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Cucumber (Cucumis sativus L.), pumpkin (Cucurbita maxima Duch. ex Lam.), and summer squash (Cucurbita pepo L.) are economically important crops in Virginia. Only a few herbicides are registered for weed control in these crops. Halosulfuron is a sulfonylurea herbicide which controls several broadleaf weeds and yellow nutsedge (Cyperus esculentus L.). Cucurbit crops have some tolerance to this herbicide. The efficacy of halosulfuron for control of several weed species and tolerance of four vine crops to halosulfuron were investigated in field and greenhouse studies in 1999, 2000, and 2001. In the field, halosulfuron was applied to cucumber, pumpkin, zucchini squash, and yellow summer squash at 4, 9, 18, and 27 g ai/ha preemergence (PRE) and postemergence (POST) in combination with clomazone at 174 g ai/ha plus ethalfluralin applied PRE at 630 g/ha. Crop injury, weed control, and crop yield was collected from the field studies. Weed control by halosulfuron was dependent upon application method. Halosulfuron applied preemergence controlled only common ragweed (Ambrosia artemisiifolia L.) and smooth pigweed (Amaranthus hybridus L.). Postemergence halosulfuron controlled common ragweed, smooth pigweed, morningglory species (Ipomoea spp.), yellow nutsedge, and rice flatsedge (Cyperus iria L.). All four crops treated with halosulfuron produced yields equal to or higher than the crops receiving clomazone and ethalfluralin alone or the hand-weeded check. In the greenhouse, tolerance of cultivars of each crop to halosulfuron was investigated with the same rates applied in the field. Cultivars responded similar to postemergence halosulfuron applications with respect to fresh and dry weights in all four crops. The response of several populations of acetolactate synthase inhibiting (ALS) resistant smooth pigweed to postemergence halosulfuron was also investigated. Halosulfuron activity against ALS-inhibitor resistant smooth pigweed was population dependent. In the greenhouse, postemergence halosulfuron at the same rates used in the field studies controlled yellow nutsedge. / Master of Science

O presente trabalho teve como objetivo avaliar a eficiência do sistema de análise de imagens de plântulas (Seedling Vigor Imaging System® - SVIS®) na determinação do potencial fisiológico de sementes de pepino, em comparação com informações fornecidas por testes de vigor recomendados para essa espécie. O trabalho foi desenvolvido em três épocas de avaliação com intervalos aproximados de três meses. Em cada época, a avaliação do potencial fisiológico foi efetuada usando-se os testes de germinação, primeira contagem de germinação, envelhecimento acelerado tradicional e com solução saturada de NaCl, comprimento de plântulas e emergência de plântulas. Os resultados desses testes foram comparados com os dados obtidos com o uso do software Seedling Vigor Imaging System (SVIS®), que avaliou o desenvolvimento de plântulas escaneadas, mediante a obtenção de valores do comprimento da raiz primária, do hipocótilo e das plântulas, do índice de vigor e de uniformidade de desenvolvimento. Além disso, foram estudadas variações na proporção da participação do crescimento e da uniformidade de desenvolvimento das plântulas para o cálculo do índice de vigor no \"software SVIS®, na tentativa de verificar possíveis variações na sensibilidade do sistema para detectar diferenças no potencial fisiológico dos lotes avaliados. Concluiu-se que a análise computadorizada de imagens de plântulas é uma alternativa consistente e promissora para avaliação do potencial fisiológico de sementes de pepino, com eficiência comprovada equivalente à verificada em testes tradicionais para determinação do vigor. As análises pelo SVIS® em plântulas com quatro dias de idade são mais precisas e a proporção crescimento/uniformidade para a composição do cálculo do índice de vigor não afeta a precisão da determinação do potencial fisiológico de sementes de pepino pela análise SVIS®. / This study aimed to evaluate the efficiency of seedling digital image analysis (Seedling Vigor Imaging System® - SVIS®) to determine the physiological quality of cucumber seed lots, compared to information provided by vigor tests recommended for this species. Research comprised three evaluation times with a threemonth interval. Physiological quality determination comprised germination, germination first count, traditional and saturated salt accelerated aging, seedling length and seedling emergence tests. Results obtained were compared to data by the evaluation using the software Seedling Vigor Imaging System (SVIS®); in this system, seedlings were scanned and the image analysis made possible to obtain values of the primary root, hypocotyl and seedling lengths in addition to a vigor index and uniformity of seedling of development. It also studied the importance of the contribution of growth intensity and uniformity to compose the value of the vigor index calculated by the software. It was concluded that digital image analysis of seedlings is a consistent and promising alternative to provide reliable information of cucumber seed physiological quality, comparable to those from traditional tests. Analyses by SVIS ® of four-day old seedlings are more accurate, and the proportion growth/uniformity in the composition of the vigor index does not affect the accuracy of determining the physiological quality of cucumber seeds by analyses SVIS®.

