Potencial do óleo de Aloysia citriodora Palau no controle de fitopatógenos e na indução de resistência ao tombamento de plântulas de feijão, pepino e beterraba

The crops are affected by pests and diseases that decrease productivity. Among them are the damping off of seedlings that can occur in pre and post-emergence. In bean crops, cucumber and beet these diseases occur, being caused by various pathogens, especialy fitopathogenic fungi. Several measures are used for the controle of such diseases, among them, is the chemical seed treatment fungicides. However, society has become increasingly concerned about the quality and food and environmental contamination, generation a growting search for sensitive products to humans and the environment. The use of essential oils to control plant pathogens is an example of alternative tested by science in the search for less aggressive technologies. This study aimed to evaluate the efficiency of the use of essential oil Aloysia citriodora, in control of pathogens causing damping off in beans, cucumber and beet. This thesis was divided in four chapters, the introductory first, and the other addressing the control of Pythium sp. in beans, Sclerotinia sclerotiorum on cucumber, and Fusarium sp. on beet. The methodology consisted of four experiments in each pathosystem, with all the work done at the Federal Technological University of Parana, Campus Dois Vizinhos. In the first experiment evaluated the fungistatic and fungicidal effect of the essential oil of A. citriodora on PDA in vitro in mycelial growth of pathogens studied. In the second experiment evaluated the in vitro effect of essential oil concentrations of A. citriodora in BD medium on microscope slides, on the germination of sporangia Pythium sp. and conidia Fusarium sp., and in Petri dishes with PDA medium, the sclerotia germination speed index of S. sclerotiorum. In the third experiment, we evaluated in germination test in paper roll (PR), the phytotoxic effect or not the use of essential oil concentrations of A. citriodora in dry bean seed, cucumber and beet. The variables used to assess this experiment were the germination percentage, mediun green mass per plant and average length of seedlings. In the fourth experiment we assessed the effect of treating bean seeds, cucumber and beet with essential oil contents of A. citriodora, seeds in their subsequent substrates contamined with pathogens studied, Pythium sp., S. sclerotiorum and Fusarium sp. In this experiment we used the following variables: percentage of emergence, percentage of post-emergence damping off, green average mass per plant, average length per plant and biochemical analyzes. The biochemistry of plant tissues evaluated were as follows: protein content, enzymatic activities of peroxidases, phenylalanine ammonia-liase (PAL), chitinases and β-1,3-glucanases. The in vitro results show that the essential oil has fungistatic and fungicidal effect on mycelial growth, on sporangia germination, conidia and sclerotia of the pathogens studied in this work, wich may be related to its major components, citral and limonene. The oil also exhibits low phytotoxicity to seeds of the species studied, only in beans decreases germination in most studied dosage (0,25%), cucumber also in the higher dosage (0,25%) reduce the length of seedlings, and beet there were no negative effects to the seedlings. In the test in substrate contaminated with the pathogens, the use of essential oil: increased germination and decreased post emergence damping off of beans seedlings; at a concentration of 0,0625% decreases post emergence damping off in cucumber. In biochemical analyzes found an increase in the enzymatic activity of peroxidases and β-1,3-glucanases on beans, and glucanases on cucumber, and increased enzyme activity of peroxidases on beet, showing action in resistance induction at damping off.

Indução de resistência e tratamento de sementes de soja com fosfitos de potássio

The use of inputs containing phosphites have been presenting results in many studies, taking on importance to the control of diseases in some cultures and demonstrating the resistance induction in seedlings, with ability to activate defense mechanisms, conferring protection to plants against microorganisms. The soybean crop is recognized for its importance in providing grains and derivatives for human consumption, animal, production of biofuels, pharmaceuticals, among others. Positive results obtained through studies based on resistance inducers in some cultures arouse the interest for further study. The objective of this study was to evaluate the effect of potassium phosphites on the resistance induction and treatment of soybean seeds. Therefore were conducted four laboratory studies at the Federal Technological University of Paraná, Campus of Dois Vizinhos. In the first study it was evaluated the quality attributes of the seeds and the resistance induction as seed treatment. Then it was verified that phosphites have action upon the seedlings metabolism in due to seed treatment, having the phosphite Reforce® contributed to seed quality attributes and phosphites FitofosK® and Fitofos K Plus® induced the resistance increasing the activity of β-1,3-glucanase. In the second study it was evaluated the the resistance induction in soybean cotyledons, in which the phosphites demonstrated induction potential of phytoalexin gliceolin. In the third study It was evaluated the soybean seed health treated with potassium phosphites.. it was observed that the phosphites reduced the incidence of many fungi on seeds, especially of storage fungi like Aspergillus sp. and Fusarium semitectum. In the fourth study it was evaluated the in vitro effect of potassium phosphites on pathogenic fungi of the culture. And it was found direct action of phosphites on the mycelial growth of Fusarium semitectum, Pythium sp. and Sclerotinia sclerotiorum. Based on these results, we concluded that potassium phosphites have potential in seeds treatment, as resistance inducer and on in vitro control of phytopathogens.

