Identification and Characterization of Pseudocercospora pyricola Causing Leaf Spots on Aronia melanocarpa

Leaf spot disease on black chokeberry (Aronia melanocarpa) was observed at several locations in Korea during 2014–2015. Leaf spots were distinct, scattered over the leaf surface and along the leaf border, subcircular to irregular and brown surrounded by a distinct dark color, and were expanded and coalesced into irregularly shaped lesions. Severely infected leaves became dry and fell off eventually. The causative agent was identified as Pseudocercospora pyricola. Morphological observations and phylogenetic analyses of multiple genes, including internal transcribed spacer, translation elongation factor 1-alpha, actin, and the large subunit ribosomal DNA were conducted. The pathogenicity test was conducted twice yielding similar results, fulfilling Koch's postulates. To our knowledge, this is the first report on P. pyricola infection of A. melanocarpa globally.

Distribution of black leaf streak disease (Mycosphaerella fijiensis Morelet) in Mato Grosso, Brazil / Distribuição de sigatoka negra (Mycosphaerella fijiensis Morelet) em Mato Grosso, Brasil

Banana black leaf streak disease caused by the present quarantine pest M. fijiensis occurs in Mato Grosso State since 1999 and requires adoption of sanitation, including detection survey. The aim of this study was to evaluate the distribution of M. fijiensis in Mato Grosso State from 1999 to 2013, as well as how black leaf streak disease periodically was spread in all regions of Mato Grosso State according to the standards of the Ministry of Agriculture, Livestock and Food Supply. Considering the first outbreak year and the previous surveys (Table 1), it can be verified that Mycosphaerella fijiensis Morelet was introduced into Mato Grosso State in accordance with the following periods of times and counties: 2001 to 2003 - Nova Bandeirantes and Paranaíta; 2001 to 2004 - Barra do Bugres and Gaúcha do Norte; 2001 to 2005 - Paranatinga; 2002 to 2004 - Porto Estrela, Santo Afonso, and Tangará da Serra; 2002 to 2005 - Rosário Oeste; 2004 - Acorizal, Guarantã do Norte, and Sinop; 2004 to 2005 - Sapezal; 2005 - Campos de Júlio, Nova Maringá, Poxoréu, and Sorriso; 2005 to 2006 -Marcelândia and Matupá; 2007 - Água Boa, Barra do Garças, Campinápolis, General Carneiro, Novo São Joaquim, and Pedra Preta; 2013 - Canabrava do Norte, Confresa, Porto Alegre do Norte, and São José do Xingu. The dispersal of M. fijiensis throughout both time and space showed to be random in Mato Grosso State and its counties, except among some counties adjacent each other, which can be explained by the movement of infected banana seedlings.

O fungo Micosphaerella fijiensis, agente causal da Sigatoka Negra, é uma praga quarentenária presente, que ocorre no estado de Mato Grosso, desde 1999, e exige adoção de medidas fitossanitárias, inclusive levantamentos de detecção. O objetivo deste trabalho foi avaliar a disseminação de M. fijiensis, em Mato Grosso, durante o período de 1999 a 2013, já que a Sigatoka Negra foi levantada em todas as regiões de Mato Grosso, periodicamente, conforme as normas do Ministério da Agricultura, Pecuária e Abastecimento. Determinou-se o ano ou o período em que o fungo M. fijiensis foi introduzido nos municípios, considerando-se o ano de detecção do primeiro foco e o levantamento anterior, resultando na seguinte constatação: (2001 a 2003 ­ Nova Bandeirantes e Paranaíta); (2001 a 2004 ­ Barra do Bugres e Gaúcha do Norte); (2001 a 2005 ­ Paranatinga); (2002 a 2004 ­ Porto Estrela, Santo Afonso e Tangará da Serra); (2002 a 2005 ­ Rosário Oeste); (2004 ­ Acorizal, Guarantã do Norte e Sinop); (2004 a 2005 ­ Sapezal); (2005 ­ Campos de Júlio, Nova Maringá, Poxoréu e Sorriso); (2005 a 2006 ­ Marcelândia e Matupá); (2007 ­ Água Boa, Barra do Garças, Campinápolis, General Carneiro, Novo São Joaquim e Pedra Preta); (2013 ­ Canabrava do Norte, Confresa, Porto Alegre do Norte e São José do Xingu). A dispersão desta praga, no tempo e no espaço, mostrou-se aleatória, exceto entre alguns municípios adjacentes entre si, fato que pode ser explicado pelo trânsito de mudas de bananeira contaminadas.

