Thesis (MSc.)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: The detrimental effect of soil salinity on crop production is a growmg problem worldwide
(Tanji, 1990b). The degree to which plants can tolerate high concentrations of salt in their rooting
medium is under genetic control with different genetic and physiological mechanisms contributing
to salt tolerance at different developmental stages (Epstein & Rains, 1987). Only limited variation
exists for salt tolerance in the cultivated cereals. This has prompted attempts to select tolerant
progeny following hybridisation of cultivated species and wild, salt-tolerant species. Thinopyrum
distichum, an indigenous wheatgrass that is naturally adapted to saline environments
(McGuire & Dvorak, 1981), was crossed with triticale (x Triticosecale) in an attempt to transfer its
salt tolerance and other hardiness characteristics (Marais & Marais, 1998). The aims of this study
were to (i) identify Thinopyrum chromosomes carrying genes for salt tolerance and to identify
molecular markers for these chromosomes, (ii) identify a number of diverse monosomic and
disomie addition plants.
Bulked segregant analysis (BSA), in combination with AFLP, RAPD and DAF marker analysis was
implemented to screen for polymorphisms associated with salt tolerance. Five putative AFLP
markers and two RAPD markers were detected using bulks composed of salt tolerant plants and
bulks composed of salt sensitive plants. The distribution of the markers in these bulks suggests that
more than one Thinopyrum chromosome carry genes for salt tolerance.
Salt tolerant monosomic and disomie addition plants were characterised for AFLP, RAPD and DAF
polymorphisms in an attempt to find markers associated with the chromosome(s) conditioning salt
tolerance. One salt tolerant monosomic and one disomie addition plant was identified. One AFLP
and two RAPD markers were identified for the Thinopyrum chromosome( s) present in the
monosomic addition plant, while three AFLP and three RAPD markers were identified for the
disomie addition plant.
An attempt was also made to identify diverse chromosome addition plants having complete or near
complete triticale genomes plus an additional random Thinopyrum chromosome. Plants with
2n = 43 /44 were identified and characterised for molecular markers (AFLP and RAPD). Cluster
analysis was used to group the putative monosomic or disomie addition plants according to the
specific Thinopyrum chromosomes they retained. Seventeen AFLP and RAPD markers could be
used to group the 24 putative addition plants into six broadly similar groups with different
additional Thinopyrum chromosomes. While the members of each group are likely to carry the same additional Thinopyrum chromosomes, this may not necessarily be the case as the
interpretation of the marker results is complicated by heterogeneity among plants with regard to the
triticale background chromosomes they possess. It is also likely that chromosome translocations
occurred during backerossing which may further complicate data. Nonetheless, it is now possible to
select disomie addition plants from each group that are likely to represent different Thinopyrum
chromosomes. The data will also be useful in future attempts to find further addition plants
carrying the remaining Thinopyrum chromosomes. / AFRIKAANSE OPSOMMING: Die skadelike effek van grond versouting op gewasproduksie neem wêreldwyd toe (Tanji, 1990b).
Die mate waartoe plante hoë konsentrasies sout in die wortelstelsel kan hanteer is onder genetiese
beheer en verskillende genetiese en fisiologiese meganismes dra by tot die soutverdraagsaamheid
tydens verskillende ontwikkelingstadia (Epstein & Rains, 1987). Slegs beperkte variasie bestaan vir
soutverdraagsaamheid in verboude grane. Dit het aanleiding gegee tot pogings om
soutverdraagsame nageslag te selekteer na hibridisasie van verboude spesies en wilde,
soutverdraagsame spesies. Thinopyrum distichum, 'n inheemse koringgras, wat aangepas is by brak
omgewings (McGuire & Dvorak, 1981), is met korog (x Triticosecale) gekruis in 'n poging om die
gene vir soutverdraagsaamheid en ander gehardheidseienskappe oor te dra (Marais & Marais,
1998). Die oogmerke van hierdie studie was om (i) Thinopyrum chromosome te identifiseer wat
gene bevat vir soutverdraagsaamheid en molekulêre merkers te vind vir hierdie chromosome, (ii) 'n
aantal diverse monosomiese en disomiese addisieplante te identifiseer.
Bulksegregaatanalise (BSA), gekombineer met AFLP-, RAPD- en DAF-merkeranalise, is gebruik
om polimorfismes geassosieerd met soutverdraagsaamheid op te spoor. Vyf moontlike AFLPmerkers
en twee RAPD-merkers is geïdentifiseer met gebruik van bulks bestaande uit
soutverdraagsame plante en bulks bestaande uit soutgevoelige plante. Die verspreiding van die
merkers in soutverdraagsame bulks dui daarop dat meer as een Thinopyrum chromosoom bydra tot
soutverdraagsaamheid.
Soutverdraagsame, monosomiese en disomiese addisieplante is gekarakteriseer vir AFLP- en
RAPD-polimorfismes in 'n verdere poging om merkers te vind vir chromosome betrokke by
soutverdraagsaamheid. Een soutverdraagsame monosomiese en een disomiese addisieplant is
geïdentifiseer. Een AFLP- en twee RAPD-merkers is geïdentifiseer vir die Thinopyrum
chromosoom(e) teenwoordig in die monosomiese addisieplant, terwyl drie AFLP- en drie RAPDmerkers
geïdentifiseer is vir die disomiese addisieplant.
'n Poging is ook gemaak om diverse addisieplante te identifiseer met 'n volledige koroggenoom
plus 'n addisionele Thinopyrum chromosoom. Plante met 2n = 43 / 44 is geïdentifiseer en
gekarakteriseer met molekulêre merkers (AFLP en RAPD). Tros-analise is gebruik om die
vermoedelik monosomiese of disomiese addisieplante te groepeer volgens die spesifieke
Thinopyrum chromosome wat hulle behou het. Sewentien AFLP- en RAPD-merkers is gebruik om
die 24 vermoedelike addisieplante in 6 groepe met verskillende Thinopyrum chromosome te groepeer. Alhoewel dit voorkom of die verskillende plante in 'n groep dieselfde addisionele
Thinopyrum chromosoom het, is dit nie noodwendig die geval nie aangesien die interpretasie van
die merkers bemoeilik word deur die heterogeniteit tussen die plante wat betref die agtergrond
korogchromosome wat hulle besit. Dit is ook moontlik dat chromosoom herrangskikkings
plaasgevind het gedurende die terugkruisings, wat die data verder kan bemoeilik. Nietemin, dit is
nou moontlik om disomiese addisies te selekteer uit elke groep wat moontlik verskillende
Thinopyrum chromosome bevat. Die data kan ook gebruik word om in die toekoms verdere
addisieplante te identifiseer wat die oorblywende Thinopyrum chromosome bevat.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/51794 |
| Date | 12 1900 |
| Creators | Badenhorst, Petrus Cornelius |
| Contributors | Marais, G. F., Stellenbosch University. Faculty of AgriSciences. Dept. of Genetics. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 82 p. : ill. |
| Rights | Stellenbosch University |
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