Please read the abstract in the section 00front of this document / Dissertation (M Inst Agrar (Agronomy))--University of Pretoria, 2006. / Plant Production and Soil Science / unrestricted

M.Tech. (Homeopathy) / The aim of this study was to evaluate the growth rate of germinating Zea mays seeds treated with homeopathically prepared Argentum nitricum in the potencies 3CH. 6CH and 9CH. The purpose was to prove that homeopathy does not work according to the "placebo effect" as suggested by some researchers. This was done by showing that homeopathic remedies have therapeutic effects on living plant matter, thereby giving credibility to homeopathy as a science. Another aspect of the study was to determine whether there is specificity in relation to selected remedy and dose. Six hundred Zea mays seeds were selected and planted in germination paper rolls. In each of the three test groups as well as the control group, there were ISO seeds each. The control group was treated with distilled water only, while the test groups were treated with varied potencies ofArgentum nitricum, which were prepared indistilled water. The germination rolls were incubated at 2SoC for a total of J3S hours. After 39 hours the germinating seeds were replanted onto fresh germination rolls. The process was repeated after a further 48 hours and thus at 87 hours the first measurement was taken and recorded. The final measurement was taken and recorded at J3S hours. Measurements comprised of the lengths of the mesocoleoptile and coleoptile ofthe Zea mays shoots. At 87 hours there was no significant difference between any of the groups. At J3S hours there were significant differences between the Argentum nitrlcum 3eH and the control, Argentum nitricum 3CH and Argentum nitricum 6CH, Argentum nitricum 3CH and Argentum nitricum 9CH. This study therefore showed that homeopathic Argentum nitricum had significant influence on the growth of germinating Zea mays seeds. The theory that homeopathy is merely due to "placebo effect" was disproved, and it was shown that there is definitely specificity with respect to homeopathic potencies.

Orientador: Fabíola Vitti Môro / Resumo: RESUMO - A inoculação com Azospirillum brasilense vem sendo praticada na cultura do milho contribuindo com ganhos na produtividade e reduzindo os impactos ambientais decorrentes da utilização de fertilizantes nitrogenados. Dessa forma, é crescente a busca por genótipos de milho que detenham genes que promovam uma associação eficiente com A. brasilense. O objetivo deste trabalho foi caracterizar genótipos de milho quanto à resposta a inoculação com A. brasilense. Foram avaliados 46 genótipos de milho na primeira safra 2018/19 em Jaboticabal-SP no delineamento de blocos ao acaso com duas repetições. Foram conduzidos na mesma área dois experimentos, sendo um com inoculação de A. brasilense via solo sem a realização de adubação nitrogenada de cobertura (AZOS) e outro com adubação nitrogenada de cobertura sem aplicação de A. brasilense (N), ambos os experimentos receberam adubação nitrogenada no plantio. Avaliou-se a produtividade de grãos, prolificidade, Comprimento da espiga, Diâmetro da espiga, Número de fileiras de grãos na espiga, Número de grãos por fileira, Peso médio de 500 grãos, altura de planta, altura de espiga, posição relativa da espiga, florescimento masculino, florescimento feminino e tombamento de plantas. Os dados foram submetidos ao teste F e comparados pelo teste de Scott-Knott a 5% de probabilidade, também para cada genótipo foi obtida a eficiência na resposta à inoculação com A. brasilense e realizada a análise estatística multivariada por componentes princip... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: ABSTRACT - Azospirillum brasilense inoculation has been practiced in maize crop improving grain yield and reducing the environmental impacts resulting from the use of nitrogen fertilizers. Thus, the search for maize genotypes with genes that promote an efficient association with A. brasilense is increasing. The aim of this study was to characterize maize genotypes in response to inoculation with A. brasilense, using 46 maize genotypes in the summer growing season 2018/19 in Jaboticabal-SP in a randomized complete block design with two replications. Two experiments were carried out in the same area, one with A. brasilense inoculation via soil without nitrogen fertilization (AZOS) and another with nitrogen fertilization without A. brasilense (N). The evaluated traits were: grain yield, prolificacy, ear length, ear diameter, lines per spike, number of grains per line, average weight 500 grains, plant height, ear height, relative ear position, male flowering, female flowering and tipping of plants. The data were submitted to the F test and compared by the Scott-Knott test at 5% probability. For each genotype was obtained the efficiency in response to inoculation with A. brasilense and multivariate statistical analysis was performed by principal components. It was possible to characterize maize genotypes in response to inoculation with A. brasilense via soil, and the response to inoculation was dependent on the genotype used. The genotypes 1, 6, 13, 18, 20, 23, 25, 32 and 33 are t... (Complete abstract click electronic access below) / Mestre

