Apple scab (causal organism: Venturia inaequalis) is an economically devastating disease of apples that is predominantly controlled with fungicides. Of the chemical classes currently available, the sterol-inhibiting (SI) and strobilurin (QoI) fungicides are the most commonly used. Recent observations indicate that V. inaequalis populations in Virginia have developed resistance to myclobutanil and other SIs. However, little is known about the frequency and distribution of SI and QoI resistance in Virginia's scab populations. The first objective of this research was to evaluate V. inaequalis populations in Virginia for SI and QoI resistance. Fungal isolates were collected from experimental orchards at the Alson H. Smith Jr., Agricultural Research and Extension Center (AHS AREC) and from commercial orchards in Virginia and Maryland. Sensitivities were determined by assessing colony growth at 19°C on potato dextrose agar (PDA) amended with 0 or 1.0 µg ml-1 of myclobutanil (SI) (N=87) or trifloxystrobin (QoI) (N=25) at 28 days. A range of fungicide sensitivity was observed for both chemical classes. The second objective of this research was to monitor the temporal dynamics of SI resistance over five sequential field seasons. To monitor shoot growth, neon rubber bands were placed over actively growing shoot tips following myclobutanil application or sample collection. Fungal isolates were collected from the same trees from 2007 through 2010 (N=176) and compared with isolates collected from wild apple seedlings (N=3). A continuum of SI resistance was observed for each year, and the V. inaequalis population exhibited a baseline shifted toward reduced sensitivity. The third objective of this research was to examine the spatial distribution of SI fungicide resistance within the tree canopy in a lower-density orchard (less than 150 trees A-1). Leaves collected from larger trees (>8m) in a lower-density orchard at the AHS AREC were analyzed for manganese deposition, pre- and post-mancozeb application. Fungal isolates (N=105) were collected from several locations within the canopy in replicated trees in the same orchard. Weather sensors also monitored the microclimates within those tree canopies. Spray deposition, microclimate and SI resistance were influenced by canopy location. The fourth objective of this research was to investigate potential SI resistance mechanisms. Previously classified isolates were screened for point mutations within the CYP51A1 gene (Appendix C), differences in polymorphic bands (alleles) (Appendix D), and differences in metabolism of myclobutanil (Appendix E). The consensus sequences for the CYP51A1 gene were identical for all isolates tested (N=9), and results from amplified fragment length polymorphism experiment (N=82) were inconclusive. There were, however, significant differences among incubation time and myclobutanil concentration in the bioassay (N=11). Our results indicate that myclobutanil is still an effective compound for control of apple scab in many areas of Virginia. / Ph. D.

Reducing apple (Malus x domestica Borkh.) crop load during bloom is a reliable option for increasing fruit quality and return bloom. In this thesis, multiple approaches to improving bloom thinning practices are discussed. The first project analyzed the pollen tube growth of several crabapple cultivars. Previous research had improved the use of bloom thinning chemicals, by coordinating the application timing with the pollen tube growth between pollination and fertilization. However, pollen tube growth rates have only been measured in a few genotypes. In Chapter 2, the pollen tube growth rates of five crabapple cultivars were measured in the styles of 'Fuji', 'Golden Delicious', and 'Pink Lady' flowers, at four temperatures 12, 18, 24 and 30 C. Complex relationships were found among paternal pollen tube growth, maternal cultivar, and temperature. Chapters 3 and 4 describe projects where organically-approved chemicals, including the biofungicide, Regalia, were evaluated for their ability to simultaneously reduce crop load and decrease early season disease infection. These chemicals were applied in conventionally managed orchards (Chapter 3), and in an organically-managed 'Honeycrisp' orchard (Chapter 4). The number of chemicals approved for bloom thinning is limited, especially in the Eastern U.S. where lime sulfur and oil applications are not permitted during bloom. These studies indicate Regalia, applied during bloom, can reduce crop load and provide early season disease control. The research presented in this thesis provides new knowledge that can be incorporated into crop load management practices in both conventional and organic apple orchards. / Master of Science

Apple scab is the most important disease of apples in most of the world. The disease, caused by Venturia inaequalis, is controlled by numerous fungicide applications, regardless of the presence of inoculum in the orchard. Better timing of fungicide applications could be achieved if the airborne ascospore concentration (AAC) was considered in decision making. AAC can be measured in real time using spore traps. In this project, the relationship between AAC and lesions development was studied under controlled and natural conditions for five cultivars: Empire, McIntosh, Jonagold, Royal Gala, and Spartan. Potted trees were exposed to different airborne ascospore inoculum and the corresponding AAC were measured using spore traps. The spatial distribution of ascospores was studied in a commercial apple orchard plot. The potential ascospore dose (PAD) and the AAC were measured in 40 quadrats in the spring of 1999. (Abstract shortened by UMI.)

