The effects of diurnal temperature fluctuation and the utility of degree days for modeling clubroot on canola (Brassica napus L.) caused by Plasmodiophora brassicae Woronin were assessed using microscopy and qPCR, and in field trials. Temperature fluctuation had little effect on pathogen development. The optimal temperature for root hair infection was 25° C. Air and soil degree days and rainfall were used as metrics for estimating clubroot development, with only limited success. Several cultivars of cabbage (Brassica oleracea L. var. capitata) with unknown clubroot resistance mechanism(s) were assessed using staining and microscopy, and qPCR. In field trials, ‘Bronco’ was susceptible to clubroot (100 DSI), ‘Kilaherb’ was resistant (0 DSI), and ‘B-2819’ was intermediate (53 DSI). Plasmodiophora brassicae was present in cortical tissue of all cultivars. A delayed disease phenotype in ‘B-2819’ may indicate a quantitative resistance genotype that could be exploited in research on resistance genes and breeding.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2005. / Härtill 5 uppsatser.

Winter oilseed rape (Brassica napus) is an important crop in the Czech Republic. Clubroot disease caused by the pathogen Plasmodiophora brassicae Wor. is a serious and still-growing problem for oilseed rape growers. Research on P. brassicae in the Czech Republic is therefore important for the development of effective strategies to manage clubroot under Czech environmental conditions. One of the aims of this study was monitoring of this pathogen. The disease was previously widespread in commercial vegetable production and in hobby gardens. Since 2010, oilseed rape clubroot started to spread across the whole country, whereas it had previously only been observed in the northeast. Clubroot occurrence was monitored for five years by the Union of Oilseed Growers and Processors on the basis of disease symptoms present on oilseed rape fields. The presence of P. brassicae and clubroot symptoms were reported in all regions of the Czech Republic, except the Ústecký Region, and in 31 out of 76 districts. At present, at least 130 fields are known to be infested by the pathogen, but this number is very likely underestimated. Some soil samples were also tested by conventional PCR (polymerase chain reaction) to evaluate the possibility of their usage. All 14 suspected samples tested positive by PCR. The next aim was to evaluate the pathotype composition of P. brassicae populations from the Czech Republic, according to the three evaluation systems, and to determine soil inoculum loads for representative fields via traditional end-point PCR as well as quantitative PCR analysis. There were considerable differences between the populations of P. brassicae, and the number of pathotypes varied depending on the evaluation system and the threshold used to distinguish susceptible vs. resistant plant reactions. This is the first study comparing the effect of different thresholds. Using an index of disease (ID) of 25 % to distinguish susceptible vs. resistants reactions, there was a total of five pathotypes identified based on the differentials of Williams, five with the system of Somé et al., and 10 with the European Clubroot Differential (ECD) set. However, based on a threshold of 50%, there were five pathotypes according to the evaluation system by Williams, four based on the differentials of Somé et al. and 8 with the ECD set. Changing of the thresholds led to the reclassification of some pathotypes. Pathotypes 7 by Williams was the most frequent in both thresholds. High amounts of pathogen DNA were found in many of the field soils analysed by quantitative PCR. Experiments with P. brassicae-resistant cultivars of winter oilseed rape were conducted in an infested field and greenhouse. In the greenhouse, six resistant cultivars were grown in infested soil collected from various fields in the Czech Republic and assessed for index of disease (ID %). The best results bring cultivar Mentor (2+- 0.7 %) closely followed by cultivar SY Alister (5+-1.1 %), the highest ID had cultivar CHW 241 (30+-3.8%). In the field experiment, seven resistant cultivars were grown, and disease development was monitored monthly. The lowest index of disease brought cultivar Andromeda (3+- 0.8 %) and PT 235 (4+-1.5 %), the highest ID has cultivar CWH 241(46 +- 6.5 %) in the first season and in the second season any cultivar achieved 25 % ID. Yields were measured at the end of the cropping season. The highest yield was achieved by cultivar SY Alister (6.1 t/ha) in the first season and cultivar PT 242 (5.03 t/ha) in the second season. The inoculum level was measured across the field by (qPCR), and a map of the infestation was created. The highest spore concentration was found on the field entrance. Collectively, the information obtained on the effectiveness of host resistance and pathogenic diversity of P. brassicae populations from the Czech Republic may help to more effectively manage clubroot in this country.

