Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1972. / Bibliography: leaves [189]-197. / xiv, 197 l illus. (part col.), map, graphs, tables

Typescript. / Thesis (Ph. D.)--University of Hawaii, 1967. / Bibliography: leaves 156-169. / 169 l

published_or_final_version / Botany / Doctoral / Doctor of Philosophy

Thesis (Ph. D.)--University of Hong Kong, 1999. / Includes bibliographical references (leaves 108-127).

Thesis (M.S.)--University of Hawaii at Manoa, 2007. / Includes bibliographical references (leaves 78-80). / viii, 82 leaves, bound ill. 29 cm

Submitted in fulfilment of the academic requirement for the Degree of Masters in Food Science and Technology, Durban University of Technology, 2017. / Amadumbe (Colocasia Esculenta) commonly known as Taro is an underutilized tuber crop that produces underground corms. It is a promising tropical tuber grown in various parts of the world including South Africa, where it is regarded as a traditional food. It is a significant subsistence crop, mostly cultivated in rural areas and by small scale farmers. Amadumbe is adapted to growing in warm and moist conditions. The tubers are characterised by a high moisture content and consequently high post-harvest losses. The losses can be minimized through the utilization of various preservation techniques such as flour and starch production. Amadumbe corms may contain up to 70-80% starch. The starch granules are characterised by a small size and relatively low amylose content. The combination of high starch content, low amylose and small starch granules thus make amadumbe a potentially good candidate for nanocrystal production. In this study two amadumbe varieties were utilized to extract starch. Amadumbe starch nanocrystals (SNC) were produced using an optimized hydrolysis method. The physicochemical properties (morphology, crystallinity, thermal properties) of the resulting SNC were investigated. The SNC were then applied as fillers in three different matrices namely, amadumbe starch, potato starch and soy protein. The influence of the SNC at varying concentrations (2.5, 5 and 10%) on the physicochemical properties of bio-composite films was examined. Amadumbe starch produced a substantially high yield (25%) of SNCs. The nanocrystals appeared as aggregated as well as individual particles. The individual nanocrystals exhibited a square-like platelet morphology with sizes ranging from 50-100 nm. FTIR revealed high peak intensities corresponding to O-H stretch, C-H stretch and H2O bending vibrations for SNCs compared to their native starch counterparts. Both the native starch and SNC exhibited the A–type crystalline pattern. However, amadumbe SNCs showed a higher degree of crystallinity possibly due to the removal of the armorphous material during acid hydrolysis to produce SNCs. Amadumbe SNC showed slightly reduced melting temperatures compared to their native starches. The SNC presented similar thermal decomposition properties as compared to their native starches. In general, the inclusion of SNCs significantly decreased water vapour permeability (WVP) of composite films whilst thermal stability and tensile strength were increased. The degree of improvement in the physicochemical properties of the films varied with the type of matrix as well as the concentration of the nanocrystals. It generally seemed that the enhancement of the physicochemical properties of starch matrices occurred at a lower SNC concentration in comparison to that of soy protein films. Amadumbe SNC can indeed potentially be used as a filler to improve the properties of biodegradable starch and protein films / M

Taro, Colocasia esculenta, is a unique root crop that serves as an important dietary component in the Pacific islands and in parts of Asia and Africa. Cultivation of taro as a food crop might have ancient origin as is evident from variety of ritualistic use of taro in different parts of the world. Even though it has been postulated that taro was domesticated in the old world, the widespread cultivation of taro calls for a discussion regarding its origin. Wild varieties of C. esculenta are known from regions of Eastern India, Sri Lanka, Sumatra, and the Malay Peninsula. Other wild varieties have been reported from the Indo-Pacific region and China. The two prominent chromosome number series are 2n=28 and 2n=42. But, chromosome number series 2n= 28, 42, 36, and 48 have been reported from India indicating the centre of highest diversity. A certain amount of controversy exists over classification and nomenclature of this polymorphic species. Primary products of the plants are the corms and cormels. Taro is also used in traditional medicine. It has been known to be nutritionally superior to other starchy crops like potato. This document reviews previous works done on classification and nomenclature of taro, morphology, origin of taro, production and agronomy, and finally ethnobotany of taro across the major taro producing countries. / text

