Incidence of pectolytic erwinias associated with blackleg of potato in Rio Grande do Sul

Erwinia carotovora subsp. atroseptica (Eca), E. carotovora subsp. carotovora (Ecc) and E. chrysanthemi (Ech) may cause potato (Solanum tuberosum) blackleg. To determine the occurrence of these pathogens in the conditions found in the State of Rio Grande do Sul (RS), potato plants showing blackleg symptoms were harvested from 22 fields in nine counties in Serra do Nordeste, Planalto, Depressão Central, and Grandes Lagoas, from September to December of 1999 (Spring-Summer season). Green pepper (Capsicum annuum) fruits were used as a host to enrich for pectolytic erwinia from potato stems with blackleg symptoms. Bacteria were subsequently isolated on non-selective medium. Isolates that were Gram-negative, facultatively anaerobic, and pitted crystal-violet-pectate medium were tested for biochemical traits to identify the species and subspecies. Four hundred strains were identified as either Eca, Ecc or Ech. Although the three erwinias were found in RS potato fields, only three strains of Ech were found in one field. Frequencies of Eca and Ecc were 55 and 42%, respectively. Eight strains could not be assigned based on the biochemical characterization.

Transmissão por afídeos e afinidade a Buchnera sp. GroEL de um mutante deletério da proteína de RTD do Potato leafroll virus

Potato leafroll virus (PLRV), gênero Polerovirus, família Luteoviridae, é transmitido por afídeos de um modo persistente e circulativo. Membros da família Luteoviridae associam-se a um homólogo de GroEL produzido pelo endosimbionte primário (Buchnera sp.) de afídeos para evitar a degradação na hemolinfa. Partículas purificadas de luteovirus contêm dois tipos de proteínas: a capa protéica (CP) de ~22 kDa e um componente "capsidial" de 54 kDa, o qual é uma forma truncada de uma proteína de "transleitura" a partir do códon de terminação do gene da CP. O domínio de transleitura (RTD) contém determinantes responsáveis pela transmissão do vírus. Um clone de cDNA infeccioso do PLRV e um mutante deletério da RTD foram usados para analisar as interações entre esse luteovirus e seu afídeo vetor Myzus persicae. As partículas mutantes do PLRV, deficientes da proteína RTD inteira, não foram transmissíveis por M. persicae e não se ligaram a Buchnera GroEL. Adicionalmente, esse mutante foi menos persistente na hemolinfa do afídeo do que o vírus selvagem.

Resistência de cultivares e linhagens de tomateiro a Tomato chlorotic spot virus e a Potato virus Y

Linhagens avançadas do programa de melhoramento do tomateiro (Lycopersicon esculentum) do IAC foram avaliadas em condições de campo em Campinas (SP) para resistência a tospovírus e a potyvírus, nos anos agrícolas 2002/2003 e 2003/2004, respectivamente. No primeiro ano, a única espécie de tospovírus que ocorreu na área experimental foi Tomato chlorotic spot virus (TCSV). As sete linhagens do grupo IAC exibiram baixa porcentagem de plantas sintomáticas em duas avaliações, com médias abaixo de 28%; as cultivares testadas mostraram-se altamente suscetíveis, com médias acima de 85%, à exceção de 'Franco', que apresentou cerca de 55% de infecção. No segundo experimento, conduzido em 2003/2004, dez linhagens do grupo IAC foram comparadas com cinco cultivares de polinização aberta e híbridos F1, além do acesso LA-444-1 de L. peruvianum. Nesse experimento, por meio de testes biológicos e sorológicos, verificou-se ocorrência generalizada de Potato virus Y (PVY). Foi determinado o percentual de plantas com sintomas e avaliada a intensidade dos sintomas mediante uso de escala de notas. Com base nos dois critérios, verificou-se que LA-444-1 apresenta alta resistência a PVY, que 'Tyrade' exibe comportamento intermediário, enquanto todos os demais genótipos demonstram alta suscetibilidade ao vírus. O comportamento dos genótipos avaliados neste trabalho mostra a necessidade de se considerar, nos programas de melhoramento do tomateiro, a introgressão de fatores de resistência não só a vírus de importância atual nas regiões produtoras, como geminivírus, mas também a outros vírus potencialmente nocivos à cultura, como tospovírus e potyvírus.