Atualmente a ordem Dendrochirotida é composta por 800 espécies, sendo que metade destas estão entre as famílias Sclerodactylidae e Phyllophoridae. Todavia, a maior parte das informações acerca dos seus táxons é proveniente de revisões morfológicas muito antigas (Phyllophoridae em 1954, e Sclerodactylidae não revisada). Este estudo, portanto, se configura como o primeiro teste formal da monofilia das famílias Sclerodactylidae e Phylllophoridae e suas subfamílias. O presente trabalho constitui um estudo morfológico minucioso das estruturas que compõem o endoesqueleto dos Holothuroidea que são os ossículos dérmicos e anel calcário, vislumbrando alcançar através de uma análise cladística os objetivos descritos a seguir: (i) testar a monofilia de Phyllophoridae; (ii) testar a monofilia de Sclerodactylidae; (iii) testar a monofilia das subfamílias de Phyllophoridae e (iv) testar a monofilia das subfamílias de Sclerodactylidae. O material estudado foi obtido a partir de visitas e/ou empréstimos de museus nacionais e internacionais. Foram estudados espécimes de todas as ordens de Holothuroidea, à exceção de Elasipodida, totalizando 956 espécimes pertencentes a 78 espécies, das quais quatro foram delimitadas como grupo externo (i.e. Aspidochirotida, Apodida e Dendrochirotida [Cucumariidae e Psolidae]) e 44 delimitadas como grupo interno (todas as espécies tipo foram analisadas). Setenta e dois caracteres foram descritos e ilustrados através de fotografias ou microscopia eletrônica de varredura. As análises foram realizadas com o programa PAUP (v. 4.0), através do algoritmo de parcimônia Tree Bissection and Reconnection (TBR) de branch-swapping, com 5000 réplicas. O estudo morfológico detalhado permitiu elencar novos caracteres, bem como reinterpretar caracteres já estabelecidos, além de fornecer correções de interpretações equivocadas acerca de tais estruturas. Sclerodactylidae foi recuperada como monofilética e está composta por três subfamílias (todas foram recuperadas como monofiléticas), Clado I, Sclerodactylinae e Thyoninae. Phyllophoridae foi recuperada como monofilética e está composta por três subfamílias (todas foram recuperadas como monofiléticas), Cladolabinae, Phyllophorinae e Semperiellinae. / Currently, the order Dendrochirotida comprises about 800 species, half of these being within the families Sclerodactylidae and Phyllophoridae. Regardless, most information about these families is from old morphological revisions (Phyllophoridae in 1954 and Sclerodactylidae not reviewed). This study appears as the first formal test of the monophyly of the families Sclerodactylidae and Phylllophoridae and their respective subfamilies. The present work constituted a detailed morphological study of the structures that compose the Holothuroidea endoskeleton which are the dermal ossicles and calcareous ring to achieve through a cladistic analysis the following objectives: (i) to test the monophyly of Phyllophoridae; (ii) to test the monophyly of Sclerodactylidae; (iii) to test the monophyly of the Phyllophoridae subfamilies and iv) to test the monophyly of the subfamilies of Sclerodactylidae. The material studied was obtained from visits and/or loans from the national and international museums. Specimens of all orders of Holothuroidea were analyzed with the exception of Elasipodida, yielding 956 specimens belonging to 78 species, of which four were delimited as outgroups (i.e. Aspidochirotida, Apodida and Dendrochirotida [Cucumariidae and Psolidae]) and 44 delimited as internal groups (all type specimens were analyzed). A total of 72 morphological characters were described and illustrated through photographs or scanning electron microscopy images. The analyses were conducted with the aid of PAUP (v.4.0) using a parsimony algorithm Tree Bisection and Reconnection (TBR) branch-swapping (5000 replicates). This detailed morphological study allowed us to list new characters, to reinterpret. already established ones as well as providing corrections of misinterpretations about such structures. Sclerodactylidae was recovered as monophyletic and is composed of three subfamilies (all were recovered as monophyletic), Clade I, Sclerodactylinae and Thyoninae. Phyllophoridae was recovered as monophyletic and consists of three subfamilies (all were recovered as monophyletic), Cladolabinae, Phyllophorinae and Semperiellinae.

