Vanessa Nogueira Soares

Influência da microbiolização de sementes de feijão sobre a transmissão de Colletrichum Lindemuthianum (Saac e Magn)

Isolates of Pseudomonas veronii (DFs513), Bacillus spp. (DFs093 and DFs348), Bacillus cereus (DFs769), Rodhococcus fascians (DFs843 and DFs912) and Pseudomonas fluorescens (DFs831 and DFs842), selected for Xanthomonas axonopodis pv. phaseoli control, and a combination of some of these bacteria isolates, were evaluated for possible influence on Colletotrichum lindemuthianum transmission from naturally infected and/or infested bean seeds to seedlings. In the first trial, using the paper roll method, seeds were sown in eight replications of 25 seeds that were incubated at 20 ± 2°C. Germination percentage and pathogen incidence were evaluated. In the second trial, pathogen transmission to seedlings was evaluated in sterile substratum and incubated for 10 days. Daily emerged seedlings, pathogen incidence, leaf and root dry mass were determined. An isolate of C. lindemuthianum was used against the biocontroller isolates to evaluate in vitro antibiosis. All of the treatments reduced C. lindemuthianum transmission to seedlings in at least one of the trials. However, isolate DFs912 (Rhodococcus fascians) was shown to be important and presented reductions in transmission that varied from 40 to 67% in all of the experiments. All the treatments promoted leaf and root mass increase on total number or on the number per plant. Results in vitro showed that isolates DFs831, DFs842, DFs843 and DFs912 produced antibiotic compounds.

Potencial fisiológico de sementes de arroz tratadas com rizobactérias ou tiametoxam

Development of new technologies, aiming at increasing productivity in different crops, involves constant research on the effectiveness and application of these techniques in seed treatment. In this study, it was aimed at evaluating physiological potential of rice seeds treated with plant growth-promoting rhizobacteria (PGPR) (strains DFs185, DFs223, DFs306, DFs416), or with two dosages of the insecticide thiamethoxam. The variables assessed were: germination (G); first count of germination (FCG); cold test (CT); length of seedlings aerial parts (LAP), root system (LRS), and total length (TL); emergence speed index (ESI); emergence (E), at 14 days; and dry phytomass (DP). Treatments have had a positive effect on percentage of G, FCG and E. The strain DFs185 has promoted increase in percentage emergence, for five of the six lots assessed. The variables: LAP; LRS; TL; ESI; and DP have undergone low or none influence of treatments; and there has been no toxic effect of rhizobacteria or insecticide thiamethoxam. In the cold test, a negative effect of treatments has been detected. Seed treatment with rhizobacteria, as well as with thiamethoxam, improve quality of low quality rice seeds. The strain DFs185 is promising for treating rice seeds, once it stimulates seed germination and emergence.

Qualidade fisiológica de sementes de soja durante o armazenamento após revestimento com agroquímicos

A protecao das sementes contra pragas e doencas nas fases iniciais do desenvolvimento da cultura e de grande importância para a cadeia produtiva da soja. A aplicacao de inseticidas e fungicidas via revestimento de sementes proporciona esta protecao, no entanto, nao deve ocasionar prejuizos a qualidade fisiologica dos lotes de sementes, seja imediatamente depois do revestimento ou apos armazenamento. Para avaliar o efeito do revestimento de sementes de soja com varios agroquimicos sobre a qualidade fisiologica das mesmas durante o armazenamento, foram realizados dois ensaios com as cultivares M6972 IPRO e M7739 IPRO. Vinte quilogramas de cada cultivar foram submetidos a revestimento com os produtos Cropstar, Derosal Plus, Standak Top e Avicta Completo, avaliando-se a primeira contagem de germinacao, germinacao, envelhecimento acelerado e emergencia em canteiro das sementes, durante 60 dias de armazenamento sob condicoes ambientais nao controladas. O armazenamento sob condicoes de temperatura e umidade relativa nao controladas influencia negativamente a qualidade fisiologica das sementes de soja. As cultivares usadas responderam de forma diferente ao revestimento de sementes com os diferentes agroquimicos testados. O revestimento de sementes de soja da cultivar M6972 IPRO com Standak Top ou com Avicta Completo mantem a percentagem de emergencia de plântulas durante os 60 dias de armazenamento. O revestimento de sementes de soja da cultivar M7739 IPRO com Standak Top ocasiona maior qualidade fisiologica de sementes do que os demais revestimentos.

