Thesis (MScAgric)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: The influence of chemical seed treatments on the germination, seedling survival and yield of canola (cv. Varola 44) was investigated in a series of incubation studies, glasshouse experiments, as well as field trials in the canola producing areas in the Western Cape Province. Incubation experiments were conducted to compare germination and seedling growth of untreated (control) seed with that of seed treated at different application rates (0.5, 1.0 and 2.0 times the recommended) of Cruiser® and SA-combination (which consists of Thiulin® at 0.5g a.i.; Apron® at 0.0815 g a.i.; Gaucho® at 0.6125 g a.i. and Rovral® at 0.9975 g a.i.). The results indicated that seed treatment (all rates of SA-combination and highest rate of Cruiser) delayed germination and seedling growth, especially if the seed was subjected to the Accelerated Ageing Test. Glasshouse studies with pasteurised soil at different water contents, seed sources (storage periods) and planting depths confirmed the phytotoxic effects of the chemical seed treatments in the absence of soil borne pathogens. From the results it became clear that extreme water conditions (very wet or dry) increased the suppressing effect on germination and seedling growth, but that no phytotoxic reactions occurred in moist (favourable soil water conditions) soil, regardless of application rate of the chemicals used, planting depth and seed source. In a second glasshouse experiment conducted in moist soil (kept at 50% of field water capacity to prevent any toxic effects) from seven different localities that were naturally infested with pathogens, both chemicals proved to be effective where soil borne pathogens (Rhizocfonia so/ani and Pythium spp.) occurred. No clear trend could however be found due to either chemical or application rates used. Finally, field trials were conducted to study the effect of chemical seed treatments on the plant populations and yield of canola planted in different row widths (17 and 34 cm) and seeding rates (3, 5 and 7 kq.ha'). Results showed that treated seeds produced more plants.rn" and yielded more than untreated seeds at Roodebloem Experimental Farm, while the highest seeding rate produced significantly more plants.rn" (Roodebloem and Langgewens Experimental Farms), but not significantly higher yields than the lowest seeding rate at the same locality. Although row width did not have an effect on plant population, yield (Roodebloem 2003) was significantly less at the wider (34 cm) rows. As in earlier experiments, no consistent differences between the two chemicals used were found. These results clearly illustrated both the negative (in the absence of pathogens) and positive (where soil borne pathogens do occur) effects that chemical seed treatments may have on the germination, seedling growth and even yield of canola under local environmental and soil conditions. Because no significant differences were found between the chemicals used, both chemicals should be regarded as efficient. More research, especially under field conditions and with more cultivars, is needed before the registration of a chemical for seed treatment could be considered. / AFRIKAANSE OPSOMMING: Die invloed van chemiese saadbehandeling op die ontkieming, saailing oorlewing en opbrengs van canola (cv. Varola 44) is ondersoek in 'n reeks inkubasie studies, glashuis eksperimente en veldproewe in die canolaproduserende gebiede in die Wes Kaap Provinsie. Inkubasie eksperimente is uitgevoer om die ontkieming en saailing groei van onbehandelde (kontrole) saad te vergelyk met dié van saad wat behandel is teen verskillende dosisse (0.5, 1.0 en 2.0 keer die aanbevole) van Cruiser® en SA-kombinasie (wat bestaan uit Thiulin® teen 0.5g a.i.; Apron® teen 0.0815 g a.i.; Gaucho® teen 0.6125 g a.i. en Rovral® teen 0.9975 g a.i.). Die resultate het aangedui dat saadbehandeling (vir alle dosisse van SAkombinasie en die hoogste dosis van Cruiser) ontkieming en saailing groei vertraag, veral wanneer die saad onderwerp was aan die Versnelde Verouderings Toets. Glashuis studies met gepasteuriseerde grond by verskillende waterinhoude, saad bronne (stoor periodes) en plantdieptes, het die fitotoksiese effekte van die chemiese saadbehandelings bevestig in die afwesigheid van grondgedraagde patogene. Vanuit die resultate het dit duidelik geword dat ekstreme water toestande (baie nat of droog) die onderdrukkende effek op ontkieming en saailinggroei verhoog het, maar dat geen fitotoksiese reaksies plaasgevind het in klam (gunstige grondwater toestande) grond nie, ongeag die dosisse of chemikalieë gebruik, plantdiepte en saad bron. In 'n tweede glashuis eksperiment uitgevoer in klam grond (gehou by 50% van veldwaterkapasiteit om toksiese effekte te voorkom) van sewe lokaliteite wat natuurlik besmet was met patogene, was beide chemikalië effektief waar grondgedraagde patogene (Rhizoctonia so/ani en Pythium spp.) voorgekom het. Geen duidelike tendens is egter waargeneem vir enige van die chemikalieë of dosisse nie. Laastens is veldproewe uitgevoer om die effek van chemiese saadbehandelings op plant populasies en opbrengs te bepaal van canola geplant in verskillende rywydtes (17 en 34 cm) en saaidigthede (3, 5 en 7 kg.ha-1). Resultate het aangedui dat behandelde saad meer plante.rn" produseer en 'n groter opbrengs lewer as onbehandelde saad by Roodebloem Eksperimentele Plaas, terwyl die hoogste saaidigtheid betekenisvol meer plante.m" (Roodebloem en Langgewens Eksperimentele Plase), maar nie betekenisvol hoër opbrengste gelewer het as die laagste saaidigtheid by dieselfde lokaliteit nie. AI het rywydte nie 'n effek op plant populasie gehad nie, was opbrengs (Roodebloem 2003) betekenisvol minder by die wyer (34 cm) rye. Soos in vroeëre eksperimente is geen konsekwente verskille tussen die twee chemikalieë gevind nie. Hierdie resultate illustreer duidelik beide negatiewe (in die afwesigheid van grondgedraagde patogene) en positiewe (in die aanwesigheid van grondgedraagde patogene) effekte wat chemiese saadbehandelings op ontkieming, saailing groei en selfs opbrengs van canola onder plaaslike omgewings en grondtoestande kan hê. Omdat geen betekenisvolle verskille tussen die chemikalieë gevind is nie, moet beide chemikalieë as doeltreffend aanvaar word. Meer navorsing, veralonder veldtoestande en met meer kultivars, is egter nodig voordat die registrasie van 'n chemiese middel vir saadbehandeling oorweeg kan word.

