Alternative products to control late season diseases in soybeans / Produtos alternativos para o controle de doenças de final de ciclo na soja

In the last crop seasons, the complex of late season diseases (CLSD) of soybean (Glycine max L. (Merrill)), has been causing considerable reductions in the crop yield. Currently, there are no cultivars resistant to all pathogens that causes CLSD. The present study evaluated the effect of applying the acibenzolar-S-methyl resistance inducer, alternative products and fungicide on the severity of CLSD in the soybean cultivar BMX Potência RR during the 2013/2014 and 2014/2015 crops, in the field. The treatments for the experiments were: 1 - control (water); 2 - acibenzolar-S-methyl; 3 - calcium; 4 - micronutrients: copper, manganese and zinc; 5 - micronutrients: manganese, zinc and molybdenum; 6 - nitrogen-potassium fertilizer; 7 - Ascophyllum nodosum and 8 - azoxystrobin + cyproconazole with the addition of the adjuvant. Four applications of alternative products and two of fungicide were carried out in both harvests. A diagrammatic scale assessed the severity of CLSD at the phenological stage R7.1. The acibenzolar-S-methyl resistance inducer, alternative products (macro and micronutrients) and A. nodosum had no effect on the severity of CLSD in the two harvests. The fungicide (azoxystrobin + cyproconazole) reduced the severity of CLSD and prevented damage to productivity in both experiments.

Nas últimas safras, o complexo de doenças de final de ciclo (DFC) da soja (Glycine max L. (Merrill)), vem provocando reduções consideráveis no rendimento da cultura. Atualmente, não há variedades resistentes a todos os patógenos causadores das DFC. O objetivo do presente trabalho foi avaliar o efeito da aplicação do indutor de resistência acibenzolar-S-methyl, produtos alternativos e fungicida na severidade de DFC na cultivar de soja BMX Potência RR durante as safras 2013/2014 e 2014/2015, em campo. Os tratamentos para os experimentos foram: 1 - testemunha (água); 2 - acibenzolar-S-methyl; 3 - cálcio; 4 - micronutrientes: cobre, manganês e zinco; 5 - micronutrientes: manganês, zinco e molibdênio; 6 - adubo NK; 7 - Ascophyllum nodosum e 8 - azoxistrobina + ciproconazol com adição do adjuvante. Foram realizadas quatro aplicações dos produtos alternativos e duas do fungicida, nas duas safras. A severidade de DFC foi avaliada por escala diagramática no estádio fenológico R7.1. O indutor de resistência acibenzolar-S-methyl, os produtos alternativos (macro e micronutrientes) e A. nodosum não apresentaram efeito sobre a severidade das DFC nas duas safras. O fungicida (azoxistrobina + ciproconazol) reduziu a severidade das DFC e evitou danos a produtividade nos dois experimentos.

Influence of Weather Parameters on Foliar Diseases of Sesame (Sesamum indicum L.) in Coastal Ecosystem of West Bengal, India

Sesame is one of the most important oilseed crops in India due to mainly its high quality seed oil and antioxidant properties. Occurrence of foliar diseases, like Alternaria leaf spot and Cercospora leaf spot has become a major constraint in recent years for successful and profitable cultivation of sesame. Field experiments were conducted with sesame var. savitri in a factorial randomized block design with three different dates of sowing with 15 days interval and two different plant protection situations (Protected i.e., treated with disease control protocols and unprotected i.e., control), replicated four times, during two consecutive summer seasons of 2018 and 2019 at Agricultural Experimental Farm, Institute of Agricultural Science, University of Calcutta, Baruipur, South 24 Parganas. The diseases incidence was estimated and correlated with the weather parameters. The average of weather parameters viz., maximum temperature, minimum temperature, relative humidity (morning), relative humidity (evening) and rainfall prior to seven days of disease appearance were considered for study the correlation between the weather factors and the disease. In 2018, disease incidences of the plants shown at third date of sowing (26th April, 2018) in both the protected and unprotected plots had significant (P=.05) but negative correlation with maximum temperature. For plants sown at first date of sowing (27th March, 2018) in 2018 had disease incidences significantly (P=.05) and positively correlated with minimum temperature. However, in 2019, except for the relation between disease incidences in the unprotected plots and maximum temperature, all other disease-temperature correlations were non-significant. Disease incidences were positively and significantly correlated with relative humidity (both morning and evening) in all dates of sowing irrespective of experimental years, except with morning relative humidity at first date of sowing in first year. Total rainfall was positively and significantly correlated with disease incidences at all dates of sowing in 2018; however, such relation was non-significant in 2019.

