Research progress on pesticide residues of Panax ginseng / 中国中药杂志

Panax ginseng, a perennial herb, is prone to diseases and insect pests in the growth process, which are primarily prevented and treated by pesticides. However, due to the lack of standardization in the types, frequencies, and doses of pesticides, pesticide residues have become the main exogenous pollutants of P. ginseng. To explore the risk of pesticide residues in P. ginseng, this paper summarized and analyzed the common pesticide residues in P. ginseng, detection techniques, and pesticide residue limit stan-dards based on the published literature in recent years. The results revealed that the main pesticide residues in P. ginseng were organochlorine pesticides, such as tetrachloronitrobenzene, pentachloronitrobenzene, and hexachlorobenzene, and the detection techniques were dominated by gas chromatography(GC), liquid chromatography(LC), or those combined with mass spectrometry(MS). Because of the long half-life and difficulty in degradation, organochlorine pesticides have become the main factor affecting the export of P. ginseng. It is worth mentioning that P. ginseng has been classified as food in Japan, South Korea, the European Union, and other countries, and the standards of pesticide residues and limits are stricter than those in China. The quality and safety of P. ginseng are prerequisites for the efficacy of Chinese medicine and the development of traditional Chinese medicine. The formulation of scientific and effective standards for pesticide application and limits would promote the high-quality development of the P. ginseng industry.

Effects and mechanisms of nitrogen application on stress resistance of Chinese materia medica / 中国中药杂志

Nitrogen fertilizers play an important role in the regulation of plant stress resistance. Impacts of nitrogen fertilizers on abiotic stress resistance and biotic stress resistance of Chinese materia medica(CMM) were summarized in this study. Adequate nitrogen application improves the abiotic stress resistance and weed resistance of CMM, however adverse effect appears when excess nitrogen is used. Generally, pest resistance decreases along with nitrogen deposition, while effects of nitrogen application on disease resistance vary with different diseases. Mechanisms underlying the impact of nitrogen fertilizers on plant stress resistance were also elucidated in this study from three aspects including physical defense mechanisms, biochemistry mechanisms and molecular defense mechanisms. Nitrogen availability modulates physical barrier of CMM like plant growth, formation of lignin and wax cuticle, and density of stomata. Growth of CMM promoted by nitrogen fertilizer may cause some decrease in pest resistance of CMM due to an increase in hiding places for pest along with plant growth. High ambient humidity caused by excessive plant growth facilitates the growth and development of CMM pathogen. Nitrogen application can also interfere with the accumulation of lignin in CMM which makes CMM more vulnerable to pest and pathogen attack. Stomatal closing delays due to nitrogen application is also a causal factor of increasing pathogen infection after nitrogen deposition. Biochemical defenses of plants are mainly achieved through nutrient elements, secondary metabolites, defense-related enzymes and proteins. Nutritional level of CMM and various antioxidant enzymes and resistance-related protein activities are elevated along with nitrogen deposition. These antioxidant enzymes can reduce the damage of reactive oxygen species content produced by plant in response to adversity and therefore enhance stress resistance of CMM. Researches showed that nitrogen application could also cause an increase in nitrogen-containing secondary metabolites content and a decrease in non-nitrogen-containing secondary metabolites content respectively. Nitrogen-mediated molecular defense mechanisms includes multiple plant hormones and nitric oxide signals. Plant hormones related to plant defense like salicylic acid, jasmonic acid and abscisic acid can be modulated by nitrogen application. Negative effect of nitrogen deposition was found on salicylic acid accumulation and the expression of related plant disease resistance genes. However, jasmonic acid level can be elevated by nitrogen. Nitric oxide signals constitute an important part of nitrogen mediated defense mechanisms. Nitric oxide signaling is related to many aspects of plant immunity. The roles of nitrogen fertilizers in CMM stress resistance are complex and may vary with different CMM varieties and environments. Further studies are urgently needed to provide a comprehensive understanding of how to improve stress resistance of CMM by using fertilizers.