Doctor of Philosophy / Department of Agronomy / Guihua Bai / Allan K. Fritz / Wheat pre-harvest sprouting (PHS), germination of physiologically matured grains in a wheat spike before harvesting, can cause significant reduction in grain yield and end-use quality. Many quantitative trait loci (QTL) for PHS resistance have been reported in different sources. To determine the genetic architecture of PHS resistance and its relationship with grain color (GC) in US hard winter wheat, a genome-wide association study (GWAS) on both PHS resistance and GC was conducted using in a panel of 185 U.S. elite breeding lines and cultivars and 90K wheat SNP arrrays. PHS resistance was assessed by evaluating sprouting rates in wheat spikes harvested from both greenhouse and field experiments. Thirteen QTLs for PHS resistance were identified on 11 chromosomes in at least two experiments, and the effects of these QTLs varied among different environments. The common QTLs for PHS resistance and GC were identified on the long arms of the chromosome 3A and 3D, indicating pleiotropic effect of the two QTLs. Significant QTLs were also detected on chromosome arms 3AS and 4AL, which were not related to GC, suggesting that it is possible to improve PHS resistance in white wheat. To identify markers closely linked to the 4AL QTL, genotyping-by-sequencing (GBS) technology was used to analyze a population of recombinant inbred lines (RILs) developed from a cross between two parents, “Tutoumai A” and “Siyang 936”, contrasting in 4AL QTL. Several closely linked GBS SNP markers to the 4AL QTL were identified and some of them were coverted to KASP for marker-assisted breeding. To investigate effects of the two non-GC related QTLs on 3AS and 4AL, both QTLs were transferered from “Tutoumai A” and “AUS1408” into a susceptible US hard winter wheat breeding line, NW97S186, through marker-assisted backcrossing using the gene marker TaPHS1 for 3AS QTL and a tightly linked KASP marker we developed for 4AL QTL. The 3AS QTL (TaPHS1) significantly interacted with environments and genetic backgrounds, whereas 4AL QTL (TaMKK3-A) interacted with environments only. The two QTLs showed additive effects on PHS resistance, indicating pyramiding these two QTLs can increase PHS resistance. To improve breeding selection efficiency, genomic prediction using genome-wide markers and marker-based prediction (MBP) using selected trait-linked markers were conducted in the association panel. Among the four genomic prediction methods evaluated, the ridge regression best linear unbiased prediction (rrBLUP) provides the best prediction among the tested methods (rrBLUP, BayesB, BayesC and BayesC0). However, MBP using 11 significant SNPs identified in the association study provides a better prediction than genomic prediction. Therefore, for traits that are controlled by a few major QTLs, MBP may be more effective than genomic selection.

