At foot of title page: Joint Coconut Research Scheme, Yandina, British Solomon Islands Includes bibliographical references. (p. 111-119)

The increasing concerns about chemical pesticides that are environmentally hazardous and the continuous development of resistance by palhogens to chemical pesticides have led to this study. Many studies have shown that some Gram-negative bacteria, such as Pseudomonas flouresens, control plant diseases and promote plant growth. In this study Gram positive bacteria, Bacillus sp., were chosen because of their ability to produce endospores. Endospores can be used in stable, dry formulations. The advantage of using endospores is their ability to survive harsh conditions such as droughts and high temperatures, which give a long shelf life to the biological control agent. Bacillus isolates were recovered from the rhizosphere of 12 different crops, and were subsequently screened in vitro for their antimicrobial activity. Of 130 isolates, 87 exhibited antimicrobial activity against the test organisms: Rhizoctonia solani, Pythium sp., Phytophthora cinnamoni, Fusarium sp., and single representatives of Gram negative and Gram positive bacteria, namely, Erwinia carotovora and Staphylococcus aureus respectively. The Bacillus isolates B77, B81 and B69 inhibited all the test organisms investigated, which suggests that they produced broad spectrum antimicrobial compounds or more than one antimicrobial compound. Of the isolates that showed antimicrobial activity, 78 of them did not inhibit Trichoderma harzianum K D, which is a registered biological control agent; indicating their potential for combined application. Selected Bacillus isolates were tested for the biological control of R. solani under greenhouse conditions in wheat, cabbage, tomato, maize, and cucumber seedlings. Bacillus isolates were applied as seed treatments, and the inoculated seeds were planted in R. solani infested speedling trays. Shoot dry weight measurement of seedlings indicated that 12 out of 19 Bacillus isolates showed significantly different shoot dry weight in wheat whereas all the isolates tested in tomato and cucumber gave significantly different shoot dry weight. No significantly different shoot dry weight was obtained for maize or cabbage. Seed emergence findings indicated that none of the Bacillus isolates gave significantly different emergence percentage on wheat, cabbage, tomato, and maize but all of them showed significantly different emergence percentage on cucumber. The results indicate that both the pathogen and the biological control agents exhibited varying levels of specificity on each crop tested. The biological control potential of the best Bacillus isolates was tested on bean and maize crops in the field. Green bean and maize seeds were coated with the selected Bacillus isolates and then sown under field conditions. For each isolate, four replicate treatment plots were established, with and without a R. solani inoculum. Percentage emergence, plant survival levels to harvesting and yield of maize cobs and green beans pods were measured. For all parameters measured the positive and negative controls were not significantly different thereby rendering the results for the entire field study inconclusive. However, Bacillus isolates B77, BII, R5 and R7 improved green bean pod yield and Bacillus Isolate B8I increased maize yield, indicating their potentials as plant growth promoting rhizobacteria (PGPR). / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2003.

Western larch (Larix occidentalis Nutt.) is an important component of the montane forest in southeastern British Columbia. It grows in cool-temperate (IDF and ICH zones) and boreal climates (MS zone and, occasionally, ESSF zone). Larch is considered a very shade-intolerant species which can tolerate low light (partial shading) only during the seedling stage (the first 5 growing seasons). Typically, it regenerates after fire in the open on seedbeds exposed by burning. However, to what extent it tolerates low light and how various light environments affect its survival and growth is not known. The objective of our study was to determine the variation in survival and growth of western larch seedlings in relation to light availability and site conditions.

