Pennisetum Rich, is one of the most important genera in the family Poaceae because it includes forage and crop species such as Pennisetum purpureum Schumach. and Pennisetum glaucum (L.) R. Br. Both P. purpureum and P. glaucum have a number of cultivars and varieties arising due to natural crossing which are very difficult to distinguish morphologically. P. purpureum and P. glaucum also hybridize naturally because they are protogynous and cross pollinated. The resulting hybrids are highly sterile and resemble P. purpureum. Lepidopteran stem borers cause great yield loss in maize produced by resource-poor farmers in Africa and are managed by habitat management or push-pull strategies, in which P. purpureum cultivars and hybrids are used as a trap crop. The aims of this project were to genotype different P. purpureum cultivars and hybrids using Amplified Fragment Length Polymorphism (AFLP) as well as Random Amplified Polymorphic DNA (RAPD) in order to identify cultivars and hybrids and possible misidentifications, assess the congruency of results between AFLPs and RAPDs and to attempt to relate these results to the oviposition preference of Chilo partellus for different P. purpureum cultivars. The individuals to be fingerprinted were collected from several countries in sub-Saharan Africa, a few from the USA and one from China. The AFLP analysis of these individuals were done with primer combinations EcoRI/MseI and Mlul/Msel on polyacrylamide gels and an ABI 3130 xl Genetic Analyzer respectively. The automated sequencer visualized more bands than the polyacrylamide gels. The RAPD technology was not developed any further after 17 primers were tested and no polymorphic bands detected. Overall results indicated that cultivars did not cluster according to geographical origin, and cultivars known by popular names did not always cluster together, indicating diversity within the cultivar or misidentifications. An example of a misidentification is the cultivar Green Gold being no other than cultivar Harare, or cultivar Swaziland 3 being cultivar Sanitas. Proper management by nursery managers cannot be stressed enough, as this will prevent plants getting mixed up, causing confusion. There was no relationship between the relatedness of cultivars and moth oviposition preference. The AFLP technology could be a powerful tool for the DNA fingerprinting and molecular characterization of this grass species, but poor germ plasm management negates its application. / Thesis (M. Environmental Science)--North-West University, Potchefstroom Campus, 2008.

Pennisetum Rich, is one of the most important genera in the family Poaceae because it includes forage and crop species such as Pennisetum purpureum Schumach. and Pennisetum glaucum (L.) R. Br. Both P. purpureum and P. glaucum have a number of cultivars and varieties arising due to natural crossing which are very difficult to distinguish morphologically. P. purpureum and P. glaucum also hybridize naturally because they are protogynous and cross pollinated. The resulting hybrids are highly sterile and resemble P. purpureum. Lepidopteran stem borers cause great yield loss in maize produced by resource-poor farmers in Africa and are managed by habitat management or push-pull strategies, in which P. purpureum cultivars and hybrids are used as a trap crop. The aims of this project were to genotype different P. purpureum cultivars and hybrids using Amplified Fragment Length Polymorphism (AFLP) as well as Random Amplified Polymorphic DNA (RAPD) in order to identify cultivars and hybrids and possible misidentifications, assess the congruency of results between AFLPs and RAPDs and to attempt to relate these results to the oviposition preference of Chilo partellus for different P. purpureum cultivars. The individuals to be fingerprinted were collected from several countries in sub-Saharan Africa, a few from the USA and one from China. The AFLP analysis of these individuals were done with primer combinations EcoRI/MseI and Mlul/Msel on polyacrylamide gels and an ABI 3130 xl Genetic Analyzer respectively. The automated sequencer visualized more bands than the polyacrylamide gels. The RAPD technology was not developed any further after 17 primers were tested and no polymorphic bands detected. Overall results indicated that cultivars did not cluster according to geographical origin, and cultivars known by popular names did not always cluster together, indicating diversity within the cultivar or misidentifications. An example of a misidentification is the cultivar Green Gold being no other than cultivar Harare, or cultivar Swaziland 3 being cultivar Sanitas. Proper management by nursery managers cannot be stressed enough, as this will prevent plants getting mixed up, causing confusion. There was no relationship between the relatedness of cultivars and moth oviposition preference. The AFLP technology could be a powerful tool for the DNA fingerprinting and molecular characterization of this grass species, but poor germ plasm management negates its application. / Thesis (M. Environmental Science)--North-West University, Potchefstroom Campus, 2008.

