Made available in DSpace on 2014-06-11T19:25:18Z (GMT). No. of bitstreams: 0 Previous issue date: 2004-06-30Bitstream added on 2014-06-13T18:26:14Z : No. of bitstreams: 1 souza_vp_me_jabo.pdf: 172982 bytes, checksum: 387d5e08d4531f6eb3f646c6fefcc7b5 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / O trabalho teve como objetivos determinar a flutuação populacional de formas aladas e ápteras de Myzus persicae (Sulzer, 1776), Brevicoryne brassicae (Linnaeus, 1758) e Lipaphis erysimi (Kaltenbach, 1843) e avaliar a influência de inimigos naturais, de fatores meteorológicos e a distribuição vertical dos pulgões em couve, Brassica oleracea L. var. acephala DC., em Jaboticabal, SP. A amostragem de formas aladas e ápteras dos pulgões foi efetuada com armadilhas amarelas com água e coleta direta na parte aérea, enquanto os inimigos naturais foram averiguados por procura visual na parte aérea da couve e armadilhas de solo. As formas aladas dos pulgões começaram colonizar a couve em meados de maio, quando prevalesceram temperatura média de 22,6ºC, umidade relativa de 68,5% e ausência de precipitação pluviométrica. A colonização da couve por ápteros de L. erysimi iniciou-se quatro dias após a chegada dos indivíduos alados, para B. brassicae e M. persicae esse intervalo foi de 9 dias e 30 dias, respectivamente. As populações mais elevadas dos pulgões ocorreram na couve de julho a setembro, com os pulgões apresentando baixa atividade durante o verão e outono. Os ápteros de M. persicae predominaram nas folhas medianas da couve, o mesmo acontecendo com B. brassicae nas folhas apicais e L. erysimi nas basais. As aranhas, Cycloneda sanguinea (Linnaeus, 1775), Lebia concinna Brullé, 1837 e Diaeretiella rapae (Mc'Intosh, 1855) foram os inimigos naturais com maior potencial para controlarem as populações dos pulgões. A umidade relativa do ar foi o principal fator meteorológico a atuar sobre alados e ápteros dos pulgões, com a densidade populacional desses insetos diminuindo com o incremento da umidade. / The objectives of this work were to determine the populational fluctuations of alate and apterous Myzus persicae (Sulzer, 1776), Brevicoryne brassicae (Linnaeus, 1758) and Lipaphis erysimi (Kaltenbach, 1843), and to evaluate the influence of natural enemies, meteorological factors and the within-plant distributions of aphids in kale, Brassica oleracea L. var. acephala DC., cultivated in Jaboticabal, São Paulo State. Alate and apterous aphids were sampled by yellow traps of water and visual search, while natural enemies were checked by visual search of the aerial parts of kale and pitfall traps. The alate aphids began to colonize the kale crop in mid May, when prevailed medium temperature of 22.6ºC, relative humidity of 68.5% and absence of rainfall. Apterous L. erysimi began to colonize the kale crop four days after the arrival of first alate individuals, while for B. brassicae and M. persicae that interval were 9 days and 30 days, respectively. The highest populations of the aphids in the crop were observed from July to September, and they showed low activity during the summer and fall. Apterous M. persicae prevailed on the middle leaves of kale, the same were observed for B. brassicae and L. erysimi on top and basal leaves, respectively. The natural enemies that showed the greatest potential to regulate the aphid populations were: spiders, Cycloneda sanguinea (Linnaeus, 1775), Lebia concinna Brullé, 1837 and Diaeretiella rapae (Mc'Intosh, 1855). The relative humidity of the air was the major meteorological factor to act on alate and apterous aphids, the population density of them decreased with the increment of that humidity.