Evaluation of the biocontrol potential of endophytic bacteria isolated from Coffea liberica (w. Bull ex hiern) against brown eyespot-causing fungal phytopathogen

Aims@#The study aims to investigate the potential of the endophytic bacteria as an alternative to control the devastating brown eyespot disease caused by Cercospora sp. in coffee plants. The fungal phytopathogen causes severe leaf fall and berry damages resulting in serious yield losses in coffee farms in the Philippines and worldwide. Currently, the management of this fungal infection relies heavily on synthetic fungicides, which may be of major environmental concern. @*Methodology and results@#Endophytic bacteria were isolated from the intercellular tissues of Coffea liberica leaves by surface sterilization, maceration, dilution technique, plating on trypticase soy agar and colony characterization. Fourteen isolated endophytic bacteria were screened for their ability to inhibit the mycelial growth of Cercospora sp. through modified dual culture assay. Isolates HCC10-3SC3, HCC10-3SC2, HCC10-1SC1, ICC10-3SC1, and ICC10-1SC1 yielded the highest percent inhibition of radial growth (PIRG) with 59.56%, 60.92%, 60.96%, 64.36%, and 67.06% respectively and are statistically significant (p<0.05) compared to the antibiotic control nystatin. The top five performing endophytic bacteria were subjected to hydrolytic enzyme production assays and found to exhibit amylolytic, lipolytic, proteolytic, chitinolytic, and cellulolytic activities. Based on the morphological and molecular identification by the 16S rRNA sequence analysis, isolates showed the similarity with Staphylococcus cohnii, Bacillus siamensis, Staphylococcus hominis, and Kosakonia cowanii found in GENBANK. @*Conclusion, significance and impact of study@#The study revealed the biological control potential of endophytic bacteria agents against the brown eyespot-causing fungus in coffee.

Metabolites from Cercospora lagenariae MT-45, an endophytic fungus isolated from Huperzia serrata / 中草药

Objective: To investigate the chemical metabolites from Cercospora lagenariae MT-45, an endophytic fungus isolated from Huperzia serrata (Thunb.) Trev. Methods: The compounds were isolated and purified by using silica gel column chromatography and semi-preparative liquid chromatography. The structures were established using physicochemical properties and MS and NMR. The anti-inflammatory activities of all the isolates were also preliminarily investigated by using in vitro model. Results: Nine polyketide derivatives including cercolagenlic acid A (1), alternariol (2), alternariol 9-methyl ether (3), (+)-nigrosporaol A (4), alternarienonic acid B (5), 2-methyl-5-carboxymethyl-7-hydroxychromone (6), 2,5-dimethyl-7-hydroxychromone (7), 1-deoxy- rubralactone (8), and (-)-alternarlactam (9) were isolated from C. lagenariae MT-45 fermented on brown rice solids. Conclusion: Compound 1 is a new compound, and compound 6 can exhibit a certain inhibition on the nitric oxide production in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophage cells with an IC50 value of (57.5 ± 1.2) μmol/L.

Validación de una técnica de Dot blot para la detección de Cercospora kikuchii en plantas de soja / Validation of the technique based on Dot blot for the detection of Cercospora kikuchii in soybean plants

Cercospora kikuchii, fitopatógeno usual en plantas de soja, ocasiona deterioro en la scosechas. Su identificación precoz y correcta evitaría el uso indebido de plaguicidas y permitiría iniciar un tratamiento adecuado. Una técnica rápida, económica y de fácil ejecución es el Dot blot, capaz de reconocer la presencia de una proteína específica del género conocida como CFP (Cercosporin Facilitator Protein). El objetivo de este trabajo fue validar dicha técnica para garantizar la fiabilidad del resultado. Para ello, se procesaron 29 plantas de soja infectadas y 31 plantas sanas teniendo en cuenta una confianza deseada del 95% y un error permitido del 5%. La técnica presentó una sensibilidad diagnóstica del 93,3% y una especificidad diagnóstica del 96,7%. La eficacia fue del 95% y los valores predictivos positivo y negativo del 96,6 y el 93,5%, respectivamente. Estos resultados la postulan como una herramienta útil para detectar precozmente c. kikuchii en plantas de soja.

