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Clubroot (casual agent Plasmodiophora brassicae Woronin,) is a major disease of crucifers, liming is the traditionally applied control method. This project aimed to identify effects of calcium and pH, in isolation, on host invasion and pathogen development. Nitrogen and boron were investigated as potential control agents in order to develop an integrated nutrient control treatment effective at high inoculum pressures. Chinese cabbage seedlings Brassica oleracea ssp. pekinensis cv. Granaat,) were grown in acid washed sand or peat: sand composts containing various concentrations of nutrients and P. brassicae propagules. pH was varied and concentrations of calcium, nitrogen and boron were raised for specific periods of the host parasite cycle. Assessments of infection number and sporogenesis in the root hair were made 10-16 days after inoculation. Clubbing symptoms, host dry weights and mineral contents of root and leat tissue were assessed at 30 days. Infection was reduced by separate increases of pH to 7.2 and calcium to 55mel-1. Sporogenesis of root hair infections was inhibited by pH 7.2, 55mel-1 calcium and 6.4ppm boron. Suppression of clubbing by pH 7.2, 55mel-1 calcium and 60mel-1 nitrate was effected 0-14 days after inoculation, applications of such inhibitory treatments later than 14 days were ineffective. In contrast 6.4ppm boron applied over 0-14 and 14-30 day periods actively reduced clubbing. Nitrate, boron pH treatments controlling clubroot were non-phytotoxic. Control due to pH7.2 may in part be attributed to enhanced uptake of calcium into host plants at higher pH. Suppressive nutrients applied at pH7.2 and calcium applied with boron showed synergistically enhanced control of clubroot when compared with single treatments. A non-phytotoxic nutrient containing intermediate levels of calcium (30mel-1), nitrate (30mel-1) and boron (6.4ppm) at pH7.2 reduced disease index from 100% to 3% in plants subject to heavy inoculum pressures. An integrated control treatment for clubroot was thus demonstrated.

La recombinaison méiotique via les Crossing-Overs (COs) est le principal mécanisme permettant le brassage de la diversité génétique. Cependant, le nombre et la position des COs entre paires de chromosomes homologues sont strictement régulés, limitant la séparation des loci en sélection variétale. Dans le cas du colza B. napus, l’utilisation d’allotriploïdes (AAC, 2n=3x=29), issus du croisement entre le colza (AACC, 2n=4x=38) et l’un de ses progéniteurs B. rapa (AA, 2n=2x=20), permet d’augmenter considérablement le nombre de COs entre chromosomes homologues A. L’objectif de cette étude était de déterminer les conséquences d’une telle variation sur la distribution des COs le long des chromosomes ainsi que d’identifier des facteurs régulant ce phénomène. Suite à la production et à la caractérisation cytogénétiques d’hybrides F1 présentant différents caryotypes, la recombinaison homologue a été évaluée par des analyses génétiques via des marqueurs SNPs physiquement ancrés sur l’ensemble duNous avons montré que l’addition du génome C chez les allotriploïdes conduit toujours à (1) la formation de COs surnuméraires, dont le nombre varie fonction des méioses mâle/femelle et du fond génétique, (2) une modification des profils de recombinaison, notamment au voisinage des centromères, et (3) une réduction de l’intensité d’interférence. De plus, nous avons révélé que le contrôle génétique de ces variations est imputé à des chromosomes C spécifiques et aurait divergé dans un contexte polyploïde. Nous avons donc identifié un levier permettant d’optimiser le brassage de la diversité gén / Meiotic recombination via crossovers (COs) is the main mechanism responsible for mixing genetic diversity. However, the number and position of COs between the pairs of homologous chromosomes are strictly regulated, limiting the loci separation in plant breeding. In the case of the rapeseed B. napus, the use of allotriploids (AAC, 2n=3x=29), resulting from the cross between rapeseed (AACC, 2n=4x=38) and one of its progenitors B. rapa (AA, 2n=2x=20), allows a substantial increase of the number of COs between homologous A chromosomes. The objective of this study was to determine the consequences of such a variation on the distribution of COs along the chromosomes and to identify factors regulating this phenomenon. Following the production and cytogenetic characterization of F1 hybrids with different karyotypes, homologous recombination was assessed by genetic analyzes via SNPs markers physically anchored on the whole A genome.We showed that the additional C genome in allotriploids always leads to (1) the formation of extra COs, for which the number depends on the male/female meiosis and the genetic background, (2) the modification of the recombination landscapes, especially in the vicinity of centromeres, and (3) the decrease of CO interference. In addition, we revealed that the genetic control of these variations is assigned to specific C chromosomes and could have evolved in a polyploid context. We have therefore identified a way to optimize the shuffling of genetic diversity in rapeseed breeding.