Submitted by Reginaldo Soares de Freitas (reginaldo.freitas@ufv.br) on 2017-03-17T17:57:14Z No. of bitstreams: 1 texto completo.pdf: 145268 bytes, checksum: 8cd1881bbadc0025cb67425dbdeaed7f (MD5) / Made available in DSpace on 2017-03-17T17:57:14Z (GMT). No. of bitstreams: 1 texto completo.pdf: 145268 bytes, checksum: 8cd1881bbadc0025cb67425dbdeaed7f (MD5) Previous issue date: 2002-08-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O objetivo deste estudo foi avaliar o mecanismo de ação da cobertura morta sobre as populações de Brevicoryne brassicae (Linnaeus 1758) (Homoptera, Aphididae) e de Myzus persicae (Sulzer 1776) (Homoptera, Aphididae), em couve comum “Manteiga da Fazenda” (Brassica oleraceae var. acephala). Foram instalados três experimentos de campo na Horta Velha da Universidade Federal de Viçosa, Minas Gerais, Brasil, com delineamento de cinco blocos ao acaso com dois tratamentos. O primeiro experimento consistiu de dezesseis plantas em cada parcela e os dados foram coletados nas quatro plantas centrais de cada parcela. Cinco folhas/planta foram amostradas, assim como no segundo experimento. No segundo e terceiro experimentos usaram-se quatro plantas, cada uma plantada em vaso de polietileno de quatorze litros. O espaçamento foi de 0,80m x 0,80m entre plantas e 1,20m entre parcelas. Os tratamentos foram: A - cobertura de palha de arroz (1,056Kg Mseca/m2 com uma camada de 10cm) e B – testemunha. No primeiro experimento, as avaliações foram realizadas diariamente no período de 18 de outubro a 1o de novembro de 2001, eliminando-se diariamente os pulgões que chegavam às folhas. A temperatura máxima diária foi medida utilizando-se termômetros max-min. No segundo experimento, as avaliações foram realizadas entre 30 de maio e 13 de junho de 2002. Após os primeiros sete dias foram coletadas duas folhas de cada parcela para análise do teor de nutrientes, tendo os vasos de cada tratamento suas posições trocadas, eliminando-se os afídeos diariamente. No terceiro experimento, utilizou-se uma folha/planta do segundo experimento por parcela, na qual foi inoculado um alado de M. persicae, utilizando-se tela anti-afídica para garantir a permanência do alado inoculado e evitar a chegada de novos alados. A inoculação ocorreu no dia 12 de junho de 2002, permanecendo por um período de 15 dias, para então, efetuar-se a contagem final de alados, ninfas, adultos e colônias. Os resultados mostraram que a cobertura morta atrasou a chegada dos alados de B. brassicae e de M. persicae, aumentou a temperatura nas parcelas e, conseqüentemente, obtiveram-se menores populações de alados dos afídeos. Com a troca de ambiente, ocorreu uma interação significativa com o tratamento e a troca de posição dos vasos, o que implicou em alteração no número de pulgões. A taxa de crescimento da população de M. persicae aumentou significativamente nas parcelas testemunhas se comparada com o tratamento. / The objective of this study was to evaluate the mechanism of the action of rice- straw mulch on the populations of Brevicoryne brassicae (Linnaeus 1758) (Homoptera, Aphididae) and Myzus persicae (Sulzer 1776) (Homoptera, Aphididae), in common kale “Manteiga da Fazenda” (Brassica oleraceae var. acephala). Three field experiments were conducted in the Old Vegetable-Garden of the Federal University of Viçosa, Minas Gerais in a five randomized blocks with two treatments each. The first experiment consisted of sixteen plants in each plot and data were colleted from the four central plants of each plot, sampling five leaves per plant as in the second experiment. The second and third experiments used four plants, each one in a fourteen-liter polyethylene vase. In all experiments the plants were spaced by 0.80 m x 0.80 m between plants and 1.20 m between plots. The treatments were: A – rice- straw mulch (1.056Kg dryM/10 cm layer) and B – control. The first experiment was sampled every day from October 18 to November 1st in 2001 and the aphids were eliminated after each check. The daily maximum temperature was evaluated using a max-min thermometer. The second experiment was sampled from May 30 to June 12 and after first seven days of sampling two leaves of each plot were collected for nutrient content analysis and the vases of both treatments had their position exchanged. The landed aphids were eliminated every day. In the third experiment, one plant of each plot of the second experiment was inoculated with an alate aphid and in order to guarantee its permanence and avoid the landing of other aphids, an anti-aphid gauze was applied on the leaves. The inoculation occurred on June 12 in 2002 and the aphid was left there for fifteen days. After that time, alates, nymphs, adults and colonies were counted. The results showed that the mulch delayed the landing of alates of B. brassicae e M. persicae, elevated the temperature in the plots and consequently, fewer aphid populations occurred. An effective interaction with the treatment occurred when the vases had their position changed, as the number of aphids was also altered. The population growth rate of M. persicae was quite larger in control plots than in mulched plots.