Cercospora kikuchii is a common pathogen in soybean plants that causes crop spoilage. Its early and precise identification would prevent the misuse of pesticides and allow the initiation of an appropriate treatment. A quick, economical and easy-to-execute technique is the Dot blot, capable of recognizing the presence of a genus-specific protein called CFP (Cercosporin Facilitator Protein). The objective was to validate this technique to guarantee the reliability of the results. For that purpose, 29 infected soybean plants and 31 healthy plants were processed, taking into account a 95% desired confidence level and a permissible error of 5%. The technique provided a diagnostic sensitivity of 93.3% and a diagnostic specificity of 96.7%. The efficiency was 95% and positive and negative predictive values were 96.6% and 93.5%, respectively. These results postulate it as a useful resource for the early detection of C. kikuchii in soybean plants.

Identification and Characterization of Cercospora malayensis Causing Leaf Spot on Kenaf

In September 2013 and 2014, a significant number of kenaf plants showing symptoms of leaf spots with approximately 50% incidence were found in experimental plots in Iksan and Namwon, Korea. Leaf spots were circular to irregular, more or less vein-limited, reaching to 10 mm in diameter. The spots were initially uniformly brown to reddish brown, turning pale brown with a purplish margin and showing grayish patches on the lesion due to heavy fructification. The causative agent of the leaf spot disease was identified as Cercospora malayensis. The pathogenicity test was conducted with similar results, which fulfilled Koch's postulates. This is the first report of C. malayensis infection of kenaf in Korea.

Óleo de melaleuca (Melaleuca alternifolia Maiden & Betche, Cheel) no controle de cercosporiose em beterraba / Tea tree oil (Melaleuca alternifolia Maiden& Betche, Cheel) in control of Cercospora beticola Sacc. on Beet

RESUMO O óleo volátil da melaleuca (Melaleuca alternifolia Maiden & Betche, Cheel) possui atividade antimicrobiana podendo causar efeitos sobre as plantas. Avaliou-se a inibição do óleo em Cercospora beticolaSacc., e seu efeito no aumento da produção e qualidade de raízes de beterraba. As doses foram de 0,13; 0,67; 0,80 e 1,00% do óleo, além das testemunhas composta pelo meio de cultura Batata Dextrose Ágar (BDA) no experimento in vitro, e água no experimento in vivo. As plantas foram pulverizadas duas vezes por semana. O delineamento foi inteiramente casualizado, com 4 repetições, e as médias foram comparadas pelo teste Tukey a 5% de probabilidade. O índice de infecção das folhas foi determinado por escala diagramática além do peso e diâmetro das raízes. Os resultados de inibição do crescimento micelial para as doses do óleo foram 0; 56; 87; 83 e 99%, e os índices de infecção: 77,08; 35,62; 21,04; 19,37 e 20,00%, respectivamente, para a testemunha e as doses 0,13; 0,67; 0,80 e 1,00% do óleo. Somente na concentração de 0,80% o óleo proporcionou relação positiva entre o ganho de peso e o diâmetro das raízes. O óleo de Melaleuca foi eficaz no controle de C. beticola e, como consequência, houve produção de raízes de beterraba com melhor desenvolvimento.

