Inibição do crescimento micelial de Cercospora calendulae Sacc. por extratos de plantas medicinais / Inhibition of the mycelial growth of Cercospora calendulae Sacc. by medicinal plants extracts

O uso de extratos e óleos essenciais de plantas medicinais tem sido amplamente estudado no controle de doenças de plantas. O objetivo da realização do presente trabalho foi avaliar o efeito de extratos de Ruta graveolens L., Mentha x villosa, Calendula officinalis L., Momordica charantia L., Symphytum officinale L., Ageratum conyzoides L. e Ricinus comunis L., nas concentrações de 0, 250, 500, 1000, 2000, 5000 e 10000 mg L-1, sobre a inibição do crescimento micelial de Cercospora calendulae Sacc. in vitro. Os extratos foram obtidos por infusão. O experimento foi desenvolvido no Laboratório de Fitopatologia da FCA/UFGD, estado de Mato Grosso do Sul, em delineamento inteiramente casualizado, esquema fatorial 7 extratos x 7 concentrações, com seis repetições. Foi detectado efeito dos extratos e suas concentrações sobre o crescimento do fungo, sendo a interação significativa. Os extratos de calêndula, arruda, hortelã e melão de São Caetano, nas maiores concentrações resultaram em maiores porcentagens de inibição, próximas de 100%, 30%, 35% e 40%, respectivamente, a 10000 mg L-1.

This study was carried out to investigate the effects of the extracts of Ruta graveolens L., Mentha x villosa, Calendula officinalis L., Momordica charantia L., Symphytum officinale L., Ageratum conyzoides L. and Ricinus comunis L., in the concentrations of 0, 250, 500, 1000, 2000, 5000 and 10000 mg L-1, on the inhibition of the mycelial growth of in vitro Cercospora calendulae Sacc. The extracts were obtained by infusion. The experiment was performed at the Laboratório de Fitopatologia - FCA/UFGD, in the Brazilian State of Mato Grosso do Sul. The experimental design was totally randomized, with a factorial arrangement of 7 extracts x 7 concentrations, with six repetitions. We detected the effect of the extracts and their concentrations on the growth of the fungus, with a significant interaction between the factor extracts and the concentration. Calendula officinalis L., Ruta graveolens L., Mentha x villosa and Momordica charantia L. extracts in higher concentration resulted in higher inhibition percentages in the order of 100%, 30%, 35% and 40%, respectively.

Inibição do crescimento in vitro de fitopatógenos sob diferentes concentrações de extratos de plantas medicinais / In vitro inhibition of fungal plant pathogens by different concentrations of medicinal plants extracts

Com o objetivo de avaliar in vitro o efeito de diferentes concentrações de extratos vegetais sobre o crescimento de Cercospora kikuchii, Fusarium solani, Colletotrichum sp. e Phomopsis sp., foram conduzidos quatro bioensaios experimentais, no Laboratório de Fitopatologia da Universidade Federal da Grande Dourados. Foi adotado o delineamento inteiramente casualizado em arranjo fatorial 3 x 6, com 8 repetições para cada bioensaio. Foram utilizados extratos aquosos de alho, canela e cravo-da-índia, nas concentrações de 0; 0,5; 1; 5; 10 e 20%. Para obtenção dos extratos foram coletadas 30 g do material vegetal e trituradas em 120 mL de água destilada. Os extratos foram filtrados em papel Wathman nº 1 e incorporados ao meio BDA, de modo a obter as concentrações desejadas. Posteriormente, a solução foi vertida em placas de Petri, onde foram transferidos discos de micélio do patógeno, de 0,3 cm de diâmetro. Em seguida, as placas foram incubadas a 25º C, com fotoperíodo de 12 horas. Foi analisado o crescimento micelial da colônia fúngica. Os resultados revelaram que o efeito do extrato aquoso de canela para todos os patógenos estudados, e do extrato de alho para F. solani, Colletotrichum sp. e Phomopsis sp. foi dependente das concentrações utilizadas, constatando-se maior atividade antifúngica com o aumento das concentrações. Verificou-se com o uso do extrato de cravo-da-índia maior eficácia no controle dos fitopatógenos testados, sendo observada supressão sobre o crescimento de Colletotrichum sp., Cercospora kikuchii, F. solani e de Phomopsis sp. a partir das concentrações de 7,4, 7,5, 8,9 e 7,0%, respectivamente. O extrato aquoso de alho, na concentração de 9,7%, apresentou efetivo controle apenas sobre C. kikuchii.