La producción de haploides y haploides duplicados es una herramienta empleada en una gran cantidad de especies que permitiría acortar sustancialmente el tiempo requerido para la obtención de nuevos individuos homocigotas. El desarrollo y la optimización de nuevas tecnologías en este sentido es de gran interés para el avance en investigación básica así como para acelerar programas de mejoramiento genético vegetal. En el presente trabajo se evaluó la producción de plantas potencialmente haploides de maíz (Zea mays L.) para su utilización en programas de mejoramiento e investigación genética. Se trabajó con la técnica de inducción de potencialmente haploides in vivo mediante el empleo de polinizadores inductores de haploidía. Estos polinizadores se destacan por su aptitud de generar un número significativo de granos potencialmente haploides al fecundar distintos parentales femeninos. Se utilizaron cinco polinizadores y se evaluó su capacidad para la inducción de granos potencialmente haploides in vivo en porcentaje. La capacidad de inducción de plantas potencialmente haploides de los diferentes polinizadores fue cuantificada en diferentes ambientes de cultivo de los parentales y utilizando diferente germoplasma como progenitor femenino. Los experimentos se realizaron en 4 ambientes, a saber, Venado Tuerto, en dos fechas de siembra (VT1, VT2), Balcarce y Rancagua (Chile). La detección de granos potencialmente haploides se basó en la expresión de un gen marcador de color, R-nj (Rojo navajo), tanto en endosperma como en embrión. Dicho marcador permite seleccionar aquellos embriones en los cuales la fecundación no tuvo lugar. La ausencia de coloración en el embrión indica la ausencia de fecundación, evidenciando la condición haploide materna de dicho individuo. No obstante la presencia de inhibidores de color estaría afectando dicha expresión en algunos de los germoplasmas evaluados en este trabajo. Se lograron identificar polinizadores inductores de haploidía con comportamiento estadísticamente superior. Dicha capacidad fue corroborada en diferentes ambientes sin encontrarse interacción entre los mismos. Los polinizadores inductores HIND 2 (X1-B1/G3-64) y HIND 4 (M4-B3/G3-64) presentaron porcentajes de inducción de haploides potenciales superiores al 8%. En este estudio los valores más elevados de inducción fueron registrados en el ambiente de Balcarce (13,8%). El ambiente en el cual se realiza la polinización es una fuente de variabilidad que debe considerarse en el momento de implementar la técnica de obtención de individuos potencialmente haploides. La técnica de obtención de haploides de maíz in vivo optimizada en esta tesis permite la obtención de estimativamente 10 granos potencialmente haploides a ser duplicados por cada 100 granos obtenidos en el cruzamiento de inducción. Esta relación permite una aplicación directa en programas de mejoramiento de maíz comerciales. / The production of haploids and double haploids is a widely used strategy in many species allowing the reduction of the time to the generation of a complete homocigous individual. The development and optimization of new technologies is of mayor interest for the basic research and to hasten processes in breeding programs. In the present work maize (Zea mays L.) haploid plants production for breeding and research purposes was evaluated. The in vivo haploid induction technique was performed by using male haploid inducers. Five haploid inducers were tested in their ability to generate haploid kernels. The inducer pollinators were selected for their ability to generate a significant number of haploid kernels over different females pollinated. The induction of haploid plants was tested for the different pollinators as affected by parental growing environment and female germplasm. Female parental material and inducers were planted in Venado Tuerto, two sowing dates (VT1, VT2), Balcarce and Rancagua (Chile). Haploid kernels detection was based on the expression of color markers, R-nj, in endosperm and embryo. Such marker allows the selection of embryos in which fertilization was not effective. The lack of color on embryo is an evidence for incomplete fecundation, leading to a putative maternal haploid kernel. However the presence of color inhibitors in some of the female germplasms evaluated in this work may be affecting the expression of the markers. It was possible to identify haploid inducers with statistically superior performance. There was no interaction between inducers and the environments tested in this work. The maternal haploid inducers HIND 2 (X1-B1/G3-64) and HIND 4 (M4-B3/G3-64) presented haploid induction rates over 8%. In the present evaluation the highest induction rates were obtained in Balcarce environment (13.8 %). The environmental condition in which pollination takes place is a source of variability that must be taken into consideration while developing the in vivo haploid induction technique. This maize haploid in vivo process produces c.a. 10 haploids to be doubled per 100 kernels obtained in the crossing between the inducers and the female parents. This efficiency rate is large enough for a direct application in commercial maize breeding programs.