A highly sensitive method for the detection of Chrysanthemum virus B

Background: Chrysanthemum plants are subject to serious viral diseases. The viruses cause severe losses of the quantity and quality of chrysanthemum. The most problematic pathogen of chrysanthemum is typically considered Chrysanthemum virus B (CVB). Thus, a method for the simultaneous detection of CVB is needed. Results: We used gene-specific primers, which were derived from the coat protein gene region of the virus, for reverse transcription to obtain cDNA. Nested amplification polymerase chain reaction (PCR) was employed to detect the viral gene. This method was sensitive enough to detect the virus at up to 10-9 dilution of the cDNA. Conclusion: A highly specific and sensitive nested PCR-based assay has been described for detecting CVB. This new method is highly specific and sensitive for the detection of CVB, which is known to infect chrysanthemum plants in the fields. Further, this protocol has an advantage over traditional methods as it is more cost-effective. This assay is ideal for an early stage diagnosis of the disease.

Efeito de extratos e óleos essenciais de plantas na germinação de urediniósporos de Phakopsora pachyrhizi / Effect of plant extracts and essential oils on the germination of urediniospores of Phakopsora pachyrhizi

Métodos alternativos para o controle de doenças e pragas de plantas vêm sendo pesquisados buscando causar menores danos ao ambiente e a saúde humana. Diante disso, o objetivo deste estudo foi identificar extratos de plantas e óleos essenciais com possíveis efeitos sobre Phakopsora pachyrhizi, agente etiológico da ferrugem-asiática da soja. Assim, 61 extratos de plantas da flora nativa da região do Alto Rio Grande, Minas Gerais e cinco óleos essenciais obtidos comercialmente foram utilizados com a finalidade de testar os efeitos na germinação de urediniósporos do referido fungo. Foram utilizadas placas de Petri de 6 cm, com meio ágar-água, adicionado com 150 µL de extrato de planta ou 6 µL do óleo essencial misturado ao meio de cultura. Como testemunhas foram utilizadas 150 µL de Tween 20 a 0,7% e 150 µL de água destilada. Após, foram adicionados 50µL de uma suspensão de urediniósporos, na concentração de 2mg.5mL-1 e espalhados com alça de Drigalsky. As placas foram colocadas em BOD, a 23(±2ºC), por 4 horas. A germinação foi paralisada com adição de lactoglicerol. A avaliação da percentagem de esporos germinados foi realizada em microscópio de luz. Dentre os extratos vegetais testados, dez apresentaram percentual de germinação abaixo de 15%, tendo os extratos obtidos das plantas Pelargonium sp., Salvia officinalis, Lavandula officinalis, Mentha pulegium e M. arvensis apresentado germinação de esporos de 3,0%, 3,5%, 3,0%, 2,0% e 4,0%, respectivamente. Todos os óleos essenciais avaliados foram efetivos na inibição da germinação, com destaque para o óleo essencial de Caryophilus aromaticus, que apresentou percentagem de germinação de 5%, resultando num percentual de inibição de 50,0%.

Alternative methods to control plant diseases and plagues have been studied, in order to cause less damages to the environment and human health. The purpose of this study was to identify plant extracts and essential oils as possible alternative products that affect the urediniospore germination of Phakopsora pachyrhizi, the causal agent of the Asian soybean rust. Plant extracts (61) from the native flora of the Alto Rio Grande region, State of Minas Gerais, Brazil, as well as five commercial essential oils were used with the purpose of testing their effects on the germination of urediniospores of the referred fungus. 6cm Petri dishes were used, with water-agar medium, added with 150 µL of plant extract or 6 µL of essential oil mixed to the culture medium. As control, 150 µL of Tween 20 at 0.7% and 150 µL of distilled water were used. Then, 50 µL of a suspension of urediniospores were added, at a concentration of 2mg5mL-1 and spread with Drigalsky spatula. Then, the plates were put in BOD, at 23(±2ºC), for 4 hours. Germination was paralyzed by adding lactoglicerol. The percentage of spore germination was evaluated in a light microscope. Among the vegetal extracts tested, ten of them presented a germination percentage below 15%. The extracts from the Pelargonium sp., Salvia officinalis, Lavandula officinalis, Mentha pulegium and M. arvensis plants presented 3.0%, 3.5%, 3.0%, 2.0% and 4.0% of urediniospore germination, respectively. All the essential oils evaluated were effective in inhibiting germination, especially the Caryophilus aromaticus essential oil that presented 5.0% of germination, with 50.0% of inhibition.