Made available in DSpace on 2014-06-11T19:34:59Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-04-26Bitstream added on 2014-06-13T19:44:45Z : No. of bitstreams: 1 rosa_dd_dr_botfca.pdf: 3769642 bytes, checksum: 6f5fb83fe76a081fea96b890323e30f2 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Dentro do setor de horticultura, as plantas da família Brassicaceae são de grande expressão, tanto em volume, como em valor agregado na comercialização, por isso, destaca-se o cultivo intensivo de brassicas, como as variedades de Brassica oleraceae L. (Couve, repolho, Couve-flor, Brócolos, Couve de Bruxelas), Brassica napus L. e Brassica oleraceae L. var. pekinensis L. (Couve chinesa), sendo a base de sustentação econômica dos pequenos e médios produtores de hortaliças. Como outras culturas de plantio intensivo, as brassicas também enfrentam inúmeros problemas com doenças, dentre estes está a “hérnia das crucíferas”, doença de enorme risco potencial ao produtor, visto seu difícil ou inexistente controle e por condenar a área, impedindo futuros cultivos de brassicas. O agente causal da “hérnia das crucíferas” (Plasmodiophora brassicae Woronin) é um endoparasita obrigatório, pertencente ao reino Protozoa, habitante do solo, sendo um dos fitopatógenos de solo menos estudados no mundo, mas sabe-se que este apresenta raças patogênicas, ou patotipos, sendo que algumas dessas já são conhecidas, principalmente os que ocorrem na Europa e no Japão sabem-se, também, que estas raças “quebram”, com certa freqüência, a pouca resistência que os melhoristas conseguem incorporar nas variedades comerciais, fazendo com que quase não haja variedade resistente disponível no mercado, principalmente ao mercado brasileiro onde, possivelmente, haja raças ainda não relatadas. O objetivo deste estudo visou conhecer a variabilidade genética e patogênica de isolados de P. brassicae oriundos das principais regiões produtoras de Brassicas do estado de São Paulo, utilizando para isso: a) testes em variedade diferenciais, nacionais e importadas, com isolados monospóricos e não monospóricos para determinação das raças; b) estudo da agressividade dos isolados frente... / Within the horticulture sector, the plants of the Brassicaceae family are widespread in both volume and value-added marketing, so we highlight the intensive cultivation of brassicas, such as varieties of Brassica oleracea L. (Kale, cabbage, cauliflower, broccoli, Brussels sprouts), Brassica napus L. and Brassica oleracea L. var. pekinensis L. (Chinese cabbage), and the basis of economic support for small and medium producers of vegetables. Like other intensive planting crops, the brassicas are also facing many problems with diseases, among these is the club root, disease of great potential risk to the producer, because its difficult or no control and order the area, preventing future crops brassicas. The agent causal of the club root (Plasmodiophora brassicae Woronin) is an obligatory endoparasites belonging to the kingdom Protozoa, inhabitant of soil, being one of the pathogens in soil less studied in the world, but it is known that this presents pathogenic races, or pathotypes, and some of these are already known, especially those taking place in Europe and Japan knows it, too, that these races break with some frequency, the little resistance that breeders can incorporate into commercial varieties, making that almost no resistant variety available in the market, especially the Brazilian market where perhaps there is not race related. This study aimed to investigate the genetic variability and pathogenic isolates of P. brassicae come from the main producing regions Brassicas state of Sao Paulo, using for this: a) testing range differential, domestic and imported, with no single spores and spore for the determination of races, b) study of the aggressiveness of the isolates in the face of cultivars available in the market, c) study of genetic variability within and between populations, using markers RAPD and Microsatellite d) genetic characterization through sequencing of genetic regions... (Complete abstract click electronic access below)