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In field experiments, thresholds, spray timings, and bollworm oviposition were conducted to evaluate the current recommended action thresholds for bollworm (Lepidoptera: Noctuidae) in cotton. Based on studies conducted evaluating thresholds, insecticide applications varied across Bt technologies. Bollgard 3 required less sprays when compared to Bollgard II and non-Bt. A second experiment highlighted the importance of timely insecticide applications for managing bollworm populations in Bollgard II cotton based on insect damage. The highest yields were associated with insecticide applications made during the timeframe that cotton is the most susceptible to bollworm damage. The last experiment was conducted to determine if oviposition varied throughout the plant canopy. Oviposition occurred throughout the whole plant, however, the greatest relationship of egg lay was observed in the top three nodes of the plant. From this research, studies would suggest that the current recommended bollworm thresholds in Mississippi cotton production systems, at this time, do not need to be adjusted.

The brown stink bug, Euchistus servus (Say), is a polyphagous pest of multiple cultivated hosts in Virginia. It recently emerged as a potentially devastating pest of maize, Zea mays L. (Poaceae), in eastern Virginia where small grain (e.g., wheat, rye) production is common. In order to develop an integrated pest management (IPM) plan, research is needed to determine if brown stink bug feeding causes economic damage in maize at different growth stages and levels of infestations. Experiments were conducted in 2018 and 2019 to determine: 1) effectiveness of seed applied and in-furrow chemical control methods, 2) infestation levels in seedling and reproductive growth stages that cause economic damage, and 3) the effect, if any, of E. servus feeding on grain quality and mycotoxin contamination. Results of these experiments demonstrated that infestation levels (i.e., number of bugs divided by number of plants) of 11% and 15% in seedling and late vegetative maize, respectively, can cause measurable yield reduction at harvest. Seedling damage from E. servus is significantly mitigated by neonicotinoid seed treatments which are applied to nearly all commercial maize seed. Further, experiments indicated that maize quality can be affected by E. servus feeding in late reproductive stages of development. Results of these experiments will help to inform Virginia maize producers of the need to manage E. servus throughout the growing season. / Master of Science in Life Sciences / The brown stink bug, Euschistus servus, has emerged as a potential economic pest of maize (commonly referred to as "corn" or "field corn") in Virginia following reduced broad-spectrum insecticide use and increased adoption of no-tillage or reduced-tillage crop production systems. Stink bug infestations in maize frequently occur at two times in the growing season: following cover crop termination and following small grain harvest. We need to determine the effects of brown stink bug infestations on maize yield and quality, as well as the effectiveness of chemical management options, to help minimize yield losses and input costs for maize producers in our region. Experiments were conducted to determine: 1) the control provided by insecticidal seed treatments and in-furrow insecticide applications, 2) the level of brown stink bug infestations that cause economic damage at different growth stages of maize, and 3) the effect of brown stink bug feeding and a Fusarium fungal pathogen on grain yield and quality. Results of these experiments determined economic injury levels in seedling corn and late vegetative stages. Additionally, we found that universally applied neonicotinoid seed treatments mitigated early damage. Further, stink bug feeding through reproductive stages of development can reduce grain quality. Our results will help Virginia maize producers to make informed pest management decisions throughout the season.