Submitted by (edna.saturno@ufrpe.br) on 2016-12-01T11:48:33Z No. of bitstreams: 1 Wellington Marques da Silva.pdf: 630452 bytes, checksum: 904c28cfeb3a339b22c1154ed6411677 (MD5) / Made available in DSpace on 2016-12-01T11:48:33Z (GMT). No. of bitstreams: 1 Wellington Marques da Silva.pdf: 630452 bytes, checksum: 904c28cfeb3a339b22c1154ed6411677 (MD5) Previous issue date: 2011-02-01 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Plutella xylostella (L.) is one of the major pests of Brassica crops. The infestations in cultivated areas of Pernambuco and other states in Brazil have led farmers to frequently spray insecticides. The evolution of insecticide resistance can be pointed as one of the main problems in the control of this pest. This resistance may be associated with the target site alteration, particularly to pyrethroids. Aside from that, other resistance factors may also be related to inefficacy of products such as behavior, where the resistant individuals are able to avoid exposure to areas where the insecticide is present. This research objective was to verify whether a relationship exists between the frequency of the L1014F mutation in the sodium channel and the deltamethrin resistance ratios in populations of P. xylostella, as well as whether they have the ability to avoid exposure to this insecticide. P. xylostella populations were collected in the Agreste region of Pernambuco and Rio Grande do Sul States. Deltamethrin resistance ratios of P. xylostella field populations were compared with a laboratory population. Mortality data were subject to Probit analysis. The populations of P. xylostella showed a variable response and significant resistance to deltamethrin. The Belo Jardim, PE population showed the highest resistance ratio (10 - times) compared with the laboratory population. It was observed an increase of the RR genotype for L1014F mutation as the resistance increased. P. xylostella larvae were exposed to deltamethrin at field rate concentration (7.5 mg/L) and at their CL99s previously determined from bioassays, and their walking behavior evaluated by the Viewpoint® tracking system. The populations of Belo Jardim, PE and Bezerros, PE showed irritability behavior across all of the walking behavioral parameters analyzed. / Plutella xylostella (L.) é uma das principais pragas das culturas de Brassica. A infestações em áreas de cultivo de Pernambuco e outros estados do Brasil levaram os agricultores a pulverização de inseticidas com frequência. A evolução da resistência a inseticidas pode ser apontada como um dos principais problemas no controle desta praga. Esta resistência pode estar associada com a alteração do sítio alvo, especialmente para os piretróides. Além de que, outros fatores de resistência podem também estar relacionados com a ineficiência deste produto, tais como comportamento, onde os indivíduos resistentes são capazes de evitar a exposição a áreas onde o inseticida está presente. O objetivo dessa pesquisa foi verificar se existe relação entre a frequência da mutação L1014F nos canais de sódio e as razões de resistência a deltametrina em populações de P. xylostella, se elas possuem a capacidade de evitar a exposição a este inseticida. P. xylostella foram coletadas na região Agreste de Pernambuco e Rio Grande do Sul. As razões de resistência a deltametrina das populações de campo de P. xylostella foram comparados com a população de laboratório. Os dados de mortalidade foram submetidos à análise de Probit. As populações de P. xylostella mostraram uma variável resposta e resistência significativa à deltametrina. A população Belo Jardim, PE mostrou maior índice de resistência (10 - vezes) comparados com a população de laboratório. Foi observado um aumento do genótipo RR para a mutação L1014F como o aumento da resistência. As larvas de P. xylostella foram expostos a deltametrina na concentração de campo de (7,5 mg / L), e na sua CL99s previamente determinada a partir de bioensaios, o comportamento de caminhamento foi avaliado pelo sistema de rastreamento Viewpoint® tracking system. As populações de Belo Jardim, PE e Bezerros, PE apresentaram comportamento irritabilidade em todos os dos parâmetros comportamentais analisados.

