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.

This thesis presents the results of experimental and archaeological investigations of microscopic plant residues on Lapita pottery from the western Pacific Islands. Lapita is a critical phase in the culture history of the Pacific region and has been associated with the development and spread of a subsistence system based on the cultivation of tropical starch crops, particularly those in the taro-yam complex. However, few archaeobotanical remains been recovered from Lapita sites to lend empirical support to this model. This study explores whether microscopic starch granules, calcium oxalate crystals and other plant microremains on Lapita potsherds can provide direct evidence for the preparation and consumption of staple plant foods, as well as important clues to the function and use of pottery in Lapita society, matters which remain the subject of some debate. This research was undertaken in two main phases. The first involved a series of technical studies aimed at developing methods for recovering and identifying starch and raphide residues on archaeological pottery. Changes to starch during cooking and charring under different heat and moisture conditions were examined to understand how granules survive differentially depending on cooking method and food type. Various methods used to extract native starch granules from charred residues were then tested and a procedure based on a weak oxidising treatment was developed for use on the archaeological residues. The reliability of calcium oxalate raphide analysis, which is much less developed than that of starch, was also critically assessed. Issues with previous identifications of raphides in Pacific microfossil assemblages were highlighted. Morphological criteria were presented for identifying aroid raphides more accurately and chemical tests were developed to differentiate them from naturally-occurring calcite crystals, which were abundant in the sites analysed. The second phase of research analysed microscopic residues on Lapita and post-Lapita potsherds from archaeological sites in the Mussau and Anir Islands (PNG), the Reef Islands (Solomon Islands), New Caledonia, and the Samoan Archipelago. Despite the generally small quantities of residue recovered from the archaeological samples, several sherds with possible use-related starch residues were identified. These initial results indicate that ceramic vessels, including both plain and dentate-decorated Lapita wares, were employed in a variety of tasks involving the cooking and/or consumption, and storage or preparation of starch-based foods. It was also found that these were among the activities performed at the ‘special purpose’ stilt house structure at the ECA site, which raises questions about the possible social or ritual status of staple starch resources in Lapita society. One of the most significant findings to emerge from this study was of taro (Colocasia esculenta) starch granules on sherds from the ERA Lapita site (Anir, New Ireland), and granules identified tentatively as taro on sherds from RF-2 (Reef Islands) and Mulifanua (Samoa). A number of unidentified morphotypes were also present on the Lapita and post-Lapita sherds, suggesting that a variety of plants not among the key root crops were also exploited. These may include some of the many fruits and nuts attested in archaeobotanical assemblages from Pacific sites. The ceramic residue data complement starch and phytolith evidence recovered from cultural sediments from RF-2, which demonstrate the presence and probable exploitation of a suite of crop plants typically associated with the Lapita ‘economic package’. In addition to taro, these include at least one cultivated species of Eumusa banana, non-domesticated (seeded) Australimusa bananas, bamboo, and possibly also Canarium, coconut, and sago. These data support models suggesting that Lapita groups were cultivating and transporting subsistence plants, including at least one of the major root crop complexes, and associated knowledge of their production and preparation across the western Pacific from the mid-late Holocene. This study demonstrated that analyses of microscopic starch residues on archaeological ceramics from the Pacific region can yield significant insights into vessel use and plant exploitation. Further methodological refinements should aim to increase starch yields, which will enable stronger associations between residues and vessel uses to be established. Expansion of reference collections is also required so that more precise identifications of the specific plant foods involved can be achieved.

This thesis presents the results of experimental and archaeological investigations of microscopic plant residues on Lapita pottery from the western Pacific Islands. Lapita is a critical phase in the culture history of the Pacific region and has been associated with the development and spread of a subsistence system based on the cultivation of tropical starch crops, particularly those in the taro-yam complex. However, few archaeobotanical remains been recovered from Lapita sites to lend empirical support to this model. This study explores whether microscopic starch granules, calcium oxalate crystals and other plant microremains on Lapita potsherds can provide direct evidence for the preparation and consumption of staple plant foods, as well as important clues to the function and use of pottery in Lapita society, matters which remain the subject of some debate. This research was undertaken in two main phases. The first involved a series of technical studies aimed at developing methods for recovering and identifying starch and raphide residues on archaeological pottery. Changes to starch during cooking and charring under different heat and moisture conditions were examined to understand how granules survive differentially depending on cooking method and food type. Various methods used to extract native starch granules from charred residues were then tested and a procedure based on a weak oxidising treatment was developed for use on the archaeological residues. The reliability of calcium oxalate raphide analysis, which is much less developed than that of starch, was also critically assessed. Issues with previous identifications of raphides in Pacific microfossil assemblages were highlighted. Morphological criteria were presented for identifying aroid raphides more accurately and chemical tests were developed to differentiate them from naturally-occurring calcite crystals, which were abundant in the sites analysed. The second phase of research analysed microscopic residues on Lapita and post-Lapita potsherds from archaeological sites in the Mussau and Anir Islands (PNG), the Reef Islands (Solomon Islands), New Caledonia, and the Samoan Archipelago. Despite the generally small quantities of residue recovered from the archaeological samples, several sherds with possible use-related starch residues were identified. These initial results indicate that ceramic vessels, including both plain and dentate-decorated Lapita wares, were employed in a variety of tasks involving the cooking and/or consumption, and storage or preparation of starch-based foods. It was also found that these were among the activities performed at the ‘special purpose’ stilt house structure at the ECA site, which raises questions about the possible social or ritual status of staple starch resources in Lapita society. One of the most significant findings to emerge from this study was of taro (Colocasia esculenta) starch granules on sherds from the ERA Lapita site (Anir, New Ireland), and granules identified tentatively as taro on sherds from RF-2 (Reef Islands) and Mulifanua (Samoa). A number of unidentified morphotypes were also present on the Lapita and post-Lapita sherds, suggesting that a variety of plants not among the key root crops were also exploited. These may include some of the many fruits and nuts attested in archaeobotanical assemblages from Pacific sites. The ceramic residue data complement starch and phytolith evidence recovered from cultural sediments from RF-2, which demonstrate the presence and probable exploitation of a suite of crop plants typically associated with the Lapita ‘economic package’. In addition to taro, these include at least one cultivated species of Eumusa banana, non-domesticated (seeded) Australimusa bananas, bamboo, and possibly also Canarium, coconut, and sago. These data support models suggesting that Lapita groups were cultivating and transporting subsistence plants, including at least one of the major root crop complexes, and associated knowledge of their production and preparation across the western Pacific from the mid-late Holocene. This study demonstrated that analyses of microscopic starch residues on archaeological ceramics from the Pacific region can yield significant insights into vessel use and plant exploitation. Further methodological refinements should aim to increase starch yields, which will enable stronger associations between residues and vessel uses to be established. Expansion of reference collections is also required so that more precise identifications of the specific plant foods involved can be achieved.