Made available in DSpace on 2015-03-26T13:37:43Z (GMT). No. of bitstreams: 1 texto completo.pdf: 2701343 bytes, checksum: b9c5cc5b07f66e4816776e04f12b0511 (MD5) Previous issue date: 2010-08-27 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Considering the importance of Meloidogyne enterolobii (= M. mayaguensis) to the culture of guava and the potential of Essential Oil of Mustard (EOM) on nematode control, was aimed to evaluate the efficiency of EOM on control of these nematodes in the field, on a orchard of plants uprooted and cut off at 0.3 m from soil level or in intact plants in production. An orchard of guava trees naturally infested with M. enterolobii, in Viçosa, MG, was selected. EOM was applied on soil at 100 μg/mL, by strips of cardboard in the rhizosphere of intact plants, or by irrigating the cultivation area with EOM diluted in water after the plants have been cut off or uprooted. Samples were collected over 140 days after the product application and evaluated on the number of J2 in soil and number of galls and eggs in roots of tomato plants in the bioassay. The J2 population in soil underwent rapid reduction, regardless of treatment, and was configured as an unreliable variable. By the bioassay, was obtained a reduction of 71%, 81% and 99% for number of galls and 60%, 80% and 83% for number of eggs at 45, 75 and 140 days after application, respectively, for plots treated with EOM, in uprooted or cutted plants. The terbuphos only reduced the number of galls during 45 days. The biological evaluation at 140 days revealed a general trend of population reduction, considering the number of galls and eggs. In intact plants, there was no control of nematodes, as the average variations of J2, galls and eggs did not differ significantly between treatments. In conclusion, the EOM was effective in controlling M. enterolobii at the field in the absence of the host. / Considerando a importância de Meloidogyne enterolobii (= M. mayaguensis) para a cultura da goiabeira e o potencial do óleo essencial de mostarda (OEM) no controle de nematoides, objetivou-se avaliar a eficiência do OEM no controle do nematoide no campo, em pomares de plantas arrancadas, recepadas ou em produção. Selecionou-se um pomar de goiabeiras naturalmente infestado por M. enterolobii, em Viçosa, MG. O OEM foi aplicado no solo a 100 μg/mL, por meio de tiras de papelão na rizosfera de plantas intactas ou irrigando a área de cultivo com OEM diluído em água, após as plantas serem recepadas ou arrancadas. Em amostras coletadas ao longo de 140 dias após aplicação do produto, avaliou-se o número de J2 no solo e número de galhas e ovos em raízes de tomateiros, no teste biológico. Como a população de J2 no solo sofreu rápida redução, independente do tratamento, ela foi considerada uma variável pouco confiável para a avaliação. Pelo teste biológico, obteve-se uma redução de 71%, 81% e 99% para número de galhas e 60%, 80% e 83% para número de ovos aos 45, 75 e 140 dias após a aplicação, respectivamente, para as parcelas tratadas com OEM, em plantas arrancadas ou recepadas. O terbufós reduziu apenas o número de galhas aos 45 dias, o qual voltou a aumentar posteriormente. Aos 140 dias, houve tendência generalizada de redução da população, considerando-se o número de galhas e ovos. Nas plantas intactas não houve controle do nematoide, pois as médias das variações de J2, galhas e ovos não diferiram significativamente entre os tratamentos. Em conclusão, o OEM foi eficiente em controlar M. enterolobii no campo na ausência do hospedeiro.