Atividade antimicrobiana de óleos essenciais no controle de alguns fitopatógenos fúngicos in vitro e no tratamento de sementes / Antimicrobial activity of essential oils on the in vitro control of some fungal phytopathogens and on seed treatment

Este trabalho verificou o efeito dos óleos essenciais (OE) extraídos de Eremanthus erythropappus (candeia), Cymbopogon martinii (palmarosa) e de Rosmarinus officinalis (alecrim) no crescimento micelial de alguns fitopatógenos fúngicos e no tratamento de sementes de milho, soja e feijão. No teste in vitro, alíquotas de 20, 40, 60, 100, 200, 500 e 1000 μL de cada um dos óleos essenciais foram distribuídas na superfície do meio de cultura. Posteriormente, discos de meio de cultura com micélio de Alternaria carthami, Alternaria sp. e Rhizoctonia solani foram transferidos para o centro de cada placa. O crescimento foi mensurado e calculada a taxa de inibição do crescimento micelial (ICM). Para verificar o efeito dos OE na germinação das sementes utilizou-se a aplicação deles por fumigação. Foi avaliada a percentagem de sementes germinadas e a incidência de patógenos nas sementes. Sobre o crescimento micelial, o óleo de palmarosa inibiu completamente todos os patógenos fúngicos, independentemente da concentração. Já os óleos de candeia e alecrim foram melhores quando foram adicionadas alíquotas superiores a 200 μL. Os óleos influenciaram diferentemente a germinação e a sanidade das sementes de milho, soja e feijão.

This study aimed to verify the effect of essential oils (EO) extracted from Eremanthus erythropappus ("candeia") Cymbopogon martinii ("palmarosa") and Rosmarinus officinalis (rosemary) on the mycelial growth of some fungal phytopathogens, as well as on the treatment of corn, soybean and bean seeds. In the in vitro test, aliquots of 20, 40, 60, 100, 200, 500 and 1000 μL of each essential oil were distributed on the surface of the culture medium. Then, discs of culture medium with mycelium of Alternaria carthami, Alternaria sp and Rhizoctonia solani were transferred to the center of each plate. Growth was measured and the mycelial growth inhibition rate (MGI) was calculated. To verify the effect of EO on seed germination, application of oils was by means of fumigation. Percentage of germinated seeds and their incidence of pathogens were evaluated. For mycelial growth, "palmarosa" oil completely inhibited all fungal pathogens, regardless of the concentration. On the other hand, "candeia" and rosemary oils were better when aliquots higher than 200 μL were added. The oils differently influenced the germination and health of corn, soybean and bean seeds.

Controle da ferrugem das folhas do capim-limão [Cymbopogon citratus (DC. ) Stapf] com produtos naturais / Rust control in leaves of lemongrass [Cymbopogon citratus (DC. ) Stapf] by using natural products

Cymbopogon citratus (DC.) Stapf é uma planta medicinal pertencente a família Poaceae, perene, importante para a indústria farmacêutica e alimentícia devido ao óleo essencial que produz. Um problema limitante para a produção comercial é a ferrugem, doença cujo agente etiológico é o fungo Puccinia nakanishikii Dietel. O presente trabalho objetivou avaliar a ação de produtos naturais no controle da doença in vitro e in vivo. Para os testes in vitro, empregaram-se os seguintes produtos sobre a germinação de esporos do patógeno: óleos essenciais de eucalipto, palma-rosa, cravo-da-índia, menta, limão, citronela e mil-folhas; extrato pirolenhoso de eucalipto e mentol cristalizado, em diferentes concentrações. Para os testes de campo foram selecionados quatro produtos, o óleo de citronela e de eucalipto, o extrato pirolenhoso, e o mentol. In vitro, todos os agentes mostraram-se promissores no controle do patógeno. Quando em condições in vivo, sob alta severidade da doença no ato da avaliação, os produtos testados foram capazes de reduzir a severidade da doença em comparação com a testemunha. O controle da doença com os agentes naturais variou de 38% (extrato pirolenhoso) a 61%(óleo essencial de eucalipto).