The aim of the research. To identify genes involved in V. inaequalis induced resistance response in Malus sp. and to develop apple hybrids with pyramidic resistance. Specific aims: 1. To characterize the genetic diversity and resistance to apple scab in the collection of apple genetic resources; 2. To develop apple hybrids of pyramidic resistance for apple breeding; 3. To characterize apple nuclear proteome and to perform a comparative genomic analysis of V. inaequalis induced Malus response; 4. To identify apple resistance genes involved in response to apple scab and to develop functional markers. / Tyrimų tikslas: identifikuoti V. inaequalis indukuojamo Malus sp. apsauginio atsako reikšmingus genus ir sukurti piramidinio atsparumo rauplėgrybiui donorus obels selekcijai. Tyrimų uždaviniai: 1. Charakterizuoti obels genetinių išteklių įvairovę bei nustatyti jų atsparumą rauplėgrybiui; 2. Sukurti ir atrinkti superjautrumo atsaku pagrįsto piramidinio atsparumo donorus obels selekcijai; 3. Charakterizuoti naminės obels ląstelės branduolio proteomą ir atlikti V. inaequalis indukuojamo atsako lyginamosios genomikos analizę; 4. Identifikuoti obels atsparumo rauplėgrybiui reikšmingus genus ir sukurti obels atsparumo ligoms funkcinius žymeklius.

Submitted by Gabriela Lopes (gmachadolopesufpel@gmail.com) on 2016-10-03T17:35:05Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertacao_Taiane_Viana.pdf: 904492 bytes, checksum: 30037558592bcb3fdf60ab01d643c574 (MD5) / Approved for entry into archive by Aline Batista (alinehb.ufpel@gmail.com) on 2016-10-06T20:46:17Z (GMT) No. of bitstreams: 2 Dissertacao_Taiane_Viana.pdf: 904492 bytes, checksum: 30037558592bcb3fdf60ab01d643c574 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2016-10-06T20:46:17Z (GMT). No. of bitstreams: 2 Dissertacao_Taiane_Viana.pdf: 904492 bytes, checksum: 30037558592bcb3fdf60ab01d643c574 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2013-12-04 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / O cultivo do trigo no Brasil é marcado pelo elevado número de doenças capazes de causar danos à produção. Entre as principais doenças que afetam o trigo está a giberela ou fusariose da espiga, causada pelo agente etiológico Gibberella zeae (Schw.) Petch, (anamorfo Fusarium graminearum Schwabe) que causa impacto negativos não somente à produtividade mas também a qualidade dos grãos produzidos. As condições ambientais para que a infecção ocorra carac terizam-se com temperaturas de 20-25°C e duração do molhamento foliar de, no mínimo, 48 horas consecutivas. O controle químico é realizado via aplicação de fungicidas a partir do inicio da floração estendendo-se até o final do florescimento, sendo que este tipo de controle caracteriza-se pela sua menor eficiência quando comparado com o controle de doenças foliares. Caso as condições climáticas impeçam a realização das aplicações de fungicidas no período indicado, o controle fica muito dificultado, por outro lado, se não ocorrer clima favorável à infecção, não se justifica o tratamento. A ineficiência dos tratos culturais no controle de giberela, associado à natureza quantitativa da característica de resistência, e o fato de sofrer alta influência do ambiente resultam na necessidade de identificar fontes efetivas de resistência que possam ser utilizadas em programas de melhoramento de trigo. De fato, existem culturas onde o controle das doenças mais importantes ocorre, quase que exclusivamente, por meio da resistência sendo que a identificação de genotipos que contenham resistência é um dos primeiros passos para selicioná-los. Desta forma, é fundamental o conhecimento de cultivares que apresentem níveis de resistência a giberela e métodos que possam identificar estas cultivares. Frente ao exposto o objetivo deste trabalho