Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2010. / Härtill 4 uppsatser.

Submitted by Marco Antônio de Ramos Chagas (mchagas@ufv.br) on 2017-05-03T16:25:19Z No. of bitstreams: 1 texto completo.pdf: 264169 bytes, checksum: 7e0b0fa3ed22dc10518d5006802eb10c (MD5) / Made available in DSpace on 2017-05-03T16:25:19Z (GMT). No. of bitstreams: 1 texto completo.pdf: 264169 bytes, checksum: 7e0b0fa3ed22dc10518d5006802eb10c (MD5) Previous issue date: 2005-03-29 / A requeima, causada por Phytophthora infestans, é uma doença destrutiva da batateira e do tomateiro. Há poucas informações quanto a potenciais fontes de inóculo primário do patógeno no Brasil. Os objetivos deste trabalho foram: determinar o tempo de sobrevivência do patógeno em hastes, folíolos e frutos de tomateiro em solo; verificar a especificidade de P. infestans por meio de teste centrífugo-filogenético com a inclusão de espécies nativas do Brasil e estudar a dinâmica temporal do inóculo de P. infestans no ar. Avaliou-se a sobrevivência em restos culturais de tomateiro, tanto em casa de vegetação como no campo. A sobrevivência do patógeno em restos culturais foi inferior a 100 e 35 dias em casa de vegetação e no campo, respectivamente. Em casa de vegetação, a quantidade de estruturas do patógeno visualizadas em microscópio estereoscópico foi maior em tratamentos mantidos em solo seco, que aqueles mantidos em solo úmido. Dois isolados de P. infestans, da linhagem clonal US-1, obtidos de tomateiro, e dois de BR-1, obtidos de batateira, foram inoculados em plantas de 43 espécies. Além das plantas de batata e tomate, apenas plantas de Petunia hybrida e Nicotiana benthamiana foram suscetíveis ao patógeno. A ocorrência de esporângios de P. infestans foi monitorada em condições de campo com armadilhas Rotorod, Burkard e plantas de tomate e batata. Esporângios foram observados ao longo de todo o ano de 2004 e início de 2005. A captura de esporângios de P. infestans realizada pela Burkard foi maior no período das 6:00 às 18:00 h. Conclui-se que o inóculo advindo do ar é mais importante para o início de epidemias de requeima, que aquele em restos de cultura. / Tomato and potato late blight, caused by Phytophthora infestans, is one of the most important diseases of these crops in Brazil. Despite its importance, little is known about inoculum dynamics in tropical/subtropical areas, particularly in Brazil. The objectives of this study were: to determine survival period of P. infestans on stems, leaflets, and tomato fruits buried or not in soil; to assess the specificity of P. infestans to different hosts, mainly towards solanaceous species commonly found in Brazil and to study aerial inoculum (sporangia) temporal dynamics. Survival of P. infestans associated with tomato plant parts under greenhouse and field conditions was less than 100 and 35 days, respectively. Under greenhouse, pathogen structures were more promptly identified on crop debris kept on dry than on wet soil conditions. Isolates of two clonal lineages of P. infestans, US-1 and BR-1, isolated from tomato or potato, respectively, were inoculated on 43 plant species. Only two species, Petunia hybrida and Nicotiana benthamiana, were susceptible to P. infestans. Sporangia were monitored by Rotorod and Burkard spore traps and also by tomato and potato trap plants. Sporangia were captured in most weeks throughout 2004 and in the first two weeks of 2005. Most airborne inoculum captured with the Burkard trap was between 6:00 and 18:00 h. Airborne inoculum is abundant and is more important to late blight outbreaks than inoculum produced in crop debris. / Dissertação importada do Alexandria