Generation of Reactive Oxygen Species via NOXa Is Important for Development and Pathogenicity of Mycosphaerella graminicola

The ascomycete fungus Mycosphaerella graminicola (synonym Zymoseptoria tritici) is an important pathogen of wheat causing economically significant losses. The primary nutritional mode of this fungus is thought to be hemibiotrophic. This pathogenic lifestyle is associated with an early biotrophic stage of nutrient uptake followed by a necrotrophic stage aided possibly by production of a toxin or reactive oxygen species (ROS). In many other fungi, the genes CREA and AREA are important during the biotrophic stage of infection, while the NOXa gene product is important during necrotrophic growth. To test the hypothesis that these genes are important for pathogenicity of M. graminicola, we employed an over-expression strategy for the selected target genes CREA, AREA, and NOXa, which might function as regulators of nutrient acquisition or ROS generation. Increased expressions of CREA, AREA, and NOXa in M. graminicola were confirmed via quantitative real-time PCR and strains were subsequently assayed for pathogenicity. Among them, the NOXa over-expression strain, NO2, resulted in significantly increased virulence. Moreover, instead of the usual filamentous growth, we observed a predominance of yeast-like growth of NO2 which was correlated with ROS production. Our data indicate that ROS generation via NOXa is important to pathogenicity as well as development in M. graminicola.

Biological control of banana black Sigatoka disease with Trichoderma / Controle biológico da Sigatoka-negra da bananeira com Trichoderma

Black Sigatoka disease caused by Mycosphaerella fijiensis is the most severe banana disease worldwide. The pathogen is in an invasive phase in Brazil and is already present in most States of the country. The potential of 29 isolates of Trichoderma spp. was studied for the control of black Sigatoka disease under field conditions. Four isolates were able to significantly reduce disease severity and were further tested in a second field experiment. Isolate 2.047 showed the best results in both field experiments and was selected for fungicide sensitivity tests and mass production. This isolate was identified as Trichoderma atroviride by sequencing fragments of the ITS region of the rDNA and tef-1α of the RNA polymerase. Trichoderma atroviride was as effective as the fungicide Azoxystrobin, which is recommended for controlling black Sigatoka. This biocontrol agent has potential to control the disease and may be scaled-up for field applications on rice-based solid fermentation.

A Sigatoka-negra causada por Mycosphaerella fijiensis é a doença mais destrutiva da bananeira em termos mundiais. O patógeno está em uma fase invasiva no Brasil e já se encontra distribuído na maior parte dos Estados do país. O potencial de 29 isolados de Trichoderma spp. para o controle da Sigatoka-negra foi estudado sob condições de campo. Quatro isolados foram capazes de reduzir significativamente a severidade da doença e foram selecionados para um segundo experimento de campo. O isolado 2.047 apresentou os melhores resultados e foi utilizado em testes de sensibilidade a fungicidas e produção massal. Esse isolado foi identificado como Trichoderma atroviride por meio do sequenciamento de fragmentos da regiões ITS do rDNA e tef-1α da RNA polymerase. Trichoderma atroviride foi tão efetivo no controle da Sigatoka-negra quanto o fungicida Azoxystrobin, que é recomendado para o controle da doença. O agente de controle biológico tem potencial para o controle da Sigatoka-negra e pode ser produzido em massa em arroz autoclavado para aplicações no campo.

