisted selection (MAS) as a tool for the identification and characterization
of breeding material has not been fully implemented in the breeding of spring
triticale at Stellenbosch University’s Plant Breeding laboratory (SU-PBL). The present
study served as a case study in order to achieve this.
The first part of the study concerned the detection of genetic diversity in 101 newly
sourced triticale cultivars, from a USDA germplasm bank, together with five local control
cultivars, in order to identify possible crossing parents. Eight SSR markers, including five
derived from rye and three from wheat, and five agronomic characteristics were used to
assess diversity. In seedling screening the foreign cultivars showed resistance towards the
stem rust isolate used, but were mostly susceptible to the leaf rust isolate. Out of the 8
SSR markers tested, 7 markers were polymorphic and revealed 140 alleles varying from 12
to 26 with an average of 17.5 alleles per locus. The observed polymorphic information
content (PIC) value ranged from 0.39 to 0.88 with an average of 0.70, indicative of the
good discriminatory ability of the SSR markers. The data revealed that the South African
cultivars were genetically closely related to cultivars from the USA and Canada.
The second part of the study focused on the introgression of a blue aleurone layer gene
(Ba), carried by a wheat cultivar, ‘Cltr1202STR’, and purple pericarp genes (Pp1; Pp3)
also carried by a wheat cultivar, ‘Amethyst’, into a triticale background. Unfortunately the
introgression of the purple pericarp genes failed. Two lines containing the blue aleurone
layer, 11T023 and 11T028, were however successfully created. Molecular typing of these
lines with SSR markers were able to show that BC4F1 line 11T023 (Ba) B was genetically
similar to the recurrent parent ‘Agbeacon’; and that the BC4F1 11T028 line (Ba) A was
closest to the ‘US2007’ recurrent parent.
The study illustrated that MAS was a reliable tool for detecting genetic diversity in newly
sourced germplasm, and assisted in making a backcross breeding effort more effective.
The data generated from MAS could therefore clearly assist in making the SU-PBL breeding
program more effective by moving, better informed, decision making toward data based partly on the genotype, thereby minimizing the risks associated with purely phenotypic
based decisions. === AFRIKAANSE OPSOMMING: Navorsing rondom die gebruik van merkers vir die bepaling van genetiese-diversiteit en
kultivar identifikasie is ‘n toenemend belangriker komponent vir die genetiese verbetering
van gewasse. Die inkorporering van merker-bemiddelde-seleksie (MBS) as gereedskap vir
die identifikasie en karaktarisering van telingsmateriaal is nog nie ten volle geïmplimenteer
in die lente korogtelingsprogram van die Stellenbosch Universiteit Planteteeltlaboratorium
(SU-PTL). Die studie het gedien as gevallestudie ten einde dit te bereik.
Die eerste gedeelte van die studie het gehandel oor die tipering van die genetiese diversiteit
van ‘n 101 kultivars verkry vanaf ‘n USDA kiemplasmabank saam met 5 plaaslike
kontroles. Dit was gedien ten einde moontlike kruisings-ouers te kon identifiseer. Agt SSR
merkers, insluitend vyf afkomstig van rog en drie vanaf koring, asook vyf agronomiese
kenmerke is aangewend om die materiaal se diversiteit te tipeer. Saailingtoetsing is ook
gedoen en het aangetoon dat die meeste kultivars weerstandig was vir die stamroes-isolaat,
maar nie die blaarroes-isolaat nie. Van die agt SSR merkers getoets het sewe getoon om
polimorfies te wees en het ‘n 140 allele gegee wat gewissel het vanaf 12 tot 26 per lokus
met ‘n gemiddeld van 17.5. Die waargenome polimorfiese inligtings inhoud (PII) waarde
het gewissel vanaf 0.39 tot 0.88 met ‘n gemiddeld van 0.70. Die merkers kon dus
suksesvol diskrimineer. Die data het aangetoon dat die Suid-Afrikaanse kultivars genetiese
die naaste verwant was aan die kultivars afkomstig vanaf die VSA en Kanada.
Die tweede gedeelte van die studie het gefokus op die introgressie van ‘n blou aleuron-laag
geen (Ba), afkomstig vanaf die koringkultivar ‘Cltr1202STR’, en twee pers-perikarp gene
(Pp1; Pp3), afkomstig vanaf die koringkultivar ‘Amethyst’, na ‘n korog agtergrond.
Ongelukkig het die oordrag van die pers-perikarp gene gefaal. Twee lyne wat die blou aleuron-
laag bevat, 11T023 en 11T028, is egter suksesvol geskep. Tipering van die lyne met
die SSR merkers het aangetoon dat die BC4F1 lyn 11T023 (Ba) B genetiese baie na aan die
herhalende ouers ‘Agbeacon’ is en dat die BC4F1 11T028 lyn (Ba) A nader is aan die
herhalende ouer ‘US2007’.
Die studie het dus geïllustreer dat MBS gebruik kan word as ‘n betroubare manier om genetiese
diversiteit te bepaal en by te dra tot die sukses van ‘n terugkruisingsprogram. Die
data wat dus voortspruit uit MBS kan dus help om die SU-PTL se telingsprogram te assisteer in die besluitnemingsproses tydens teling deur beter genotipe gebaseerde besluite te
neem wat die riskio van fenotipe gebaseerde besluite kan help verminder.
|
|---|