To determine the optimum nitrogen application level required for the production of good quality ‘Drumhead’ cabbage (Brassica oleracea var. capitata) transplants, a glasshouse experiment was conducted. Depending on water requirements, transplants were fertigated every two days (for the first four weeks) and every day (for the last two weeks) by floating trays in plastic tubs containing nutrient solution at 0, 30, 60, 90 and 120 mg•L-1 N until field capacity was reached. Increasing nitrogen from 0 to 120 mg•L-1 increased shoot and root mass of cabbage transplants with more dry mass being partitioned to the shoot than to the roots. Nitrogen at 120 mg•L-1 N produced greatest fresh and dry shoot mass, plant height, leaf area, leaf tissue nitrogen, net assimilation rate, relative growth rate and leaf mass ratio. Nitrogen at 90 mg•L-1 improved dry root mass, pulling success, specific leaf area and leaf area ratio. Greatest values of root: shoot ratio and root mass ratio were obtained at 0 mg•L-1 N. Nitrogen at 90 mg•L-1 was best as it produced transplants with more vigorous root growth which pulled out easily from the seedling trays. To determine the best combination of spacing and nitrogen top-dressing for improved cabbage production under local conditions, a field experiment was conducted. Cabbage ‘Copenhagen Market’ transplants were spaced at 30 x 50 cm, 40 x 50 cm or 50 x 50 cm and fertilized with nitrogen as top-dressing at 50, 100 or 150 kg•ha-1 N applied in two splits (fourth and eighth week after transplanting). There were no interactions between spacing and nitrogen top-dressing for all measured variables. Nitrogen and spacing did not influence dry matter production and leaf tissue nitrogen. Furthermore, spacing did not affect core height and yield (per unit area) of trimmed cabbage heads. Nitrogen at 100 kg•ha-1 produced the greatest head mass and yield for untrimmed cabbage heads. The 30 x 50 cm spacing produced the highest yield of untrimmed heads while 50 x 50 cm spacing produced heavier heads. For trimmed heads, 100 kg•ha-1 N again produced the greatest head mass, head diameter, head height, core diameter and yield. Spacing did not affect the yield for trimmed heads. However, 40 x 50 cm spacing improved head diameter, head height and head mass while core diameter was larger with 50 x 50 cm spacing. The split application of 100 kg•ha-1 N as top-dressing was best for head mass and yield (per unit area) for trimmed and untrimmed heads. Choice of spacing would depend on whether trimmed or untrimmed heads are targeted. / Dissertation (M Inst Agrar (Horticulture))--University of Pretoria, 2005. / Plant Production and Soil Science / unrestricted

Submitted by Nathália Faria da Silva (nathaliafsilva.ufv@gmail.com) on 2017-07-14T14:22:16Z No. of bitstreams: 1 texto completo.PDF: 505026 bytes, checksum: f472695b009916c9bc17613b60e07be7 (MD5) / Made available in DSpace on 2017-07-14T14:22:16Z (GMT). No. of bitstreams: 1 texto completo.PDF: 505026 bytes, checksum: f472695b009916c9bc17613b60e07be7 (MD5) Previous issue date: 2001-03-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O presente trabalho teve por finalidade caracterizar os efeitos da temperatura e da modificação da atmosfera sobre a conservação de couve minimamente processada, visando selecionar uma combinação adequada de embalagem e atmosfera modificada, para a conservação prolongada do produto. Em couve minimamente processada em um sistema experimental aberto, com fluxo de ar contínuo, um acréscimo de 10°C causou uma elevação da taxa respiratória de duas a duas vezes e meia, na faixa de 5 a 20°C. A redução da concentração de oxigênio resultou na diminuição da taxa respiratória em até quatro vezes, sem que fosse atingido o seu ponto de compensação anaeróbica. A exposição por 24 h à falta de oxigênio, à temperatura ambiente, reduziu a taxa respiratória em 26 vezes. Avaliou-se o efeito de 16 diferentes combinações embalagem x misturas gasosas, sobre a concentração de sólidos minimamente processada, solúveis totais armazenada e a de o C, 5 vitamina C durante 14 de couve dias de armazenamento. Embalagens com permeabilidade a oxigênio inferior a 8.500 cm³ .m^-2 .dia^-1 , não foram eficientes na conservação da couve minimamente processada, a 5°C, e a injeção de gases nas embalagens acelerou a deterioração do produto. Dentre as 16 combinações testadas, selecionaram - se as duas mais eficazes: poliolefina multicamadas (permeabilidade a O2 = 9.745 cm³ .m^-2 .dia^-1), com modificação ativa da atmosfera (0% de O2/ 5% de CO2) e com modificação passiva da atmosfera. No