Chemical management in fungicide sensivity of Mycosphaerella fijiensis collected from banana fields in México

The chemical management of the black leaf streak disease in banana caused by Mycosphaerella fijiensis (Morelet) requires numerous applications of fungicides per year. However this has led to fungicide resistance in the field. The present study evaluated the activities of six fungicides against the mycelial growth by determination of EC50 values of strains collected from fields with different fungicide management programs: Rustic management (RM) without applications and Intensive management (IM) more than 25 fungicide application/year. Results showed a decreased sensitivity to all fungicides in isolates collected from IM. Means of EC50 values in mg L-1 for RM and IM were: 13.25 ± 18.24 and 51.58 ± 46.14 for azoxystrobin, 81.40 ± 56.50 and 1.8575 ± 2.11 for carbendazim, 1.225 ± 0.945 and 10.01 ± 8.55 for propiconazole, 220 ± 67.66 vs. 368 ± 62.76 for vinclozolin, 9.862 ± 3.24 and 54.5 ± 21.08 for fludioxonil, 49.2125 ± 34.11 and 112.25 ± 51.20 for mancozeb. A molecular analysis for β-tubulin revealed a mutation at codon 198 in these strains having an EC50 greater than 10 mg L-1 for carbendazim. Our data indicate a consistency between fungicide resistance and intensive chemical management in banana fields, however indicative values for resistance were also found in strains collected from rustic fields, suggesting that proximity among fields may be causing a fungus interchange, where rustic fields are breeding grounds for development of resistant strains. Urgent actions are required in order to avoid fungicide resistance in Mexican populations of M. fijiensis due to fungicide management practices.

Aceitação de cultivares de bananas resistentes à Sigatoka Negra junto ao consumidor da região Nordeste do Brasil / Acceptance of banana cultivars resistant to Black Sigatoka by the consumer market of Northeast Brazilian region

O Mal da Sigatoka Negra é devastador para as cultivares tradicionais de banana. No Brasil, cultivares resistentes estão sendo desenvolvidas, mas se a preferência do consumidor não for considerada, o programa de melhoramento pode falhar. Neste trabalho, a aceitabilidade de quatro cultivares resistentes foi acessada no Nordeste brasileiro e comparada a quatro variedades comerciais. Dois grupos de consumidores participaram: adultos jovens e donas de casa. Escala hedônica foi aplicada para aparência externa dos cachos, aceitação global e aceitação por atributos dos frutos (aparência sem a casca, aroma, sabor e textura), além de testes de preferência e intenção de compra. Os dados foram submetidos à ANOVA e Mapa de Preferência Interno. Mulheres e jovens mostraram opiniões semelhantes. As cultivares 'Preciosa' e 'Pacovan Ken' mostraram ser as mais promissoras, sendo que a primeira já pode substituir as cultivares comerciais 'Prata' e 'Pacovan' sem prejudicar a sua aceitabilidade, mas a 'Pacovan Ken' ainda precisa ser melhorada quanto à aparência.

The Black Sigatoka Disease is devastating to traditional banana cultivars. In Brazil, resistant cultivars are being developed but if the consumer's preference is not taken into account, the breeding program may not succeed. In this research the acceptability of four resistant cultivars was accessed in the Northeastern Brazilian region and compared to four commercial varieties. Two groups of consumers participated: young adults and housewives. Hedonic scale was applied to external appearance of bunches, global acceptance and acceptance of fruits' attributes (appearance without peel, aroma, flavor and texture). Preference and purchase intent were also evaluated. Data were submitted to ANOVA and Preference Mapping. Women and young adults showed similar opinions. 'Preciosa' and 'Pacovan Ken' cultivars showed to be the most promising ones. 'Preciosa' can already substitute the commercial 'Prata' and 'Pacovan' cultivars without impairing their global acceptability, but 'Pacovan Ken' still needs to be improved regarding its appearance.

Amostragem, caracterização de sintomas e escala diagramática da mancha graxa dos citros (Mycosphaerella citri) no Recôncavo Baiano / Sampling, characterization of citrus greasy spot (Mycosphaerella citri) symptoms in Recôncavo Baiano and development of a diagrammatic scale for assessment of severity