Entre as hospedeiras de invasão sistêmica do vírus do mosaico do mamoeiro - estirpe mamoeiro (Papaya ringspot virus type P; PRSV-P) encontram-se espécies de cucurbitáceas, cuja suscetibilidade à transmissão experimental, mecânica e com afídeos, é variável. A literatura nacional e internacional apresenta resultados distintos quanto à recuperação desse vírus a partir de cucurbitáceas presentes próximas ou no interior de plantios de mamoeiros infectados com esse vírus. O presente trabalho teve como objetivo avaliar em casa de vegetação a suscetibilidade de quatro espécies de cucurbitáceas a cinco isolados do PRSV-P obtidos de diferentes regiões do Brasil e inoculados de forma mecânica. Visou também estudar a infecção natural de cucurbitáceas cultivadas nas entrelinhas ou próximas de mamoeiros com mosaico. Para o desenvolvimento do trabalho em casa-de-vegetação os isolados do PRSV-P mantidos em mamoeiros, foram inoculados nos cotilédones de abobrinha de moita cv. Caserta, moranga cv. Exposição, pepino híbrido Primepack Plus e melancia cv. Crimson Sweet. As plantas foram avaliadas com base nos sintomas e indexadas por PTA-ELISA, e recuperação biológica do biótipo P do PRSV através de inoculações em mamoeiro. A confirmação da infecção dos mamoeiros foi realizada da mesma forma, por sintomatologia e indexação por PTA-ELISA. A abobrinha de moita foi a espécie mais suscetível aos cinco isolados do PRSV-P, seguida da melancia e do pepino. Não foi possível transmitir o vírus a moranga cv. Exposição. Para estudar a infecção natural realizou-se um ensaio com plantas de abobrinha de moita em Linhares-ES, três ensaios independentes em Rinópolis-SP e quatro em Piracicaba-SP, incluindo-se nessa última localidade a melancia e o pepino. Depois de aproximadamente 40 a 60 dias de exposição em campo coletaram-se amostras individuais ou compostas (de 3 a 5 plantas) das folhas dos ponteiros das plantas para realizar a recuperação biológica do PRSV-P para mamoeiros em casa de vegetação. A presença de afídeos foi monitorada em Piracicaba durante a execução dos experimentos no campo. No único teste de exposição em Linhares, nenhuma planta de abobrinha cultivada entre mamoeiros com mosaico mostrou-se infectada com esse vírus. O PRSV-P foi recuperado da abobrinha de moita em proporções variáveis em 2 dos 3 testes realizados em Rinópolis, e em 3 dos 4 testes realizados em Piracicaba. Nenhuma planta de melancia e pepino cultivada entre mamoeiros com mosaico foi infectada com o PRSV-P. Não foi possível recuperar o PRSV-P de nenhuma planta de abobrinha cultivada entre 5 e 80 metros de distância dos mamoeiros com mosaico em Piracicaba. Foram capturados afídeos vetores do PRSV-P e foi possível detectar plantas infectadas com os potyvirus PRSV-W e ZYMV, o que demonstra a presença e atividade dos vetores de vírus. Os resultados confirmaram a suscetibilidade variável das espécies de cucurbitáceas ao PRSV-P. Embora a abobrinha de moita fosse a única espécie encontrada naturalmente infectada pelo PRSV-P quando cultivada entre linhas de mamoeiro com mosaico, a presença de cucurbitáceas nos campos de produção de mamoeiro, especialmente quando o controle do mosaico do mamoeiro é feito através do roguing, não é recomendada. / Besides Carica papaya, Papaya ringspot virus type P (PRSV-P) infects systemically only species belonging to the family Cucurbitaceae. Their susceptibility varies according to the species/cultivar, virus isolate and the method of inoculation. Attempts to recovery PRSV-P from naturally infected cucurbit plants grown near to or among diseased papaya trees have shown distinct results worldwide. This study aimed to evaluate the susceptibility of Cucurbita pepo cv. Caserta, Cucurbita maxima cv. Exposiçao, Cucumis sativus hybrid Primepack Plus, and Citrullus lanatus cv. Crimson Sweet to five isolates of PRSV-P obtained from different regions of Brazil. It was also evaluated the natural infection of cucurbit plants grown between rows and in the vicinity of papaya trees infected with PRSV-P. The five PRSV-P isolates were maintained in papaya plants. Cucurbit plants grown in pots under greenhouse conditions were mechanically inoculated with each isolate at the cotiledonary stage. The plants were assessed based on symptoms and infection was confirmed by PTA-ELISA using extracts from the inoculated cotyledons and upper leaves. The same extracts were also mechanically inoculated on papaya plants in order to recover the virus isolate. Inoculated papaya plants were also tested by PTA-ELISA. Zucchini squash was the most susceptible species to PRSV-P, followed by watermelon and cucumber. Pumpkin cv. Exposição was not infected. To study the natural infection of zucchini squash cv. Caserta by PRSV-P, a trial was carried out in Linhares, State of Espírito Santo; three independent trials were carried out in Rinópolis; and four trials were carried out in Piracicaba, both regions located in the State of São Paulo. Watermelon and cucurbit were also included in some trials in Piracicaba. After approximately 40 to 70 days, leaf samples were collected