Epidemiological analysis of clones and cultivars of potato in soil naturally infested with Ralstonia solanacearum biovar 2

The objectives of this study were to evaluate the progress of Ralstonia solanacearum bacterial potato wilt biovar 2 (race 3) in 14 potato (Solanum tuberosum L.) cultivars or clones, the resistance of potato clone MB 03 (selected in Brasília, Brazil) to race 1 of R. solanacearum, and the occurrence of the pathogen in tubers harvested from asymptomatic potato plants. During the spring (September to the end of November in the southern hemisphere) of 1999 and 2000, 14 cultivars or clones were grown in a field naturally infested with R. solanacearum biovar 2, in Caxias do Sul, RS. The number of wilted potato plants was recorded each week and a disease progress curve plotted, the resistance of the potato genotypes to bacterial wilt being evaluated by determining the area under the curve. Various models were evaluated to fit the curves, with the logistic model being the best fit. At the end of each growing season tubers produced by asymptomatic plants were harvested and stored until budding and then tested for the presence of R. solanacearum. Cultivar Cruza 148 and clone MB 03 were the most resistant but both showed tubers with latent infections. The epidemiological implications of the incidence of R. solanacearum biovar 2 (race 3) in potato crops, as well as the resistance of certain genotypes that may harbor latent infections, are important aspects to be considered in the integrated management of bacterial wilt.

Effect of Potato virus X on total phenol and alkaloid contents in Datura stramonium leaves

The present paper reports results of the effect of Potato virus X (PVX) on the contents of total phenols and alkaloids in leaves of Datura stramonium. A significant decrease in the contents of phenols and alkaloids was observed in leaves inoculated with PVX (X-I). However, there was an increase in the percentage of phenols in leaves rubbed with phosphate buffer (C1-I) and in leaves from the nodes immediately above, possibly induced by mechanical injury. Gas chromatography/mass spectroscopy revealed amounts of scopolamine in samples submitted to all treatments, except X-I, in which the amount of this alkaloid was low. High amounts of an unidentified compound (molecular ion m/z 302 and a prominent peak at m/z 129) were noted in extracts from leaves X-I, C1-I and leaves from the nodes immediately above the leaves inoculated with PVX. It is suggested that the synthesis and accumulation of the unidentified compound is a result of stress from mechanical injury and virus inoculation.

Solanum americanum: reservoir for Potato virus Y and Cucumber mosaic virus in sweet pepper crops

Weeds can act as important reservoirs for viruses. Solanum americanum (Black nightshade) is a common weed in Brazil and samples showing mosaic were collected from sweet pepper crops to verify the presence of viruses. One sample showed mixed infection between Cucumber mosaic virus (CMV) and Potato virus Y (PVY) and one sample showed simple infection by PVY. Both virus species were transmitted by plant extract and caused mosaic in tomato (Solanum lycopersicum cv. Santa Clara), sweet pepper (Capsicum annuum cv. Magda), Nicotiana benthamiana and N. tabaccum TNN, and local lesions on Chenopodium quinoa, C. murale and C. amaranticolor. The coat protein sequences for CMV and PVY found in S. americanum are phylogenetically more related to isolates from tomato. We conclude that S. americanum can act as a reservoir for different viruses during and between sweet pepper crop seasons.

Antimicrobial activity of extracellular metabolites from antagonistic bacteria isolated from potato (Solanum phureja) crops

Microorganisms for biological control are capable of producing active compounds that inhibit the development of phytopathogens, constituting a promising tool toob tain active principles that could replace synthetic pesticides. This study evaluatedtheability of severalpotentialbiocontrol microorganismsto produce active extracellular metabolites. In vitro antagonistic capability of 50 bacterial isolates from rhizospheric soils of "criolla" potato (Solanum phureja) was tested through dual culture in this plant with different plant pathogenic fungi and bacteria. Isolates that showed significantly higher antagonistic activity were fermented in liquid media and crude extracts from the supernatants had their biological activities assessed by optical density techniques. Inhibitory effecton tested pathogens was observed for concentrations between 0.5% and 1% of crude extracts. There was a correlation between the antimicrobial activity of extracts and the use of nutrient-rich media in bacteria fermentation. Using a bioguided method, a peptidic compound, active against Fusarium oxysporum, was obtained from the 7ANT04 strain (Pyrobaculum sp.). Analysis by nuclear magnetic resonance and liquid chromatography coupled to mass detector evidenced an 11-amino acid compound. Bioinformatic software using raw mass data confirmed the presence of a cyclic peptide conformed by 11 mostly non-standard amino acids.