In Bolivia, tomato acreage is 6717 and has a yield of 12005 kg/ha and the total production is 80,636 TM. Departments that harvest tomato are Santa Cruz, Cochabamba and La Paz, Santa Cruz being the department that shows the highest rates of production with 40653 TM in comparison with La Paz which has a production of 3109 TM and Cochabamba of 2420 TM. The principle factors in affect are, the best climatic conditions in Santa Cruz, while Cochabamba and La Paz have differences in seasonal changes (National Institute of Statistics, 1998). The importance of the tomato harvest lies in consumption preference, for the nutritional properties, as they provide a rich source of Vitamins A and C, principally for its qualities of high productivity in terms of yield per area, being a factor of great importance in the economy of the farmer. The repeated production of tomato in the same area or locality tends to create problems phytopathologicals caused by fungi, bacteria and viruses, that at times become difficult to handle, thus becoming serious limiting factors that are able to seriously affect the yields, as such the investigation of sickness control is of extreme importance. The community of Carmen Pampa belonging to the municipality of Coroico, Nor Yungas, constituting a suitable area for the cultivation of tomato, but the attack of diseases caused by fungi, principally Phytophtora infestans, with an incidence of rate of 98%, which is increased by high temperature, humidity, precipitation and fog, all of which favor the spread of this fungus. For this reason farmers are forced to use chemical products that cause problems of resistance of the causal agent of the illnesses. The FAO (1992) estimates 3 million poisonings annually at a global level of farmers and families as a result of chemicals, which cause in turn a residual effect, environmental pollution and creates and additional cost in production. In the investigation of intoxication by agrochemicals in Bolivia, in a population of 870 persons studied mentioned that, 88% are unaware of the risks associated with the use and management of using them; the cases of poisonings are more frequent in tropical plains with 46%, the valleys with 26%, the inter-Andean valleys with 14% and the high plains with 12%, without mentioning those of suicide origin. For this reason, the object of the present investigation is to try to control the late blight disease (Phytophtora infestans) in the cultivation of the tomato (Lycopersicum sculentum), with biocides, to eliminate or diminish the use of agrochemical products.

No description available.

Maize grey leaf spot (GLS), caused by Cercospora zeae-maydis, and potato late blight (LB), caused by Phytophthora infestans, are foliar diseases of maize and potato, two of the most widely grown crops in KwaZulu-Natal (KZN), after sugarcane and timber. Commercial maize in KZN accounts for just on 4.3% of the national maize crop. This is worth R563 million using an average of the yellow and white maize price for the 2001/02 season (at R1 332.87 ton(-1)). In 2003 KZN produced about 5% of the national potato crop (summer crop: 7531 300 10kg pockets from 2243 hectares). This equates to a gross value of R89.4 million based on an average price of R1 188 ton(-1) in 2001. Successful commercial production of maize and potatoes depends upon control of these diseases by translaminar fungicides with highly specific modes of action. This study extends an existing model available for timing of fungicide sprays for GLS and tests and compares two LB models for two calendar-based spray programmes. The study also evaluated the use of an early blight model which is caused by Alternaria solani, and over the single season of evaluation showed potential for use in KZN. For the GLS model it was found that a number of refinements are needed, e.g., the amount of infected maize stubble at planting and not the total amount of maize residue at planting. Based on two years' data, it was found that for the LB models there are no significant differences in levels of control between using a predicted fungicide programme and a calendar-based programme. The importance of knowing initial infection sites, and hence initial inoculum, was demonstrated. This led to the creation of a KZN LB incidence map, now being used to more accurately time the start of a preventative spray programme and to time the inclusion of systemic fungicides in the preventative spray programme. This study has contributed to the further development and expansion of the Automatic Weather Station Network (AWSN) at Cedara, which now comprises 15 automatic weather stations in KZN. The AWSN is currently used to aid farmers and advisers in decision-making regarding fungicide spray timing for GLS and LB. / Thesis (M.Sc.Agric.)-University of Natal, Pietermaritzburg, 2003.

Plants are fundamental to life on earth, crucially providing the basis of our food supply. As world population continues to grow, so too does the pressure on our agricultural systems, with one of the biggest challenges being the control of plant pathogens to ensure a healthy crop. The interaction between plant and pathogen is complex, with subtleties at the molecular level dictating the boundary between health and disease. This is exemplified by pathogen effectors; secreted proteins which enter the plant cell and interact with host targets to facilitate infection. AVR2 is one such effector, secreted by the oomycete pathogen Phytophthora infestans; the pathogen responsible for potato late blight. AVR2 interacts with a family of kelch-repeat containing phosphatases in potato, the BSLs, implicated in brassinosteroid pathway signalling – a major hormone signalling pathway in plants associated with growth and development. This work investigates the role of AVR2 and its host targets in pathogen virulence, with focus on the link between the brassinosteroid pathway and immunity in S. tuberosum. StBSL1 is shown to be a ‘susceptibility factor’ in P. infestans infection – a host protein with a positive effect on pathogen virulence. AVR2 stabilises BSL1 in planta, and both AVR2 and BSL1 are shown to suppress primary defence responses in the plant. Transcriptional analysis of brassinosteroid-treated S. tuberosum is used to identify a set of marker genes for active BR signalling. Strikingly, AVR2 is shown to upregulatethis pathway, and specifically upregulates the transcription factor StHBI1-like, identified as a suppressor of immunity. These findings reveal a novel mechanism in oomycete effector biology; the exploitation of crosstalk between the brassinosteroid pathway and immune signalling in plants.