and tested individually or in groups of three to five plants for the presence of PRSV-P by mechanical inoculation on papaya plants under greenhouse conditions. None of the zucchini squash plants grown between rows of infected papaya trees in Linhares was found infected by PRSV-P based on the virus recovery test to papaya plants. The virus was also not recovered from watermelon and cucurbit plants grown between rows of infected papaya trees in Piracicaba. On the other hand, PRSV-P was recovery from zucchini squash plants grown intercalated with diseased papayas in Rinópolis and Piracicaba. The number of infected plants varied among the trial. Several attempts to recover PRSV-P from innumerous zucchini squash plants grown approximately five to 80 meters from diseased papaya trees in Piracicaba failed. Alates of several species of aphids were captured in the field at Piracicaba. Also, innumerous cucurbit plants were found infected by the potyviruses Papaya ringspot virus type W and Zucchini yellow mosaic virus, suggesting aphids activity in the area. The results confirmed the variable susceptibility of cucurbit species to infection with PRSV-P. Although natural infection with PRSV-P was restricted to zucchini squash cv. Caserta grown among infected papaya trees, the presence of cucurbit plants in the vicinity of papaya orchards, especially where disease control is done by systematic rouging of diseased plants, should not be allowed.

Viruses can affect plant-insect interactions by altering emission of plant volatile organic compounds (VOCs). Previous work in the lab suggested that VOCs emitted by tomato (Solanum lycopersicum) plants infected with cucumber mosaic virus (CMV) were more attractive to bumblebees (Bombus terrestris) in free choice assays. I extended this work using Arabidopsis thaliana mutants with lesions in genes encoding factors in RNA silencing. In conditioning assays, I confirmed that plant VOC emission is controlled in part by the microRNA regulatory pathway. I used gas chromatography coupled to mass spectrometry and principal component analysis to confirm that CMV infection caused changes in VOC emission by tomato. VOCs collected from non-flowering mock-inoculated and CMV-infected plants were qualitatively distinct from each other. CMV-infected plants also released greater quantities of VOCs than mock-inoculated plants. CMV appears to be both ‘turning up the volume’ of plant volatile emission, whilst ‘tuning’ volatile blend composition so as to diminish levels of a repellant signal. These data are likely to explain how bumblebees can discriminate between VOCs emitted by mock-inoculated and CMV-infected plants. To determine if CMV infection of tomato plants affects plant reproductive success, I carried out a series of bumblebee pollination experiments. Bumblebees pollinate tomato by ‘buzzing’ (sonicating) the flowers, which releases pollen and enhances self-fertilization and seed production as well as pollen export. First, I established that CMV-infected tomato plants produced fruits with a lower seed yield than mock-inoculated plants. When single bumblebees were allowed to buzz-pollinate flowers in a small flying arena, the fruit that developed from buzz-pollinated flowers on virus infected plants had significantly more seeds than fruit from non-visited flowers. Subsequent experiments were performed in a large flying arena. Bumblebees consistently spent longer foraging on the mock-inoculated tomato plants but seed yield was increased by bumblebee pollination in both mock-inoculated as well as virus-infected tomato plants. However, although buzz-pollination significantly enhanced seed yield from CMV-infected plants compared to fruit from non-buzz-pollinated flowers, the yield was higher in buzz-pollinated fruits from mock-inoculated plants. Similar experiments were carried out utilizing a transgenic line of tomato that constitutively expresses the green fluorescent protein in order to estimate the level of cross-pollination from either CMV-infected plants to mock-inoculated plants or vice versa. More pollen from virus-infected plants was transferred to mock-inoculated plants than the reciprocal cross. However, some caution is needed in the interpretation of the larger scale experiments because the tomato plants were affected by a fungal infection. I investigated if the defensive plant hormone salicylic acid (SA) affects bee-perceivable VOC emission. Exogenous SA treatment renders non-flowering tomato plants more attractive to bumblebees in free choice experiments in which bees could only perceive VOCs, but bumblebees spent less time visiting SA-treated flowering tomato plants in the glasshouse (when the bumblebees were allowed unimpeded access to the flowers). Taken together, these data provide evidence that virus infection can affect host-pollinator interactions. Speculatively, CMV infection may change the fitness of susceptible plants via changes in production of pollinator-attractive VOCs and this may affect the balance of resistant or susceptible plants within the host population.