O Recôncavo da Bahia é uma região de clima propício à mancha graxa dos citros (Mycosphaerella citri), doença nunca antes estudada no Brasil. Os objetivos deste trabalho foram definir o tamanho mínimo de amostra para quantificar a incidência, caracterizar os sintomas da doença e elaborar uma escala diagramática para a avaliação de sua severidade. A partir de uma amostragem piloto realizada por avaliação de cinco folhas por quadrante, quatro quadrantes por planta e 30 plantas em cada um dos 10 pomares visitados no município de Cruz das Almas, foi determinado que o tamanho mínimo da amostra em quadrantes e folhas seria de quatro e 16 plantas, respectivamente. De 320 folhas coletadas de diferentes plantas em 11 pomares, foi constatada uma grande quantidade de lesões (média de 131) por folha sintomática, em sua maioria diminutas (média de 0,014cm²). A severidade variou de 0,15 por cento a 35,85 por cento, com média de 7,3 por cento. Com base na severidade real em campo, foi elaborada uma escala diagramática com seis níveis: 1 por cento, 2 por cento, 5 por cento, 9 por cento, 18 por cento e 36 por cento de área foliar lesionada. Cinqüenta imagens de folhas foram submetidas a avaliadores por duas vezes, os quais estimaram a severidade com e sem a utilização da escala, constatando-se um discreto benefício no grau de precisão e de acurácia das estimativas com o uso da escala.

Weather conditions make the Recôncavo Region in the State of Bahia, a favorable region to the occurrence of citrus greasy spot (Mycosphaerella citri), a disease that hadn't been studied before in Brazil. Thus, this research aimed to develop a sampling method to quantify its incidence, to characterize its symptoms, and to develop a diagrammatic scale for assessing disease severity. The minimum sample size to estimate greasy spot incidence in leaves (16 plants) was calculated based on a prospective sampling of five leaves per quadrant, four quadrants per tree, and 30 trees per grove, in ten groves. From 320 mature leaves collected in different plants of 11 groves, it was observed a high number of lesions per symptomatic leaf (mean of 131±102), most of them small (mean of 0.014±.,011cm²). Greasy spot severity varied from 0,15 percent to 35,85 percent, with a mean of 7,3 percent. Based on those severity values, a six level (1 percent, 2 percent, 5 percent, 9 percent, 18 percent e 36 percent of lesioned leaf area) diagrammatic scale was developed. 50 images of symptomatic leaves were showed to evaluators, which estimated the severity with and without the use of the scale. The diagrammatic scale use, slightly increased the estimates accuracy and precision.

Plantio adensado não controla a sigatoka-negra da bananeira / Dense plantation do not control banana black-sigatoka

Algumas publicações relatam que o adensamento populacional dos bananais reduz a severidade da sigatoka-negra (Mycosphaerella fijiensis). Instalou-se um ensaio com cinco tratamentos e quatro repetições. Os tratamentos 1.600, 2.000, 2.400, 2.800 e 3.200 plantas.ha-1 da cultivar D'Angola foram instalados em parcelas agrupadas de 2.000 m² cada. O tamanho das parcelas foi fixo e o número de plantas por parcela variou conforme o espaçamento adotado para cada população. A área de 2.000 m² foi dividida em quatro subáreas de 500 m², considerando-as como parcelas. Em cada subárea selecionaram-se 15 plantas centrais para serem avaliadas. Na época do florescimento registraram-se a severidade da doença na folha n.°10 e o número de folhas viáveis. Na colheita, a altura e o diâmetro do pseudocaule e o peso dos cachos, das pencas e dos frutos. A análise conjunta dos dados indica que todos os tratamentos foram semelhantes entre si e que o adensamento das plantas não controlou a sigatoka-negra.

Many publications show that plantations of high density of bananas decrease the severity of black-sigatoka (Mycosphaerella fijiensis). To test this hypothesis it was instaled an experiment with five treatments and four repetitions. The treatments were density plant of 1.600, 2.000, 2.400, 2.800 e 3.200 plant.ha-1. The cultivar planted was D'Angola and each plot had fixed 2.000 m², the number of plants in each plot changed in accordance with the treatment tested. The plots were divided in four subplots of 500 m² where 15 plants located in the center were measured. The evaluation of severity was carried out in the leaf number ten during the flowering period. It was also evaluated the numbers of viable leaves, height, diameter and weight of production (banch, bunches and fruits). The analyses did not show effect of high density in the parameter measured and it was conclued that the treatments tested had not control black-sigatoka.