foi: i) separar genótipos suscetíveis e que contenham diferentes níveis de resistência utilizando avaliações morfológicas e moleculares; ii) verificar a resistência à giberela nas cultivares Frontana e Pampeano. Para isso foram utilizadas avaliações de características morfológicas citadas na literatura e associadas a resistência à giberela, assim como, o meprego de primers descritos na literatura significativamente associados à QTL de resistência à giberela. Como resultado do estudo espera-se auxiliar no desenvolvimento de ferramentas que possam ser utilizadas em programas de melhoramento de trigo visando facilitar a identificação de fontes de resistência. / The cultivation of wheat in Brazil is marked by the large number of diseases that can damage the production. Among the major diseases affecting wheat is wheat scab or Fusarium head blight (FHB), caused by the agent Gibberella zeae (Schw.) Petch (anamorph Fusarium graminearum Schwabe ) that causes negative impact not only on productivity but also the quality of the grain produced. The environmental conditions for infection are temperatures between 20-25°C and 48 consecutive hours of leaf wetness. Chemical control is performed via application of fungicides from the start extending until the end of flowering, and this type of control is characterized by its low efficiency when compared to the disease control. If the weather conditions prevent the aplication of fungicide applications within this period, there is no possibility control, on the other hand, if it does not favorable environment for infec tion treatment is not justified. The inefficiency of cultural control of FHB, associated with the quantitative trait (QTL- Quantitative traits loci)of resistance, and the fact of suffering high influence of the environment results in the need to identify effective sources of resistance that can be used in wheat breeding programs. In fact, there are cultures where control of major diseases occurs almost exclusively through resistance where the identification of genotypes containing resist ance is one of the first steps in their selection. Thus it is crucial to understand cultivar present levels of resistance to FHB and methods that can identify these cultivars.The objective of this study was: i) separate susceptible and containing different levels of resistance using molecular and morphological evaluations; ii) determine FHB resistance using cultivars Frontana and Pampeano as a source of resistance. Using morphological assessments cited in the literature and associated with resistance to FHB, as, primers as described in the literature as significantly associated with QTL for resistance to FHB. As a result of the study one expects to develop tools that can be used to facilitate the identification of sources of resistance.

The aim of this master‘s thesis was to determine the aroma active compounds and monitor the sensory quality of apples. The theoretical part deals with the description, composition and properties of apples, information about the aroma compounds, their determination and possibilities for sensory evaluation of apples is also given. The gas chromatography method combined with the solid-phase microextraction, utilized for the specification of aroma compounds, is described. In the experimental part, the SPME-GC-FID method was applied on selected cultivars of apples specially cultivated against apple scab (Venturia inaequalis), i.e. 24 genotypes and Golden Delicious as the control variety. In total 60 various aroma compounds were identified, 22 alcohols, 12 aldehydes, 11 ketones, 10 esters and 5 organic acids. The number and concentration of compounds identified differed according to the cultivars. Sensory analysis was performed using category ordinal scales and the profile test.

