André Dusi

Garlic viruses often occur in mixed infections under field conditions. In this study, garlic samples collected in three geographical areas of Brazil were tested by Dot-ELISA for the detection of allexiviruses using monoclonal specific antibodies to detect Garlic virus A (GarV-A), Garlic virus B (GarV-B), Garlic virus C (GarV-C) and a polyclonal antiserum able to detect the three virus species mentioned plus Garlic virus D (GarV-D). The detected viruses were biologically isolated by successive passages through Chenopodium quinoa. Reverse Transcriptase Polimerase Chain Reaction (RT-PCR) was performed using primers designed from specific regions of the coat protein genes of Japanese allexiviruses available in the Genetic Bank of National Center of Biotechnology Information (NCBI). By these procedures, individual garlic virus genomes were isolated and sequenced. The nucleotide and amino acid sequence analysis and the one with serological data revealed the presence of three distinct alle...

Two transgenic potato clones of cv. Achat, denominated 1P and 63P were challenged with two Potato virus Y strains (PVY O and PVY N), under greenhouse conditions, to be evaluated for resistance to these strains. Optical density values of the Elisa readings of samples from the transgenic plants were compared to readings from samples of the inoculated non-transformed plants. Clone 1P was extremely resistant to both PVY strains, reflected by not being systemically infected. Clone 63P, however, presented partial resistance to both PVY strains as local or systemic infection was delayed in some days. These results confirm the previously reported extreme resistance to PVY of clone 1P.

Um isolado do vírus do enrolamento-da-folha-da-batata (PLRV) foi purificado segundo procedimento envolvendo extração enzimática, clarificação com Triton X - 100, clorofórmio e butariol, precipitação com PEG, centrifugações diferenciais e gradiente congelado de sacarose. A preparação purificada foi submetida a uma centrifugação isopícnica em gradiente de CsCl, estabilizada com formaldeido e injetada em coelho para produção de anti-soro. Este foi avaliado por DAS-ELISA no CNPH/EMBRAPA e por diversas instituições públicas e privadas. Os resultados indicam que o anti-soro produzido é específico e adequado ao uso em sistemas de indexação de batata-semente e para fins de pesquisa. Este trabalho concluiu o programa de produção de anti-soros para diagnose de vírus em batata, do CNPH/EMBRAPA, que também conta com anti-soros para detecção de APMV, PVS, PVX e PVY.An isolate of potato leaf roll virus (PLRV) was purified through enzimatic extraction, Triton X-100 and chloroform:butanol clarifica...

Com o objetivo de disponibilizar aos agricultores e, por conseguinte aos consumidores, cultivares de batata-doce com melhores teores de betacaroteno, a Embrapa realiza selecao de clones no âmbito do programa BioFORT: Biofortificacao no Brasil - desenvolvendo produtos agricolas mais nutritivos, que tem por finalidade desenvolver alimentos naturais com quantidades de nutrientes capazes de suprir a necessidade nutricional do corpo humano. O objetivo deste trabalho e apresentar os resultados obtidos numa avaliacao prelimar de 96 clones de batata-doce de polpa amarela e alaranjada, e identificar os promissores para avaliacoes subsequentes em difeentes regioes.

A cultura do ocupa, em média, 600 dias/homem/ha. Tem grande impacto social, pois é fator de fixação do homem no campo. Cada hectare gera quatro empregos diretos e quatro indiretos na cadeia produtiva. A abertura de mercado, especialmente com a entrada da China no comércio mundial, afetou a cadeia do alho no Brasil. Até início dos anos 2000, havia cerca de 14 mil ha da cultura no Brasil. A redução da área plantada a partir de 2004 para 8 mil ha causou a redução de 56 mil para 24 mil no número de postos diretos de trabalho. Historicamente, verifica-se uma correlação negativa altamente significativa (r = -0,81, p = 0,0001) entre a importação de alho e a área plantada no Brasil no ano seguinte (Figura 1). O aumento da importação é causador direto da redução de área plantada no Brasil.

Garlic shoot tip culture associated with dry heat thermotherapy (cloves exposed to 37°C for 35 days) were essential for recovering virus free plants of the cv Amarante. In this condition 70% of the explants developed in vitro and produced plants. A total of 77% of those plants was virus free when indexed by ISEM, which resulted in a final index of 54% of virus free plants from treated cloves. The percentage of regeneration decreased to 20% as the temperature increased up to 40°C. However 90% of those plants were virus free, leading to a final index of 18% virus free plants out of treated cloves.

<strong>Overview:</strong>The aim of the studies described in this thesis was to obtain a thorough understanding of the main factors determining the spread of a potyvirus in a high plant density crop. The factors studied included the relationships between virus, host and vector, the spread of the virus around an initial virus source consisting of one or more infected plants, the

Plantas de alho da cv. Amarante, cultivadas em casa de vegetação para detecção da ocorrência de viroses, foram naturalmente infestadas por afídeos de coloração escura durante a primavera de 2001. Com o objetivo de identificar a espécie em questão foram coletados indivíduos alados, capturados com armadilha constituída por bandeja amarela com água, além de formas ápteras. A identificação da espécie foi feita segundo a chave descritiva elaborada por Blackman…

ABSTRACT A viroid was detected in Chrysanthemum plants showing symptotns of stunting in a commercial field in Brazil. Analysis by return polyacrylamide gel electrophoresis (R-PAGE) of the nucleic acid preparations of leaves and flowers revealed the presence of a nucleic acid of low molecular weight with mobility within the range of viroids. The viroid-like band was completely eliminated by ribonuclease treatment or alkaline hydrolysis. The Chrysanthemum viroid was readily transmissible to Chrysathemum, tomnato and Gynura, which suggests that it may be an isolate of chrysanthemum stunt viroid.