ABSTRACT The volatile oil from Melaleuca (Melaleuca alternifolia Maiden & Betche Cheel.) has antimicrobial properties and can promote several effects on plant cultivation. The aim of this study was to evaluate the inhibition of the oil in Cercospora beticola Sacc. and if it favors the growth and development of beet root. The doses were 0.13, 0.67, 0.8 and 1% of oil, besides the control PDA (potato-dextrose-agar) in vitro (laboratory condition) and with water as treatment control in vivo (field conditions). The plants were sprayed twice a week. The treatments were completely randomized and the averages were compared using the Tukey test at 5%. The infection rate of leaves was measured by diagrammatic scale besides the weight and diameter of tubers. The inhibition results of the radial growth by oil treatments were 0; 56, 87, 83 and 99%, while the infection rate showed: 77.08, 35.62, 21.04, 19.37 and 20% respectively to the control and to the oil concentration of 0,13; 0,67; 0,80 e 1,00%. Only at concentration of 0.8% the tea tree oil showed a positive relationship between tuber´s weight and tuber´s diameter gains. It can be concluded that tea tree oil is effective to controlling C. beticola, and also promotes an increase on development in beet tubers.

Immobilization of Lipases Produced by the Endophytic Fungus Cercospora kikuchii on Chitosan Microparticles

This work studied the immobilization of Cercospora kikuchii lipases on chitosan microparticles by chemical attachment on chitosan acetate microparticles activated by glutaraldehyde (CAM) added before or after the enzyme and physical adsorption on highly deacetylated chitosan hydrochloride microparticles (CHM). Lipases covalently immobilized on pre-activated CAM showed better performance retaining 88.4% of the enzymatic activity, with 68.2% of immobilization efficiency (IE). The immobilized enzyme retained an activity of about 53.5 % after five reuses, using p-NPP as substrate. Physical adsorption of lipase onto highly deacetylated CHM showed 46.2 % of enzymatic activity and 28.6% of IE. This immobilized derivative did not lose activity up to 80 days of storage at 4°C, while lipases immobilized on pre-activated CAM maintained its activity up to 180 days at same conditions. Taken together the results indicate that chitosan microparticles provide an optimal microenvironment for the immobilized enzyme to maintain good activity and stability.

Antifungal activity using medicinal plant extracts against pathogens of coffee tree / Atividade antifúngica utilizando extratos de plantas medicinais contra fitopatógenos do cafeeiro

Generally, the medicinal plants have antifungal substances that can be used for the plant protection against phytopathogens. The objective of this study was to know the efficiency of aqueous extracts from medicinal plants against the major etiological agents of coffee tree. The aqueous extracts used were extracted from bulbs of Allium sativum, leaves of Vernonia polysphaera, Cymbopogon citratus, Cymbopogon nardus, Cordia verbenacea, Eucalyptus citriodora, Ricinus communis, Azadirachta indica, Piper hispidinervum and flower buds of Syzygium aromaticum. The etiological agents considered for this study were Cercospora coffeicola, Colletotrichum gloeosporioides, Fusarium oxysporum, Phoma tarda, Rhizoctonia solani and Hemileia vastatrix. The screening for harmful extracts was done based on mycelial growth and conidial germination inhibition. All experiments performed were in vitro conditions. The inhibition of mycelial growth was performed mixing the extracts with the PDA. This mixture was poured in Petri dishes. On the center of the dishes was added one PDA disc with mycelium. It was incubated in a chamber set to 25ºC. The evaluation was done daily by measuring the mycelial growth. The germination assessment was also performed with Petri dishes containing agar-water medium at 2%. These were incubated at 25ºC for 24 hours. After this period the interruption of germination was performed using lactoglycerol. The experiments were conducted in a completely randomized design. The most effective plant extracts against the micelial growth and conidial germination were V. polysphaera, S. aromaticum and A. sativum.

