Resumo em Inglês:

Plant pathogenic fungi have long been documented through concerted efforts of mycologists and plant pathologists; these records have served as the basis for regional and countrywide checklists which have since been put into databases listing hosts and associated fungi. They are used by governments and scientists to formulate trade quarantine policies and determine research funding, such as in plant breeding programs and disease control. With the ability to use molecular characters to study the systematics of fungi it is clear that morphologically defined species are often large complexes comprised of genetically and biologically distinct species. Use of molecular techniques to examine species complexes has revealed cryptic species in many important plant pathogenic genera, e.g. Botryosphaeria, Colletotrichum, Fusarium, and Mycosphaerella. It has occurred to such an extent that existing checklists and databases need updating. It is important that the data from these studies, including changes in taxonomy and nomenclature, be incorporated into the databases of plant pathogenic fungi to support accurate plant quarantine decisions. In addition, epitypifying fungi by re-collecting material from type habitats and isolating the organism into pure culture will provide essential materials for systematics studies to further clarify the taxonomy and phylogeny of plant pathogenic fungi. Overall, we conclude that disease lists are likely to be highly outdated and advocate the need for countrywide re-inventory of plant pathogens. As a result of these studies, tools can be developed that use morphological or molecular characters, or both, to promote accurate identification of plant pathogenic fungi.

Resumo em Português:

A supressão da podridão de raiz (Pythium aphanidermatum) e a promoção de crescimento de pimentão hidropônico por Pseudomonas chlororaphis 63-28 foram avaliadas em plantas predispostas ou não ao patógeno. O bioagente foi introduzido na solução nutritiva 10 dias antes das raízes serem inoculadas com o patógeno. A zona radicular foi mantida a 23ºC, exceto nos três dias antes da inoculação quando as plantas foram expostas a 33ºC. Na temperatura de 23ºC (sem predisposição), P. chlororaphis na concentração de 10(7) UFC mL-1, aplicada na solução nutritiva, atrasou o aparecimento dos sintomas da doença. As concentrações de 10(6), 10(7) e 10(8) UFC mL-1 do bioagente foram mais eficientes em controlar a doença nas plantas inoculadas com o patógeno. A densidade do bioagente nas raízes, nos dois regimes de temperatura, variou de 5,88 a 6,45 log da UFC g-1 de raiz fresca, do sétimo ao 19º dia após a aplicação de 10(7) UFC mL-1 Nas plantas inoculadas ou não, o bioagente atrasou o aparecimento do escurecimento radicular, remediou a predisposição a doença e incrementou o desenvolvimento das plantas. A expansão foliar foi um indicador adequado para a podridão de raiz e a remediação com P. chlororaphis. Conclui-se que P. chlororaphis 63-28 tem potencial para o manejo da podridão da raiz em sistemas hidropônicos, independentemente da predisposição.

Resumo em Inglês:

The ability of Pseudomonas chlororaphis 63-28 to suppress Pythium root rot (Pythium aphanidermatum) and promote plant growth was investigated in hydroponic peppers that were predisposed or not predisposed to the disease. The biocontrol agent was introduced into the nutrient solution 10 days before the roots were inoculated with the pathogen. The root zone was maintained at 23ºC except when roots were exposed to 33ºC for three days before inoculation to induce predisposition to root rot. At constant 23ºC (no predisposition) application of P. chlororaphis at 10(7) CFU mL-1 nutrient solution delayed root browning more effectively than did higher or lower densities. In predisposed plants, densities of 10(6), 10(7) and 10(8) CFU mL-1 were equally superior. When applied at 10(7) CFU mL-1, the density of P. chlororaphis on roots of the two temperature regimes ranged from log10 5.88 to 6.45 CFU g-1 fresh roots at seven to 19 days after application. The agent delayed root browning, re-mediated predisposition to root rot, and increased growth of inoculated and non-inoculated plants. Leaf expansion was a sensitive marker of root rot and remediation by P. chlororaphis. We conclude that P. chlororaphis 63-28 has substantial potential for managing the disease regardless of predisposition.

Resumo em Inglês:

Genetic diversity and identification of fumonisin-producing isolates of Fusarium verticillioides from two provinces in the Philippines were analyzed using molecular techniques. Using a Polymerase Chain Reaction (PCR)-based technique, 49 of the 54 isolates were identified as F. verticillioides, with an amplified product of 800 bp using VERT-1 and VERT-2 primers. Of these, VERTF-1/VERTF-2 primers detected 38 fumonisin-producing F. verticillioides isolates producing a single fragment of 400 bp. The other five isolates, which had previously been identified as F. verticillioides by TEF sequences, morphology and sexual crosses, were negative using this method. Using Universally Primed-PCR (UP-PCR) markers for F. verticillioides, no grouping was observed based on geographical origin and species, but intermediate (53.8%) to high (99.6%) bootstrap values and high genotypic diversity (H=0.99) were generated, suggesting that all isolates clearly belonged to F. verticilliodes. Unweighted Pair Group Method with Arithmetic Mean (UPGMA) cluster analysis with Jaccard's coefficient showed that similarities among F. verticillioides isolates were intermediate at 71% similarity level.

Resumo em Inglês:

Three yeast antagonists (two strains of Cryptococcus laurentii and one of Candida sake) from orange trees reduced incidence of green mold by 80 to 95% when tested in wounded orange fruits inoculated with Penicillium digitatum and incubated at 7ºC for 30 days. The yeasts inhibited conidial germination of the pathogen, but did not kill the spores. Effectiveness of the three yeasts as antagonists was associated in part with their ability to rapidly colonize wound sites, despite low nutrient availability. Observations suggested that production of extracellular matrix by the yeasts may have facilitated rapid wound colonization. Germination of P. digitatum conidia was significantly inhibited when the pathogen and antagonists were in direct physical contact in a culture suspension. The results supported the view that competition for nutrients is also a mode of action of yeasts against P. digitatum.