Master of Science / Department of Entomology / Brian P. McCornack / Winter canola production in the south-central US is commonly threatened by a complex of aphid species that can cause up to 70% in yield loss. Aphid species vary in their life-history traits, performance (sequestration/excretion of secondary compounds; glucosinolates), vertical distribution within the plant, and temporal dynamics across the growing season. Colonizing behavior of these aphids may be affected by intrinsic characteristics of the host plant (bottom-up effects), such as nutritional value, secondary compounds, or plant architecture. Understanding bottom-up effects may enable the evaluation of plant-level interactions that are influencing predator-prey dynamics. The goal of my research project is to understand aphid population dynamics in different canola plant structures, assess whether aphid quality (sequestration/ excretion of glucosinolates) is influenced by feeding location on the canola plant, and if so, assess the impact on the existing predator communities, specifically the development and fitness of immature and adult Hippodamia convergens. A combination of filed and greenhouse experiments provided novel contributions that will help shape our understanding of key factors regulating aphid population growth in canola fields, which will lead to more judicious use of insecticides and better sampling strategies.

Our earth is currently undergoing unprecedented human induced climate change, which is expected to drive widespread changes in species distributions and abundances that will affect natural pest suppression. Recent studies have suggested that climate change may cause changes to predator and herbivore assemblages in ways that alter multi-trophic food webs and affect the stability of ecosystems. Moreover, higher temperatures and increased climatic variability are expected to induce differential responses from predators and their prey that will undoubtedly disrupt species interactions. This thesis aims to test how climate change will impact the ability of natural enemies to continue to control pests in agroecosystems, and how they will continue to survive and function. In a field experiment using 13 farm sites across a natural temperature gradient, I found that temperature had direct positive effects on the abundances of the dominant parasitoid (an aphid specialist) and hyperparasitoid species, highlighting the importance of specific species responses in shaping larger communities. I also found that overall community composition was affected by temperature, with composition in warmer sites changing more throughout the season than cooler sites. In a future of inevitable climatic changes this result tells us we can expect arthropod community structure to change, which will have questionable impacts on overall population dynamics. To build on the field experiments, I used laboratory experiments to test differential responses of species to both drought and temperature and found that natural enemies responded to drought and temperature in a non-additive way, suggesting that the interaction between various climate change drivers is more important than their singular effect. Also, different species of natural enemies responded differently to abiotic factors, highlighting the importance of conserving natural enemies that can maintain important functional attributes in the face of climate change. Although biodiversity can be important for ensuring ecosystem functioning, response diversity, rather than species richness, may better promote ecosystem resilience, especially in the face of changing climate. The mechanisms underlying biodiversity effects are often difficult to disentangle, however, by manipulating the diversity of climate responses exhibited by ecosystem service providers, I tested how the rates and stability of prey suppression by predators are affected by climate warming and drought. I found that predator combinations with different individual responses to climate change maintained greater and less variable (i.e. more stable) prey suppression, compared with single predator species or combinations of predators with similar climate responses. This response complementarity became strongest through time and under drought or high temperature treatments. I suggest that response complementarity provides ‘insurance’ effects, which may be more important than previously envisaged for maintaining ecosystem functions such as biological control under global environmental change. Overall, the non-additive effects of different climate drivers, combined with differing responses across trophic levels, suggests that predicting future pest outbreaks will be more challenging than previously imagined.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv. / Härtill 5 uppsatser.

