3 research outputs found
Manejo da podridão-de-Sclerotium em pimentão em um argisolo no Amazonas
A podridão-de-Sclerotium é uma doença comum em plantas da famÃlia Solanaceae na Amazônia. Visando avaliar estratégias de manejo para esta doença em pimentão (Capsicum annuum, L. Solanaceae), foi conduzido experimento em campo em blocos casualizados com parcelas subdivididas e seis repetições, em Argissolo Vermelho-Amarelo artificialmente infestado com Sclerotium rolfsii. O tratamento principal foi a cobertura do solo (cobertura do solo com serragem ou solo nu). Os tratamentos secundários consistiram na adição ao solo de: 1) composto vegetal (3 L por cova), 2) arroz colonizado com Trichoderma harzianum (90 g por cova contendo ≈ 1,4 x 10(9) conÃdios g-1), 3) composto vegetal e T. harzianum nas mesmas proporções descritas anteriormente e 4) testemunha. Todas as plantas receberam apenas adubação orgânica com composto vegetal na proporção de 1,5 L por cova, exceto as dos tratamentos com 3 L de composto por cova. A parcela principal foi constituÃda de três fileiras com dez plantas de pimentão (0,50 x 1,0 m) e cada subparcela continha três fileiras com cinco plantas. A incidência da podridão-de-Sclerotium foi avaliada duas vezes por semana. A cobertura morta favoreceu significativamente a ocorrência da doença. Nas parcelas com esse tratamento o aumento da intensidade da doença, expressa em área abaixo da curva de progresso da doença (AACPD), foi 35,5% maior, em comparação com as parcelas sem cobertura morta. A aplicação de T. harzianum ou o incremento na quantidade de composto (de 1,5 para 3 L por cova) reduziu a AACPD em 38,1% e 37,5%, respectivamente. A aplicação de T. harzianum ou o incremento na quantidade de composto, mesmo nos tratamentos com cobertura morta, reduziu significativamente a AACPD em 52,8% e em 55,1%, respectivamente, em comparação com o tratamento apenas com cobertura morta. Esses resultados sugerem que a utilização de T. harzianum e o aumento na quantidade de composto por cova são estratégias eficientes de manejo da podridão-de-Sclerotium em pimentão. A cobertura morta com serragem não deve ser utilizada em áreas infestadas com S. rolfsii
GENETIC ENGINEERING OF ENDOPHYTIC BACTERIA: A NOVEL APPROACH FOR PRODUCING PEST-RESISTANT CORN
Genetic engineering techniques currently permit several approaches to produce crop plants with enhanced resistance to pests. Many groups are directly introducing genes which encode for pest resistance into the plant's genome. Crop Genetics International is developing an endophyte based technology for systemic delivery of biopesticides to corn and other crops. Defined broadly, an endophyte is a plant dependent microorganism that lives protected within the tissues of its host. Among endophytic bacteria, those associated with plant disease have been the past object of study. However, nonpathogenic bacterial endophytes present an opportunity for systemic delivery of genetically-engineered biopesticides and plant growth regulators. Crop Genetics has chosen a xylem-limited endophytic bacterium, Clavibacter xyli subsp. cvnodontis (Cxc) which occurs naturally in bermudagrass and is distributed throughout the southern two-thirds of the U.S. as well as Europe and Asia. Cxc is a fastidious microorganism with precise nutritional and environmental requirements. Cxc survival is brief outside the host plant in plant debris, soil, air or water, and the endophyte is not seed transmitted. Cxc, when modified with recombinant DNA techniques, provides a systemic delivery system for biopesticides within plants. The first product under development involves Cxc producing the delta-endotoxin of Bacillus thurinqiensis toxic to European corn borer (Ostrina nubilalis). Follow-on products will deliver other insecticides, fungicides, and plant growth enhancers. Crop Genetics has developed an inoculation technology to introduce the bacterium into seeds. The protocol includes imbibition followed by pressure treatment in a buffered solution containing the bacterium. Seeds are removed from the solution, dried, and coated with conventional seed coatings. This inoculation technology does not alter seed vigor or germination and provides a satisfactory shelf life of the product
Optimization and evaluation of heat-shock condition for spore enumeration being used in thermal-process verification: Differential responses of spores and vegetative cells of Clostridium sporogenes to heat shock
To evaluate a heat-shock condition for the enumeration of Clostridium sporogenes spores, a surrogate for C. botulinum spores, we examined the heat tolerance of C. sporogenes spores and vegetative cells exposed to a heat shock at 90°C. From the D values of the spores determined in the temperature range of 113–121°C, z value (±SD) and D90°C value were estimated to be 10.16±0.90°C and 1,071.52 min, respectively, and the inactivation rates were predicted to be only approximately 2% at 90°C for up to 10 min. Meanwhile, the viable count of spores was significantly higher when activated under a heat-shock condition of 90°C for over 9 min than those activated for shorter time periods. The heat tolerance of vegetative cells was extremely low, showing a D90°C value (±SD) of 0.21±0.01 min. Finally, 3 different heat-shock conditions were compared: 70°C for 30 min, 80°C for 20 min, and 90°C for 10 min, and the experimental comparative data showed no significant differences in viable spore counts. Consequently, these results support that the heat-shock treatment at 90°C for 10 min is suitable to activate spores and to inactivate vegetative cells of C. sporogenes