Characterization of Cassava Germplasm and Screening for Differences in Starch Production and Resistance to Cassava Mosaic Virus Disease

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.