This thesis describes structural studies on the interactions between the fucosylated chondroitin sulfate (fCS) oligosaccharides and human proteins known as selectins. fCS is a carbohydrate obtained from sea cucumbers, that can be classified as a branched glycosaminoglycan (GAG). It has attracted much attention due to its anti-coagulant, anti-inflammatory, antimetastatic and anti-HIV properties and its structure was previously determined by NMR. Selectins constitute a family of proteins involved in cell adhesion processes, such as inflammation, attachment of viral particles and migration of tumour cells. fCS oligosaccharides have been shown to bind to selectins, which is likely a reason behind their biological activity. However, the mechanism of this interaction is currently unknown. The initial part of the thesis describes the experimental work on expression and purification of the recombinant L- and P-selectin constructs in Pichia pastoris, Escherichia coli and HEK 293 cells. The aim of these experiments was to produce two constructs for each selectin, a single domain construct, consisting of the C-type lectin domain only, and a double domain construct, consisting of both the C-type lectin and the EGF-like domains. The intention was that the recombinant proteins would be labelled with 13C and 15N to allow for the in-depth structural NMR studies on the fCS-selectin interaction. Various experimental approaches have been explored, including the use of different cell lines, modifications to construct design, as well as alterations to expression and purification conditions. Although it was not possible to produce soluble selectin constructs in either bacterial or yeast cells, protein expression tests in HEK293 cells, performed in collaboration with the Oxford Protein Production facility (OPPF), led to production of a soluble L-selectin construct, consisting of the L-selectin C-type lectin domain. The produced L-selectin construct, as well as two commercially available constructs of the Land P-selectin extracellular domains, were used in the Saturation Transfer Difference (STD) NMR experiments to provide new information about the nature of the fCS-selectin binding. The STD experiments allowed to identify the regions within the fCS oligosaccharides that are in direct contact with the protein and likely play an important role in this interaction. Experiments on different protein constructs allowed the comparison of fCS binding to P-selectin and to two different recombinant constructs of L-selectin. Results of these studies suggest that the binding occurs via a similar mechanism for both L- and P-selectins and that the fCS oligosaccharides bind to one-domain L-selectin construct with similar affinity as to a larger construct, consisting of the entire extracellular region of the protein. Alongside the experimental work, theoretical in silico studies on the fCS-selectin binding were undertaken as part of this project. The existing X-ray structures of selectin complexes were subjected to Molecular Dynamics (MD) simulations, which allowed to explore the dynamic behaviour of E-selectin upon binding to sialyl Lewis x (sLex). It was found that sLex forms a more favourable interaction with the extended conformation of E-selectin and that the protein in this conformation is characterised by a high degree of interdomain flexibility, with a new type of interdomain movement observed in the MD studies on this complex. In further in silico studies, the fCS oligosaccharides were docked to the existing P-selectin structures. The docking tests were performed on the computationally produced fCS trisaccharides with fucose branches either 2,4 or 3,4-sulfated. Results were evaluated with MD simulations and analysed in the light of current knowledge of selectin-ligand binding and the STD NMR experimental results. The in silico studies allowed to identify a subset of P-selectin residues that are likely involved in the interaction with fCS oligosaccharides in vivo. The conformational behaviour of P-selectin upon binding to fCS was also explored and it was found that the interdomain hinge is flexible during this interaction and allows transition from bent to extended conformational state. Finally, a new NMR method was developed to facilitate the studies of complex carbohydrates, incorporating the concepts of G-matrix Fourier Transform (GFT) NMR into 2D HSQC and 2D HSQC-TOCSY experiments. The method allows to separate peaks in the regions of high spectral overlap, providing information that can simplify the assignment process. The new experiments facilitated the structural evaluation of a sample containing a mixture of oligosaccharides resulting from the depolymerisation of fCS polysaccharide.

