Sunflower (Helianthus annuus L.) is one of the most important oil crops in South Africa and genetic improvement for grain yield and oil-content was initiated in the country in the early 1970s. Commercial production of sunflower in South Africa is done under natural rainfall conditions in areas where frequencies of drought are high hence the requirement for drought tolerant cultivars. An assessment of the genetic gains in seed and oil yield achieved since 1970, the effects of re-cycling inbred lines and strategies for developing drought tolerant sunflower cultivars has not been done for South African sunflower breeding programmes. Two data-sets were used for the genetic gain studies: side-by-side evaluation of historical and current sets of popular cultivars in the same environment under one set of trial management practices; and yield trends in commercial farmers’ fields based on annual production estimates. The estimated relative genetic gain for seed yield based on side-by-side trials was 1.5% year−1 and the relative gain in seed yield per year under commercial production was 1.9% year−1. The contribution of new cultivars to total seed yield progress in sunflower were 56.3% for the period 1970 to 1989; 23.9% from 1990 to 2009 and the mean over the four decades under consideration from 1970 to 2009 was 41.6%. Quantifying the usefulness of inbred lines in advanced cycle plant breeding was done using four base breeding populations based on: phenotypic or genetic variability; heterosis; and combining ability. Significant genetic variation was evident for seed yield and oil yield while genetic variability for oil content was low. Genetic advance (GA%), with a 10% selection intensity, was high for seed yield and oil yield for each of the four populations ranging from 36-42% and 38-43%, respectively. The GA% for oil content was low ranging from 1.3% to 5.1% indicating the need to introgress high oil content germplasm in the present breeding populations in advanced cycle pedigree breeding. Founder parent heterosis (FPH), mid-standard heterosis (MSH) and high standard heterosis (HSH) indicated that some new testcross hybrids from the advanced cycle pedigree breeding populations were performing better than their founder parents in hybrid combination as well as the standard commercial hybrid checks. From variance component analysis, general combining ability (GCA) was predominant over specific combining ability (SCA) for seed and oil yields indicating that superior hybrids can be identified based on positive and significant GCA effects of the female lines. For oil content, SCA was predominant over GCA indicating that it would be best to select for specific hybrids combinations with high oil content rather than selecting female lines with high GCA effects. Variable moisture conditions characterise the sunflower production environments in South Africa. Breeding for such environmental conditions requires a combination of strategies including use of secondary traits and developing appropriate test environments. Three secondary traits, head diameter, stem diameter and stay green canopy which are easy to measure in the field were evaluated for their appropriateness for selecting for drought tolerance under three moisture conditions: random stress environments (RSE), managed drought stress environments (MSE) and well watered nonstress environments (NSE). Type A genetic correlations indicated that stay green canopy (SG) had the potential to be used as secondary trait to indirectly improve oil yield under the three moisture conditions. The indirect selection efficiency (ISE) for SG using genetic correlations based on H2 were 0.79, 0.82 and 0.78 in the RSE, MSE and NSE, respectively, while that using genetic correlation based on h2 were 0.67, 0.98, and 0.93 in the RSE, MSE and NSE, respectively. In both cases selection in the MSE had the highest efficiency using genetic correlations based on either H2 or h2. Estimates of indirect selection based on type B genetic correlations indicated that indirect selection for oil yield (OY) in the MSE and NSE for the target RSE was as effective as direct selection of OY in the RSE based on additive genetic correlations of 0.96 obtained in both selection environments. Overall, the results from the exploratory drought tolerance study should inform the development of breeding strategies to improve drought tolerance and associated yield stability of sunflower cultivars grown in South Africa and associated environments. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.

The influence of herbivory, grass competition and grazing system on emergence, growth and survival of Acacia seedlings in burnt and unburnt areas was investigated in their first growing season, from September 1997 to May 1998. The study was aimed at determining possible reasons for the increase in woody plant density in semi-arid savannas, specifically the effect of excluding small-mouthed herbivores from domestic and livestock systems, and switching from continuous grazing to rotational grazing systems. The effect of fire intensity and maximum fire temperature on seed viability, germination and mortality, specifically with regard to back versus head fires and seed size , were investigated. Variability among species in the number of seedlings emerging generally resembled differences in viability. Emergence of Acacia karroo and Acacia tortilis was poorer than that of Acacia nilotica under grass competition. Emergence was lower in burnt and open areas, the latter depending on Acacia species. Herbivory did not affect seedling emergence, in both domestic and wildlife systems. Seedling survival and growth was adversely affected by small-mouthed herbivores in both domestic and livestock systems, whilst large-mouthed herbivores exerted no direct effects on woody seedlings, except to a small degree by trampling. Seedlings showed better growth and survival under low grass competition, which also resulted in greater leaf-to-height ratios , indicating that grass interference with irradiance affects woody seedlings. This effect appeared to be greater for cattle and rotational grazing, and for burning, in domestic and wildlife systems respectively. Woody seedling establishment was also better in burnt areas. Whilst seedling growth was better under rotational than continuous grazing, survival was not significantly different. Grass competition influenced seedling establishment to a greater extent than herbivory, whilst burning made a greater impact than grass competition. Seed mortality in response to maximum fire temperature was inversely related to seed size, and trends in seed germination and mortality, although very variable, appeared to be influenced by threshold fire intensities and maximum temperatures. Back fires had hotter maximum temperatures and fire intensities at ground level than head fires, which result in greater seed mortality following fire. Based on the current study it is likely that the removal of grass competition, burning, and a change from continuous to rotational grazing systems, and small-mouthed to large-mouthed herbivores, will result in an increase in woody seedling establishment. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2001.