sistema de poliolefina multicamadas com modificação ativa de atmosfera, a injeção de gases inibiu a respiração e a produção de etileno sob as duas temperaturas de armazenamento testadas. Tais fatos não se reverteram em maior manutenção do teor de vitamina C e aceitação do consumidor, em relação a mesma embalagem com a modificação passiva de atmosfera. Os dois sistemas de modificação da atmosfera também não produziram resultados estatisticamente diferentes em relação à concentração de sólidos solúveis totais, textura e cor. / The present work evaluated the effects of packaging and modified atmosphere on the conservation of fresh cut collard greens, stored at 5 and 10°C. The effects of temperature, oxygen concentration and prolonged exposition under the absence of oxygen on the respiratory rate of the fresh cut collard greens were determined in an experimental open flow through system. An increase of 10°C in the storage temperature resulted in a 2.4 fold increase in the respiratory rate. The reduction in oxygen concentration resulted in a four fold decrease in the respiratory rate, even though the anaerobic compensation point were not attained. Fresh cut collard greens maintained for 24 h in the system without O2 resulted in a 26 fold decrease in the respiratory rate. Fresh cut collard greens stored at 5 °C in sixteen different combinations of package and gaseous mixtures, for 14 days, were evaluated for total soluble solids and vitamin C concentration during the storage period. In these experiments, it was observed that packages, with permeability rate to oxygen lower than 8,500 cm³ .m^-2 .day-^1, were not efficient for the conservation of the fresh cut collard greens at 5°C, and that injection of gases in theses packages accelerated the product deterioration. Of these 16 combinations, the most efficient ones were: multilayer polyolephinic (oxygen permeability rate = cm³ .m^-2 .day^-1) with active modified 9,745 atmosphere (0% O2/ 5% CO2) and with passive modified atmosphere. The two systems were submitted to new tests showing that although the injection of gases inhibited respiration and ethylene production in storage at 5 and 10 °C, these facts did not result in delayed conservation of vitamin C levels or in quality maintenance of and improved consumer's acceptance, as compared with the same packaging with the passive modified atmosphere.

No description available.

Entre todas las especies de brasicáceas, la de mayor importancia es Brassica napus L. (colza), que se destaca por su elevada participación en la producción mundial de aceites comestibles. Muchas especies de brasicáceas, cultivadas y silvestres, no sólo tienen importancia en la alimentación humana, sino que han sido mencionadas como fuentes de polen y néctar. Es decir, que el solo hecho de formar parte de la comunidad vegetal aumenta las posibilidades de alimento para un gran número de polinizadores y visitantes florales. La presencia de visitantes florales de brasicáceas en el centro-sur de la Provincia de Buenos Aires (República Argentina) fue evaluada en parcelas de colza y en parches de brasicáceas espontáneas ubicados en la localidad de Tres Arroyos, en la Chacra Experimental Integrada Barrow (-38.319305, - 60.239380). Para realizar los muestreos se utilizaron redes entomológicas, trampas de agua de colores y el método de observación directa. Además, con el objetivo de determinar el efecto de los polinizadores sobre el rendimiento y sus componentes, en las parcelas de colza se colocaron jaulas excluidoras de polinizadores. Otra parte del trabajo se realizó en dependencias del Departamento de Agronomía de la Universidad Nacional del Sur con el fin de evaluar la germinabilidad in vitro del polen expuesto a condiciones ambientales de la colmena. Para esto, se seleccionaron colmenas de Apis mellifera L. y se colocaron en su interior muestras de polen de colza que se obtuvieron de plantas cultivadas en macetas de 10 litros. En la zona de estudio se comprobó que numerosas especies de insectos, de diversas familias y órdenes, visitaron el cultivo de colza al igual que los parches de especies espontáneas. Todas las especies capturadas se encontraron tanto en el cultivo como en las malezas aledañas. Esto indica que los polinizadores utilizan ambos recursos. Las zonas con vegetación espontánea aledañas a las parcelas de colza presentaron una floración más extensa, brindando recursos a los visitantes florales antes, durante y después de la floración del cultivo. Los resultados de este trabajo muestran que la visita de insectos polinizadores en el cultivo de