This diploma thesis focused on screening for bacterial pathogens and antagonists suppressing common scab mainly caused by Streptomyces scabiei. Common scab affects some agricultural crops causing significant economical losses. Bacterial strains, mostly streptomycetes, were isolated from potato rhizosphere because they belong to most important producents of secondary metabolites and the causative agents of the disease are also members of this genus. The isolated bacteria were characterised by PCR amplification and sequencing of 16S rRNA gene to reveal their phylogenetic relationships. The ability of isolated strains to suppress growth of Streptomyces scabiei was tested by a simple co-cultivation experiment. The strains were tested by PCR for presence of specific genes for biosynthesis of thaxtomin A, a common virulence factor found in all described pathogens causing symptoms of this disease on the surface of affected tubers. Genes for synthesis of thaxtomin belong to pathogenicity island. Standard of phytotoxin thaxtomin A was used to optimize its analysis by mass spectroscopy for further in vivo and in vitro experiments. Phylogenetic analysis of strains harboring one of the genes necessary for thaxtomin A biosynthesis supported the hypothesis of sharing the pathogenicity island by horizontal gene...

No description available.

O gênero Streptomyces constitui-se em um grupo diferenciado de procariotos fitopatogênicos, por serem morfologicamente similares aos fungos e produzirem diversos importantes metabólitos secundários. A sarna comum da batata é principal doença causada pelo gênero. O principal agente causal da doença, Streptomyces scabies, produz fitotoxinas denominadas concanamicinas, porém, não foi comprovada a importância da produção das mesmas na agressividade dos isolados de S. scabies. Dessa forma, neste trabalho procurouse avaliar a reação dos cultivares mais plantados no Brasil a isolados de S. scabies exibindo diferentes níveis de produção de concanamicinas. O nível de produção de concanamicinas A e B de dez isolados de Streptomyces spp. foi avaliado por cromatografia líquida de alta pressão (HPLC) e dois isolados (produtor de alto nível da toxina; baixo produtor) foram selecionados e utilizados na avaliação da resistência de seis cultivares de batata em casa de vegetação. Vasos contendo o substrato esterilizado receberam a suspensão de esporos bacterianos junto com os tubérculos sadios no momento do plantio e após quatro meses, a severidade da doença foi avaliada. Os resultados demonstraram aumento na agressividade do isolado produtor de elevadas quantidades de concanamicinas apenas sobre os cultivares Mondial, Monalisa e Asterix. Por sua vez, os resultados da avaliação do nível de resistência ao patógeno demonstraram que os cultivares Monalisa, Ágata, Asterix e Cupido são suscetíveis e os cultivares Atlantic e Mondial mostraram-se resistentes aos dois isolados de Streptomyces spp. avaliados. Por outro lado, a fitotoxina taxtomina A é a toxina mais frequentemente produzida pelas espécies fitopatogênicas de Streptomyces spp. O estudo do mecanismo de ação desta fitotoxina poderá auxiliar no entendimento de sua contribuição no desenvolvimento da doença. A taxtomina A é uma fitotoxina não específica e causa efeitos semelhantes em plantas de diferentes famílias botânicas. Desta forma, modificações citológicas, ultraestruturais e bioquímicas induzidas pela taxtomina A foram analisadas em plântulas de sorgo. Os tecidos foram tratados com taxtomina A e avaliados após sete dias do tratamento. Observou-se desorganização em todas as células dos tecidos tratados com a taxtomina A. A membrana plasmática das células do mesofilo foliar foi retraída e destacada da parede celular em diversos pontos. Entretanto, o plasmalema não pareceu rompido. O efeito sobre a permeabilidade seletiva da membrana plasmática também foi avaliado bioquimicamente, onde foi observado aumentos na saída de eletrólitos. Os cloroplastos apresentaram deformações na superfície e perda de turgidez. Estas deformações provavelmente contribuíram para a redução do teor de clorofilas A e B. As plântulas também apresentaram elevado acúmulo de fitoalexinas do tipo deoxiantocianidinas. Desta forma, conclui-se que a taxtomina A age principalmente sobre a membrana plasmática e organelas membranosas. Em contrapartida, o acúmulo de fitoalexinas evidencia que