RESUMO O comportamento alimentar de cigarrinhas vetoras de Xylella fastidiosa, agente causal da clorose variegada dos citros, pode influenciar sua eficiência de transmissão. Avaliou-se a influência das condições hídricas do solo e da temperatura ambiente na sobrevivência e alimentação do vetor Oncometopia facialis (Hemiptera: Cicadellidae) em "seedlings" de laranjeira doce (Citrus sinensis).O estudo foi realizado em câmara de crescimento, simulando-se condições de temperatura média e de fotofase de verão (24º C e 13h) e de inverno (19º C e 11h) da região Central do Estado de São Paulo. As plantas foram submetidas a dois regimes hídricos: capacidade de campo e déficit hídrico. A sobrevivência de O. facialis foi menor quando mantida em "seedlings" sob déficit hídrico, independentemente das condições de temperatura ("verão" ou "inverno"). A taxa de ingestão de seiva, medida indiretamente pela excreção de "honeydew", foi maior nos tratamentos mantidos em capacidade de campo para as duas condições de temperatura. Comprovou-se, então, que o déficit hídrico do solo reduz a sobrevivência e a taxa de alimentação de O. facialis em "seedlings" de citros. Os resultados sugerem uma menor adequação da planta cítrica às cigarrinhas durante épocas mais secas do ano.

ABSTRACT The feeding behavior of the leafhopper vectors of Xylella fastidiosa, the causal agent of Citrus Variegated Chlorosis, can influence its transmission efficiency. The influence of soil water conditions and environmental temperature on survival and feeding behavior of the leafhopper Oncometopia facialis (Hemiptera: Cicadellidae) was evaluated on sweet orange (Citrus sinensis) seedlings. This study was carried out in a growth chamber adjusted for mean temperature and photophase of summer (24º C and 13h) and winter (19º C and 11h) seasons in the Central Region of Sao Paulo State. The plants were submitted to two soil water treatments: field capacity and water deficit. The survival of the O. facialis was lower on seedlings under water deficit, regardless of the temperature conditions (summer or winter). The sap ingestion rates, which were indirectly measured by the honeydew excretion, were higher on seedlings under field capacity for both temperature conditions. This study shows that soil water deficit reduces leafhopper survival and ingestion rates on citrus seedlings, thus providing evidence that host plant suitability to the vector is affected during the dry season.

The reverse transcription-polymerase chain reaction (RT-PCR) is the most sensitive method used to evaluate gene expression. Although many advances have been made since quantitative RT-PCR was first described, few reports deal with the mathematical bases of this technique. The aim of the present study was to develop and standardize a competitive PCR method using standard-curves to quantify transcripts of the myogenic regulatory factors MyoD, Myf-5, Myogenin and MRF4 in chicken embryos. Competitor cDNA molecules were constructed for each gene under study using deletion primers, which were designed to maintain the anchorage sites for the primers used to amplify target cDNAs. Standard-curves were prepared by co-amplification of different amounts of target cDNA with a constant amount of competitor. The content of specific mRNAs in embryo cDNAs was determined after PCR with a known amount of competitor and comparison to standard-curves. Transcripts of the housekeeping ß-actin gene were measured to normalize the results. As predicted by the model, most of the standard-curves showed a slope close to 1, while intercepts varied depending on the relative efficiency of competitor amplification. The sensitivity of the RT-PCR method permitted the detection of as few as 60 MyoD/Myf-5 molecules per reaction but approximately 600 molecules of MRF4/Myogenin mRNAS were necessary to produce a measurable signal. A coefficient of variation of 6 to 19% was estimated for the different genes analyzed (6 to 9 repetitions). The competitive RT-PCR assay described here is sensitive, precise and allows quantification of up to 9 transcripts from a single cDNA sample.

Com o objetivo de estudar os efeitos das aplicações de cálcio via foliar e de boro via solo na produção e ocorrência de podridão apical em tomate em estufa, conduziu-se um experimento no município de Regente Feijó, SP, com solo classificado como Podzólico Vermelho-Amarelo, fase arenosa. Os tratamentos consistiram de três doses de boro (0, 1 e 2 g cova-1) e três freqüências de aplicação foliar de cloreto de cálcio a 0,6% (sem aplicação, aplicação semanal e quinzenal). Os resultados obtidos sugeriram que a aplicação de 1 g cova-1 de boro e freqüência de aplicação quinzenal de CaCl2 a 0,6% e a aplicação semanal de CaCl2 a 0,6% na ausência de boro constituíram-se nas melhores opções no sentido de conciliar maior produtividade e menor número de frutos com incidência de podridão apical.

With the objective of studying the effects of applying calcium through leaves and boron through soil on the productivity and blossom end rot of tomatoes, an experiment was carried out in a soil classified as a Sandy Red-Yellow Podzol. The treatments were three rates of B (0, 1 and 2 grams) and three rates of CaCl2 0.6% (without application and application each 7 or 14 days). The results obtained suggested that the application of 1 g B and of CaCl2 0.6% each 14 days and application of CaCl2 0.6% each 7 days in the absence of boron can be considered good options in order to obtain higher tomato production and lower number of fruits with the blossom end rot.

Com o propósito de avaliar a eficiência do gesso agrícola e do superfosfato simples em controlar as perdas de amônia por volatilização durante o processo de compostagem de estéreos, foi conduzido um experimento em frascos de vidro fechados de 1,6 litro de capacidade, nos quais diferentes quantidades (50, 100, 150 e 200 kg.t-1) daqueles materiais foram misturadas com um substrato composto de uma mistura de partes iguais (em massa) de estéreos frescos de galinha e de bovino. A amônia perdida por volatilização foi determinada após 7, 14, 21, 28 e 35 dias, coletando-se o gás em solução de ácido sulfúrico encerrada em pequeno recipiente o qual era, por sua vez, colocado no interior do frasco. O ácido remanescente após o período de exposição à amônia era determinado por titulação com solução de NaOH 0,025N. A quantidade de amônia perdida do estéreo por volatilização diminuiu com a adição de ambos os materiais estudados, mas para todas as doses aplicadas o gesso agrícola foi mais eficiente do que o superfosfato simples. Os decréscimos da volatilização foram tanto maiores quanto mais elevadas eram as doses de ambos os aditivos. Houve evidências de que a redução das perdas de amônia deveu-se à presença do gesso nos materiais estudados.

With the purpose of evaluating the effectiveness of phosphogypsum and simple superphosphate in controlling ammonia losses by volatilization during the process of manure composting, an experiment was carried out in closed flasks of 1.6 liter, in which different rates (50, 100, 150 and 200 kg.t-1) of phosphogypsum and simple superphosphate were mixed with a substrate composed of equal amounts (on weight basis) of fresh chicken manure and cattle manure. Ammonia lost by volatilization was determined after 7, 14, 21, 28 and 35 days by trapping the gas in sulfuric acid solution placed in a small glass vial which, in turn, was maintained inside the volatilization flask The remaining acid after the exposure to ammonia was determined by titration with 0.025N NaOH. The amount of ammonia lost by volatilization from the samples decreased with the addition of both products, but for all rates applied, phosphogypsum was more efficient than simple superphosphate. The reduction in volatilization increased with the rate of application of both additives. There was an evidence that the reduction of ammonia loss was due to the presence of gypsum in the additives.