Bibliography: leaves 300-321. / xiii, 321 leaves [11] leaves of plates : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis aims to extend knowledge and understanding of the seed-seedling dynamics and productivity of annual Medicago pastures. In particular this study concentrates on the impact of grazing by sheep on Medicago pasture herbage and seed production and sheep body weight gains. / Thesis (Ph.D.)--University of Adelaide, Depts. of Agronomy and Farming Systems and Plant Science, 1997

The decline of kereru (Hemiphaga novaeseelandiae) may limit dispersal of large-seeded plants in New Zealand, but the consequences of this are unknown. I determined kereru disperser effectiveness by modelling seed dispersal distances (using seed retention times and movement patterns). Mean seed retention time was significantly longer for larger-seeded species, ranging from 37-181 minutes. Wild radiotracked kereru were sedentary, remaining at one location for up to 5.25 hours. The mean flight distance was 77 m and the maximum was 1, 457 m. Estimated mean seed dispersal distances for tawa (Beilschmiedia tawa), puriri (Vitex lucens), and fivefinger (Pseudopanax arboreus) were 95, 98, and 61 m respectively. Kereru dispersed 66-87% of ingested seeds away from the parent tree, with 79-88% of seeds dispersed <100 m and < 1% dispersed over 1,000 m. In a field seed-fate experiment, "pre-human" conditions (cleaned seeds, low density, away from parent, and protected from mammals) increased survival compared to "post-human" conditions (whole fruits, high density, under parent, not protected) for both taraire (Beilschmiedia tarairi; 15% vs. 2% survival to one year respectively) and karaka (Corynocarpus laevigatus; 60% vs. 11% to two years, respectively). Fruit diameter varied considerably within karaka, taraire, and tawa, although theoretically not enough for them to be swallowed by other birds. Nevertheless, other birds are reported to occasionally take fruits of nearly all large-seeded species. Small tawa seeds produced smaller seedlings in the glasshouse; therefore selection of only smaller seeds by alternative dispersers may negatively affect tawa recruitment. Kereru are generally not gape-limited, and fruit size preferences were independent of mean fruit size. Kereru provide effective dispersal by moving most seeds away from the parent, and enhancing seed and seedling survival. Therefore, both dispersal failure and introduced mammals negatively affect the regeneration of large-seeded trees in New Zealand.

[Truncated abstract] Faba bean (Vicia Faba L.) ranks third worldwide in overall production among coolseason legume crops and is used as a main source of protein both for food and feed purposes in many parts of the world. Australia is a major exporter of faba beans and the price received depends on the quality of the seed especially colour of the seed coat. Consumers don?t like faba beans that are dark coloured or that have blemishes on the seed coat. Environmental staining and storage discolouration deteriorate seed colour causing substantial economic losses to growers and grain handlers. To investigate the influence of environmental conditions, especially during pod/seed development and maturity, on the degree of environmental staining, field trials were conducted using four faba bean varieties (Fiord, Fiesta, Ascot and Cairo) in a range of environmental conditions under the Mediterranean-type climate of south western Australian grain belt. Although a majority of seeds had good colour but 3-25% were stained up to an unacceptable level across the trials and this varied with location and variety. Seeds formed later in plant development (located on the upper nodes of the plant) were more stained than seeds formed earlier (located on the lower nodes). This may be due to end of season environmental factors, such as high temperature and light intensity, and water and nutrient stress. Similarly seeds formed on small and weak plants, which may have developed under stressful conditions, had more staining than seeds formed on normal sized and healthy plants. Genotypic variation was also evident with Fiord showing greater staining than Ascot, Fiesta and Cairo. The cause of environmental staining appears to be complex but was associated with phenolic contents. Storage discolouration was influenced by a number of factors including temperature, seed moisture content, light and storage period and these were critical in determining storage life. ... Faba bean hardness, examined by the hard-to-cook test, also increased with increased storage temperature. There was a high negative correlation (r2 = 0.98) between storage temperature and cooking ability of faba bean. There was a three-fold increase in lignin content of faba bean stored at 50°C compared to those stored at 5°C and it was correlated with bean hardness (r2 = 0.98). Reduction in free phenolics was negatively correlated (r2 = 0.75) with bean hardness. The environmental staining in faba bean can be minimized with correct choice of varieties, robust agronomic practices to establish and maintain healthy plants and the use of mechanical graders and colour sorters. For minimizing storage discolouration faba beans must be dehydrated to ≤12% seed moisture content and stored in insulated bins (silos) or at least bins painted white and constructed under trees shades. In addition occasional flushing with N2 will further help reduce the colour darkening. The above approaches will improve quality, market opportunities, price and hence profitability of faba bean in the farming systems.

Thesis (Ed. D.)--Boston University, 2005. / Vita. Includes bibliographical references (p. 560-575).

Diss. (sammanfattning). Uppsala : Sveriges lantbruksuniv., 2003. / Härtill 4 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv. / Härtill 6 uppsatser.

Mémoire (M.Ress.Renouv.)-- Université du Québec à Chicoutimi, 1994. / Document électronique également accessible en format PDF. CaQCU

These (Ph.D.)--University of Waterloo, 2007. / Title from PDF title page. Available through UMI ProQuest Digital Dissertations. Includes bibliographical references (leaves 118-131). Also issued in print.