Operational performance of the mechanized and semi-mechanized potato harvest

Potato is an important crop plant throughout the world. Harvesting is a fundamental step in its production system. Maybe, it is the most complex and expensive operation. Thus, the objective of this work was to compare the cost of the mechanized and semi-mechanized harvest, the operational capacity and the production losses during the potato harvest process. The work was accomplished in a commercial farming, cultivated under pivot system, in the municipal district of Perdizes - MG, Brazil. A completely randomized design with two treatments was used: mechanized and semi-mechanized harvest. The mechanized harvest used a self-propelled harvester. In the semi-automated harvest, a digger mounted on tractor was used and the potato was manually harvested. It was concluded that the cost of mechanized harvest was 49.03% lower than the cost of semi-mechanized harvest. On average, the harvester had a work for 23 workers in manual harvest. Mechanized harvest showed losses of 2.35% of potato yield, while the semi-mechanized harvest showed losses of 6.32%.

Impact of elevated temperature scenarios on potato leaf development

The objective of this study was to simulate the impact of elevated temperature scenarios on leaf development of potato in Santa Maria, RS, Brazil. Leaf appearance was estimated using a multiplicative model that has a non-linear temperature response function which calculates the daily leaf appearance rate (LAR, leaves day-1) and the accumulated number of leaves (LN) from crop emergence to the appearance of the upper last leaf. Leaf appearance was estimated during 100 years in the following scenarios: current climate, +1 °C, +2 °C, +3 °C, +4 °C e +5 °C. The LAR model was estimated with coefficients of the Asterix cultivar in five emergence dates and in two growing seasons (Fall and Spring). Variable of interest was the duration (days) of the crop emergence to the appearance of the final leaf number (EM-FLN) phase. Statistical analysis was performed assuming a three-factorial experiment, with main effects being climate scenarios, growing seasons, and emergence dates in a completely randomized design using years (one hundred) as replications. The results showed that warmer scenarios lead to an increase, in the fall, and a decrease, in the spring growing season, in the duration of the leaf appearance phase, indicating high vulnerability and complexity of the response of potato crop grown in a Subtropical environment to climate change.

Evapotranspiration and crop coefficient for potato in organic farming

The aim of this study was to quantify the water consumption and the crop coefficients (Kc) for the potato (Solanum tuberosum L.), in Seropédica, Rio de Janeiro (RJ), Brazil, under organic management, and to simulate the crop evapotranspiration (ETc) using the Kc obtained in the field and the ones recommended by the Food and Agriculture Organization (FAO). The water consumption was obtained through soil water balance, using TDR probes installed at 0.15m and 0.30m deep. At the different stages of development, the Kc was determined by the ratio of ETc and reference evapotranspiration, obtained by Penman-Monteith FAO 56. The crop coefficients obtained were 0.35, 0.45, 1.29 and 0.63. The accumulated ETc obtained in the field was 109.6 mm, while the ETc accumulated from FAO's Kc were 142.2 and 138mm, respectively, considering the classical values and the values adjusted to the local climatic conditions. The simulation of water consumption based on meteorological data of historical series from 1961 to 2007 provided higher value of ETc when compared with the one obtained in the field. From the meteorological data of historical series, it was observed that the use of Kc recommended by FAO may overestimate the amount of irrigation water by 9%, over the same growing season.

Distribution pattern, surface tension and contact angle of herbicides associated to adjuvants on spraying and control of Ipomoea hederifolia under rainfall incidence

ABSTRACTScarlet Morning Glory is considered to be an infesting weed that affects several crops and causes serious damage. The application of chemical herbicides, which is the primary control method, requires a broad knowledge of the various characteristics of the solution and application technology for a more efficient phytosanitary treatment. Therefore this study aimed to characterize the effect of rainfall incidence on the control of Ipomoea hederifolia, considering droplet size, surface tension, contact angle of droplets formed by herbicides liquid on vegetal and artificial surfaces, associated to adjuvants and the volumetric distribution profile of the spray jet. The addition of the adjuvants to the herbicide spraying liquid improved the application quality, as it influenced the angle formed by the spray by broadening the deposition band of the spray nozzle and thus the possible distance between the nozzles on spray boom and due the changes at droplet size, which contribute to a safety application. The rainfall occurrence affected negatively the weed control with the different spraying liquids and also the dry matter weight, suggesting that the phytosanitary product applied was washed off.

