Dissertation (PhD(Agric))--University of Stellenbosch, 2007. / Bibliography.

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Field trials were conducted in 2010/11, 2012 and 2013 at the Royal Agricultural University’s Soil Association certified organic Harnhill Manor Farm, Gloucestershire, UK (NGR SP 075 006), to investigate suitable cultivation techniques and legume cover crops for winter and spring wheat production. Cultivation treatments included conventional tillage (CT), low residue non-inversion tillage (LRNiT) and high residue non-inversion tillage (HRNiT) as main plots while undersowing white clover (WC), black medic (BM) or no undersowing (Nus) as subplots. Wheat establishment, growth, grain yield and weeds infestation were assessed to determine the feasibility of these husbandry techniques. For winter wheat in 2010/11, LRNiT seems to be an acceptable alternative for CT. However, for spring wheat in 2012 and 2013, CT seems to be more reliable management option. The performance of undersown legumes was highly weather reliant and inconsistent in the seasons studied. Plant establishment and the succeeding yield parameters were positively related to grain yield. CT had significantly higher plant establishment than LRNiT or HRNiT in each season. For winter wheat, the competition and compensation on shoot density among CT and LRNiT did potentially outweighed cultivation-induced effects on plant establishment. This condition resulted in statistically equivalent crop growth and yields with LRNiT to that of CT. In contrast, for spring wheat in 2012 and 2013, CT that had significantly higher plant establishment also resulted in better crop growth and greater grain yields than other cultivation treatments. In all seasons, HRNiT had significantly lower plant establishment and also reduced grain yields, compared with LRNiT or CT. More soil cultivation also significantly reduced total weeds than less tilled soil such as HRNiT. On the basis of weed species, significantly higher broadleaf weeds were present under CT and significantly higher grass weeds were present under HRNiT. Out of three investigated years, legume cover crops effects were clearly observed only in 2012 with spring wheat. More vigorous growth of WC showed a significantly inverse relationship with broadleaf weeds and total weeds, compared with slow growing BM. This situation, resulted in non-significant yield components or grain yield reduction, compared with non-undersown spring wheat. In this context, white clover seems to be more suitable legume cover crop than black medic.

Bambara groundnut (Vigna subterranea (L.) Verdc.) is a leguminous crop indigenous to Africa, which is grown by small-scale farmers. It is a protein rich legume crop, which is mostly grown to supply rural and urban poor communities with a nutritious source of food. In this study six cultivars of bambara groundnut seeds differing in seed coat colour were used to determine the seed-borne mycoflora present on the seed and whether this was related to surface topography and/or, the amount and localisation of polyphenolic compounds in the seed. Bambara groundnut seeds were surface sterilised with 1.5% sodium hypochlorite for 5min, plated on PDA petri dishes and incubated at ±25°C. After 7d of incubation, percentage of fungal infestation was determined. It was found that dark coloured seeds (Sb4- 4A and Sb 8-1) of bambara groundinut were less infected, with the exception of one dark cultivar (Swazi Vs A), than the light coloured seeds (As7 and Sbas 1-8). Aspergillus, Fusarium and Chaetomium spp. were found to be the dominant fungal species. Scanning electron microscopy was used to determine if seed infection of the various cultivars could be linked to seed surface topography. Seeds were cut in half, placed directly on stubs and coated with gold. Examination of surface topography indicated that there were no distinct morphological differences among the different cultivars. The seeds had smooth surfaces and although some showed a little shrinkage, none had structures like pores or pits. Hilum structures differed among cultivars and were either tightly or loosely packed. As seed fungal infection could not be linked directly to surface topography, the amount and localization of polyphenolic compounds was then studied to determine whether these factors may influence fungal infection. In the histochemistry study, 10μm seed coat sections were mounted in glycerine or vanillin-HCI. Other sections were stained with Neu reagent. Illumination was recorded at 420nm and 360nm for blue and UV light respectively. Thin layer chromatography (TLC) was performed to separate phenolic compounds. It was found that dark coloured seeds were stained dark red showing the presence of polyphenolic compounds in the epidermis and parenchymatous layer. Dark coloured seeds emitted a strong blue fluorescence under UV illumination indicating the presence of large quantities of polyphenolic compounds in the epidermis. This was not apparent in the light coloured seeds. Under blue illumination, the green colouration of the epidermis indicated the presence of flavonoids, which also appeared to be more apparent in darker seeds than in light coloured seeds. This difference is brought about by the different amounts of total phenolic compounds in the seeds. The amount of phenolic compounds was higher in the seed coats than in the embryo and cotyledons. A TLC study showed more compounds in the dark coloured seeds than in light coloured seeds. The results of this study indicated that the pdlyphenolic compounds present in the seed coats of bambara groundnut may indeed play a role in the resistance or susceptibility of different coloured seeds to fungal infection. / Dissertation (Magister Institutionis Agrariae)--University of Pretoria, 2005. / Plant Production and Soil Science / unrestricted

In North America, Hedysarum taxa extend from southern Arizona to Banks Island and from northern Alaska to Newfoundland. They exhibit a high degree of polymorphism which is usually expressed in the form of a gradient in morphological characteristics. Four species, one subspecies and four varieties are recognized, including one new combination, H. boreale ssp. boreale var. rivulare (Williams) Northstrom. Comparative anatomical and morphological studies revealed two basic patterns. Chromosome numbers of all taxa were determined. The basic chromosome number of H. alpinum, H. sulphurescens and H. occidentale is n=7. The basic chromosome number of H. boreale is n=8. Seed protein electrophoresis revealed two basic patterns which correspond to the two sections of the genus now delimited by classical methods. Total seed protein was estimated for each species. Tissue and seed extracts were tested for various ureides, uncommon amino acids and phytohemagglutinins. All taxa were found to be nonhemagglutinating and positive for canavanine, mangiferin, arginine and uric acid. Leaf element accumulation characters for each species were determined.

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Master of Science

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

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