Agricultura urbana: desenvolvimento de um protótipo para o cultivo de hortaliças em ambiente residencial

O desenvolvimento de tecnologias e processos para a produção de alimentos em residências e na área urbana, tem sido uma tendência emergente nas áreas metropolitanas. O objetivo do presente trabalho foi o desenvolvimento e teste de um protótipo para o cultivo de hortaliças em ambiente residencial, para promover a segurança alimentar no meio urbano. Esse protótipo foi baseado nos princípios de um lisímetro de nível freático constante, pois permitiria um fluxo contínuo de água para a cultura pelo princípio da capilaridade, não demandava energia, e foi construído com materiais disponíveis para comercialização no meio urbano, como tubos, acessórios e conexões de PVC, e reservatórios de plástico. A instalação e testes hidráulicos do lisímetro foram realizados em uma residência na cidade de Sorocaba, reproduzindo as condições para a finalidade de produção residencial de alimentos. Após a construção e teste hidráulico, procedeu-se ao plantio da salsa (Petroselinum crispum). Três plantios foram realizados para se determinar a melhor profundidade do lençol freático, a qual foi de 0,20 m. Posteriormente, procedeu-se ao plantio do espinafre (Tetragonia expansa). Nesse experimento, além da matéria seca na época da colheita, foi levantada a cobertura vegetal e a altura do espinafre, ao longo do ciclo. As condições de umidade do solo permitiram um crescimento potencial da cultura, como pôde ser constatado por meio da avaliação visual e fotográfica da planta colhida, além dos dados de altura da planta, a qual atingiu 21 cm. Na colheita, a produtividade alcançou 1.265,1 kg.ha-1, considerando a matéria seca. Ao longo do ciclo da cultura do espinafre, o consumo de água foi monitorado e atingiu 74 mm, correspondendo a uma eficiência do uso da água de 0,25 kg.m-3, ou 17,10 t.ha-1.mm-1. A simplicidade construtiva e operacional, além da independência do suprimento de energia, demonstrou que o sistema foi adequado para o uso em residências, contribuindo para o planejamento do uso de recursos naturais voltados a promover a soberania e segurança alimentar no meio urbano.

Effect of Gamma Radiation on the Reduction of Salmonella strains, Listeria monocytogenes, and Shiga Toxin–Producing Escherichia coli and Sensory Evaluation of Minimally Processed Spinach (Tetragonia expansa)

This study evaluated the effects of irradiation on the reduction of Shiga toxin–producing Escherichia coli (STEC), Salmonella strains, and Listeria monocytogenes, as well as on the sensory characteristics of minimally processed spinach. Spinach samples were inoculated with a cocktail of three strains each of STEC, Salmonella strains, and L. monocytogenes, separately, and were exposed to gamma radiation doses of 0, 0.2, 0.4, 0.6, 0.8, and 1.0 kGy. Samples that were exposed to 0.0, 1.0, and 1.5 kGy and kept under refrigeration (4°C) for 12 days were submitted to sensory analysis. D10-values ranged from 0.19 to 0.20 kGy for Salmonella and from 0.20 to 0.21 for L. monocytogenes; for STEC, the value was 0.17 kGy. Spinach showed good acceptability, even after exposure to 1.5 kGy. Because gamma radiation reduced the selected pathogens without causing significant changes in the quality of spinach leaves, it may be a useful method to improve safety in the fresh produce industry.