In order to evaluate the in vitro effect of different concentrations of plant extracts on the growth of Cercospora kikuchii, Fusarium solani, Colletotrichum sp. and Phomopsis sp., 4 bioassays experiments were conducted at the Plant Pathology Laboratory of the Federal University of Grande Dourados, Brazil. The experimental design was a completely randomized design in a 3 x 6 factorial arrangement, with 8 replicates for each bioassay. Aqueous extracts of garlic, cinnamon and clove were evaluated in concentrations of 0, 0.5, 1, 5, 10 and 20%. Extracts were obtained through maceration of 30 g of plant material in 120 mL of distilled water. The extracts were filtered in grade-1 Whatman paper and incorporated into PDA medium to obtain the desired concentrations. Subsequently, the solution was poured into Petri dishes, and then 3 mm-diameter-PDA plugs with pathogen mycelium were transferred to the center of the PDA + plant extract Petri dish. Plates were incubated at 25° C with a 12-h-day photoperiod. Fungal growth was performed daily by measuring the colony diameter. The results showed that the effect of aqueous extract of cinnamon for all pathogens studied, and garlic extract for F. solani, Colletotrichum sp. and Phomopsis sp., was dependent on the concentrations used, noting a higher antifungal activity with increased concentrations used. Clove extract presented the greatest effectiveness for the control of the plant pathogens tested, with observed suppression on the growth of Colletotrichum sp. C. kikuchii, F. solani and Phomopsis sp. at the concentrations 7.4, 7.5, 8.9 and 7.0%, respectively. The aqueous extract of garlic at a concentration of 9.7% presented effective control only for C. kikuchii.

Influência de diferentes metodologias de esterilização sobre a atividade antifúngica de extratos aquosos de plantas medicinais / Influence of different sterilization methods on the antifungal activity of aqueous extracts of medicinal plants

Foram conduzidos no Laboratório de Fitopatologia da Universidade Federal da Grande Dourados três experimentos com o objetivo de avaliar in vitro a atividade antifúngica dos extratos aquosos de alho, canela e cravo-da-índia, submetidos a diferentes processos de desinfestação e/ou esterilização sobre o desenvolvimento de Fusarium solani. O delineamento experimental utilizado para cada ensaio foi inteiramente casualizado, com 5 tratamentos e 8 repetições. Utilizaram-se os extratos aquosos na concentração de 20 por cento, submetidos às metodologias de filtragem (FI), banho maria a 65°C (BM), autoclavagem a 100ºC (AT1), autoclavagem a 120ºC (AT2) e a testemunha (somente BDA). Posteriormente os extratos foram incorporados em meio BDA, acondicionados em placas de Petri, onde foram transferidos discos de micélio de F. solani medindo 0,3 cm de diâmetro. Após, as placas foram incubadas a 25ºC, com fotoperíodo de 12 horas. Os tratamentos foram analisados em relação ao crescimento micelial da colônia, a porcentagem de inibição e a taxa de crescimento de F. solani. Foi observado em todos os ensaios maior crescimento do fungo na testemunha, evidenciando o potencial antifúngico dos extratos. Foi observada influência da metodologia de esterilização sobre a eficiência dos extratos de alho e canela. Para o alho a FI proporcionou os melhores resultados, enquanto que para o extrato de canela não houve diferenças entre as metodologias FI, BM e AT1. As diferentes metodologias utilizadas não interferiram na eficiência do extrato aquoso de cravo-da-índia.

Three experiments were conducted in the Laboratory of Phytopathology of Federal University of Grande Dourados, Mato Grosso do Sul State, Brazil, to evaluate in vitro the antifungal activity of aqueous extracts of garlic, cinnamon and clove subjected to different processes of disinfection and/or sterilization against the development of Fusarium solani. The experimental design for each trial was completely randomized, with 5 treatments and 8 replicates. Aqueous extracts at a concentration of 20 percent were subjected to the methods of filtering (FI), water bath at 65ºC (WB), autoclaving at 100ºC (AT1), autoclaving at 120ºC (AT2) and control treatment (PDA alone). Subsequently, the extracts were incorporated into PDA medium, added to Petri dishes, to where F. solani mycelium discs of 0.3cm diameter were transferred. Then, the plates were incubated at 25ºC with 12-h photoperiod. The treatments were analyzed as to mycelial growth of the colony, percentage of inhibition and growth rate of F. solani. Increased fungal growth was observed for the control treatment, demonstrating the antifungal potential of the extracts. The sterilization method influenced the efficiency of garlic and cinnamon extracts. For garlic, FI led to the best results, whereas for cinnamon extract there were no differences among the methodologies FI, WB and AT1. The different methods used did not interfere with the efficiency of the aqueous extract of clove.

Water stress response of conventional and transgenic soybean plants monitored by chlorophyll a fluorescence.