concentrações mínimas desta toxina podem ser exploradas como eliciador da resposta de defesa em plantas. / The genus Streptomyces is a different prokaryote phytopathogen group, being morphologically similar to fungi and able to produce several important secondary metabolites. The potato common scabies is the main plant disease caused by the members of the genus. The main causal agent of the plant disease, Streptomyces scabies, is able to produce the phytoxins concanamycins. However, the importance of these toxins in the aggressiveness of S. scabies strains was not proven. This research aimed to evaluate the reaction of main potato cultivars used in Brazil to Streptomyces spp. strains, exhibiting different levels of concanamycins production. The toxin production by several strains was quantified by high performance liquid chromatography (HPLC) and two strains (higher and lower producers) were chosen and used for resistance evaluation of six potato cultivars under greenhouse. Pots containing sterile substratum received a suspension of bacterial spores and the healthy seed tubers at the same time. After four months, the level of disease was evaluated and the results showed increasing in aggressiveness for the higher concanamycins producer only in the Mondial, Monalisa and Asterix cultivars. For the two strains, the cultivars Atlantic and Mondial were resistant and the cultivars Monalisa, Cupido, Ágata and Asterix were susceptible. On the other hand, the thaxtomin A is the main phytotoxin of plant pathogenic Streptomyces spp. Therefore, the study of the thaxtomin A action mechanism is important to explain its contribution to disease development. The thaxtomin A is not a specific toxin and causes similar effect in several plants of different botanical families. Thus, the cytological, ultrastructural and biochemical modifications induced by thaxtomin A were evaluated in sorghum seedlings. Leaf tissues of seedlings were treated with high levels of thaxtomin A and evaluated 7 days after treatment. Cytological disorganization was observed in all treated cells. The plasmma membrane of the cells of immature leaves was detached from the wall in several places. However, plasmmalema did not seem degraded. The chloroplasts had showed significant deformations in the surface and volume reduction. Theses changes in chloroplasts probably contributed for the reduction of chlorophylls A and B levels. The sorghum seedlings also showed high phytoalexin accumulation (deoxiantocianydins) in response to thaxtomin A treatment. Thus, the thaxtomin A acts mainly on plasmma membrane and membranous organelles, causing plasmolises, cell disorganization, deformations in chloroplasts and chlorophyll reduction in sorghum seedlings. Finally, the accumulation of phytoalexins in response to thaxtomin A treatment points out it potential to induce resistance in plants.

O gênero Streptomyces constitui-se em um grupo diferenciado de procariotos fitopatogênicos, por serem morfologicamente similares aos fungos e produzirem diversos importantes metabólitos secundários. A sarna comum da batata é principal doença causada pelo gênero. O principal agente causal da doença, Streptomyces scabies, produz fitotoxinas denominadas concanamicinas, porém, não foi comprovada a importância da produção das mesmas na agressividade dos isolados de S. scabies. Dessa forma, neste trabalho procurouse avaliar a reação dos cultivares mais plantados no Brasil a isolados de S. scabies exibindo diferentes níveis de produção de concanamicinas. O nível de produção de concanamicinas A e B de dez isolados de Streptomyces spp. foi avaliado por cromatografia líquida de alta pressão (HPLC) e dois isolados (produtor de alto nível da toxina; baixo produtor) foram selecionados e utilizados na avaliação da resistência de seis cultivares de batata em casa de vegetação. Vasos contendo o substrato esterilizado receberam a suspensão de esporos bacterianos junto com os tubérculos sadios no momento do plantio e após quatro meses, a severidade da doença foi avaliada. Os resultados demonstraram aumento na agressividade do isolado produtor de elevadas quantidades de concanamicinas apenas sobre os cultivares Mondial, Monalisa e Asterix. Por sua vez, os resultados da avaliação do nível de resistência ao patógeno demonstraram que os cultivares Monalisa, Ágata, Asterix e Cupido são suscetíveis e os cultivares Atlantic