The taro landraces that are most preferred by farmers from Umbumbulu, KwaZulu-Natal were identified through focus group discussions with farmers. Farmers ranked taro landraces on the basis of preference as determined by economic value, social significance, ecological importance and food characteristics. Using pairwise ranking, the farmers' preference of taro landraces across all locations was found to be in the following order: Dumbe-dumbe, Mgingqeni, Pitshi and Dumbe-lomfula. Dumbe-dumbe was identified as the currently actively cultivated taro whereas Mgingqeni was regarded as a less desirable cultivated taro. Pitshi was regarded as an antiquated landrace and Dumbe-lomfula was generally regarded as a taro type of no economic, social or food value that grew on river banks as a wild species. Glasshouse and field studies were conducted to determine the effects of temperature and growing location [Pietermaritzburg (UKZN) and Umbumbulu] on emergence, plant growth and yield of taro. Starch and mineral composition of taro corms were determined in harvest-mature corms. Effects of three day/night temperature levels (22/12°C, 27/17°C and 33/23°C) were examined on the growth of four taro landraces Dumbe-dumbe, Mgingqeni, Pitshi and Dumbe-lomfula. Pitshi-omhlophe, an ecotype of Pitshi for which there was a limited amount of planting material, was also included in the glasshouse studies. The farmers stated that the normal growing season for the economically important landraces, Dumbe-dumbe and Mgingqeni, was six months, but in this study plants were grown in glasshouses for nine months, and in the field, for seven months before the attainment of harvest maturity. Emergence was determined daily for glasshouse experiment until all plants had emerged and it was determined monthly for the field experiment. Leaf number, plant height and leaf area were measured every month to determine growth and development, while number of corms and fresh corm weight were used at harvest to determine yield. For all landraces, time to emergence increased significantly with decrease in temperature from 33/23°C to 27/17°C, but it increased significantly for only Dumbe-dumbe and Mgingqeni from 27/17°C to 22/12°C. Mgingqeni showed the shortest time to emergence, whereas, Pitshi showed the longest delay in emergence. The locations were not significantly different in emergence. Mgingqeni displayed the highest emergence in UKZN (91.4%), whereas, Dumbe-dumbe displayed the highest emergence (95.5%) and Dumbe-lomfula displayed the lowest emergence (55.9%) in Umbumbulu. Leaf number was highest for Pitshi-omhlophe, in glasshouse experiment due to its tendency to produce multiple shoots compared with the other landraces. Plant height increased with increase in temperature for all landraces except for Pitshi, for which height decreased with an increase in temperature. Leaf area was greatest for Dumbe-lomfula at all temperatures and lowest for Pitshi at both 22/12°C and 27/17°C. Leaf number was highest for Mgingqeni and lowest for Dumbe-lomfula at both sites, although it was significantly lower only for Dumbe-lomfula in UKZN. Plant height and leaf area were significantly highest for Dumbe-lomfula at both sites. The highest total number of corms per plant was shown by Pitshi-omhlophe at 22/12°C. Total fresh corm weight was highest for Dumbe-lomfula at 27/17°C and lowest for Pitshi at 22/22°C. The field experiment results showed Pitshi and Dumbe-lomfula with significantly higher total fresh corm weight in UKZN compared with Umbumbulu. Corms were analysed for mineral elements and starch. There were significant differences in starch content between temperatures (P = 0.017) and taro landraces (P = 0.025). There was also a significant interaction of temperatures and landrace (P = 0.002). Starch content increased with temperature for all landraces except for Pitshi-omhlophe and Dumbe-lomfula which showed a decrease at 27/17°C. There were significant differences in corm mineral content between temperatures, locations and landraces (P < 005). It is concluded that the chemical composition of taro corms is influenced by growth temperature and the location (site) where the crop is grown. The results of this study also indicated that taro plant growth is enhanced by high temperatures (33/23°C). High temperatures are, however, associated with short leaf area duration and subsequently low yield. The findings of this study may also be useful in determining taro quality for processing. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.

Despite the importance of taro (Colocasia esculenta L. Schott) as a food security crop, scientific research on it is scanty in South Africa. Production site, planting date and fertiliser regime affect crop performance and quality, particularly that of cultivars, because they tend to be adapted to specific localities. Storage temperature and packaging method on the other hand affect the shelf-life. To investigate performance and quality of three taro cultivars in response to planting date and fertilisation, a study was carried out at two sites in KwaZulu-Natal, South Africa (Ukulinga and Umbumbulu), during the 2007/2008 growing seasons. The effect of two storage temperatures (12oC and ambient temperature) and three packaging methods (polyethylene bags, mesh bags and open boxes) on cormel quality following storage was also investigated for three cultivars. Delayed planting negatively affected the number of cormels plant-1 and fresh cormel mass plant-1. Fertilisation and cultivar affected the number of cormels plant-1 and fresh cormel mass plant-1 only when planting was done in October and November at both sites. Fertilisation increased the number of cormels plant-1 for all cultivars except Dumbe-dumbe. Dumbe-dumbe had the lowest number of cormels plant-1 but the highest number of marketable cormels plant-1. Dumbe-dumbe showed the lowest fresh cormel mass plant-1 in October and the highest in November at Ukulinga. Fertisation increased fresh cormel mass plant-1 in October at Umbumbulu. Dry matter content was negatively affected by fertilisation at Ukulinga. The response of dry matter content, specific gravity, protein, minerals, reducing sugars and starch content was variable depending on cultivar. Delayed planting negatively affected starch content for Dumbe-dumbe and Pitshi at Ukulinga. Fertilisation decreased starch content of Pitshi, while delayed planting increased sugar content for Dumbe-dumbe and decreased it for Mgingqeni and Pitshi at Umbumbulu. Dumbe-dumbe had higher starch content and higher reducing sugars. Considering all growth and quality parameters, it is recommended that Dumbe-dumbe is the best taro cultivar for crisping and the best time to plant it is October with 160 kg N ha-1 of organic fertiliser and November with 320 kg N ha-1 at Ukulinga whereas at Umbumbulu the best time to plant Dumbe-dumbe is October with 320 kg N ha-1 of the fertiliser. Starch granules degradation, alpha-amylase activity and sprouting increased with storage time and storage temperature. Cormels of Mgingqeni stored in polyethylene bags showed highest alpha-amylase activity and sprouting. Reducing sugar content increased and starch content decreased with time in storage and decline in storage temperature. It is recommended that taro cormels be stored in mesh bags at 12oC. The chapters of this thesis represent different studies presented as different papers. Chapter 1 is a general introduction to explain the study background and hypothesis. Chapter 2 is a general review of literature. Chapter 3 is on growth, development and yield of taro in response to planting date and fertilisation. Chapter 4 is on the influence of planting date and organic fertiliser on crisping quality of taro cormels. Chapter 5 is on changes in the surface morphology of starch granules and alpha-amylase activity of taro during storage. Chapter 6 is on the effects of pre- and post-harvest practices on starch and reducing sugars of taro. The last chapter is a general discussion and conclusions. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.

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.