colza mejora la producción de semilla y esto se traduce en un mayor rendimiento, que es, en definitiva, el objetivo de todo productor. También se demostró que el aumento de rendimiento de semilla tuvo implicancia directa sobre la producción de aceite por hectárea, dado que la visita de los polinizadores mejoró la cantidad de semilla y no generó variaciones significativas en el tenor de materia grasa. Por otro lado, se demostró que las condiciones ambientales dentro de la colmena de Apis mellifera son adversas para la germinabilidad de los granos de polen de colza, independientemente de las condiciones ambientales externas. Las zonas de cría son las de mayor temperatura y en 24 h no se registraron granos de polen con capacidad de germinar. A partir de las 48 h la capacidad de germinabilidad del polen disminuyó significativamente y el bajo porcentaje que germinó presentó tubos completamente atrofiados. Aunque el polen que se ubicó alejado de las zonas de cría mantuvo más tiempo su capacidad de germinar, sólo lo hizo por menos de 72 h. Los resultados de este trabajo respaldan una reducción sustancial del tiempo de carencia que exigen las empresas semilleras y abren la posibilidad de que se utilice una misma colmena en dos servicios de polinización consecutivos sin riesgo de contaminación por polen no deseado. / Among all the species of brassicas, the most important one is Brassica napus L. (rapeseed), which stands out for its significant contribution to the global production of edible oils. Many species of brassicas, both cultivated and wild, are not only important for human consumption but have also been mentioned as sources of pollen and nectar. In other words, simply being part of the plant community increases the food possibilities for a large number of pollinators and floral visitors. The presence of brassica floral visitors in the central-southern region of Buenos Aires Province (Argentina) was evaluated in rapeseed plots and patches of spontaneous brassica plants located in Tres Arroyos, at the Chacra Experimental Integrada Barrow (- 38.319305, -60.239380). Entomological nets, colored water traps, and direct observation methods were used for sampling. Additionally, exclusion cages were placed in the rapeseed plots to determine the effect of pollinators on yield and its components. Another part of the study was conducted at the Department of Agronomy, Universidad Nacional del Sur, to assess the in vitro germinability of pollen exposed to hive environmental conditions. Honey bee (Apis mellifera L.) colonies were selected, and samples of rapeseed pollen obtained from plants cultivated in 10-liter pots were placed inside the hives. The study in the area confirmed that numerous insect species from different families and orders visited both the rapeseed crop and the patches of spontaneous species. All captured species were found in both the crop and the surrounding weeds, indicating that pollinators utilize both resources. The areas with spontaneous vegetation adjacent to the rapeseed plots exhibited more extensive flowering, providing resources for floral visitors before, during, and after the crop's flowering period. The results of this study demonstrate that the visitation of pollinating insects in the rapeseed crop improves seed production, ultimately resulting in higher yields, which is the goal of every farmer. It was also shown that the increased seed yield directly impacted oil production per hectare, as pollinator visitation improved seed quantity without generating significant variations in fat content. On the other hand, it was demonstrated that the environmental conditions within the Apis mellifera hive are unfavorable for the germinability of rapeseed pollen grains, regardless of external environmental conditions. The brood areas have the highest temperatures, and within 24 hours, no pollen grains capable of germinating were recorded. From 48 hours onward, the germination capacity of the pollen significantly decreased, and the low percentage that did germinate exhibited completely atrophied tubes. Although pollen placed away from the brood areas maintained its germination capacity for a longer period, it did so for less than 72 hours. The results of this study support a substantial reduction in the required waiting time demanded by seed companies and open up the possibility of using the same hive for two consecutive pollination services without the risk of contamination by undesired pollen.

京都大学 / 新制・課程博士 / 博士(農学) / 甲第24653号 / 農博第2536号 / 新制||農||1097(附属図書館) / 学位論文||R5||N5434(農学部図書室) / 京都大学大学院農学研究科農学専攻 / (主査)教授 土井 元章, 教授 田尾 龍太郎, 教授 那須田 周平 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