Geralmente, as plantas medicinais têm substâncias antifúngicas que podem ser utilizadas para a proteção das plantas contra fitopatógenos. O objetivo deste estudo foi conhecer a eficiência de extratos aquosos de plantas medicinais contra os principais agentes etiológicos do cafeeiro. Os extratos aquosos utilizados foram extraídos de bulbos de Allium sativum, folhas de Vernonia polysphaera, Cymbopogon citratus, Cymbopogon nardus, Cordia verbenacea, Eucalyptus citriodora, Ricinus communis, Azadirachta indica, Piper hispidinervum e botões florais de Syzygium aromaticum. Os agentes etiológicos considerados neste estudo foram Cercospora coffeicola, Colletotrichum gloeosporioides, Fusarium oxysporum, Phoma tarda, Rhizoctonia solani e Hemileia vastatrix. A triagem dos extratos foi realizada com base no crescimento micelial e na inibição da germinação de conídios. Todos os experimentos foram realizados em condições in vitro. A inibição do crescimento micelial foi realizada misturando-se os extratos com PDA. Esta mistura foi vertida em placas de Petri. No centro das placas foi adicionado um disco de PDA com micélio. Incubou-se em câmara programada para 25°C. A avaliação foi feita diariamente através da medição do crescimento micelial. O experimento sobre a germinação também foi realizado com placas com meio ágar-água a 2%. Estas foram incubadas durante 24 horas. Após este período, a interrupção da germinação foi realizada utilizando lactoglicerol. Os experimentos foram conduzidos em delineamento inteiramente casualizado. Os extratos de plantas mais eficazes contra o crescimento micelial e germinação de conídios foram V. polysphaera, S. aromaticum e A. sativum.

Comparison and validation of diagrammatic scales for brown eye spots in coffee tree leaves / Comparação e validação de escalas diagramáticas para cercosporiose em folhas de cafeeiro

A diagrammatic scale with six levels (0.1-3.0; 3.1-6.0; 6.1-12.0; 12.1-18.0;18.1-30.0; 30.1-49.0 percent) was developed, compared, and evaluated along with two other scales to measure the severity of brown eye spots in coffee trees leaves. The scale was designed based on two others already in use in order to increase the efficiency of evaluation and for estimation values to approach as close as possible to their actual values. Two evaluations were performed using each of the three diagrammatic scales and one was performed without a diagrammatic scale, in seven day intervals. Using the proposed scale, the evaluators demonstrated better precision levels, accuracy, reproducibility, and repeatability in the estimations, when compared to the evaluators who did not use the diagrammatic scale, or who used existing scales. The proposed diagrammatic scale provided a reliable estimation to evaluate brown eye spot severity on coffee tree leaves.

Foi desenvolvida, comparada e avaliada com outras duas escalas uma escala diagramática com seis níveis (0,1-3,0; 3,1-6,0; 6,1-12,0; 12,1-18,0; 18,1-30,0; 30,1-49,0 por cento), para medir a severidade da cercosporiose em folhas de cafeeiro. A escala foi construída baseada em outras duas já existentes, procurando aumentar a eficiência da avaliação e aproximar os valores estimados o mais próximo dos valores reais. Foram realizadas duas avaliações com a utilização de cada uma das três escalas diagramáticas e uma avaliação sem o seu auxílio, em intervalos de sete dias. Com o emprego da escala proposta, os avaliadores apresentaram melhores níveis de precisão, acurácia, reprodutibilidade e repetibilidade nas estimativas, quando comparados aos avaliadores que não utilizaram a escala diagramática, ou que utilizaram as escalas existentes. A escala diagramática proposta demonstrou fornecer uma estimativa confiável para avaliar a severidade da cercosporiose em folhas de cafeeiro.

Aerobiologia de Cercospora kikuchii / Aerobiology of Cercospora kikuchii

Neste estudo, foram quantificados os conídios de Cercospora kikuchii [crestamento foliar em soja (Glycine max)] presentes no ar, sua relação com a intensidade da doença e com os fatores ambientais [temperatura, umidade relativa do ar (UR), precipitação e molhamento foliar] no período de novembro a março de 2006/07 e 2007/08 em Brasília, DF. Para tanto, foi instalada uma armadilha volumétrica capta-esporos 'Burkard' de sete dias em campo experimental com soja. Houve maior captura de conídios no período diurno, com mais de 60 por cento dos esporos coletados entre 8h e 15h. Os dados climáticos variaram de acordo com a safra, mas, de modo geral, em ambos os experimentos, o período de maior captura de esporos ocorreu quando houve redução da precipitação e do molhamento foliar. A UR acima de 80 por cento e temperatura entre 20 e 24°C foram mais favoráveis para a captura de conídios e a intensidade do crestamento foliar. Nos dois anos de avaliação, a maior quantidade de esporo capturado ocorreu quando a soja se apresentava no estádio R6-R7, assim como a intensidade da doença foi maior após o início do estágio reprodutivo da cultura. Apesar da quantidade de conídio capturado em 2006/07 ter sido maior que em 2007/08, o padrão da flutuação aérea de conídios foi semelhante.