Replication of Grapevine leafroll-associated virus-7 (GLRaV-7) by Cuscuta Species and Its Transmission to Herbaceous Plants

Grapevine leafroll-associated virus-7 (GLRaV-7) was transmitted from an Albanian grapevine accession to Tetragonia expansa by the parasitic dodder Cuscuta reflexa and to Nicotiana occidentalis by Cuscuta europea. Cuscuta campestris was infected by GLRaV-7 but could not transfer the virus to an experimental host. Transmission of the virus was verified by reverse transcription–polymerase chain reaction (RT-PCR) from total nucleic acid (TNA) and double-stranded RNA (dsRNA) extracts from all five plant species. DsRNA extractions separated on agarose gels showed strong visible bands corresponding to high-molecular-weight virus genome and to subgenomic RNA. GLRaV-7 was maintained in C. reflexa, C. campestris, T. expansa, and N. occidentalis for more than 4 years. Infected T. expansa and the Cuscuta species remained symptomless while N. occidentalis showed severe symptoms leading to stunting and decline of the plants. Quantitative PCR showed great differences in the titer of GLRaV-7 between the tissues of its natural and experimental host plants. This is the first report on a virus of the Closteroviridae that was successfully transmitted to an herbaceous plant by dodder. Virus replication could be demonstrated in Cuscuta. Both the new experimental hosts of GLRaV-7 and Cuscuta allowed extraction of dsRNA for further characterization of the viral genome, which previously required grapevine scraping of phloem. This is time-consuming and does not always lead to satisfactory results. These alternative hosts of GLRaV-7 facilitate nucleic acid extractions and could be used as model plants for etiological studies.

Chlorotic spots on Clerodendrum, a disease caused by a nuclear type of Brevipalpus (Acari:Tenuipalpidae) transmitted virus

Chlorotic spots have been observed in plants of Clerodendrum x speciosum growing in residential gardens and parks in Piracicaba, SP, Brazil. Thin sections of diseased tissues revealed characteristic cytopathic effects of the nuclear type of the Brevipalpus (Acari: Tenuipalpidae) mite-transmitted viruses (BTrV). Brevipalpus mites, identified as B. phoenicis, infesting symptomatic C. x speciosum plants transmitted the pathogen to healthy C. x speciosum and to C. thomsonae, Gomphrena globosa, Hibiscus cannabinus, H. coccineus, H. schizopetalus, Salvia leucantha, Spathiphyllum wallasi and Tetragonia expansa causing chlorotic spots on their leaves. Mechanical inoculation using leaf extracts from infected C. x speciosum resulted in chlorotic spots on inoculated C. x speciosum, Chenopodium quinoa, C. amaranticolor, G. globosa, H. cannabinus, H. coccineus and T. expansa leaves. C. amaranticolor and C. quinoa kept at 28 - 30°C became systemically infected. The same cytopathic effects caused by the nuclear type of BTrV were seen in tissues from all infected test plants by electron microscopy. The virus was purified from systemically infected leaves of C. amaranticolor and C. quinoa. A polyclonal antiserum obtained from an immunized rabbit presented a strong reaction with the homologous antigen in ELISA tests. The results suggest that this chlorotic spot disease of C. x speciosum is caused by a new species of the nuclear type of BTrV, tentatively named Clerodendrum chlorotic spot virus (ClCSV).

Characterization of a U.S. Isolate of Beet black scorch virus

The first reported U.S. isolate of Beet black scorch necrovirus (BBSV) was obtained and characterized. Host range of the virus for localized and occasionally systemic infection included the Chenopodiaceae and Tetragonia expansa; Nicotiana benthamiana supported symptomless systemic infection by the virus. The complete nucleotide sequence of the genomic RNA of the virus, designated BBSV-Co, exhibits 93% similarity to the genome of the ‘Ningxia’ isolate of BBSV from China. Amino acid sequence similarity in predicted genes ranged from 95% in the p4 gene to 97% in the p82 and coat protein genes. A potential additional gene exists within the U.S. isolate of BBSV that is absent from Chinese isolates of BBSV due to nucleotide differences between these isolates within the coat protein gene. Coat protein analysis by isoelectric focusing and by mass spectroscopy indicated the presence of phosphorylated residues. Using primer extension analysis of the 5′ end of the genome and site-directed mutants of genomic clones of BBSV-Co from which infectious RNA was produced, the native 5′ end of the BBSV-Co genome was determined to be 5′-GAAACCTAACC…3′, lacking the two terminal adenosine nucleotides in the published sequences of BBSV from China.