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M. Tech. (Department of Biotechnology, Faculty of Applied and Computer Sciences), Vaal University of Technology / Taro [Colocasia esculenta (L) Schott] belongs to the family Araceae. It is an important staple food crop grown mainly by small scale farmers in many parts of the world. Taro is also grown in South Africa from the costal parts of the northern Eastern Cape to the KwaZulu-Natal north coast. Although it is an important staple crop in South Africa, very little information exists on the genetic diversity of the crop. Knowledge of the genetic diversity of a crop is important for breeding programmes. The aim of this study is to assess the genetic diversity of taro using morphological and molecular techniques and to determine the calcium oxalate content of 25 South African taro accessions. This study showed that the aerial portions of taro are variable for most quantitative characters. Most of the morphological variation was due to lamina length, petiole length, lamina width and plant girth that explained 54% of the variance in principal component analysis. The number of raphides was able to divide the accessions into two groups, one with relatively low counts and the other with high counts. Ntumeni had the lowest raphide count of only 27 ±12 raphides and Modderfontein had the highest count with 1150 ±104 raphides. Twelve accessions having low raphide counts ranging from 27 ±12 to 147 ±28 raphides per cell have been identified. RAPD data separated the accessions into three main groups that were further divided into five subgroups. The accessions did not group according to geographical locations. The ITS2 sequence generated clustering patterns that were similar to that obtained from RAPDs. The variation in the ITS2 secondary structure of taro included one common motif that was present in all 25 accessions. Some motifs were only present in some accessions. The discovery of these motifs strengthens the potential of the ITS2 region as a taxonomic marker and a powerful barcode for taro. The ITS2 motifs provide the means of identifying each of the 25 accessions of taro. The high genetic diversity, morphological variation and accessions with low calcium oxalate content found in this study provide taro breeders a selection of parent crops for the improvement of taro.

Konjac glucomannan (KGM), the main biologically active constituent of konjac flour extracted from corms of Amorphophallus konjac (konjac), can be used to prepare functional foods and may also have potential as a pharmaceutical product to combat obesity. The current study employed three experimental approaches to study the biology and chemistry of konjac, namely (1) glasshouse experiments to study the morphogenesis, growth and productivity of konjac plants, (2) a histological and immunocytochemical investigation of the localisation and developmental regulation of the deposition and metabolism of KGM in developing corm tissues, and (3) a comparative study of methodologies for the extraction and analysis of KGM. The current data demonstrated a morphological and functional separation between the ventral and dorsal regions of corms. The ventral region appeared to function as a source during the initial period of shoot development, while the dorsal region appeared to operate as a sink after the development of mature canopy. Once the corm reached maturity, both an inflorescence and a leaf were produced within a single season. It has also been demonstrated that the age of the ‘mother’ corm is an important factor affecting the quality of offsets produced. An anti-mannan antiserum detected a temporally regulated pattern of mannan epitope production within glucomannan idioblasts in developing corm tissues, with increased expression as the corm approached maturity/dormancy. The current observations also suggest that the mobilization of KGM initiates at the periphery of the corm and proceeds inwards towards the centre of the corm. Compositional analysis showed that the purified konjac flour (PKF) produced using a modified extraction procedure contained 92% glucomannan, with a weight average molecular weight (Mw), polydispersity index (PDI) and degree of acetylation (DA) of 9.5 ± 0.6 x 105 gmol-1, 1.2 and 2.8 wt. %. These data, plus Fourier-transform infrared spectral (FTIR) and zero shear viscosity analyses of the extract (PKF) were all consistent with the literature. Comparison of three existing methodologies for the quantitative analysis of the KGM content, namely 3,5-dinitrosalicylic acid (3,5-DNS), phenol-sulphuric acid and enzymatic colorimetric assays; indicated that the 3,5-DNS colorimetric assay was the most reproducible and accurate method, with a linear correlation coefficient of 0.997 and recoveries between 97% and 103% across three spiking levels of starch. In summary, this study has provided a better understanding of aspects of the biology and cultivation of A. konjac and has also produced methodologies which can be used as the basis for an improved good laboratory practice (GLP) for the commercial extraction and analysis of this multifunctional natural polymer.