A cana-de-açúcar é uma das plantas cultivadas mais importantes no cenário econômico devido à produção de etanol, açúcar e subprodutos, sendo que o estado de São Paulo responde por 60% da produção nacional. Visto que a parte aérea da cana-de-açúcar é formada por colmos e estes contêm além de fibras e água, sólidos solúveis, destacando-se a sacarose, glicose e frutose, quando a planta cresce, o teor de sacarose aumenta nos entrenós mais velhos até a maturação; assim, as variedades se classificam em precoces, médias e tardias devido à época em que acumulam açúcar. A mobilização da sacarose envolve a atuação de enzimas invertases, as quais, através da hidrólise da sacarose, produzem glicose e frutose, disponibilizando às células carbono e energia para a respiração e síntese de compostos. Essas enzimas são importantes para caracterizar e avaliar o comportamento das variedades durante a safra agrícola. Para isso, estudou-se o comportamento de mini-toletes de cinco variedades de cana-de-açúcar, provenientes de gemas apicais, medianas e basais no colmo, durante as fases de emergência e perfilhamento, tendo como parâmetros a avaliação de caracteres fisiológicos como brotação de gemas, altura e diâmetro das plantas, perfilhamento, análises tecnológicas e a atividade de enzimas ligadas ao acúmulo de sacarose. Para a obtenção dos toletes, foi montado um viveiro no CTC Centro de Tecnologia Canavieira, na cidade de Piracicaba/SP, em abril de 2010 e após 10 meses, os colmos foram cortados e os mini-toletes foram separados de acordo com a origem da gema no colmo: apicais, medianas e basais. Em seguida, estes foram plantados em bandejas plásticas, em casa de vegetação, no CTC. Os tratamentos foram montados em blocos casualizados em fatorial, com 6 repetições, sendo os parâmetros biométricos avaliados semanalmente até os 45 dias após o plantio (DAP). As amostras foliares foram coletadas, armazenadas e congeladas. Em seguida, uma planta de cada repetição foi transferida para caixa plástica e o experimento foi conduzido até os 90 DAP, realizando-se avaliações fisiológicas semanalmente. Aos 90 DAP, novas amostras de folhas foram coletadas e congeladas para uso posterior. Os resultados foram submetidos a análise de variância pelo teste F e comparados pelo teste de Tukey a 5% de probabilidade. No experimento aos 45 DAP, as gemas apicais apresentaram maior brotação e maior altura de plantas. Além disso, CTC9 apresentou a maior porcentagem de brotação e maior altura de plantas, tal como a CTC2. Para o experimento conduzido dos 45 aos 90 DAP, CTC6 apresentou maior altura e diâmetro de plantas quando comparada as demais. Houve diferença significativa para a atividade da invertase ácida aos 45 e 90 DAP, ao nível de variedades e gemas. Comparando-se as análises realizadas aos 45 e 90 DAP, verifica-se que a atividade das invertases ácidas foi menor quando comparada a invertase neutra. A quantidade de açúcares redutores totais, açúcares solúveis totais e teor de proteínas aumentou no período avaliado, tanto para as variedades testadas quanto para a origem das gemas no colmo. / Nowadays, the sugarcane is one of the major important crops around the world, because of the production of ethanol, sugar and byproducts, and the state of Sao Paulo represents 60% of national production. Since the aerial part of the sugarcane is formed by stalks and besides fiber and water, they contain soluble solids, especially sucrose, glucose and fructose, when the plant grows, the sucrose content increased in the older internodes until it reaches ripeness, so the varieties are classified into early, mid and late season, according the sugar concentration. The mobilization of sucrose involves the action of invertase enzymes, which promotes the sucrose hydrolysis, producing glucose and fructose, providing carbon and energy for respiration and synthesis of cell compounds. They are important to characterize and evaluate the behavior of varieties during the growing season. For this, we studied the behavior of small stalks of five sugarcane varieties, from apical, middle and basal buds in the stem during the emergency and tillering, evaluating physiological parameters as sprouting, height and diameter of plants, tillering, technological analysis and activity of some sucrose accumulation enzymes. To obtain the stalks with one bud, an experimental field was planted in april 2010 at CTC Centro de Tecnologia Canavieira, Piracicaba/SP. After 10 months, the stalks were cut in singlebud stalks and separated according the origin of buds in the stem: apical, middle and basal. Then, these small stalks were planted in plastic trays in a greenhouse at the CTC. Experiments were conducted in a randomized factorial blocks with six replications, and biometric parameters were evaluated weekly until 45 days after planting (DAP). The leaf samples were collected, stored and frozen for analysis. Then one plant per replicate was transferred to plastic boxes and the experiment was conducted until 90 DAP, evaluating some physiological parameters weekly. At 90 DAP, others leaf samples were collected and frozen for later use determinations. The results obtained were subjected to analysis of variance by F test and compared by Tukey test at 5% probability. In the experiment conducted until 45 DAP, apical buds showed larger amount of buds and higher plant height. Moreover, CTC9 had the highest percentage of sprouting and higher plant height, such as CTC2. For the experiment conducted from 45 to 90 DAP, CTC6 showed higher plant height and diameter when compared to the others. Significant differences were observed for the acid invertase activity during 45 and 90 DAP, for varietis, buds and the effect of interaction varieties x buds. Comparing the analyzis carried out at 45 DAP and 90 DAP, it appears that the acid invertase enzyme activity was lower when compared to neutral invertase. The amount of reducing sugars, total soluble sugars and protein content increased in the study period for the varieties tested and the origin of the buds on the stem.

