The use of genetic markers that are linked to specific traits in sugarcane has the potential to
increase the efficiency of the selection of improved varieties. Conventionally, markers are
identified by analysing the segregation of potential markers and traits in the progeny of single
crosses. However, this approach is not practical for sugarcane breeding programmes where
replicated, well characterized progenies do not exist. The objective of this project was to
investigate the potential of using commercial varieties for identifying markers associated with
some of the important traits in sugarcane. This approach would be far more effective than
dealing with single progenies since the traits of commercial varieties have already been
characterized.
The DNA of fifty commercial varieties of sugarcane was amplified by RAPD PCR using forty-one
arbitrary decamer primers. Analysis of the resulting banding profiles, obtained by agarose
gel electrophoresis, yielded fifty-four reliable polymorphic fragments. Two approaches were
used to identify putative markers linked to the traits of resistance to eldana, sugarcane mosaic
virus, and smut: (1) a correlation approach which attempted to identify whether the presence
of any polymorphisms could be used to imply the existence of a particular phenotypic state,
and (2) multiple regression analysis, in order to determine whether polymorphisms could be
used to predict the performance of the varieties for each of the traits. Both approaches
appeared to identify associations between polymorphisms and the traits, although multiple
regression analysis yielded the most informative results and was able to assign statistical values
to the associations.
Using multiple regression, the best predictive model was obtained for sugarcane mosaic virus
resistance. This model consisted of four polymorphisms and had an r² of 0.40l. By dividing the
resistance ratings into three groups (resistant, intermediate and susceptible), 52% of the varieties
were correctly classified and only 2% of the varieties were predicted in opposite groups (i .e.
predicted susceptible when actually resistant, and vice versa). The predictive model for eldana
resistance consisted offour polymorphisms and had an r² of 0.347. This model classified 30% of
the varieties in the correct group of three while none of the varieties were predicted in opposite groups. The predictive model for smut resistance consisted of three polymorphisms and had an
r² of 0.316. This model classified 30% of the varieties in the correct group of three while 2% of
the varieties were predicted in opposite groups.
Further analysis of sugarcane varieties using additional polyrnorphisrns has the potential to identify
markers linked to important traits. These markers could be used for marker-assisted selection to
increase the efficiency of selecting for improved sugarcane genotypes for commercial release. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1996.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ukzn/oai:http://researchspace.ukzn.ac.za:10413/10344 |
| Date | 14 January 2014 |
| Creators | Barnes, Julie Megan. |
| Contributors | Botha, Frikkie C. |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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