Pennisetum Rich, is one of the most important genera in the family Poaceae because it includes forage and crop species such as Pennisetum purpureum Schumach. and Pennisetum glaucum (L.) R. Br. Both P. purpureum and P. glaucum have a number of cultivars and varieties arising due to natural crossing which are very difficult to distinguish morphologically. P. purpureum and P. glaucum also hybridize naturally because they are protogynous and cross pollinated. The resulting hybrids are highly sterile and resemble P. purpureum. Lepidopteran stem borers cause great yield loss in maize produced by resource-poor farmers in Africa and are managed by habitat management or push-pull strategies, in which P. purpureum cultivars and hybrids are used as a trap crop. The aims of this project were to genotype different P. purpureum cultivars and hybrids using Amplified Fragment Length Polymorphism (AFLP) as well as Random Amplified Polymorphic DNA (RAPD) in order to identify cultivars and hybrids and possible misidentifications, assess the congruency of results between AFLPs and RAPDs and to attempt to relate these results to the oviposition preference of Chilo partellus for different P. purpureum cultivars. The individuals to be fingerprinted were collected from several countries in sub-Saharan Africa, a few from the USA and one from China. The AFLP analysis of these individuals were done with primer combinations EcoRI/MseI and Mlul/Msel on polyacrylamide gels and an ABI 3130 xl Genetic Analyzer respectively. The automated sequencer visualized more bands than the polyacrylamide gels. The RAPD technology was not developed any further after 17 primers were tested and no polymorphic bands detected. Overall results indicated that cultivars did not cluster according to geographical origin, and cultivars known by popular names did not always cluster together, indicating diversity within the cultivar or misidentifications. An example of a misidentification is the cultivar Green Gold being no other than cultivar Harare, or cultivar Swaziland 3 being cultivar Sanitas. Proper management by nursery managers cannot be stressed enough, as this will prevent plants getting mixed up, causing confusion. There was no relationship between the relatedness of cultivars and moth oviposition preference. The AFLP technology could be a powerful tool for the DNA fingerprinting and molecular characterization of this grass species, but poor germ plasm management negates its application. / Thesis (M. Environmental Science)--North-West University, Potchefstroom Campus, 2008.

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Le but de ce travail était d’accroitre notre connaissance des mécanismes qui gouvernent la formation, la spécification et la différentiation des cellules souches, à l’aide du modèle métazoaire non-bilatérien Clytia hemisphaerica. Clytia possède une population particulière de cellules multipotentes appelées cellules interstitielles (i-cells). Ces cellules, présentes au cours du développement larvaire et chez la méduse adulte, sont capables de donner naissances a des cellules somatiques et aux gamètes. Chez les bilatériens, la signalisation Wnt/β-caténine (Wntβc) régule les processus développementaux fondamentaux ainsi que la prolifération, la spécification et la différenciation des cellules souches. Mon travail s’est porté sur l’implication de la signalisation Wntβc dans les dynamiques des i-cells. Mes résultats suggèrent que la signalisation Wntβc est impliquée dans la dernière étape de la différenciation de certains neurones, mais pas pour la spécification du destin cellulaire. D’autre part, j’ai aussi observé qu’en condition contrôle, la formation des i-cells est Wntβc-indépendante et probablement entraînée par le héritage de plasma germinatif contenant les ARNm localisées au pôle animal. Cependant, suite à des expériences de microdissection, j’ai observe que la reformation des i-cells dans la moitie végétative des embryons requérait l’activation de la voie Wntβc. En conclusion, deux mécanismes distincts peuvent conduire à la formation des i-cell pendant l'embryogenèse. Globalement, les résultats obtenus ont fourni une meilleure idée de la façon dont i- cellules et leurs dérivés se posent lors de l'embryogenèse et le développement larvaire. / The aim of this work was to extend our understanding of the mechanisms regulating stem cell formation, specification and differentiation by studies in the non-bilaterian metazoan model Clytia hemisphaerica. Clytia, like other hydrozoan cnidarians, possess a particular population of multipotent stem cells called interstitial cells (i-cells), present during larval development and in the adult medusa, which are able to give rise both to somatic cell types and to gametes.In bilaterian animals Wnt/β-catenin signalling regulates fundamental developmental processes such primary body axis specification, but also regulates stem cell proliferation, lineage specification and differentiation. I investigated the role of Wnt/β-catenin signalling in i-cell specification and differentiation. The results obtained suggest that Wnt/β-catenin signalling is involved in the last step of differentiation for certain neuronal cell types, but not for somatic cell fate choice. In the second part of my study I investigated the role of Wnt/β-catenin signalling in i-cell formation during embryogenesis. The results indicated that during normal development i-cell formation is Wnt/β-catenin independent and probably driven by inheritance of germ plasm containing localised mRNAs from the egg animal pole. In contrast in embryo re-patterning following embryo bisection, Wnt/β-catenin signalling appears to be necessary for de novo i-cell formation in the absence of germ plasm. Thus two distinct mechanisms can lead to i-cell formation during embryogenesis. Overall the results obtained provided a better picture of how i-cells and their derivatives arise during embryogenesis and larval development.

No description available.