In northeast Brazil grazing is a major use of much of the semiarid woodlands (caatinga). Animal production is limited by lack of dry season forage, primarily deciduous tree leaves. Management is constrained by the persistence of undesirable trees that sprout from the stump (coppice). This study evaluates the possibility of manipulating coppicing trees to improve caatinga management, particularly dry season forage production. The season of cutting can influence coppicing. Trees were cut early and late in the wet and dry seasons. After two years, trees of all species cut in the late wet season produced less biomass than those cut in other seasons. Production of most species was maximized by cutting in the dry season. Desirable species should be cut during the dry season to maximize production and less desirable ones in the late rainy season to reduce coppicing. Seasonal cutting does not cause mortality, nor can it cause any prolonged change in the leaf: stem ratio. Another study quantifies the response to defoliation of coppice growth by goat browsing or manual removal. The palatable browse species sabia and catingueira suffered no mortality while less palatable species experienced significant mortality. One year after defoliation, defoliated trees still produced less biomass than non-defoliated trees. Browsed stumps sprouted again during the dry season. Changes in the abscission phenology of coppice growth were observed. Coppice growth retained leaves from 2 to 12 weeks longer than intact trees of the same species. Regrowth on browsed stumps remained green for the duration of the S month dry season. Delaying abscission regulates the availability of dry season forage, and has implications for animal production that merit further investigation. Coppice growth can be manipulated to change the species composition of the regenerating stand, improve seasonal forage balance, and reduce site disturbance. Changing from even-aged to uneven-aged management might facilitate these changes. Prospects for improving wood production are better than animal production because of the limits imposed by mixed production systems, land tenure, and human population growth.