The objectives of this research were: 1) to quantify the amount of supplemental nitrogen (N) to maximize organic broccoli (Brassica olearcea var. italica) on transition soils, 2) to evaluate the ability of leguminous cover crops lablab (Dolichos lablab L.), soybean (Glycine max L.), sunn hemp (Crotalria juncea L.) and a sunn hemp and cowpea mixture (Vigna sinensis Endl.) to supply N and suppress weeds and, 3) to compare the effect on N availability and broccoli yield potential of incorporating cover crops with conventional tillage (CT) or mulching cover crops with no-tillage (NT) practices. Broccoli was grown during the third year of organic transition in the spring and fall of 2006 at the Kentland Agricultural Research Farm in Blacksburg, VA. Supplemental N significantly increased broccoli yield up until 112 kg ha-1 with a quadratic correlation with leaf N. The NT treatment yielded no difference during the spring, but in the fall CT surpassed NT. On the other hand, N uptake, measured by leaf N, under NT conditions increased with supplemental N, which suggests NT has equivalent yield potential as CT when N is not limiting. Yields from leguminous residues did not differ, even though quality and quantity of cover crop biomass did. This suggests that N availability from cover crop legumes may be impacted other ecological process such as soil microbial activity. Also, cover crop residues differed in their ability to suppress weeds. The results from this study give organic growers in transition tools to maximize productivity and sustainability. / Master of Science

Leptosphaeria maculans, agent de la nécrose du collet des crucifères, est un agent pathogène majeur du colza (Brassica napus). La lutte génétique est aujourd’hui le procédé le plus utilisé afin de protéger les cultures des attaques de ce champignon. Cette méthode se base principalement sur l’utilisation de cultivars possédant des gènes de résistance spécifique (Rlm) qui permettent le déclenchement des réactions de défense de la plante parla reconnaissance directe ou indirecte des produits des gènes d’avirulence correspondants (AvrLm) présents dans la population pathogène. Plusieurs de ces résistances ont déjà été massivement déployées en France et dans le monde, connaissant dans un premier temps un fort succès commercial grâce à la protection fournie, suivie d’une perte d’efficacité très rapide. Avant cette thèse, le nombre d’études au champ des processus impliqués dans le contournement d’un gène de résistance était très limité, en particulier chez les champignons. L’objectif de cette thèse était d'étudier l’évolution moléculaire du gène d’avirulence AvrLm4-7sous pression de sélection, en profitant de son clonage et de la commercialisation récente de cultivars Rlm7, afin d’obtenir une étude précoce et détaillée des mécanismes moléculaires à l’origine du contournement d’une résistance spécifique. Le gène AvrLm4-7 présente l’originalité de coder pour une protéine responsable d’une double spécificité d’interaction vis-à-vis des gènes Rlm4 et Rlm7. Dans un premier temps, j’ai pu valider par mutagenèse dirigée le rôle primordial de l’acide aminé 120 dont la mutation affecte la reconnaissance d’AvrLm4 par Rlm4 sans toutefois altérer la reconnaissance d’AvrLm7 par Rlm7.Le contournement de la résistance Rlm7 a été ensuite analysé à l’aide d’une importante collection de souches prélevée sur deux sites expérimentaux indépendants (Grignon ; Versailles) sur une période de trois ans. Sur le premier site était cultivée une variété Rlm7 en monoculture avec un travail du sol simplifié tandis que sur le second site, le mode de culture incluait rotation culturale et enfouissement par labour des résidus de cultures. Il a ensuite été montré que, au contraire de la reconnaissance AvrLm4/Rlm4, un grand nombre d’évènements de mutation peuvent être à l’origine de la virulence d’une souche vis-à-vis de Rlm7. L’analyse moléculaire des souches virulentes et avirulentes de cette collection a ainsi permis de répertorier sept catégories d’évènements de mutation. La grande majorité des cas concerne la délétion d’AvrLm4-7 mais des mutations dues au RIP et plusieurs autres évènements de mutation provoquant l’introduction prématurée de codons stop dans la séquence codante du gène sont aussi observés. La majorité de ces évènements de mutation sont liés à la reproduction sexuée du champignon et ont lieu au sein même de la parcelle d’étude. Le phénotypage de cette collection a par ailleurs révélé un fort contraste