Studies were conducted to determine basic aspects of intake and digestion of native pastures by young sheep in the Falkland Islands, and to evaluate practical methods to improve the productivity of these animals. The studies were conducted in support of Industry and Government initiatives to reinvigorate Falklands’ agriculture. The current industry is based on broad diameter wools harvested from sheep grazing poor quality native pastures, and sheep suffer low growth rates, poor productivity and high mortality, and farmers rely on small flocks to produce a single commodity for their total income. The dramatic collapse of wool markets in the 1980’s crippled the Falklands’ wool industry and farmers have relied heavily on subsidies for more than 12 years. The studies in this thesis were initiated to support the efforts to reinvigorate Falklands’ agriculture, and they examined basic aspects of the nutrition provided to sheep by native pastures and evaluated practical methods to improve the survival of sheep, their subsequent rate of growth and productive value to the economy. Five studies examined specific hypotheses posed at the outset of the research programme and they were broadly supported by the data presented in the thesis: · A wether trial was used to benchmark the productivity of wool sheep in the Islands, and the trial demonstrated that substantial genetic variation exists within the national flock that may be exploited in the future to improve the productivity of the wool industry, · Microhistological techniques were used in conjunction with n-alkane marker technology to investigate the diets consumed by sheep grazing native pastures. The diet studies concluded that the low quality of native pasture in the Falklands during autumn, winter and spring restricts growth and productivity of young sheep, · Studies with weaner sheep treated with controlled release anthelmintics established that infection with gastrointestinal nematodes exacerbates poor nutrition of young sheep consuming native pastures, · A short-term metabolism study demonstrated that native pasture hay fortified with molasses and urea, or winter forage crops may be used as supplements to enhance sheep productivity, and · Forage crops were grown and evaluated under Falklands’ conditions, and when lambs were fed the resulting highly productive and nutritious forages, the study demonstrated that lamb growth can be increased significantly, and lamb carcasses offer local farmers the potential to diversify farm income by using existing Falklands’-bred lambs to develop an export meat industry The data presented in this thesis demonstrate that the potential to improve the productive and financial position of Falklands’ farmers is substantial. If both the local Industry and Government maintain their joint commitment to industry-restructure, pastoral development and enterprise diversification, the Falklands’ agricultural economy stands to benefit considerably by adopting low risk solutions to address widespread problems.

Studies were conducted to determine basic aspects of intake and digestion of native pastures by young sheep in the Falkland Islands, and to evaluate practical methods to improve the productivity of these animals. The studies were conducted in support of Industry and Government initiatives to reinvigorate Falklands’ agriculture. The current industry is based on broad diameter wools harvested from sheep grazing poor quality native pastures, and sheep suffer low growth rates, poor productivity and high mortality, and farmers rely on small flocks to produce a single commodity for their total income. The dramatic collapse of wool markets in the 1980’s crippled the Falklands’ wool industry and farmers have relied heavily on subsidies for more than 12 years. The studies in this thesis were initiated to support the efforts to reinvigorate Falklands’ agriculture, and they examined basic aspects of the nutrition provided to sheep by native pastures and evaluated practical methods to improve the survival of sheep, their subsequent rate of growth and productive value to the economy. Five studies examined specific hypotheses posed at the outset of the research programme and they were broadly supported by the data presented in the thesis: · A wether trial was used to benchmark the productivity of wool sheep in the Islands, and the trial demonstrated that substantial genetic variation exists within the national flock that may be exploited in the future to improve the productivity of the wool industry, · Microhistological techniques were used in conjunction with n-alkane marker technology to investigate the diets consumed by sheep grazing native pastures. The diet studies concluded that the low quality of native pasture in the Falklands during autumn, winter and spring restricts growth and productivity of young sheep, · Studies with weaner sheep treated with controlled release anthelmintics established that infection with gastrointestinal nematodes exacerbates poor nutrition of young sheep consuming native pastures, · A short-term metabolism study demonstrated that native pasture hay fortified with molasses and urea, or winter forage crops may be used as supplements to enhance sheep productivity, and · Forage crops were grown and evaluated under Falklands’ conditions, and when lambs were fed the resulting highly productive and nutritious forages, the study demonstrated that lamb growth can be increased significantly, and lamb carcasses offer local farmers the potential to diversify farm income by using existing Falklands’-bred lambs to develop an export meat industry The data presented in this thesis demonstrate that the potential to improve the productive and financial position of Falklands’ farmers is substantial. If both the local Industry and Government maintain their joint commitment to industry-restructure, pastoral development and enterprise diversification, the Falklands’ agricultural economy stands to benefit considerably by adopting low risk solutions to address widespread problems.