Analyses of the community compositions of root rot pathogenic fungi in the soybean rhizosphere soil

Soybean ( Glycine max [L.] Merr.) root rot is an important disease of soybean under continuous cropping, and root rot is widely distributed throughout the world. This disease is extremely harmful, and it is difficult to prevent and control. The study aimed to elucidate the composition of root rot pathogenic fungal communities in the continuous cropping of soybean. In this study, we employed PCRDGGE technology to analyze the communities of root rot pathogenic fungi in soybean rhizosphere soil subjected to continuous cropping during a season with a high incidence of root rot in Heilongjiang province, China, the main soybean producing area in China. The results of 13 DGGE bands were analyzed by phylogenetic revealed that the predominant root rot pathogenic fungi in rhizosphere soil in the test area were Pythium ultimum and Fusarium species. The results of cluster analysis showed that the duration of continuous cropping, the soybean variety and the plant growth stage all had significant effects on the diversity of root rot pathogenic fungi in rhizosphere soil.

Chemical control of tomato basal rot caused by Pythiuma phanidermatum

p.73-78

Controle da podridão de raiz e promoção de crescimento em hidroponia com bactérias.

2009

Potencial de hidrolisado de peixe para o controle de fitopatógenos.

Os produtos obtidos da fermentação de pescados marinhos frescos registrados como fertilizantes orgânicos são ricos em nutrientes, possuem em sua composição quitina e quitosana, podendo-se constituir em um produto alternativo adequado para o controle de fitopatógenos. O objetivo deste trabalho foi estudar o potencial de um hidrolisado de peixe em controlar o oídio em abobrinha, F. oxysporum f. sp. lycopersici raça 3 em tomate e Pythium spp. em pepino. Nesse sentido, um fertilizante orgânico obtido da fermentação de resíduos de pescados marinhos frescos foi pulverizado semanalmente nas plantas de abobrinha, com o auxílio de um compressor de pintura 10 1b/pol2 m a 0%, 0,5%, 1%, 2%, 3%, 4%, 5% e 10% (v/v) para o controle do oídio. Este mesmo fertilizante foi incorporado ao substrato nas concentrações de 0%, 5%, 10%, 20%, 30%, 40%, 50% e 100% (por volume de água necessária para atingir a capacidade de campo), em experimento realizado dentro e fora de casa de vegetação. Outros experimentos realizados avaliaram a eficiência do hidrolisado de peixe no controle do tombamento causado por Pythium spp., em pepino e a murcha-de-fusário causada por Fusarium oxysporum f. sp. lycopersici raça 3, em tomate. Os experimentos foram realizados em casa de vegetação e o delineamento experimental foi inteiramente casualizado, com dez repetições por tratamento. Para o pepino, foi utilizada a técnica de estimular a população original do solo com aveia. Assim, o hidrolisado de peixe foi incorporado ao solo dez dias após a mistura com aveia, em concentrações de 0%, 5%, 10%, 20%, 30%, 40%, 50% e 100% do volume de água, para atingir a capacidade de campo do solo e com incubação aberta e fechada. Após dez dias de incubação, 200 ml da mistura foram adicionados ao colo das plantas de pepino no estádio de 2° folhas verdadeiras. A avaliação foi realizada após cinco dias, determinando-se o número de plântulas tombadas. O hidrolisado de peixe, tanto pulverizado na folhas quanto incorporado no substrato, não controlou o oídio da abobrinha. Por outro lado, pode ser observado o efeito do hidrolisado de peixe no desenvolvimento das plantas e no desenvolvimento de Trichoderma no substrato. A partir da concentração de 30%, não houve tombamento de plantas. Por outro lado, o tombamento foi de 100% para os tratamentos com 0 e 5% do fertilizante. Para o experimento do Fusarium, foram utilizados três isolados da raça 3 de Fusarium oxysporum f. sp. lycopersici (isolados 145, 146 e 149). Após a infestação, o substrato foi incubado por quinze dias com o hidrolisado de peixe e foi incorporado ao substrato nas seguintes concentrações: 0%, 5%, 10%, 20%, 30%, 40% e 50% volume de água necessária para atingir a capacidade de campo. Uma muda de tomate cultivar Santa Clara suscetível à raça 3 com 30 dias de idade, foi transferida para cada vaso. A severidade da doença foi avaliada após 40 dias, por meio de escala de notas para escurecimento vascular e sintomas externos. De modo geral, todas as doses do hidrolisado de peixe reduziram, significativamente, a severidade da doença.

Seleção de bactérias endofíticas com ação antagônica a fitopatógenos.

Muitos métodos rápidos e eficientes de seleção de agentes de biocontrole de fitopatógenos tem sido utilizados, visando reduzir tempo e custo dispendido em testes de campo. Neste trabalho realizou-se uma seleção de isolados endofíticos com potencial de uso no biocontrole de fitopatógenos em testes de antagonismo in vitro. De um total de 95 isolados de bactérias endofíticas do milho, seis foram selecionados quanto à inibição a Pythium aphanidermatum. A essa seleção, foram incluídos um isolado de Bacillus subtilis 0G, Bacillus lentimorbus e Streptomyces sp., para verificação de antagonismo a Rhizoctonia solani, Fusarium moniliforme, Sclerotium rolfsii e Exserohilum turcicum. Verificou-se que os endofíticos B. subtilis 0G, B. lentimorbus e Streptomyces sp., apresentaram ação antagônica superior aos demais, com taxas de inibição entre 32,0% e 53,8%. Dentre os endofíticos do milho, Bacillus agaradhaerens foi o que mais se destacou, com taxas de inibição variando entre 43,7% e 52,3% e indicando uma inespecificidade de ação. Este estudo, embora preliminar, permite vislumbrar a utilização desses endofíticos na supressão de doenças em diferentes sistemas patógeno-hospedeiro em testes subseqüentes, sob condições de casa-de-vegetação e a campo.