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.

Cultivation of Napier grass, Pennisetum purpureum, the most important livestock crop in East Africa is severely constrained by Napier Grass Stunt (NGS) disease. The disease spreads via an insect vector or vegetative propagation of infected plant material and is caused by a phytoplasma. This necessitates the development of an integrated management approach for the disease. Therefore, objectives of this study were to assess the incidence of the disease and its severity, to identify its wild hosts and farmers‟ knowledge on these hosts, to assess the threat of NGS disease to cultivated grasses and to establish the role of wild inoculum sources in its spread. The study showed NGS incidence ranging from 33% in Uganda to 95% in Kenya with 49% of the farmers interviewed, being able to discern NGS disease by its symptoms. Most farmers cited roguing and use of alternative fodder grasses as control measures, making these strategies the likely components of an integrated management approach for the disease. Responders named Sedge grass (Cyperus spp.) and Star grass (Cynodon dactylon) as the likely hosts of diseases caused by phytoplasma. Phytoplasmas were detected in leaves of 11 of 33 wild grass species collected using polymerase chain reaction (PCR) based on the highly conserved phytoplasma-specific 16S ribosomal DNA fragment. Sequence determination of amplified PCR fragments revealed the presence of NGS-related phytoplasmas in 11 grass species, Bermuda grass white leaf (BGWL) phytoplasmas in three and goosegrass white leaf (GGWL) in two wild grass species, showing that the geographical distribution and diversity of phytoplasmas and their grass hosts are greater than previously thought. The relationships between NGS and Hyparrhenia grass white leaf (HGWL) phytoplasmas were determined using sequences based on secA gene and immunodominant protein (imp). Results showed a very low genetic diversity between NGS and HGWL and produced a phylogenetic tree congruent to that produced by the 16S, affirming the inclusion of HGWL in the 16SrXI group. NGS phytoplasma was transmissible to food crops through Maiestas banda Kramer (Hemiptera: Cicadellidae) under screen-house conditions. With 56.3%, Saccharum officinarum showed the highest infection level followed by Eleusine coracana with 50%, Sorghum bicolor with 43.8%, Oryza sativa with 31.3% and Zea mays with 18.8%. All the phytoplasma-infected plants were asymptomatic except S. officinarum plants, which showed mild to moderate symptoms consisting of foliar yellow leaves and bright white or yellow midribs. This hints that besides wild hosts, food crops may also serve as alternative source of inoculum enabling a complex NGS disease cycle, which may add to challenges in the development of the disease control strategies. However, failure by M. banda to transmit HGWL and BGWL phytoplasmas back to Napier grass is an indication that it could be the exclusive vector of NGS. Therefore, there is need to initiate transmission trials using planthoppers and leafhoppers occurring on HGWL and BGWL phytoplasma-infected grasses to determine whether insect vectors capable of transmitting phytoplasmas from native grasses to Napier grass, are present in the region. / PhD (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

Cultivation of Napier grass, Pennisetum purpureum, the most important livestock crop in East Africa is severely constrained by Napier Grass Stunt (NGS) disease. The disease spreads via an insect vector or vegetative propagation of infected plant material and is caused by a phytoplasma. This necessitates the development of an integrated management approach for the disease. Therefore, objectives of this study were to assess the incidence of the disease and its severity, to identify its wild hosts and farmers‟ knowledge on these hosts, to assess the threat of NGS disease to cultivated grasses and to establish the role of wild inoculum sources in its spread. The study showed NGS incidence ranging from 33% in Uganda to 95% in Kenya with 49% of the farmers interviewed, being able to discern NGS disease by its symptoms. Most farmers cited roguing and use of alternative fodder grasses as control measures, making these strategies the likely components of an integrated management approach for the disease. Responders named Sedge grass (Cyperus spp.) and Star grass (Cynodon dactylon) as the likely hosts of diseases caused by phytoplasma. Phytoplasmas were detected in leaves of 11 of 33 wild grass species collected using polymerase chain reaction (PCR) based on the highly conserved phytoplasma-specific 16S ribosomal DNA fragment. Sequence determination of amplified PCR fragments revealed the presence of NGS-related phytoplasmas in 11 grass species, Bermuda grass white leaf (BGWL) phytoplasmas in three and goosegrass white leaf (GGWL) in two wild grass species, showing that the geographical distribution and diversity of phytoplasmas and their grass hosts are greater than previously thought. The relationships between NGS and Hyparrhenia grass white leaf (HGWL) phytoplasmas were determined using sequences based on secA gene and immunodominant protein (imp). Results showed a very low genetic diversity between NGS and HGWL and produced a phylogenetic tree congruent to that produced by the 16S, affirming the inclusion of HGWL in the 16SrXI group. NGS phytoplasma was transmissible to food crops through Maiestas banda Kramer (Hemiptera: Cicadellidae) under screen-house conditions. With 56.3%, Saccharum officinarum showed the highest infection level followed by Eleusine coracana with 50%, Sorghum bicolor with 43.8%, Oryza sativa with 31.3% and Zea mays with 18.8%. All the phytoplasma-infected plants were asymptomatic except S. officinarum plants, which showed mild to moderate symptoms consisting of foliar yellow leaves and bright white or yellow midribs. This hints that besides wild hosts, food crops may also serve as alternative source of inoculum enabling a complex NGS disease cycle, which may add to challenges in the development of the disease control strategies. However, failure by M. banda to transmit HGWL and BGWL phytoplasmas back to Napier grass is an indication that it could be the exclusive vector of NGS. Therefore, there is need to initiate transmission trials using planthoppers and leafhoppers occurring on HGWL and BGWL phytoplasma-infected grasses to determine whether insect vectors capable of transmitting phytoplasmas from native grasses to Napier grass, are present in the region. / PhD (Environmental Sciences), North-West University, Potchefstroom Campus, 2015