entre les deux sites expérimentaux, démontrant ainsi l’importance des pratiques culturales dans le maintien de l’efficacité de la résistance Rlm7 dans le temps. En effet, après trois années de culture de cultivars Rlm7, la fréquence des souches virulentes a7 dans les populations du site de Versailles reste inférieure à 1 % contre environ 30 % sur le site de Grignon. Finalement, le phénotypage de la collection de souches a également montré que le contournement de Rlm7 s’accompagnait dans plus de 98% des souches de la résurgence de l’avirulence AvrLm3. Par l’étude de cette collection et par croisements génétiques, j’ai pu montrer que AvrLm3 n’était pas un nouvel allèle d’avrLm4-7 mais un second gène situé en région télomérique à 19.3 cM d’AvrLm4-7. J’ai également démontré une interaction fonctionnelle antagoniste entre AvrLm4-7 et AvrLm3 qui empêche la reconnaissance Rlm3 /AvrLm3 en présence d’AvrLm4-7 et explique la restauration de l’avirulence AvrLm3 lors de la perte de l’avirulence AvrLm7.Par une association originale de biologie moléculaire, de génétique des populations et d’agronomie, j’ai ainsi pu apporter une nouvelle illustration à la course aux armements entre un agent pathogène et sa plante hôte, les gènes AvrLm3 et AvrLm4-7 utilisant deux stratégies distinctes afin d’échapper à la reconnaissance de leurs gènes de résistance spécifiques. / Leptosphaeria maculans is a filamentous ascomycete causing stem canker of oilseed rape (Brassica napus). This disease is often controlled by the use of B. napus cultivars harbouring major resistance genes (Rlm). Direct or indirect recognition of the corresponding avirulence protein (AvrLm) in the pathogen triggers plant defence reactions. Several resistances have been massively deployed in France and worldwide, they initially showed commercial success due to the protection provided and in a second time, a very fast decrease of efficiency (resistance breakdown).Prior to this thesis, field studies of resistance gene breakdown mechanisms were rare, especially for fungi. The purpose of this PhD thesis was to study the molecular evolution of the avirulence gene AvrLm4-7 under selection pressure, by exploiting our knowledge of the gene, and the recent release of Rlm7 cultivars, to obtain an early and detailed study of the molecular mechanisms involved in a resistance gene breakdown. AvrLm4-7 induces resistance responses in plant harbouring either Rlm4 or Rlm7 and I validated by targeted point mutagenesis the central role of the amino acid 120 in the avrLm4-7-Rlm4 interaction. Its mutation prevents AvrLm4-7 recognition by Rlm4 without affecting avrLm4-7-Rlm7 recognition.Loss of avirulence towards Rlm7 was then studied by the analysis of an important isolate collection originating from two independent French experimental fields (Grignon; Versailles) over three years. In the first field was cropped Rlm7 cultivars in monoculture with low tillage agronomical practices whereas crop rotation and ploughing were done in the second field. In contrast to AvrLm4-Rlm4 evolution, a great number of mutations were found to explain the “gain” of virulence towards Rlm7. Seven mutational event categories were found. The great majority of these categories involve AvrLm4-7 deletion but mutation due to RIP and several other mutational events causing premature apparition of stop codons in the coding sequence of the gene were observed too. The majority of these events are linked to the sexual reproduction of the fungus and occurs in the experimental field.In addition, our work showed the importance of the cultural practices in preserving Rlm7 efficacy. Indeed, after three years using Rlm7 cultivars, a7 frequency was below 1% whereas representing around 30% of the isolates observed in Grignon.Finally, phenotyping of the isolate collection also showed the resurgence of an A3 phenotype linked with the loss of AvrLm7 avirulence in more than 98% of the isolates. Genetic analysis and collection phenotyping showed that AvrLm3 is not a new AvrLm4-7 allele but a distinct gene located in a telomeric region at 19.3 cM of AvrLm4-7. I also demonstrated that an antagonistic interaction between AvrLm4-7 and AvrLm3 exists: the presence of Avrlm4-7 prevents Rlm3 to detect AvrLm3 and explains the surge of the AvrLm3 avirulence along with the loss of the AvrLm7 avirulence.By an original association of molecular biology, population genetic and agronomy, this work provided a new illustration of the plant-pathogen arms race, AvrLm3 and AvrLm4-7 using two different strategies to escape their respective resistance genes.