Studies were conducted to determine basic aspects of intake and digestion of native pastures by young sheep in the Falkland Islands, and to evaluate practical methods to improve the productivity of these animals. The studies were conducted in support of Industry and Government initiatives to reinvigorate Falklands’ agriculture. The current industry is based on broad diameter wools harvested from sheep grazing poor quality native pastures, and sheep suffer low growth rates, poor productivity and high mortality, and farmers rely on small flocks to produce a single commodity for their total income. The dramatic collapse of wool markets in the 1980’s crippled the Falklands’ wool industry and farmers have relied heavily on subsidies for more than 12 years. The studies in this thesis were initiated to support the efforts to reinvigorate Falklands’ agriculture, and they examined basic aspects of the nutrition provided to sheep by native pastures and evaluated practical methods to improve the survival of sheep, their subsequent rate of growth and productive value to the economy. Five studies examined specific hypotheses posed at the outset of the research programme and they were broadly supported by the data presented in the thesis: · A wether trial was used to benchmark the productivity of wool sheep in the Islands, and the trial demonstrated that substantial genetic variation exists within the national flock that may be exploited in the future to improve the productivity of the wool industry, · Microhistological techniques were used in conjunction with n-alkane marker technology to investigate the diets consumed by sheep grazing native pastures. The diet studies concluded that the low quality of native pasture in the Falklands during autumn, winter and spring restricts growth and productivity of young sheep, · Studies with weaner sheep treated with controlled release anthelmintics established that infection with gastrointestinal nematodes exacerbates poor nutrition of young sheep consuming native pastures, · A short-term metabolism study demonstrated that native pasture hay fortified with molasses and urea, or winter forage crops may be used as supplements to enhance sheep productivity, and · Forage crops were grown and evaluated under Falklands’ conditions, and when lambs were fed the resulting highly productive and nutritious forages, the study demonstrated that lamb growth can be increased significantly, and lamb carcasses offer local farmers the potential to diversify farm income by using existing Falklands’-bred lambs to develop an export meat industry The data presented in this thesis demonstrate that the potential to improve the productive and financial position of Falklands’ farmers is substantial. If both the local Industry and Government maintain their joint commitment to industry-restructure, pastoral development and enterprise diversification, the Falklands’ agricultural economy stands to benefit considerably by adopting low risk solutions to address widespread problems.

Studies were conducted to determine basic aspects of intake and digestion of native pastures by young sheep in the Falkland Islands, and to evaluate practical methods to improve the productivity of these animals. The studies were conducted in support of Industry and Government initiatives to reinvigorate Falklands’ agriculture. The current industry is based on broad diameter wools harvested from sheep grazing poor quality native pastures, and sheep suffer low growth rates, poor productivity and high mortality, and farmers rely on small flocks to produce a single commodity for their total income. The dramatic collapse of wool markets in the 1980’s crippled the Falklands’ wool industry and farmers have relied heavily on subsidies for more than 12 years. The studies in this thesis were initiated to support the efforts to reinvigorate Falklands’ agriculture, and they examined basic aspects of the nutrition provided to sheep by native pastures and evaluated practical methods to improve the survival of sheep, their subsequent rate of growth and productive value to the economy. Five studies examined specific hypotheses posed at the outset of the research programme and they were broadly supported by the data presented in the thesis: · A wether trial was used to benchmark the productivity of wool sheep in the Islands, and the trial demonstrated that substantial genetic variation exists within the national flock that may be exploited in the future to improve the productivity of the wool industry, · Microhistological techniques were used in conjunction with n-alkane marker technology to investigate the diets consumed by sheep grazing native pastures. The diet studies concluded that the low quality of native pasture in the Falklands during autumn, winter and spring restricts growth and productivity of young sheep, · Studies with weaner sheep treated with controlled release anthelmintics established that infection with gastrointestinal nematodes exacerbates poor nutrition of young sheep consuming native pastures, · A short-term metabolism study demonstrated that native pasture hay fortified with molasses and urea, or winter forage crops may be used as supplements to enhance sheep productivity, and · Forage crops were grown and evaluated under Falklands’ conditions, and when lambs were fed the resulting highly productive and nutritious forages, the study demonstrated that lamb growth can be increased significantly, and lamb carcasses offer local farmers the potential to diversify farm income by using existing Falklands’-bred lambs to develop an export meat industry The data presented in this thesis demonstrate that the potential to improve the productive and financial position of Falklands’ farmers is substantial. If both the local Industry and Government maintain their joint commitment to industry-restructure, pastoral development and enterprise diversification, the Falklands’ agricultural economy stands to benefit considerably by adopting low risk solutions to address widespread problems.