Magistro darbe tiriama kai kurių medelyno ekologizavimo priemonių įtaka paprastosios eglės (Picea abies (L.) H. Karst.) sodmenų augimui, vystimuisi, išlikimui, išeigai, dirvožemiui. Darbo objektas – vienerių metų paprastosios eglės sėjinukai ir 2+1 sodinukai bei sideralinis pūdymas. Darbo tikslas – ekologizuoti miško medelyną, pakeičiant mineralines trąšas organinėmis. Darbo metodai – literatūros loginė analizė, apskaitos aikštelių metodas; matematinės statistikos metodai. Darbo rezultatai. Paprastosios eglės sodmenų (pirmamečių sėjinukų ir 2+1 sodinukų) biometrinių požymių matavimai rodo, kad tręšimas kompostu, pagamintu iš mėšlo ir durpės, naudojant 50 ir 100 t ha-1 komposto normas yra netikslingas, nes sodmenims neužtikrinamas pakankamas mitybos lygis. Eglės sodmenis tikslinga tręšti 150 t ha-1 ir didesne komposto norma. Ši tręšimo norma sąlygoja panašius, kaip ir tręšiant mineralinėmis trąšomis, daugelio sodmenų antžeminės ir požeminės dalies biometrinius matavimus (augalų aukštį, šaknies kaklelio skersmenį, šoninių pumpurų skaičių, spyglių ilgį, pagrindinės šaknies ilgį, pirmos eilės šoninių šaknų skaičių). Dažniausiai biometriniai eglių sodmenų parametrai yra mažesni, nei mineralinėmis trąšomis tręštų sodmenų, tačiau skirtumai nėra esminiai. Eglės sodinukų, tręštų 150 t ha-1 komposto norma metinis aukščio prieaugis buvo 10 proc. patikimai mažesnis, nei tręštų mineralinėmis trąšomis sodinukų. Geriausiai eglės sėjinukai ir sodinukai augo dirvožemį patręšus 150 t ha-1... [toliau žr. visą tekstą] / The master thesis examined some of the nurseries’ ecology tools impact on simple spruce (Picea abies (L.) H. Karst.) planting stock cultivation, growth, survival, stocks yield, soil. Object of the work – first year seedlings and first year sapling of simple spruce and sideralic lea. The aim of work – to assess ecological organic fertilizer (green manure and compost) usage impact on simple spruce planting stock growth. Methods of the work – logical analysis of the literature, method of accounting sites, methods of mathematical statistics. The results of the work. Simple spruce planting stocks’ (first year seedlings and first year sapling) biometric features measurements demonstrate that fertilization with compost, made from dung and peat, with 50 and 100 t ha-1 compost rate is pointless, as sufficient nutritional level is not ensured for spruce planting stocks. Spruce planting stocks are appropriate to fertilize with 150 t ha-1 and a higher compost rate. This results in similar fertilization rate, as the fertilization with mineral fertilizers, the biometric measurements of many saplings in surface and underground part (plant height, root neck diameter, lateral bud number, spine length, main root length, the number of lateral root in first order). Frequently the biometric parameters of spruce planting stocks are lower than fertilized with mineral fertilizers, but the differences are not essential. The annual growth of spruce saplings, fertilized with 150 t ha-1 compost rate was... [to full text]

Dominant understorey species, such as herbs, ferns, palms and shrubs may influence forest tree species diversity and dynamics. Their influence may be through shading the forest floor, thereby affecting regeneration of shade-intolerant species and reducing species diversity, or it may be through competition with seedlings for space and belowground resources, thus modifying or changing the structure of the forest. These effects may be compounded if the life cycle of the understorey species consists of synchronized reproductive and mortality events. This study examines the influence of a dominant understorey species, Isoglossa woodii (Acanthaceae), on regeneration of trees in Indian Ocean subtropical coastal dune forest in southern Africa. The species is a semiwoody herb and has population-wide synchronous reproduction at 4-7 year cycles after which it dies and regenerates from seed. In this thesis I examine three aspects of the ecology of this suppressive herb: (i) the ecological and environmental correlates of the distribution of I. woodii; (ii) the evolutionary advantages of synchronous monocarpy; and (iii) the ecological effects of the extensive cover and putative recruitment window caused by I. woodii on forest tree seedling dynamics and diversity. Isoglossa woodii covered 65–95 % of the understorey, while gaps in this understorey cover occupied the remaining 5–35 % of the area. The spatial distribution of I. woodii was strongly related to tree canopy structure, with the species excluded from sites with dense canopy cover. Woody seedling establishment was inhibited by low light availability ( / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.