ABSTRACT O objetivo deste trabalho foi avaliar a resistência de clones geneticamente modificados de batata ao Potato virus Y (PVY) em condições de campo. As plantas geneticamente modificadas foram comparadas com plantas não modificadas da mesma cultivar. As parcelas foram delimitadas com plantas infectadas com as estirpes PVYº e PVYN (linhas disseminadoras), para tornar disponível, na área experimental, a fonte de inóculo de vírus, que foi naturalmente disseminada pela população nativa de afídeos. O experimento foi monitorado semanalmente por inspeção visual e por DAS-Elisa nas plantas produzidas a partir dos tubérculos colhidos, para avaliar a resistência de plantas transgênicas ao longo do ciclo de crescimento. Ao final do terceiro ano, nenhum sintoma de infecção foi observado no clone 1P; o clone 63P apresentou 1% de infecção, em contraste com cerca de 90% de plantas-controle infectadas. A expressão estável da resistência ao PVY, conferida pelo gene da capa proteica, foi obtida em clones de batata geneticamente modificados da cultivar Achat, em condições de campo, durante três anos consecutivos.

ABSTRACT In order to understand the various factors which affect Beet mosaic virus (BtMV) epidemics, different aspects of the relationships between this virus, its vectors and sugar beet were studied. The latency and incubation periods, determined under growth chamber and field conditions, responded inversely to the temperature and leaf growth rate. Field-infected plants could function as virus sources during the whole growing season. The virus was transmitted by Acyrthosiphon pisum, Aphis fabae, Macrosiphum euphorbiae, Metopolophium dirhodum, Myzus persicae and Ropalosiphum padi. Myzus persicae retained the virus for at least 16 h. Alatae and apterae of M. persicae transmitted the virus with the same efficiency, and in at least two consecutive probes. The proportion of infected plants increased as a logarithmic function of the number of alatae of six aphid species used in the arena tests.ZusammenfassungBeet mosaic virus: Vektor und WirtsbeziehungenUm die verschiedenen Faktoren, die Beet mosaic virus (BtMV)-Epidemien beeinfluen, besser verstehen zu können, wurden unterschiedliche Aspekte in der Beziehung zwischen diesem Virus und dessen Vektoren sowie der Zuckerrübe untersucht. Sowohl die Latenz- als auch die Inkubationszeit, emittelt unter Bedingungen in Klimakammem und im Feld, reagierte umgekehrt mit der Temperatur und der Blattwachstumsrate. Infizierte Pflanzen im Feld könnten als eine Virusquelle über die ganze Wachstumsperiode dienen. Das Virus kann durch Acyrthosiphon pisum, Aphis fabae, Macrosiphum euphorbiae, Metopolophium dirhodum, Myzus persicae und Ropalosiphum padiübertragen werden. Das Virus kann durch M. persicaeüber einen Zeitraum von mindestens 16 Std. übertragen werden. Beflügelte und unbeflügelte M. persicaeübertrugen das Virus mit gleicher Wirksamkeit, auch über zwei aufeinander folgende Proben. Der Anteil an infizierten Pflanzen nahm als eine logarithmische Funktion der Anzahl der beflügelten Blattlausspezies im Test zu.

An arracacha (Arracacia xanthorrhiza) plant collected in Brazil was found to be infected by a new virus. This viral isolate (named C17) systemically infected Nicotiana benthamiana and Apium graveolens. A polyclonal antibody was raised, and analysis of our arracacha germplasm collection showed a high infection rate of C17-like viruses (93% infection). Sequencing of the ca. 1.7 kb 3'-terminal genomic region revealed a typical potyvirus genome organization. It shared less than 70% nucleotide identity with any other potyvirus sequence, which thus indicated that it is possibly a member of a new Potyvirus species tentatively named Arracacha mottle virus (AMoV).

Arracacha mottle virus (AMoV) is the only potyvirus reported to infect arracacha (Arracacia xanthorrhiza) in Brazil. Here, the complete genome sequence of an isolate of AMoV was determined to be 9,630 nucleotides in length, excluding the 3' poly-A tail, and encoding a polyprotein of 3,135 amino acids and a putative P3N-PIPO protein. Its genomic organization is typical of a member of the genus Potyvirus, containing all conserved motifs. Its full genome sequence shared 56.2 % nucleotide identity with sunflower chlorotic mottle virus and verbena virus Y, the most closely related viruses.

ABSTRACT The effect of the inoculation date on the spread of Beet mosaic virus (BtMV) in sugar beet field plots was studied. Two plants in the centre of each plot were inoculated with BtMV using Myzus persicae. The spread of the infection around these sources was monitored by inspecting the plants on two diagonal transects through the centre of the plot. Early inoculations resulted in a greater spread than late inoculations, but any inoculation before the onset of the aphid migration resulted in a similar-sized spread. The spread was concentrated in patches around the inoculated plants, and its rate was explained by vector pressure, as shown by regression analysis and a mechanistic simulation model. This vector pressure was quantified using data obtained by catching aphids in a green water trap in the crop, catching aphids in a 12 m high suction trap at a distant location, and infection of bait plants from adjacent virus source plants. The daily total aphid catches obtained by a suction trap provided the best statistical explanation for the spread of this virus. The parameter r, describing the relationship between vector pressure and the rate of disease progress, was remarkably robust. This parameter varied less than 10␋etween treatments (infection date) within a single experiment, and less than a factor two between four experiments performed at different sites in two years. The robustness of this parameter suggests that the spread of a potyvirus may be predicted on the basis of the initial infection date and vector abundance