La variation quantitative résulte de l’action combinée des gènes et de leur environnement. Pour comprendre la relation génotype-phénotype et disséquer l’architecture des caractères complexes, deux approches sont couramment employées. D’une part l’évolution expérimentale qui permet de quantifier le nombre et l’effet des mutations dans la construction d’un phénotype soumis à une pression de sélection, d’autre part la cartographie de QTL (Quantitative Trait Loci) et/ou la génétique d’association qui permettent d’identifier les locus responsables de la variation phénotypique. Au cours de cette thèse, nous avons combiné l’ensemble de ces approches pour (1) évaluer le rôle relatif des nouvelles mutations et de la variabilité résiduelle dans la réponse à la sélection ; (2) identifier les déterminants génétiques sous tendant cette réponse ; (3) disséquer, pour un locus candidat, les mécanismes génétiques de sa contribution à la variation phénotypique. Pour cela, nous disposons d’un matériel génétique résultant d’une expérience de sélection divergente pour la date de floraison menée depuis plus de dix ans. Cette expérience a été conduite en parallèle à partir de deux lots de semences de lignées commerciales de maïs (F252 et MBS847). Pour chaque lignée de départ, deux populations ont été constituées, une population précoce et une population tardive produites en sélectionnant et autofécondant les génotypes les plus précoces/tardifs à chaque génération. Nous avons caractérisé la réponse à la sélection après 7 générations. Cette réponse est rapide, asymétrique entre populations et significative dans 3 des 4 populations. Elle est linéaire avec le temps ce qui indique que des nouvelles mutations contribuent à créer de la variance génétique à chaque génération. Nous avons identifié un locus majeur contribuant à 35% de la variation pour la date de floraison dans la population F252 tardive et pour lequel les deux allèles étaient présents dans le lot de semence initial sous forme d’hétérozygotie résiduelle. Les deux allèles présentent des haplotypes très divergents autant au niveau de leur variation nucléotidique (5.7%) que d’un point de vue structural (16 indels) sur une région proche du gène eIF-4A (Eukaryotic Initiation Translation Factor 4A). L’association de ce locus avec la date de floraison et d’autres caractères corrélés tels que la hauteur et le nombre de feuilles a été confirmée par une caractérisation développementale fine de génotypes précoces et tardifs et également dans un panel d’association comprenant 317 lignées de maïs cultivé. En plus d’un effet pléiotrope, nous avons montré grâce au développement de méthodes statistiques que ce locus présente des interactions épistatique fortes avec d’autres locus en ségrégation puisque son effet dépend largement du fond génétique. Nous avons finalement utilisé des AFLP (Amplified Fragment Length Polymorphisms) sur tous les génotypes issus des 7 premières générations de sélection afin d’identifier d’autres polymorphismes potentiellement impliqués dans la réponse à la sélection. Nos résultats préliminaires montrent une différenciation génétique et épigénétique entre les populations sélectionnées qui semble être préférentiellement due à de l’hétérozygotie résiduelle. / Quantitative variation results from the combined action of multiple genes and their environment. Two approaches are currently employed to gain insights into the link between genotype and phenotype and to dissect the genetic architecture of complex traits. On one hand, experimental evolution allows quantifying the number of mutations and their effect on the evolution of a phenotype subject to artificial selection. On the other hand, QTL (Quantitative Trait Locus) and association mapping are used to identify loci responsible for phenotypic variation. In this work, we have combined all 3 approaches in order to (1) evaluate the role of new mutations and standing genetic variation to the response to selection ; (2) to identify the genetic determinants underlying this response ; (3) to dissect at one candidate locus the genetic mechanisms of its contribution to phenotypic variation. We have used the material produced by a divergent selection experiment for flowering time conducted for over 10 years in the field. This experiment was conducted in parallel from two commercial maize inbred line, F252 and MBS847. From each initial seed lot, two populations, an early population and a late population, were created by selecting and selfing the earliest/latest individuals at each generation. We characterized the response to selection after 7 generations. The response was fast, asymmetric between populations and significant in 3 out of 4 populations. It was linear through time indicating that new mutations have generated new additive genetic variance at each generation. We identified a major locus contributing to 35% of the variation for flowering time in the late F252 population. At this locus, two alleles were present as residual heterozygocity in the initial seed lot. The two alleles exhibited haplotypes extending on a region around the eIF-4A (Eukaryotic Initiation Translation Factor 4A) that diverged drastically both at the nucleotide (5.7%) and structural level. We were able to confirm the association of the candidate locus to flowering time variation and other traits such as height and leaf number, first using an association panel containing 317 maize lines, second through the developmental characterization of early and late genotypes. In addition, to its pleiotropic effect, we have shown by developing a specific statistical framework that this locus exhibit pervasive epistatic interactions with other loci segregating in the population. Hence, its effect largely depended on the genetic background. We have finally applied methyl-sensitive AFLP (Amplified Frgament length Polymorphisms) to screen all genotypes in order to identify the polymorphisms potentially involved in the response to selection during the first 7 generations Our preliminary results indicate both a genetic and epigenetic differentiation between early and late populations. This differentiation seems however to be mainly driven by standing genetic variation.