The objective of this study was to evaluate the relation of airborne released conidia of Cercospora kikuchii [cercospora leaf blight of soybean (Glycine max)] with the disease intensity and some environmental factors [temperature, relative humidity (RH), precipitation and leaf wetness period) under experimental field conditions in Brasília, DF, Brazil. The evaluation was from November to March of 2006/07 and 2007/08. Data for the amount of airborne conidia were collected using a Burkard's seven-day volumetric spore trap set in a field with soybean. Most of the conidia were collected during the day, with over 60 percent of the spores collected between 8h and 15h. Climatic data varied according to the crop period, but for both periods the highest amount of spores occurred with reduction of precipitation and leaf wetness period. RH above 80 percent and temperature from 20 to 24°C were more favorable to capture of conidia and disease intensity. For both crop period of evaluation the major amount of spores were collected when plant stage was R6-R7, as well as, disease intensity increased after beginning of reproductive stage of soybean. Although the number of captured conidia in the 2006/07 crop period was higher than in 2007/08, the variation of fluctuation of airborne spores occurred similarly.

Efeito do silício na intensidade da cercosporiose e na nutrição mineral de mudas de cafeeiro / Effect of silicon on the intensity of brown eye spot and on the mineral nutrition of coffee seedlings

O presente trabalho objetivou estudar o efeito do silício na intensidade da cercosporiose e na nutrição mineral de mudas de cafeeiro. No experimento 1, testou-se seis doses de ácido silícico (0, 0,5; 1; 2; 4 e 6 g kg­1 de solo) em mudas da cultivar Catuaí Vermelho IAC 99 inoculadas com o fungo Cercospora coffeicola. No experimento 2, foram realizadas microanálises de raios-X para a avaliação de nutrientes presentes nas folhas das mudas de cafeeiro das cultivares Topázio MG1190 e Icatu Precoce IAC 3282, inoculadas e não inoculadas com C. coffeicola, com e sem silicato de cálcio (1 g kg-1 de solo). Com o aumento das doses de ácido silícico observou-se redução na área abaixo da curva de progresso do número de lesões por folha (AACPNLF), redução linear nos teores foliares de magnésio e fósforo e aumento nos teores de enxofre e cobre. Os teores foliares de boro apresentaram comportamento quadrático, diminuindo com o aumento das doses de ácido silícico e aumentando a partir da dose de 4 g kg-1 de solo. Em microanálise de raio X, mudas de cafeeiro com cercosporiose apresentam menores picos de potássio e cálcio, independente da cultivar utilizada.

Our objective was to verify the effect of silicon on the intensity of brown eye spot and on the mineral nutrition of coffee seedlings. In the first experiment, 6 doses of silicic acid (0, 0.5, 1, 2, 4 and 6 g kg-1 soil) were tested using a complete randomized block design with 4 replicates with 6 coffee seedlings cultivar Catuaí Vermelho IAC 99 inoculated with the fungus Cercospora coffeicola. In the second experiment, X-ray microanalysis in a scanning electron microscope was performed on 2 coffee cultivars (Topazio MG1190 and Icatu Precoce IAC 3282), inoculated and non-inoculated with C. coffeicola, treated and untreated with calcium silicate (1 g kg-1 of soil). With the increase of the silicic acid doses, there was observed a reduction in the area under the disease progress curve of the number of lesions per leaf (AUPCNLL), coupled with a linear reduction in the foliar contents of magnesium and phosphorus as well as an increase in the contents of sulfur and copper. The foliar contents of boron presented a quadratic behavior, decreasing with the increase of silicic acid and increasing with the dose of 4 g kg-1 of soil. In X-ray microanalysis, coffee seedlings with brown eye spot presented lower peaks of potassium and calcium, regardless of the cultivar used.