Studies were conducted to determine basic aspects of intake and digestion of native pastures by young sheep in the Falkland Islands, and to evaluate practical methods to improve the productivity of these animals. The studies were conducted in support of Industry and Government initiatives to reinvigorate Falklands’ agriculture. The current industry is based on broad diameter wools harvested from sheep grazing poor quality native pastures, and sheep suffer low growth rates, poor productivity and high mortality, and farmers rely on small flocks to produce a single commodity for their total income. The dramatic collapse of wool markets in the 1980’s crippled the Falklands’ wool industry and farmers have relied heavily on subsidies for more than 12 years. The studies in this thesis were initiated to support the efforts to reinvigorate Falklands’ agriculture, and they examined basic aspects of the nutrition provided to sheep by native pastures and evaluated practical methods to improve the survival of sheep, their subsequent rate of growth and productive value to the economy. Five studies examined specific hypotheses posed at the outset of the research programme and they were broadly supported by the data presented in the thesis: · A wether trial was used to benchmark the productivity of wool sheep in the Islands, and the trial demonstrated that substantial genetic variation exists within the national flock that may be exploited in the future to improve the productivity of the wool industry, · Microhistological techniques were used in conjunction with n-alkane marker technology to investigate the diets consumed by sheep grazing native pastures. The diet studies concluded that the low quality of native pasture in the Falklands during autumn, winter and spring restricts growth and productivity of young sheep, · Studies with weaner sheep treated with controlled release anthelmintics established that infection with gastrointestinal nematodes exacerbates poor nutrition of young sheep consuming native pastures, · A short-term metabolism study demonstrated that native pasture hay fortified with molasses and urea, or winter forage crops may be used as supplements to enhance sheep productivity, and · Forage crops were grown and evaluated under Falklands’ conditions, and when lambs were fed the resulting highly productive and nutritious forages, the study demonstrated that lamb growth can be increased significantly, and lamb carcasses offer local farmers the potential to diversify farm income by using existing Falklands’-bred lambs to develop an export meat industry The data presented in this thesis demonstrate that the potential to improve the productive and financial position of Falklands’ farmers is substantial. If both the local Industry and Government maintain their joint commitment to industry-restructure, pastoral development and enterprise diversification, the Falklands’ agricultural economy stands to benefit considerably by adopting low risk solutions to address widespread problems.

Studies were conducted to determine basic aspects of intake and digestion of native pastures by young sheep in the Falkland Islands, and to evaluate practical methods to improve the productivity of these animals. The studies were conducted in support of Industry and Government initiatives to reinvigorate Falklands’ agriculture. The current industry is based on broad diameter wools harvested from sheep grazing poor quality native pastures, and sheep suffer low growth rates, poor productivity and high mortality, and farmers rely on small flocks to produce a single commodity for their total income. The dramatic collapse of wool markets in the 1980’s crippled the Falklands’ wool industry and farmers have relied heavily on subsidies for more than 12 years. The studies in this thesis were initiated to support the efforts to reinvigorate Falklands’ agriculture, and they examined basic aspects of the nutrition provided to sheep by native pastures and evaluated practical methods to improve the survival of sheep, their subsequent rate of growth and productive value to the economy. Five studies examined specific hypotheses posed at the outset of the research programme and they were broadly supported by the data presented in the thesis: · A wether trial was used to benchmark the productivity of wool sheep in the Islands, and the trial demonstrated that substantial genetic variation exists within the national flock that may be exploited in the future to improve the productivity of the wool industry, · Microhistological techniques were used in conjunction with n-alkane marker technology to investigate the diets consumed by sheep grazing native pastures. The diet studies concluded that the low quality of native pasture in the Falklands during autumn, winter and spring restricts growth and productivity of young sheep, · Studies with weaner sheep treated with controlled release anthelmintics established that infection with gastrointestinal nematodes exacerbates poor nutrition of young sheep consuming native pastures, · A short-term metabolism study demonstrated that native pasture hay fortified with molasses and urea, or winter forage crops may be used as supplements to enhance sheep productivity, and · Forage crops were grown and evaluated under Falklands’ conditions, and when lambs were fed the resulting highly productive and nutritious forages, the study demonstrated that lamb growth can be increased significantly, and lamb carcasses offer local farmers the potential to diversify farm income by using existing Falklands’-bred lambs to develop an export meat industry The data presented in this thesis demonstrate that the potential to improve the productive and financial position of Falklands’ farmers is substantial. If both the local Industry and Government maintain their joint commitment to industry-restructure, pastoral development and enterprise diversification, the Falklands’ agricultural economy stands to benefit considerably by adopting low risk solutions to address widespread problems.