Orientador: Edson Luiz Furtado / Banca: Marli Teixeira de Almeida Minhoni / Banca: Cesar Junior Bueno / Banca: Juliana Cristina Sodário Cruz / Banca: Kátia Regiane Brunelli / Resumo: Dentro do setor de horticultura, as plantas da família Brassicaceae são de grande expressão, tanto em volume, como em valor agregado na comercialização, por isso, destaca-se o cultivo intensivo de brassicas, como as variedades de Brassica oleraceae L. (Couve, repolho, Couve-flor, Brócolos, Couve de Bruxelas), Brassica napus L. e Brassica oleraceae L. var. pekinensis L. (Couve chinesa), sendo a base de sustentação econômica dos pequenos e médios produtores de hortaliças. Como outras culturas de plantio intensivo, as brassicas também enfrentam inúmeros problemas com doenças, dentre estes está a "hérnia das crucíferas", doença de enorme risco potencial ao produtor, visto seu difícil ou inexistente controle e por condenar a área, impedindo futuros cultivos de brassicas. O agente causal da "hérnia das crucíferas" (Plasmodiophora brassicae Woronin) é um endoparasita obrigatório, pertencente ao reino Protozoa, habitante do solo, sendo um dos fitopatógenos de solo menos estudados no mundo, mas sabe-se que este apresenta raças patogênicas, ou patotipos, sendo que algumas dessas já são conhecidas, principalmente os que ocorrem na Europa e no Japão sabem-se, também, que estas raças "quebram", com certa freqüência, a pouca resistência que os melhoristas conseguem incorporar nas variedades comerciais, fazendo com que quase não haja variedade resistente disponível no mercado, principalmente ao mercado brasileiro onde, possivelmente, haja raças ainda não relatadas. O objetivo deste estudo visou conhecer a variabilidade genética e patogênica de isolados de P. brassicae oriundos das principais regiões produtoras de Brassicas do estado de São Paulo, utilizando para isso: a) testes em variedade diferenciais, nacionais e importadas, com isolados monospóricos e não monospóricos para determinação das raças; b) estudo da agressividade dos isolados frente... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Within the horticulture sector, the plants of the Brassicaceae family are widespread in both volume and value-added marketing, so we highlight the intensive cultivation of brassicas, such as varieties of Brassica oleracea L. (Kale, cabbage, cauliflower, broccoli, Brussels sprouts), Brassica napus L. and Brassica oleracea L. var. pekinensis L. (Chinese cabbage), and the basis of economic support for small and medium producers of vegetables. Like other intensive planting crops, the brassicas are also facing many problems with diseases, among these is the club root, disease of great potential risk to the producer, because its difficult or no control and order the area, preventing future crops brassicas. The agent causal of the club root (Plasmodiophora brassicae Woronin) is an obligatory endoparasites belonging to the kingdom Protozoa, inhabitant of soil, being one of the pathogens in soil less studied in the world, but it is known that this presents pathogenic races, or pathotypes, and some of these are already known, especially those taking place in Europe and Japan knows it, too, that these races "break" with some frequency, the little resistance that breeders can incorporate into commercial varieties, making that almost no resistant variety available in the market, especially the Brazilian market where perhaps there is not race related. This study aimed to investigate the genetic variability and pathogenic isolates of P. brassicae come from the main producing regions Brassicas state of Sao Paulo, using for this: a) testing range differential, domestic and imported, with no single spores and spore for the determination of races, b) study of the aggressiveness of the isolates in the face of cultivars available in the market, c) study of genetic variability within and between populations, using markers RAPD and Microsatellite d) genetic characterization through sequencing of genetic regions... (Complete abstract click electronic access below) / Doutor