e Mondial mostraram-se resistentes aos dois isolados de Streptomyces spp. avaliados. Por outro lado, a fitotoxina taxtomina A é a toxina mais frequentemente produzida pelas espécies fitopatogênicas de Streptomyces spp. O estudo do mecanismo de ação desta fitotoxina poderá auxiliar no entendimento de sua contribuição no desenvolvimento da doença. A taxtomina A é uma fitotoxina não específica e causa efeitos semelhantes em plantas de diferentes famílias botânicas. Desta forma, modificações citológicas, ultraestruturais e bioquímicas induzidas pela taxtomina A foram analisadas em plântulas de sorgo. Os tecidos foram tratados com taxtomina A e avaliados após sete dias do tratamento. Observou-se desorganização em todas as células dos tecidos tratados com a taxtomina A. A membrana plasmática das células do mesofilo foliar foi retraída e destacada da parede celular em diversos pontos. Entretanto, o plasmalema não pareceu rompido. O efeito sobre a permeabilidade seletiva da membrana plasmática também foi avaliado bioquimicamente, onde foi observado aumentos na saída de eletrólitos. Os cloroplastos apresentaram deformações na superfície e perda de turgidez. Estas deformações provavelmente contribuíram para a redução do teor de clorofilas A e B. As plântulas também apresentaram elevado acúmulo de fitoalexinas do tipo deoxiantocianidinas. Desta forma, conclui-se que a taxtomina A age principalmente sobre a membrana plasmática e organelas membranosas. Em contrapartida, o acúmulo de fitoalexinas evidencia que concentrações mínimas desta toxina podem ser exploradas como eliciador da resposta de defesa em plantas. / The genus Streptomyces is a different prokaryote phytopathogen group, being morphologically similar to fungi and able to produce several important secondary metabolites. The potato common scabies is the main plant disease caused by the members of the genus. The main causal agent of the plant disease, Streptomyces scabies, is able to produce the phytoxins concanamycins. However, the importance of these toxins in the aggressiveness of S. scabies strains was not proven. This research aimed to evaluate the reaction of main potato cultivars used in Brazil to Streptomyces spp. strains, exhibiting different levels of concanamycins production. The toxin production by several strains was quantified by high performance liquid chromatography (HPLC) and two strains (higher and lower producers) were chosen and used for resistance evaluation of six potato cultivars under greenhouse. Pots containing sterile substratum received a suspension of bacterial spores and the healthy seed tubers at the same time. After four months, the level of disease was evaluated and the results showed increasing in aggressiveness for the higher concanamycins producer only in the Mondial, Monalisa and Asterix cultivars. For the two strains, the cultivars Atlantic and Mondial were resistant and the cultivars Monalisa, Cupido, Ágata and Asterix were susceptible. On the other hand, the thaxtomin A is the main phytotoxin of plant pathogenic Streptomyces spp. Therefore, the study of the thaxtomin A action mechanism is important to explain its contribution to disease development. The thaxtomin A is not a specific toxin and causes similar effect in several plants of different botanical families. Thus, the cytological, ultrastructural and biochemical modifications induced by thaxtomin A were evaluated in sorghum seedlings. Leaf tissues of seedlings were treated with high levels of thaxtomin A and evaluated 7 days after treatment. Cytological disorganization was observed in all treated cells. The plasmma membrane of the cells of immature leaves was detached from the wall in several places. However, plasmmalema did not seem degraded. The chloroplasts had showed significant deformations in the surface and volume reduction. Theses changes in chloroplasts probably contributed for the reduction of chlorophylls A and B levels. The sorghum seedlings also showed high phytoalexin accumulation (deoxiantocianydins) in response to thaxtomin A treatment. Thus, the thaxtomin A acts mainly on plasmma membrane and membranous organelles, causing plasmolises, cell disorganization, deformations in chloroplasts and chlorophyll reduction in sorghum seedlings. Finally, the accumulation of phytoalexins in response to thaxtomin A treatment points out it potential to induce resistance in plants.