Potential of essential oils for the control of brown eye spot in coffee plants / Potencial de óleos essenciais no controle da cercosporiose-do-cafeeiro

The objectives of this work were to assess the in vitro effect of essential oils extracted from cinnamon, citronella, lemon grass, India clove, tea tree, thyme, neem and eucalyptus on the conidia germination and on mycelial growth of Cercospora coffeicola, and their efficacy to control the brown eye spot in coffee seedlings (cultivars Catucaí 2SL, Catuaí IAC 62 and Mundo Novo 379/19) in a greenhouse, as well as their effects on the initial germination and infection events by scanning electron microscopy. All essential oils promoted the inhibition of conidia germination with increasing concentrations. India clove, cinnamon, neem, thyme and lemon grass oils inhibited the mycelial growth of C. coffeicola. The cinnamon and citronella oils were the most promising for brown eye spot control in all cultivars. In scanning electron microscopy, the cinnamon and citronella oils reduced germination and mycelial development of C. coffeicola in vivo, eight and 16 hours after inoculation, promoting, in some cases, the leakage of the cellular content. Essential oils of cinnamon and citronella reduced the incidence and severity of brown eye spot, in addition to presenting direct toxicity to the pathogen.

Este trabalho avaliou o efeito in vitro de óleos essenciais extraídos de canela, citronela, capim-limão, cravo-da-índia, árvore-de-chá, tomilho, nim e eucalipto na germinação de conídios e no crescimento micelial de Cercospora coffeicola, a eficácia destes óleos no controle da cercosporiose-do-cafeeiro em mudas das cultivares Catucaí 2SL, Catuaí IAC 62 e Mundo Novo 379/19 em casa de vegetação; e seus efeitos sobre os eventos iniciais de germinação e infecção do patógeno in vivo por meio de microscopia eletrônica de varredura. Todos os óleos essenciais inibiram a germinação dos conídios com o aumento das concentrações. Os óleos de cravo-da-índia, canela, nim, tomilho e capim-limão inibiram o crescimento micelial de C. coffeicola. Os óleos de canela e citronela foram os mais promissores no controle da cercosporiose em todas as cultivares. Em microscopia eletrônica de varredura, os óleos de canela e citronela reduziram a germinação e o desenvolvimento micelial in vivo de C. coffeicola oito e 16 horas após a inoculação, promovendo, em alguns casos, o extravasamento do conteúdo celular. Óleos essenciais de canela e citronela reduziram a incidência e a severidade da cercosporiose, além de apresentar efeito tóxico direto ao patógeno.

Tratamento de sementes de híbridos de milho com fluquinconazol / Effect of seed treatment in maize hybrids with fluquinconazol

A evolução na severidade e incidência das doenças na cultura do milho (Zea mays), tornou-se um entrave para o aumento da produtividade e da produção brasileira deste grão. Com isso o uso de fungicidas tem sido cada vez mais constante. O presente trabalho teve por objetivo avaliar o fungicida fluquinconazol em tratamento de sementes de diferentes híbridos de milho no controle da ferrugem comum e cercosporiose do milho. O delineamento experimental utilizado foi o de blocos casualizados, em esquema fatorial 8 (híbridos) x 4 (doses de fungicida) com 3 repetições. Foram avaliadas a porcentagem de plântulas emergidas, a incidência, a severidade, a evolução das doenças, a área abaixo da curva de progresso da doença e também a tolerância dos híbridos às doenças ocorridas. Pelos resultados obtidos verificou-se que o uso de fluquinconazol no tratamento de sementes de milho é eficaz para diminuir a severidade e o progresso de cercosporiose e de ferrugem comum na dose de 0,34g i.a.500g de sementes-1. O uso de fluquinconazol no tratamento de sementes em milho reduziu a porcentagem de emergência em até 2,4%.

