Epsilon Archive for Student Projects

Abstract

Cassava roots are one of the most important sources of starch on a global scale. Two
aspects of cassava as a starch crop were studied in this thesis work; 1) determining if
the amylose-free (waxy) mutation is coupled with a reduction in yield, and 2) the
environmental impact on yield, yield components and starch functional properties of
cassava. The waxy trait, resulting from a mutation in the GBSS locus, is in several
other crops associated with a yield penalty. In this study, siblings from eight full-sibling
families, segregating for the waxy trait, were used to determine if the waxy mutation
has implications for yield, dry matter content and harvest index in cassava. The only
significant effect of starch type was on the dry matter content, with the waxy clones
having a 0.8% lower dry matter than their wild type siblings. The environmental effects
on cassava yield and starch functional properties were examined by comparing data
from two contrasting environments of Colombia; the Cauca river valley and the
Caribbean coast. Significant differences were found in yield, dry matter content and
harvest index between cassava clones from different environments. There were
significant effects of environment on starch pasting properties, solubility and dispersed
volume fraction. Starches from the higher temperature, Caribbean coast had an
elevated pasting temperature (5°C higher for waxy starches and 3.6° C for wild type),
whereas the peak viscosity was lower in starches from this environment (114 cP lower
in waxy starch and 205 cP in wild type). The gravimetric method for determining dry
matter content in cassava roots was also evaluated.