Abstract:
Cassava (Manihot esculenta Crantz) is a staple in sub-Saharan Africa.
It is an important source of starch. Production is, however, constrained by
many factors.
Forty-three accessions were assessed for morphological and genetic
diversity using morphological descriptors and Simple Sequence Repeat (SSR)
markers. The accessions were scored for their tolerance/resistance to the
cassava mosaic disease. The properties of mixtures of cassava and sweet
potato starch were also investigated.
Morphological descriptors revealed 4 clusters of accessions while
Simple Sequence Repeat (SSR) markers revealed 9 distinct clusters of
accessions, indicating a wider genetic diversity. Capevars was highly resistant
to cassava mosaic virus disease, while most of the accessions were
susceptible. Starch content was moderate, swelling volume, percentage
solubility and swelling power were 14.5-35.3 ml g-1, 8.3-27.5 % and 16.0-41.6
g g'1 respectively. Maximum viscosity, breakdown and setback viscosity were
643.7 BU, 443.1 BU, and 141.9 BU. The pasting and peak temperatures of
cassava starch increased with increase in the proportion of sweet potato starch.
Set back viscosity was low for all accessions at a ratio of 20:80 cassava to
sweet potato starch (C2Sps).
SSR markers are recommended for the efficient management of
germplasm and for effective utilisation of materials in breeding programmes to
produce more resistant cultivars. Field screening for mosaic resistance should
always be complemented with PCR or inoculation test. Genotype with good
quality starch could be employed in the production of industrial starch.