A soja (Glycine max) é uma das culturas mais importantes do mundo, os seus grãos servem tanto para a alimentação quanto para a extração de óleo para a fabricação do biodiesel. O vírus do mosaico do pepino (CMV, do inglês, “Cucumber mosaic virus”) é um vírus de RNA, patogênico a diversas plantas. O RNA de interferência é um sistema de silenciamento de RNA presente na maioria dos eucariotos no qual precursores de RNA de dupla fita (dsRNA) são processados em pequenos RNAs (sRNAs) de 21-24 nucleotídeos (nt), que podem regular a atividade de genes, elementos genéticos e vírus de uma maneira sequência específica. A integração de vírus de DNA e de retrovírus no genoma do hospedeiro já é bem conhecida tanto para sistemas eucarióticos quanto para procarióticos. Mais recentemente, foi observada a integração de vírus de RNA não retrovirais (NIRVs) em mamíferos. O presente trabalho é o primeiro a demonstrar tal evento no genoma de plantas. A partir das sequências dos sRNAs de 19-24 nt de 15 bibliotecas de sRNAs sequenciados de amostras de tecidos de soja, foram montadas sequências contíguas (“contigs”) pelo programa SOAP, algumas das quais apresentaram homologia de sequência ao RNA 1 do CMV. Por montagem de novo desses contigs foi obtida uma sequência de 3.092 nt do RNA 1 do CMV, presente em todas as bibliotecas pesquisadas de pelo menos cinco cultivares diferentes de soja. A presença dessa sequência foi confirmada em outras sete cultivares, exceto em "Willians". Foi observada uma maior presença de sRNAs derivados do CMV senso do que anti-senso nas 15 bibliotecas sequenciadas. Os sRNAs de 22-nt foram os mais abundantes. Para o vírus da mancha da vagem do feijoeiro (BPMV, do inglês “Bean pod mottle virus”) presente em uma das bibliotecas, os sRNAs de 21-nt e 22-nt representaram em torno de 80% do total de sRNAs. Foram encontrados sRNAs que variaram sob estresse biótico (Phakospora pachyrhizi) e abiótico (seca) e entre diferentes cultivares. A expressão do RNA 1 aumentou nas plantas sob estresse. Provavelmente o evento de integração ocorreu via recombinação à um retrotransposon. / The Soybean (Glycine max) is one of the world's most important crops, its seeds are used both as food and for the extraction of oil to manufacture biodiesel. The Cucumber mosaic virus (CMV) is a pathogenic RNA virus of plants. The RNA interference is a system of RNA silencing present in most eukaryotes in which precursors of double-stranded RNA (dsRNA) are processed into small RNAs (sRNAs) of 21-24 nucleotides (nt), which can regulate the activity of genes, genetic elements and virus in a sequence-specific manner. The integration of DNA virus and retrovirus into the host genome is well known both for prokaryotic and eukaryotic systems. The integration of non-retroviral RNA virus (NIRVs) in mammals was previously observed, but the present work is the first to demonstrate such an event in a plant genome. The sequences of the sRNAs ranging from 19 to 24 nt, in 15 libraries of sRNAs sequenced from samples of soybean tissues, were assembled in contigs by the program SOAP, with some preentering sequence homology to the RNA 1 of CMV. By de novo assembling of these contigs it was obtained a sequence of 3,092 nt of the CMV RNA 1, present in all libraries surveyed in at least five different varieties of soybeans. The presence of this sequence was confirmed by PCR in seven other cultivars, but in "Williams". We observed a greater presence of sRNAs derived from CMV of sense orientation than antisense in the 15 libraries sequenced. The 22-nt sRNAs were the most abundant. For the Bean pod mottle virus (BPMV), present in one of the libraries, the 21 and 22 nt sRNAs were represented by around 80% of all sRNAs. The sRNAs were found varying under biotic stress (Phakospora pachyrhizi) and abiotic (drought) and among different cultivars. RNA 1 expression increased in plants under stress. Probably the integration event occurred via recombination of a retrotransposon.

Includes bibliographical references (leaves 147-171). Studies factors affecting the rate of epidemic progress of cucumber mosaic virus in Lupinus angustifolius.

Includes bibliographical references (leaves 147-171). / xx, 171 leaves : ill. (some col.), photos ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Studies factors affecting the rate of epidemic progress of cucumber mosaic virus in Lupinus angustifolius. / Thesis (Ph.D.)--Dept. of Crop Protection, University of Adelaide,1992