Cooling of soybean seeds and physiological quality during storage

The aim of this study was to evaluate the physiological quality of soybean seeds submitted or not to dynamic cooling, and kept in cold storage (CS) and non-cold storage (NCS). A soybean seeds lot, variety M7639RR, was divided into two parts, and each one was subdivided into three parts that were subjected to one of these cooling procedure: seeds without cooling (SWC), dynamic cooling at 17 °C (SC17), and dynamic cooling at 13 °C (SC13). Seeds were kept in CS and NCS at 20 °C. Samples were collected at six times (0, 45, 90, 135, 180 and 225 days), and then submitted to germination, tetrazolium, accelerated aging and seedling emergence tests. Dynamic artificial cooling at 13 °C followed by maintenance at 20 °C ensured the preservation of physiological quality of soybean seeds for up to 225 days. The vigor of the soybean seeds subjected to dynamic cooling at 13 °C was better preserved than that of the non-cooled or of the cooled at 17 °C ones and kept in NCS for 225 days. CS at 20 °C contributed to the preservation of the physiological quality of the soybean seeds, regardless of whether or not they were submitted to the dynamic procedure.

Performance fisiológica de sementes de milheto (Pennisetum americanum) tratadas com bioativador

No Brasil, de entre as especies de gramineas forrageiras tropicais utilizadas para pastagens, que se reproduzem por sementes, destaca-se o milheto como promissor pela sua ampla adaptacao a diferentes tipos de clima, inclusive o da regiao sul do pais. Geralmente, os inseticidas e fungicidas sao avaliados quanto a eficiencia no controle de pragas e doencas, todavia, alguns podem provocar efeitos ainda pouco conhecidos, nomeadamente a capacidade de modificar o metabolismo e a morfologia vegetal (bioativador). O objetivo deste trabalho foi avaliar a influencia do inseticida tiametoxam no comportamento fisiologico de sementes de milheto. Foram utilizados tres lotes de sementes de milheto, e as concentracoes do produto 100; 200; 300 e 400 ml de tiametoxam para 100 kg de sementes; tambem se analisou a nao aplicacao do inseticida. Para a avaliacao da qualidade fisiologica das sementes foram conduzidos os testes de primeira contagem de germinacao e germinacao final, teste de frio, teste de envelhecimento acelerado e testes de comprimento de plântula (parte aerea e radical). Verificou-se que o produto tiametoxam estimula o desempenho fisiologico de sementes de milheto, com intensidade variavel de acordo com o lote. Doses de 210 a 230 ml de produto por 100 kg de semente mostram maior eficiencia ao favorecer o desempenho fisiologico de sementes de milheto.

Calidad fisiológica de semillas de berenjena, morrón y tomate tratadas con bioactivador

El objetivo de este trabajo es definir la frontera de produccion de arroz y definir los niveles de ineficiencia tecnica y economica a nivel de chacra para un grupo de productores arroceros del Este de Uruguay. La frontera se determino utilizando la metodologia analisis envolvente de datos (DEA). Se determinaron cuatro tipos de eficiencias: tecnica, de escala, de asignacion y economica. En un segundo paso se estimo el efecto de las variables de manejo y ambientales sobre los resultados de eficiencia. La estimacion se realizo mediante una regresion truncada debido a la naturaleza del proceso generador de datos. Los datos corresponden a 573 chacras de arroz, de 26 productores diferentes y corresponden a las zafras entre 2004/05 y 2008/09. Los resultados indican que son 10 las chacras que definen la frontera de produccion considerando rendimientos constantes a escala (eficientes) y que el promedio de eficiencia tecnica es de 0,6. Con rendimientos variables a escala el numero de chacras eficientes aumenta a 25 y el promedio de eficiencia tecnica aumenta a 0,74. Al considerar los precios de insumos y productos el numero de chacras economicamente eficientes es 3 y el promedio de eficiencia es 0,53. Los resultados de la regresion truncada sobre los distintos indicadores de eficiencia indican que los determinantes mas importantes son la eleccion de variedades y el tipo de suelo. Tipo de siembra, laboreos y epoca de laboreo tienen efectos significativos sobre algunos tipos de eficiencia.