Wild mustard is an indigenous leafy vegetable. Its use is limited by a lack of knowledge of its agronomy. However, it is a rich source of nutrients and other minerals. Nowadays, the use of indigenous crops has been replaced by exotic crops. Climate change is affecting agricultural productivity. South Africa is a water scarce country with uneven rainfall distribution. Therefore, studies on water stress effects on plant growth were promoted by the Water Research Commission and the University of KwaZulu-Natal to understand plant responses to water stress for commercial and subsistence farming. The objective of the study was to characterise local wild mustard cultivars morphologically and physiologically with respect to production, and for the purposes of identifying their drought tolerance. Three experiments were conducted at the University of KwaZulu-Natal in order to evaluate the responses of local wild mustard cultivars to water stress. Seeds of wild mustard cultivars were characterised according to seed coat colour. Seed quality was determined by a standard germination test. Vigour was then tested using electrolyte conductivity. Seeds were sown in seedling trays under two water regimes of 25% field capacity (FC) and 75% (FC) on pine bark growing media. The experiment was terminated at 21 days when root and shoot lengths were measured. The effect of water stress on protein content and seedling growth parameters was determined. Soil was collected from the University of KwaZulu-Natal Research Farm for a pot trial. Seeds of wild mustard were sown in 81 pots, each filled with 2 kg of soil, under three water regimes (25% FC, 50% FC and 75% FC). Pots were maintained at the corresponding field capacity level by re-weighing the pots, three times a week. Measurements of plant height and leaf number were recorded weekly. The experiment was terminated at the flowering stage. At the end of the experiment, plant growth parameters (plant height, leaf area and number, dry and fresh mass) were measured in order to evaluate the effects of water stress at the vegetative stage. A field trial was conducted at the University of KwaZulu-Natal Ukulinga Research Farm in Pietermaritzburg. The experiment was conducted during the winter and spring of 2009. A completely randomised design was used for non-irrigated and irrigated (25 mm/week) trials. Emergence was measured as well as plant height and leaf number. Plant growth parameters were also measured at the end of the experiment. Leaf samples were taken for proline determination. There was a significant interaction (p<0.05) between seed colour, landraces and days to germinate with respect to germination capacity. Isaha and Masihlalisane landraces showed higher germination percentages than Kwayimba. There was also a significant interaction (p<0.05) between landraces and seed colour with respect to electrolyte conductivity. Lighter seeds of wild mustard landraces showed higher solute leakage. Isaha and Masihlalisane had higher solute leakage than Kwayimba. Significant interactions (p<0.05) between landraces and field capacity with respect to emergence, leaf number, root and shoot length and total proteins were also observed. Isaha and Masihlalisane showed higher emergence than Kwayimba. Leaf number was reduced for all landraces under water stress. Total protein content was high in black seeded landraces under water stress. There was a significant interaction (p<0.05) between landraces and field capacity with respect to seedling fresh and dry masses. Under moderate water stress conditions, Isaha and Masihlalisane showed increased biomass accumulation. There were highly significant differences (P<0.001) in plant height, leaf area, fresh and dry mass with respect to planting date. Plants performed significantly (p<0.05) better in spring than in winter. Isaha and Masihlalisane performed significantly (p<0.05) better than Kwayimba. There was a highly significant interaction (p<0.001) between landrace and irrigation treatments with respect to proline accumulation. Under water stress, Kwayimba black seeded landrace accumulated more proline. It is concluded that light-coloured seeds of wild mustard landraces were associated with good seed quality. Masihlalisane brown seeds have good early seedling establishment. Kwayimba black seeds showed tolerance to water stress through accumulation of proteins. Isaha and Masihlalisane showed an increase in biomass accumulation under moderate water stress. Water stress tolerance in some of wild mustard landraces was negatively correlated with proline accumulation. Masihlalisane brown type can grow well, with good yields, under water stress. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.

Wild mustard (Brassica spp.) is used as an edible wild leafy vegetable by indigenous people in South Africa. The potential of wild leafy vegetables in agriculture is not well understood, because there is generally no agronomic research on their production practices. The objective of this study was to examine the performance of three wild mustard species (herein referred to as I, K and M) over four cropping seasons in an intercropping system with green beans (Phaseolus vulgaris L. cv. Imbali). The crops were grown with and without organic fertiliser under dryland conditions at two sites (The University of KwaZulu-Natal Research Farm, Ukulinga and in a rural area of Umbumbulu, KwaZulu-Natal within the farmers' locality) during autumn, winter, spring and summer of 2004 to 2005. Plant development (leaf number, plant height and fresh biomass) during the first six weeks after sowing and seed yield were used to determine agronomic performance of each species. Nutrient status of the rhizosphere soil was determined at 42 days after sowing for each species to determine what effect growing the species would have on mineral availability. Wild mustard production significantly (P < 0.01) performed better at Ukulinga than Umbumbulu. Polyculture was beneficial for wild mustard leaf accumulation and green bean production as determined by land equivalent ratios greater than one for all species combinations, regardless of fertiliser application. Cool environmental conditions occurring in autumn and spring were more favourable (P < 0.05) for wild mustard and green bean biomass accumulation than summer and winter conditions. However, wild mustard seed yield was highest in winter compared with autumn and spring, and there was no measurable seed production in summer. Soil analysis results at 42 days after sowing showed an increase in P, K, Cu and Mg in the rhizosphere of wild mustard without organic fertiliser. Polyculture improved Zn, Cu, Mn and K in wild mustard leaf tissue. It is concluded that wild mustard can be grown as a leafy vegetable throughout the year, but it requires cool environmental conditions to enhance seed yield. Species M significantly yielded better biomass and seeds than species I and K during all the seasons. However, species K performed the least in all aspects. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.