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Biotechnology
applications in breeding for Striga
asiatica resistance at the University of Zimbabwe
P.B. Tongoona,
C.S. Mutengwa, C. Musimwa, I. Sithole-Niang & A. Matibiri
Biotechnology has the potential to revolutionise the
breeding of crop cultivars because of the potential speed and precision
of selection for desirable genotypes. One aspect of biotechnology that
can be used in crop breeding is marker-assisted selection (MAS), which
involves indirect selection for a trait of interest through molecular
markers that ‘tag’ single genes or quantitative trait loci (QTL).
At the University of Zimbabwe, we have chosen Striga asiatica resistance in Sorghum
bicolor as an ideal character for application of MAS because field
screening is difficult and imprecise, S.
asiatica resistance is simply inherited and controlled by a single
recessive gene, and no resistant, high yielding sorghum cultivars have
been developed to date. Random
amplified polymorphic DNA (RAPD) and simple sequence repeat (SSR)
markers were used to identify markers that are linked to S.
asiatica resistance in an F2 sorghum population derived from a cross
between a susceptible and a resistant parent. Details of this work are
to be presented at this meeting. We also sought to study molecular
diversity of S. asiatica
populations collected from different regions of the country and from
different host plants. This was done because differential responses of
different cereal crops have been noted when they are grown in different
geographical regions. RAPD analysis of S.
asiatica populations collected from different geographical regions
of Zimbabwe and different host plants revealed significant diversity.
The 24 populations that were used in this study clustered in five
groups. One of the groups contained accessions from the same
geographical region while the other groups contained accessions from
different regions. This made it difficult to make generalizations on the
regional basis of the relationships. It is noteworthy that different
biotypes were identified in this study. However, it is not known if
these biotypes differ in their virulence to different cultivars and host
cereals. Further investigations are required to elucidate this issue.
The presence of these biotypes apparently indicated the need for multi-locational
testing of any cultivars developed for resistance against S.
asiatica.
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