The objective of this study was to evaluate the influence of biofortification with selenium in the bioactive compounds of broccoli; to test their toxicity and mutagenicity in vivo to prove their safety for consumption; to develop microparticles by the spray dryer technique and to evaluate its physicochemical properties. The broccoli seedlings were biofortified through the addition of 2 mL of 50 μM sodium selenate solution 15 days after sowing (DAS), and collected 30 DAS. The samples were analyzed by different methods for the quantification of selenium (ICP-MS, benchtop and handheld EDXRF). The energy-dispersive X-ray fluorescence spectrometry made either in bench or in a portable equipment presented a good performance for the quantification of selenium, together with low cost and less analysis time. The selenium biofortification technique increased the concentration of this micronutrient in broccoli seedlings. In addition, it also allowed a significant increase in bioactive compounds, such as chlorophyll (12%), phenolic (26%) and flavonoid (19%) compounds, vitamin C (32%) and sulforaphane (12%), the main bioactive compound with anticarcinogenic potential. The efficiency of biofortification with selenium in the culture was verified, and toxicity and mutagenicity studies were conducted in female and male mice treated with different doses of selenium-biofortified broccoli seedlings. After 40 consecutive days of treatment, broccoli seedlings with selenium at doses of 45 and 70 μg Se/kg body weight resulted in significant changes in the relative weights of vital (liver, spleen and kidneys) and reproductive organs (ovary/testis), with the presence of histological alterations in the kidneys and spleen in mice of both sexes. In male mice, the dose of 70 μg Se/kg body weight increased the frequency of micronucleated polychromatic erythrocytes. In females this increase was not observed, demonstrating greater sensitivity of males to the treatment. Finally, microparticles of ethanolic extracts of broccoli seedlings with and without selenium were developed through the spray drying microencapsulation technique. The samples presented low moisture (4-5%) and hygroscopicity (11-12 g of water absorbed 100/g of microparticle) and high solubility (99%). However, there was a significant reduction in the content of phenolic compounds and antioxidant activity after the microencapsulation process. The results of this study demonstrate the importance of biofortification of selenium as a strategy to increase the content of bioactive compounds in broccoli and that the dose of 15 μg Se/kg body weight had no significant toxic or mutagenic effects. In addition, microencapsulation has been shown to allow the elaboration of samples with good technological characteristics however, optimization studies should be conducted to increase the retention power of bioactive compounds and their antioxidant activity. / Os objetivos desse estudo foram avaliar a influência da biofortificação com selênio nos compostos bioativos de brócolis; testar sua toxicidade e mutagenicidade in vivo como forma de comprovar sua segurança para consumo; desenvolver micropartículas pela técnica de spray dryer e avaliar suas propriedades físico-químicas. As mudas de brócolis foram biofortificadas pela adição de 2 mL de solução de 50 μM de selenato de sódio 15 dias de após a semeadura (DAS) e coletadas aos 30 DAS. As amostras foram analisadas por diferentes métodos para a quantificação de selênio (ICP-MS, XRF portátio e EDXRF de bancada). O método de fluorescência de Raios X por dispersão em energia feito em equipamentos de bancada ou portátil apresentou desempenho adequado para quantificação de selênio aliado à baixo custo e menor tempo de análise. A técnica de biofortificação com selênio aumentou a concentração desse micronutriente nas mudas de brócolis. Além disso, também proporcionou aumento significativo nos compostos bioativos, tais como, clorofila (12%), compostos fenólicos (26%) e flavonoides (19%), vitamina C (32%) e sulforafano (12%), principal composto bioativo com potencial anticarcinogênico do brócolis. Verificada a eficiência da biofortificação com selênio, conduziu-se estudos de toxicidade e mutagenicidade em camundongos fêmeas e machos tratados com diferentes doses de mudas de brócolis biofortificadas com selênio (15, 45 e 70 μg Se/kg peso corporal). Após 40 dias consecutivos de tratamento, observou-se que os animais tratados com mudas de brócolis com selênio nas doses de 45 e 70 μg Se/kg peso corporal provocaram significativas alterações nos pesos relativos dos órgãos vitais (fígado, baço e rins) e reprodutivos (ovário/testículos), com presença de alterações histológicas nos rins e no baço, em camundongos de ambos os sexos. Nos camundongos machos, a dose de 70 μg Se/kg peso corporal provocou aumento da frequência de eritrócitos policromáticos micronucleados. Nas fêmeas este aumento não foi observado, demonstrando maior sensibilidade dos machos ao tratamento. Por fim, através da técnica de microencapsulação por spray dryer desenvolveu-se micropartículas a base de extratos etanólicos de mudas de brócolis com e sem selênio. As amostras apresentaram baixa umidade (4-5%) e higroscopicidade (11-12 g de água absorvida 100-1 g de micropartícula) e alta solubilidade (99%). No entanto, houve uma redução significativa no teor de compostos fenólicos e atividade antioxidante após o processo. Os resultados desse estudo demonstram a importância da biofortificação do selênio como uma estratégia para aumentar o teor de compostos bioativos no brócolis. Com relação à toxicidade, a dose de 15 μg Se/kg peso corporal não apresentou efeitos tóxicos significativos em machos e fêmeas, porém apresentou pontencial mutagênico em machos. Além disso, comprovou-se que a microencapsulação possibilitou a elaboração de amostras com boas características tecnológicas, porém, estudos de otimização devem ser conduzidos a fim de aumentar o poder de retenção dos compostos bioativos e atividade antioxidante.