Intoxicações experimental e natural por Ipomoea asarifolia (Convolvulaceae) em búfalos e outros ruminantes

Através de experimentos por via oral, verificou-se que o búfalo é tão sensível quanto o bovino à intoxicação por Ipomoea asarifolia R. et Schult., planta responsável por ocasionais surtos de intoxicação em bovinos, ovinos e caprinos. Uma a quatro doses diárias de 10-20g/kg provocaram o aparecimento de sintomas acentuados e bastante semelhantes em ambas as espécies, consistindo principalmente em incoordenação, tremores musculares e balanço da cabeça, inclusive da parte anterior do corpo (movimento pendular). Em búfalos, os sintomas de incoordenação eram um pouco menos acentuados, com tendência de os animais permanecerem em decúbito esternal. Embora não haja nenhum relato de intoxicação natural por I. asarifolia em búfalos, é possível que casos de intoxicação nessa espécie estejam passando despercebidos.

Experimental swainsonine poisoning in goats ingesting Ipomoea sericophylla and Ipomoea riedelii (Convolvulaceae)

Ipomoea sericophylla and Ipomoea riedelii cause a glycoprotein storage disease in goats. This paper reports the experimental poisoning in goats by dried I. sericophylla and I. riedelii containing 0.05% and 0.01% swainsonine, respectively. Three groups with four animals each were used. Group 1 received daily doses of 2g/kg body weight (bw) of dried I. sericophylla (150mg of swainsonine/kg). Goats from this group had clinical signs 36-38 days after the start of ingestion. Group 2 received dried I. riedelii daily doses of 2g/kg of I. riedelii (30mg of swainsonine/kg) for 70 days. No clinical signs were observed, therefore the swainsonine dose was increased to 60mg/kg for another 70 days. Goats from Group 2 had clinical signs 26-65 days after increase in swainsonine dose to 60mg/kg. Group 3 was used as control. In these experiments the minimum toxic dose was 60mg/kg which represents 0.0004% of the dry matter in goats ingesting 1.5% bw of the dry matter. For goats ingesting 2%-2.5% bw of dry matter this dose would be 0.00024%-0.0003% of the dry matter. After the end of the experiment two goats were euthanized and another six were observed for recovery of clinical signs. Four goats that continued to consume swainsonine containing plant for 39-89 days after the first clinical signs had non reversible signs, while two goats that ingested the plant for only 15 and 20 days after the first clinical signs recovered completely. These and previous results indicate that irreversible lesions due to neuronal loss occur in goats that continue to ingest the plants for about 30 days after the first clinical signs. Clinical signs and histological lesions were similar to those reported previously for goats poisoned by swainsonine containing plants. No significant alterations were found in packed cell volume, red and white blood cell counts, hemoglobin and mean corpuscular hemoglobin concentrations, mean corpuscular volume, and serum levels of glucose, total protein, and albumin, and the serum activities of gamma glutamyl transferase and aspartate aminotransferase. Swainsonine concentration of 0.05% in I. sericophylla and 0.01% in I. riedelii are different from samples of these plants used in previous experiments, which contained 0.14% and 0.5% swainsonine, respectively, demonstrating a wide variation in the toxicity of different samples.

Intoxicação espontânea por Ipomoea carnea subsp. fistulosa (Convolvulaceae) em bovinos no Pantanal Matogrossense

Relata-se a intoxicação espontânea por Ipomoea carnea subsp. fistulosa (canudo, algodoeiro) em bovinos no Pantanal Matogrossense. As investigações iniciaram após a morte de 12 bovinos, de um rebanho de 500 animais, criados em uma extensa área intensamente infestada por I. carnea subsp. fistulosa com escassa disponibilidade de outra forragem. As mortes ocorreram entres os meses de junho e setembro de 2006. O quadro clínico foi caracterizado por emagrecimento e sinais neurológicos com dificuldade locomotora. Um bovino foi necropsiado sem que se observassem alterações macroscópicas significativas. Histologicamente havia tumefação e vacuolização celular, em neurônios, células acinares pancreáticas, tubulares renais e foliculares da tireóide. Bovinos com quadro clínico similar foram retirados da área invadida por I. carnea subsp. fistulosa e colocadas em áreas com pastagem nativa e de Brachiaria sp. e apresentaram melhora clínica após período de 15 dias.