Various Trichoderma and Bacillus spp. have been documented as being antagonistic to a wide range of soilborne plant pathogens, as well as being plant growth stimulants. Successes in biological control and plant growth promotion research has led to the development of various Trichoderma and Bacillus products, which are available commercially. This study was conducted to evaluate the effect of six Trichoderma spp. and three Bacillus spp. and their respective combinations, for the biological control of Rhizoctonia solani damping-off of cucumber and plant growth promotion of dry bean (Phaseolus vulgaris L.). In vivo biological control and growth promotion studies were carried out under greenhouse and shadehouse conditions with the use of seed treatment as the method of application. In vitro and in vivo screening was undertaken to select the best Trichoderma isolates from 20 Trichoderma isolated from composted soil. For in vitro screening, dual culture bioassays were undertaken and assessed for antagonisms/antibiosis using the Bell test ratings and a proposed Invasive Ability rating based on a scale of 1-4 for possible mycoparasitic/hyperparasitic activity. The isolates were further screened in vivo under greenhouse conditions for antagonistic activity against R. solani damping-off of cucumber (Cucumis sativus L.) cv. Ashley seedlings. The data generated from the in vivo greenhouse screening with cucumber plants were analysed and grouped according to performance of isolates using Ward‟s Cluster Analysis based on a four cluster solution to select the best isolates in vivo. Isolates exhibiting marked mycoparasitism of R. solani (during ultrastructural studies) viz, T. atroviride SY3A and T. harzianum SYN, were found to be the best biological control agents in vivo with 62.50 and 60.06% control of R. solani damping-off of cucumber respectively. The in vitro mode of action of the commercial Trichoderma product, Eco-T®, and Bacillus B69 and B81 suggested the production of antimicrobial substances active against R. solani. In vitro interaction studies on V8 tomato juice medium showed that the Trichoderma and Bacillus isolates did not antagonise each other, indicating the possibility of using the two organisms together for biological control and plant growth promotion studies. Greenhouse studies indicated that combined inoculation of T. atroviride SYN6 and Bacillus B69 gave the greatest plant growth promotion (43.0% over the uninoculated control) of bean seedlings in terms of seedling dry biomass. This was confirmed during in vivo rhizotron studies. However, results obtained from two successive bean yield trials in the greenhouse did not correlate with the seedling trials. Moreover, no increase in protein or fat content of bean seed for selected treatments was observed. In the biological control trials with cucumber seedlings, none of the Trichoderma and Bacillus combinations was better than single inoculations of Eco-T®, T. atroviride SY3A and T. harzianum SYN. Under nutrient limiting conditions, dry bean plants treated with single and dual inoculations of Trichoderma and Bacillus isolates exhibited a greater photosynthetic efficiency that the unfertilized control plants. Bacillus B77, under nutrient limiting conditions, caused 126.0% increase in dry biomass of bean seedlings after a 35-day period. Nitrogen concentrations significantly increased in leaves of plants treated with Trichoderma-Bacillus isolates. However, no significant differences in potassium and calcium concentrations were found. Integrated control (i.e. combining chemical and biological treatments) of R. solani damping-off of cucumber seedlings proved successful. In vitro bioassays with three Rizolex® concentrations, viz., 0.01g.l-1, 0.1g.l-1 and 0.25g.l-1 indicated that the selected Trichoderma isolates were partly sensitive to these concentrations whereas the Bacillus isolates were not at all affected. In a greenhouse trial, up to 86% control was achieved by integrating 0.1g.l-1 Rizolex® with T. harzianum SYN, which was comparable to the full strength Rizolex® (1g.l-1) application. Irrespective of either a single or dual inoculations of Trichoderma and/or Bacillus isolates used, improved percentage seedling survival as achieved with the integrated system, indicating a synergistic effect. The results presented in this thesis further reinforce the concept of biological control by Trichoderma and Bacillus spp. as an alternative disease control strategy. Furthermore, this thesis forms a basis for Trichoderma-Bacillus interaction studies and proposes that the two organisms could be used together to enhance biological control and plant growth promotion. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.