Two soybean cultivars, one conventional and a glyphosate-tolerant (transgenic), were submitted to the water stress and the chlorophyll a fluorescence induced by UV light was monitored daily during 16 days. In this work, 40 pots in total, 20 per cultivar were used in the investigation. Each cultivar was divided in two groups, the control group and the group submitted to the water stress. The stress response of the cultivars was monitored by red to far-red fluorescence ratio. The data indicate that the water stress induced the earliest changes on the fluorescence ratio and chlorophyll content for the conventional cultivar. In addition, a comparative analysis of the fluorescence ratios of the cultivars reveals that conventional plants have higher chlorophyll content than transgenic ones. This result might be useful in the development of methodologies able to distinguish conventional to transgenic apart.

Effects of Tillage Practices on Dissemination and Spatial Patterns of Heterodera glycines and Soybean Yield.

Two field experiments were conducted in central Iowa to assess the effects of tillage on Heterodera glycines dissemination and reproduction and soybean (Glycine max) yield. Plots in both experiments were artificially infested with equivalent numbers of H. glycines cysts. In one experiment, plots were left noninfested or received aggregated or uniform infestation, and a susceptible soybean cultivar was grown for 3 years. By the end of the first growing season and through the second, H. glycines population densities were consistently greater (P ≤ 0.05) in uniformly infested plots than in plots with aggregated infestations. No differences in soybean yield among the treatments were detected. In a second experiment, a 1-m2 area of each plot was infested with H. glycines cysts, susceptible soybeans were grown for four seasons, and crop residue was managed with either ridge-, conventional-, reduced-, or no-tillage. After 1 year, nematode population densities were significantly (P ≤ 0.05) greater in conventional- and reduced-tillage treatments than in no- and ridge-tillage treatments. After 2 years, H. glycines had been disseminated 6.9 m from the infestation site in conventional- and reduced-tillage treatments but only 0.5 and 1.4 m for no-tillage and ridge-tillage treatments, respectively. After 3 years, H. glycines population densities were 10 times greater in conventional- and reduced-tillage treatments than in the no-tillage treatment; conventional-tillage was the only treatment with yield significantly lower (P ≤ 0.05) than the noninfested control. Aggregation of H. glycines eggs was greater (P ≤ 0.05) in no- and ridge-tillage treatments than in conventional- and reduced-tillage treatments. Results indicate tillage can quickly disseminate H. glycines in newly infested fields, facilitating more rapid nematode reproduction and subsequent yield loss.

Relationships Between Tillage and Spatial Patterns of Heterodera glycines.

ABSTRACT The dynamics of Heterodera glycines spatial patterns were studied under different tillage systems in two naturally infested soybean fields in Iowa from 1994 to 1997. At each location, there were four different tillage treatments (conventional tillage, reduced tillage, ridge tillage, and no tillage). Soil samples were taken from 98 contiguous quadrats (5.2 m(2)) per plot in the fall of 1994, before any tillage was performed, and in the spring of the following 3 years shortly after planting. Cysts were extracted from soil samples by elutriation and counted, and eggs were extracted from cysts and enumerated. Spatial patterns of H. glycines populations were characterized by geostatistical analysis and variance-to-mean (VM) ratios. Semivariance values were calculated for cyst and egg densities and semivariograms were constructed. In general, there was greater spatial dependence among cyst populations than egg populations. In one field with a strongly aggregated initial H. glycines population, tillage practices resulted in changes in spatial patterns of H. glycines populations, characterized by spherical-model semivariogram parameters (sill, nugget effect, and range of spatial dependence). These parameters indicated increasing aggregation over time in no tillage and ridge tillage treatments, but decreasing aggregation in reduced and conventional tillage treatments. There was an increase of 350% in sill values (maximum semivariance) for cyst populations after 3 years of no tillage, but in the conventional tillage treatment, sill values remained unchanged or decreased over time as tillage was implemented. Semivariograms for cyst and egg population densities revealed strong anisotropy (directional spatial dependence) along soybean rows, coincident with the direction of tillage practices. VM ratios for cyst counts increased each year in the no tillage and ridge tillage treatments, but decreased for 2 years in reduced tillage and conventional tillage treatments. Final VM ratios for cyst and egg counts were highest in the no tillage treatment. In a second field, with low initial aggregation of H. glycines populations, there was little measurable change in semivariogram parameters after 3 years of no tillage, but in the conventional tillage treatment, populations became less aggregated, as the range, sill, and the proportion of the sill explained by spatial dependence decreased for cyst population densities. Our results indicated that in soybean fields with initially aggregated populations of H. glycines, no tillage and ridge tillage systems promoted aggregation of the nematode population, whereas conventional and reduced tillage systems resulted in a less aggregated spatial pattern.