O transporte de água nas plantas é um processo complexo e que envolve a passagem por membranas celulares. Nelas existem aquaporinas, proteínas integrais de membrana, que facilitam o fluxo passivo de água e pequenos solutos. Um fator importante que influencia o transporte de água nas plantas é a condutância hidráulica radicular (LPr), que pode contribuir com até 50% de toda a resistência ao fluxo de água na planta. Várias metodologias são propostas para estimar a LPr, porém os dados obtidos são altamente variáveis, ainda que para a mesma espécie vegetal. Diante do exposto, pretende-se desenvolver e propor uma nova metodologia, o sistema hidráulico de sucção para estimativa da LPr e avaliar a contribuição das aquaporinas no transporte de água radicular em plântulas de milho. O sistema hidráulico de sucção foi construído no Laboratório de Estudos de Plantas sob Estresse (LEPSE/USP) em parceria com Laboritoire d\'Ecophysiologie des Plants sous Stress Environnementaux de Montpellier, França. Os experimentos foram conduzidos no LEPSE, onde as plântulas cresceram em hidroponia na casa de vegetação. Para avaliação da atividade de aquaporinas foi utilizado o tratamento com peróxido de hidrogênio, que em concentrações milimolares inibe os canais de água. As medidas de condutância foram realizadas sempre na mesma hora do dia, uma vez que a própria LPr e as aquaporinas apresentam ritmo circadiano. Houve redução de 53% da condutância no tratamento com peróxido em relação ao controle e correlação significativa entre a LPr e o pH, de modo que o aumento do pH provocou queda de LPr, provavelmente causada por alterações na abundância e/ou atividade de aquaporinas nas raízes de milho. Esses resultados permitem afirmar que o método de sucção foi eficaz na estimativa da condutância hidráulica, podendo ser adotado como técnica alternativa na estimativa da LPr em plantas. / The water transport in plants is a complex process which involves passage through cell membranes. In them there are aquaporins, integral membrane proteins, that facilitate passive flux of water and small solutes. An important factor influencing the water transport in plants is root hydraulic conductance (LPr), which can contribute up to 50% of the water flow resistance in the plant. Various methods are proposed for estimating LPr, but the data are highly variable, even for the same plant species. Therefore, we intend to develop and propose a new methodology, the hydraulic suction system to estimate LPr and evaluate the contribution of aquaporins in root water transport in maize seedlings. The hydraulic suction system was built at the Laboratório de Estudos de Plantas sob Estresse (LEPSE / USP) in partnership with Laboritoire d\'Ecophysiologie Plants des sous Stress Environnementaux Montpellier, France. The experiments were conducted in LEPSE where the seedlings grew in the hydroponics greenhouse. To evaluate the activity of aquaporins was used treatment with hydrogen peroxide, which in millimolar concentrations inhibits water channels. The conductance measurements were performed at the same time of day, since the LPr itself and aquaporins presents the circadian rhythm. There was a 53% reduction in conductance peroxide treatment compared to control and significant correlation between LPr and pH, so that the pH increase caused a drop LPr probably caused by alterations in the abundance and/or activity of aquaporins in maize roots. These results indicate that the suction method was efficient in estimated hydraulic conductance, may be adopted as an alternative technique to estimate the LPr in plants.