This study was undertaken to determine the effect of vegetation structure (the ratio of re-seeding to re-sprouting plants) on post-fire catchment water yield. Plant communities are the only components of mountain catchments which can be manipulated to augment water supplies on any practical scale. Burning, which is one of the options available to catchment managers, reduces plant biomass and increases water yield by reducing transpiration and interception losses. Communities dominated by re-seeding species tend to recover more slowly after fires than when sprouters predominate. The rate of vegetation recovery will determine the rate at which streamflow returns to pre-fire levels. Sprouters may use more water than seeders in the early post-fire period by virtue of their greater leaf area, which both increases interception and transpiration losses. Leaf area development could be used as a simple determinant of post-fire water yield if transpiration losses per unit leaf area are similar in seedlings and sprouters. In this study, a comparison was made of the transpiration rates of seedlings and sprouters of Protea nitida after a fire in Swartboskloof (Cape Province) in 1987. Plant water potentials were determined (index of the degree of stress) and leaf stomatal conductances were measured. Results indicate that transpiration rates are similar throughout the year except during the short summer drought period when the seedlings have comparatively low transpiration rates (< 1 mmo1 m-2 s-1 compared to 2-3 mmo1 m-2 s-1 of the sprouter), and i immediately after the first winter rains where the seedlings have comparatively high rates (approxi.mately 4 mmol m-2 s-1 compared to 2 mmol m-2s-1.) The 1ow summer rates are thought to be the result of drought stress induced by limited water supply and the shallow root systems of the seedlings. The higher winter rates suggest that the shallow surface roots of the seedlings respond quickly to increased surface moisture. Differences in root structure (Le. shallow seedling roots and well-developed deep sprouter roots) rather than regeneration mode appear to be responsible for the marginal differences observed in transpiration rates. These differences are expected to disappear as seedling roots develop and occupy the profile. Leaf area could therefore, be used as a determinant of catchment water yield. / Thesis (M.Sc.)-University of Natal, 1990

High output commercial nurseries that cater for the forestry industry are continuously challenged to efficiently and cost effectively produce good quality planting stock to establish large plantations. Currently, South African commercial nurseries produce planting stock in solid compartmentalized trays. One of the major drawbacks of these containers is the susceptibility of trees to root deformation following outplanting, combined with the need for the return of empty containers to the nursery. A potential solution to these challenges is the introduction of wall-less plugs for the production of planting stock. Wall-less plugs are volumes of growing medium, usually cylindrical in shape, devoid of an impenetrable wall in which a plant can grow and establish itself. Such plugs may enable the production of planting stock with improved root systems, without the need for the return of empty containers after outplanting. In this research four prototypes of wall-less plugs were developed, produced on a small scale and tested. These were: 1) Paper-maché plugs made using the original WRIBLOK protocol whereby composted pine bark was bound together with repulped newspaper, 2) Sponge blocks, 3) Hessian bags and 4) Covetan bags. The performance of these prototype wall-less plugs was compared with the performance of four tray types used commercially by the forestry industry: 1) Poly 128 shallow, 2) Poly 98 deep, 3) Unigro 128 and 4) Sappi 49. These are polystyrene and polypropylene-based containers. Of these containers the Unigro 128 and Sappi 49 containers were of similar performance. Performance in terms of height and root collar diameter increase over ten weeks from the time of sowing of the paper-maché plugs was similar to that of the Unigro and Sappi 49 containers. The sponge block, Hessian bags and Covetan bags produced inferior quality planting stock compared to the other treatments tested. Although little progress was made in the ability to describe how one root system differs from another in terms of their branching patterns, a technique was developed to determine root surface area by image analysis software that is freely available. This method may prove useful for further research and for determining seedling quality in commercial nurseries. / Thesis (M.Sc.Agric.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.

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.

Diss. (sammanfattning) Alnarp : Sveriges lantbruksuniv. / Härtill 4 uppsatser.