Cymbopogon citratus (DC.) Stapf is a medicinal plant that belongs to the Poaceae family; it is perennial and important for the pharmaceutical and food industry due to the essential oil it produces. A limiting problem for commercial production is rust, a disease that has as etiological agent the fungus Puccinia nakanishikii Dietel. The present study aimed to evaluate the action of natural products on the disease control, in vitro and in vivo. For the in vitro tests, the following products were employed on the germination of the pathogen spores: essential oils from eucalyptus, palmarosa, clove, peppermint, lemon, citronella and yarrow, pyroligneous extract from eucalyptus, and crystallized menthol, at different concentrations. Four products were selected for the tests in the field: citronella and eucalyptus oil, pyroligneous extract and menthol. In vitro, all agents showed promising in controlling the pathogen. Under in vivo conditions and great severity of the disease at evaluation, the tested products were capable of reducing the disease severity when compared to the control. The disease control by the natural products varied from 38% (pyroligneous extract) to 61% (eucalyptus essential oil).

Desempenho agronômico e divergência genética na seleção de linhagens S5 de milho / Agronomic performance and genetic divergence in the selection of strains of maize S5

O objetivo deste trabalho foi selecionar linhagens de milho por meio desempenho agronômico juntamente com a divergência genética, no Sul do Tocantins. Foram avaliadas 63 linhagens de milho S5, obtidas de germoplasma de milho. O experimento foi instalado no município de Gurupi, Estado do Tocantins, na safra 2008/2009, em blocos casualizados, com duas repetições. Foram formandos 20 grupos divergentes, selecionado dentro de cada grupo as melhores linhagens. Os caracteres, área abaixo da curva de progresso da Mancha Branca (P. maydis) e avaliação do ataque de lagarta do cartucho (S. fugiperda), não foram utilizados como critério na seleção das linhagens. A utilização do desempenho agronômico conjuntamente com a análise de divergência genética foi eficaz na diferenciação das linhagens S5 de milho para possíveis genitores.

The objective in this work was to select strains of maize through the agronomic performance, together with the genetic divergence, in the south of Tocantins. They were evaluated 63 S5 maize lines, obtained from the germplasm of maize. The experiment was conducted at the Gurupi, State of Tocantins, in the 2008/2009 harvest, in the randomized block design with two replications. They were formed 20 divergent groups, and within each group selected the best strains. The characteristics of the area under the curve of progress of White Spot (P. maydis) and assessment of attack fall armyworm (S. fugiperda) were not used as criteria in the selection of strains. The use of agronomic performance together with the analysis of genetic divergence was effective in differentiating the strains S5 corn for possible parents.

Antimicrobial activity and potential use of monoterpenes as tropical fruits preservatives

Banana, papaya and pineapple are the most consumed tropical fruits in the world, being Brazil one of the main producers. Fungi Colletotrichum musae, Colletotrichum gloeosporioides and Fusarium subglutinans f.sp. ananas cause severe post harvest diseases and losses in fruits quality. The aim of this work was to evaluate the effectiveness of five monoterpenes to inhibit the mycelial growth and conidia germination of these three phytopathogens. The monoterpenes citral, citronellal, L-carvone, isopullegol and a-pinene were diluted in ethanol to final concentrations from 0.2 to 1 percent. All monoterpenes were found to inhibit the growth of the three studies fungi in a dose-dependent manner. Citral was the most effective of the oils tested and showed potent fungicidal activity at concentrations above 0.5 percent. Also, in vivo evaluation with these tropical fruits demonstrated the efficiency of citral to inhibit fungal growth. These results indicate the potential use of citral as a natural pesticide control of post-harvest fruit diseases.

Banana, mamão e abacaxi são as frutas tropicais mais consumidas no mundo, sendo o Brasil um dos principais produtores. Os fungos Colletotrichum musae, Colletotrichum gloeosporioides e Fusarium subglutinans f.sp ananas são os principais causadores de doenças e perdas em pós-colheita de frutas. A proposta deste estudo foi avaliar a eficácia de cinco monoterpenos em inibir o crescimento micelial e a germinação dos conídios destes três fitopatógenos. Os monoterpenos citral, citronelal, L-carvona, isopulegol e a-pineno foram diluídos em etanol à concentração final de 0,2 a 1 por cento. Todos os monoterpenos testados inibiram os três fungos estudados de maneira dose-dependente. Citral foi o mais efetivo dos óleos testados e apresentou uma potente atividade fungicida em concentrações acima de 0,5 por cento. Mais ainda, avaliação in vivo com estas frutas tropicais demonstrou a eficácia de citral como inibidor do crescimento fúngico. Estes resultados indicam o uso em potencial de citral como um pesticida natural no controle das doenças em pós-colheita de frutas tropicais.