Post-traumatic epilepsy is a common outcome of severe traumatic brain injury (TBI). The development of spontaneous seizures after traumatic brain injury generally follows a latent period of little to no symptoms. The series of events occurring in this latent period are not well understood. Additionally, there is no current treatment to prevent the development of epilepsy after TBI (i.e. antiepileptogenics). One cell signaling pathway activated in models of TBI and in models of epilepsy is the mammalian target of rapamycin (mTOR). mTOR activity is sustained for weeks after the initial insult in models of TBI, and the inhibition of mTOR using rapamycin has shown promising pre-clinical outcomes in rodent models. This makes rapamycin an ideal therapeutic to test various outcomes associated with epileptogenesis after TBI. The results from this study suggest that rapamycin treatment after controlled cortical impact reduces aberrant axonal sprouting of ipsilateral dentate granule cells, prevents increased neurogenesis in the subgranular zone, and differentially alters phasic and tonic inhibition in dentate granule cells. However, rapamycin treatment did not prevent all forms of axon sprouting in the dentate gyrus or cell loss in selected regions of the hippocampus. Collectively these results support a role of mTOR activity in both excitatory and inhibitory plasticity in the mouse dentate gyrus after TBI.

No description available.

Typecript Includes bibliographical references

The potential of hot water dipping, vapour heating or ultraviolet irradiation to eliminate the use of chemicals for control of sprouting and post-harvest diseases of the potato (Solanum tuberosum L.) was examined. The microorganisms on which these treatments were tested were the fungal dry rot (Fusarium solani) and the bacterial soft rot (Erwinia carotovora pv. carotovora), two major post-harvest pathogens of potatoes. The study focused on short-term storage (three months) at 8$ sp circ$C or 18$ sp circ$C, which are representative of storage temperatures used by producers in northern temperate and semi-arid tropical regions, respectively. / Response surface methodology was used in experimentation to facilitate analysis of data and identification of optimal operating conditions for the treatments. The following parameters were used to assess tuber quality after the treatments and 3-month storage: firmness, color and structure. / It was found possible to obtain 100% control of sprouting and diseases for the three-month storage without resorting to the use of chemicals. This was achieved without significantly altering the quality attributes of the tubers under certain conditions of hot water, ultraviolet radiation or combinations of these two with storage at 8$ sp circ$C for three months. Although 100% control was not possible for the storage at 18$ sp circ$C, treated tubers performed much better than the controls. Vapour heat (50-70$ sp circ$C) was much less effective at controlling sprouting and was therefore not tested on the pathogens. / A numerical model of the heat transfer phenomenon in the tuber was also developed. It was used to predict the transient temperature distribution in the tuber. The model was solved using the line-by-line technique and model simulations were validated against experimental data.

No description available.

Nod factors, lipo-chitooligosaccharides (LCOs), are rhizobial signal molecules important in the establishment of nodule formation, leading to atmospheric dinitrogen fixation in legume-rhizobium symbioses. Recently, LCOs were also found to regulate other plant processes. We demonstrated that, at 10 -6 M, four LCOs produced by Bradyrhizobium japonicum enhanced soybean seed germination. Evaluation of G-protein inhibitors showed that U-73122, a phospholipase C inhibitor, also increased soybean seed germination, similar to the increase by LCO NodBj-V(C18:1 MeFuc), indicating different mechanisms for the plant perception to LCOs for nodule initiation and seed germination. This was confirmed as LCOs were not able to break dormancy of skotodormant lettuce seeds. Soybean early seedling growth was also increased by the application of LCOs. Pulse 14Ca2+ experimentation showed that the increase might also be related to an increase in Ca 2+ uptake by shoots. We confirmed this with both genistein-induced and non-induced B. japonicum 532C; however, strain 168 (a mutant unable to produce LCO) and non-host rhizobia (Rhizobium leguminosarum, Sinorhizobium meliloti), did not increase Ca2+ uptake. Addition of 1.6 g L-1 casein hydrolysate in yeast extract mannitol broth drastically increased bacterial growth and increased volume-basis LCO production, but decreased LCO production per cell. Best conditions for sterilizing and storing LCOs were determined. LCO should be sterilized by using polyestersulfone filter or autoclaving for up to 30 minutes. LCO was degraded faster when stored at room temperatures (23 +/- 2°C) than low temperature (4 +/- 1°C) and can be stored more than one year.