Downy mildew has been a potentially devastating constraint to crop production within the Brassicaceae family worldwide (CABI, 2022) and on the Central Coast of California (Smukler, et al, 2008; Koike, et al. 2007). Downy mildew is a foliar disease, caused by the pathogens in the Hyaloperonospora genus on plants within the Brassicaceae family (Goker, et al, 2009). Downy mildew is a disease that is common in region of the world with Coastal climates that provide humidity and moderate temperatures (Sarahan, et al, 2017). Crops within the Brassicaceae family maintain a predominant role in agricultural systems worldwide (Cartea, et al, 2011) and on the Central Coast of California, in Monterey, San Luis Obispo, Santa Cruz, San Benito, and Ventura Counties (Hidalgo, et al, 2022; Settevendemie, et al, 2022; Sanford, et al, 2022; Griffin, et al, 2022; Chang, et al, 2022; Williams, et al, 2022). The crop production within the Brassicaceae family includes broccoli, cabbage, and cauliflower, and the spring mix production of wild arugula, cultivated arugula, and baby kale. In the first study, an in-lab screening of wild arugula (Diplotaxis tenuifolia) for downy mildew resistance was conducted to identify accessions that contain potential resources of resistance to Hyaloperonospora diplotaxidis. The germplasm of 199 wild arugula accessions was grown out under greenhouse conditions and inoculated with a v single isolate of H. diplotaxidis. A subset of 40 accessions of wild arugula were further inoculated with an additional three isolates of H. diplotaxidis and the ten most resistant accessions were selected for further inoculations. The inoculations of the final subset of ten accessions with the same three isolates were replicated an additional two times. When a factorial ANOVA was conducted to test the interaction between the isolate and accession used, it was found that the impact of the accession on disease incidence was independent from the isolate (P=0.993). Three accessions, 185, 79, and 17 were identified as a potential source of resistance to the isolates utilized in this study, for maintaining a disease incidence below 1%. To compare the results found in the in-lab resistance screening, a field trial was conducted with a subset of wild arugula accessions with diverse reactions to downy mildew. When a regression was conducted comparing the disease incidence under field and lab conditions, the R2 value was found to be 0.37. A second study was conducted to characterize the genetic, morphological, and host range diversity of downy mildew causing pathogens in the Hyaloperonospora genus of hosts in the Brassicaceae family. An isolate collection of approximately 40 isolates of Hyaloperonospora spp. was established and the phylogenetic relationships of these isolates were analyzed by creating two phylogenetic trees using their cox2 mtDNA and ITS rDNA sequences. The H. brassicae and H. diplotaxidis isolates from this study formed separate monophyletic groups in both the cox2 mtDNA and ITS rDNA phylogenetic analyses. When the host range of H. brassicae and H. diplotaxidis were characterized by inoculating a genetically and morphologically diverse set of four host plant species, the H. brassicae and H. diplotaxidis were found to have distinct host ranges. The H. brassicae isolate was found to be parasitic of all B. oleracea morphotypes including broccoli, cabbage, kale, kohlrabi, and ornamental cabbage. The H. diplotaxidis isolate was found to only be parasitic on wild arugula, not cultivated arugula, wild mustard, or any of the B. oleracea morphotypes. The difference between sporangia of H. brassicae and H. diplotaxidis were found to be statistically significant, where the sporangia of H. brassicae were nearly circular and the sporangia of H. diplotaxidis were closer to an oval.