Molecular variability in the maize grey leaf spot pathogens in Brazil

Isolates of Cercospora species from leaves displaying symptoms of grey leaf spot were collected in maize-producing areas of south-central Brazil in 2001 and 2002. Restriction digests of the internal transcribed spacer region of rDNA detected the presence of the same two Cercospora species described on maize in the United States, namely C. zeae-maydis and the recently described species, C. zeina. Genetic variability among isolates was assessed by analysing 104 amplified fragment length polymorphism loci. Cluster analysis confirmed the genetic separation of isolates into two species with a mean similarity of 35%. Similarity levels within species were high, averaging 93% and 92% among isolates of C. zeae-maydis and C. zeina, respectively. The mean genetic similarity between C. zeae-maydis and C. zeina and two isolates of C. sorghi f. sp. maydis was 45% and 35%, respectively. Results of this study showed that populations of the grey leaf spot pathogens in Brazil are similar to those in the United States regarding species composition and that C. zeina is also present in Brazil.

Escala diagramática para avaliação da severidade da cercosporiose em caupi / Diagrammatic scale for assessment of Cercospora leaf spot severity in cowpea

A cercosporiose, causada por Cercospora cannescens e Pseudocercospora cruenta, é uma importante doença do caupi (Vigna unguiculata) no Brasil. Devido à inexistência de métodos padronizados para quantificação dessa doença, foi desenvolvida uma escala diagramática com níveis de 1, 2, 4, 8, 16, 32, 64 e 82 por cento de área foliar lesionada. A escala diagramática foi validada por 10 avaliadores, usando 50 folíolos de caupi com diferentes níveis de severidade, mensurados previamente com o programa Assess®. A acurácia, a precisão e a reprodutibilidade das estimativas de cada avaliador foi determinada por regressão linear simples entre a severidade real e a estimada, com e sem o auxílio da escala. Com a escala, os avaliadores obtiveram melhores níveis de acurácia e precisão das estimativas, com os erros absolutos concentrando-se na faixa de 10 por cento. Os avaliadores apresentaram elevada repetibilidade (94 por cento) e reprodutibilidade (90 por cento em 82,3 por cento dos casos) das estimativas com a utilização da escala. Portanto, a escala diagramática proposta é adequada para avaliação da severidade da cercosporiose do caupi.

Cercospora leaf spot caused by Cercospora canescens and Pseudocercospora cruenta is an important disease of cowpea (Vigna unguiculata) in Brazil. Due to the inexistence of standard methods for the assessment of this disease, a diagrammatic scale was developed with 1, 2, 4, 8, 16, 32, 64 and 82 percent of diseased leaf area. The diagrammatic scale was validated by 10 raters using 50 cowpea leaflets with different levels of severity previously measured by the software Assess®. The accuracy, precision and reproducibility of the estimative of each rater were determined by simple linear regression between actual and estimated severity, with and without the use of the scale. With the scale raters obtained better levels of accuracy and precision, with absolute errors concentrating around 10 percent. Raters showed high repeatability (94 percent) and reproducibility ( 90 percent in 82.3 percent of the cases) of the estimates by using the scale. The proposed diagrammatic key is suitable for the evaluation of Cercospora leaf spot severity in cowpea.

Detección de variabilidad genética en aislamientos de Cercospora kikuchii contaminantes de un mismo sembradío de soja / Detection of genetic variability in Cercospora kikuchii isolates from a single soybean field

El conocimiento de la epidemiología y la estructura poblacional de Cercospora kikuchii está poco desarrollado y no se han comunicado estudios al respecto en la Argentina. El objetivo de este trabajo fue seleccionar oligonucleótidos que permitan detectar variabilidad genética en aislamientos de C. kikuchii obtenidos a partir de soja proveniente de un mismo sembradío, mediante la aplicación de RAPD. Se trabajó con 6 aislamientos de C. kikuchii, 5 de ellos se obtuvieron a partir de trozos de tejido enfermo y el restante provenía de una colección de cultivos. De los 7 oligonucleótidos empleados, 5 resultaron útiles para el estudio poblacional de los aislamientos de C. kikuchii.

Current knowledge about epidemiology and population structure of Cercospora kikuchii is little developed and no studies regarding this subject have been reported in Argentina. The aim of this work was to select primers to study genetic variability in C. kikuchii isolated from the same soybean field using RAPD (Random Amplified Polymorphism DNA). RAPD was applied to the DNA of 5 C. kikuchii, isolated from diseased tissue of the soybean in the same field, another isolate, from a strain collection. Out of seven primers, five of them proved to be useful to study the population of C. kikuchii isolates.