Faculty of Science
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The Faculty of Science is respected within South Africa, Africa and the world arena as a knowledge-partner of note that builds on the scientific, technological and intellectual capacity of Africa and plays an active role in the development of South African society. The faculty is placed in the top 300 within the category Natural Sciences of the QS World University Ranking list.
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Browsing Faculty of Science by browse.metadata.advisor "Allsopp, Michael H."
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- ItemHow do honey bees handle their stress? A focus on their gut microbiota and immune system. (Apis mellifera subsp. capensis)(Stellenbosch : Stellenbosch University, 2018-12) Lawson, Kayla; Jacobs, Karin; Allsopp, Michael H.; Stellenbosch University. Faculty of Science. Dept. of Microbiology.ENGLISH ABSTRACT: Gut microbial symbionts have recently been shown to play roles in ensuring overall host health, a hot topic in honey bee research. Honey bees harbour a stable, core bacterial community in the gut, suggested to play a role in host health homeostasis, metabolic functioning, immune regulation, and food degradation. This gut microbiota provides a unique opportunity to observe the effects of common stressors on honey bees. Extrapolating the relationship of host-gut microbiota and immune system from higher hosts, we examined the effects of two common honey bee stressors; the indirect fungicide contamination and nutrient limitation. Honey bee colonies were exposed to the fungicide chlorothalonil and limited to only a single pollen food source, respectively. Effects of these treatments were observed through shifts in their gut microbiota using Automated Ribosomal Intergenic Spacer Analysis (ARISA). The immune response of honey bees was examined through gene expression levels of three immune genes, namely; immune deficiency (imd), prophenoloxidase (proPO), and spaetzle. The longevity of the honey bees was monitored through expression levels of vitellogenin (Vg). Overall colony metadata was also taken to observe changes in colony productivity. Both treatment groups were compared to an untouched, negative control group and a positive control group infected with Paenibacillus larvae. Both the fungicide and nutrient limited treatments showed no significant effect on the hindgut microbial communities but showed significant effects on the midgut communities. These treatments caused downregulation in the energy expensive Imd pathway, vital in the production of Anti-Microbial Peptides (AMPs), an invaluable defence against microbial pathogens. The phenoloxidase pathway was upregulated, ensuring a higher activity of the encapsulation and melanisation process, perhaps to compensate for the observed reduction in activity in the other immune pathways. Both treatments showed no significant effect on the gut-immune communicating Toll-like pathway. Honey bees within the nutrient limited group showed reduced colony productivity, probably as a result of delayed foraging, observed using Vg expression levels. Overall the treatments tested in this study significantly reduced the immune system of honey bees, opening the colonies up to potential secondary infections. This study does not provide any reason to discontinue the current beekeeping practices tested here, but attention should be paid to prevent the possibility of infection of colonies under similar conditions as a result of reduced immune system.
- ItemInfluence of polliniser position and honeybee colony distance in the set and quality of deciduous fruit in the Western Cape(Stellenbosch : Stellenbosch University, 2010-12) Ramongalo, Boipelo Kgomotsego; Wossler, Theresa C.; Allsopp, Michael H.; Stellenbosch University. Faculty of Science. Dept. of Botany and ZoologyENGLISH ABSTRACT: Most modern deciduous fruit cultivars are self-incompatible, and require polliniser trees to be planted in the orchard to provide the pollen necessary for cross-pollination, fertilization and fruit set. Polliniser trees are either non-commercial cultivars interspersed in the orchard solely to provide pollen, or crosscompatible cultivars inter-planted in the same orchard. 90% of the commercial crops dependent on bee pollination are courtesy of a single species, Apis mellifera. Both polliniser planting pattern and honey bee colony distance are known to influence crop production and crop quality, resulting in a rapid decrease in fruit weight, fruit set and seed number with increasing distance from the polliniser or honeybee colonies. However, the response of different crops and cultivars to polliniser and pollinator proximity on optimal crop yield is not known for deciduous fruit crops in the Western Cape, South Africa. The effect of polliniser position and honeybee colony distance on fruit set and weight was investigated in plums, apples and pears on the Lourensford Estate. The relationship between fruit set and fruit weight was investigated for deciduous fruit cultivars. In addition, fruit weight and seed number was also investigated in apples and pears. Fruit set tended to increase on sides of trees closer to the polliniser but not significantly so, except for apples. This suggests that there is probably better pollination closer to the pollinisers but this does not equate to increased yield. In fact, smaller fruit was produced on the sides of the trees closer to the polliniser for all orchards and significantly so for plum and for ‘Packham’s Triumph’ in Hillside 1. This negative relationship between fruit set and weight may indicate ‘over-set’ beyond the physiological limits of the trees. Fruits closer to the polliniser had significantly more seeds for both pear and apple cultivars indicating sufficient pollination. A significant relationship was found between the seed number in any particular fruit and the weight of the fruit in all the cultivars except ‘Packham’s Triumph’ where the relationship was negative, suggesting that ‘Packham’s Triumph’ set parthenocarpically. Colony distance had no effect on fruit weight, fruit set and on seed number indicating that colonies were adequately distributed and that there was no “pollination depression” in the centre of the orchards at Lourensford. In conclusion, the fact that we did not get a yield gradient with increased distance from the colonies suggested that the orchards at Lourensford Estate were sufficiently pollinated.