Resumo em Português:

A mancha foliar de Glomerella (MFG) é uma doença emergente e tem se tornado uma grande preocupação para os produtores brasileiros de maçã, porque a cultivar mais plantada, Gala, é altamente suscetível à doença. Desta forma, este trabalho teve como objetivos investigar as fases iniciais do processo infeccioso de C. gloeosporioides e verificar o envolvimento das enzimas peroxidase (POD) e β-1,3-glucanases (GLU) em plântulas de macieira de genótipo suscetível ('Gala') e resistente ('Fuji'). Para tanto, plântulas com 75 dias foram inoculadas com C. gloeosporioides e a severidade da MFG foi avaliada aos 10 dias pós-inoculação. Os eventos iniciais da infecção (germinação dos conídios e a formação de apressórios) de C. gloeosporioides foram avaliados às 24, 48 e 72 horas após a inoculação. Paralelamente, a atividade da POD e GLU foi monitorada nos mesmos intervalos de tempo. Plântulas do genótipo resistente não apresentaram sintomas da MFG, enquanto que as do genótipo suscetível exibiram 11% de severidade média. O padrão dos eventos iniciais de penetração do C. gloeosporioides foi o mesmo em ambos os genótipos. A resistência cultivar-especifica foi associada a um aumento da atividade de POD, enquanto que a atividade de GLU não variou entre os genótipos.

Resumo em Inglês:

The Glomerella leaf spot (GLS) is an emerging disease and has become a major concern to Brazilian apple producers because the most widely grown cultivar, 'Gala', is highly susceptible to the disease. So, this study aimed to investigate the early stages of infectious process of C. gloeosporioides, and understand the role of peroxidase (POD) and β -1,3-glucanases (GLU) in susceptible ('Gala') and resistant ('Fuji') apple seedling genotypes. Seedlings (75 days-old) were inoculated with C. gloeosporioides and the severity of GLS was assessed at 10 days after inoculation. Conidial germination and appressoria formation of C. gloeosporioides were evaluated at 24, 48 and 72 hours after inoculation. Enzyme activity for POD and GLU were also determined at the same time interval. Seedlings of the resistant genotype did not show symptoms of GLS, whereas the susceptible genotype exhibited 11% of necrotic leaf area. The early penetration events of C. gloeosporioides were similar in both genotypes. Cultivar-specific resistance was associated with an enhanced POD activity, while GLU activity was similar in both genotypes.

Resumo em Português:

Barley yellow dwarf virus-PAV é a espécie predominante na região sul-brasileira entre as espécies de vírus que causam o nanismo amarelo em cereais de inverno. A resistência genética e a tolerância ao vírus e ao afídeo vetor são importantes estratégias de controle dessa virose. BRS Timbaúva apresenta reduções menores de produtividade, comparativamente a outras cultivares de trigo, quando exposta ao complexo afídeo-vírus, e é resistente ao vetor Rhopalosiphum padi. Esse estudo visou determinar se esta cultivar também apresenta resistência ou tolerância ao BYDV-PAV. Os ensaios foram realizados comparando-se BRS Timbaúva a Embrapa 16 (suscetível e intolerante). A resistência ao vírus foi avaliada por meio de estimativas do título viral por ELISA. A tolerância foi estimada avaliando-se componentes morfológicos e de rendimento, considerando a redução em relação a plantas não infectadas. O efeito da pressão de inóculo sobre a produtividade também foi avaliado. BRS Timbaúva foi tão suscetível à infecção viral quanto Embrapa 16 porém, comparativamente a esta cultivar, em todos os ensaios os danos e redução de produtividade em BRS Timbaúva foram menores, o que sugere tolerância ao BYDV-PAV. O comportamento a campo desta cultivar pode estar associado a resistência ao vetor e tolerância ao vírus.

Resumo em Inglês:

Barley yellow dwarf virus-PAV, among the virus species that cause yellow dwarf disease in winter cereals, is predominant in Southern Brazil. Genetic resistance and tolerance to the virus and to the aphid vector are important strategies to control this virus. BRS Timbaúva shows low reduction of productivity, in relation to other wheat cultivars, when exposed to aphid-virus complex, and is resistant to the Rhopalosiphum padi vector. This work aimed to establish if this cultivar is also resistant or tolerant to BYDV-PAV. The experiments were carried out comparing BRS Timbaúva and Embrapa 16 (susceptible and intolerant). Virus resistance was evaluated by viral growth curves and tolerance estimated by morphological and yield components in relation to healthy plants. Inoculum pressure effects on resistance/tolerance were also evaluated. BRS Timbaúva was as susceptible to viral infection as Embrapa 16, but in all experiments its productivity loss was lower than that of Embrapa 16, which suggests its BYDV-PAV tolerance. BRS Timbaúva field behavior may be associated with vector resistance and virus tolerance.

Resumo em Português:

Tomato chlorosis virus (ToCV) é uma espécie do gênero Crinivirus, transmitida por Bemisia tabaci biótipo B e que foi primeiramente detectada no Brasil em 2006 no município de Sumaré, Estado de São Paulo. No período de 2007 a 2010, análises de RT-PCR seguida de "nested-PCR", com oligonucleotídeos iniciadores específicos para a detecção do ToCV e o sequenciamento dos fragmentos amplificados confirmaram a presença desse vírus em amostras de plantas sintomáticas de tomate (Solanum lycopersicum) provenientes de plantações em municípios dos estados da Bahia (BA), Espírito Santo (ES), Goiás (GO), Minas Gerais (MG) e Rio de Janeiro (RJ). Este é o primeiro relato do ToCV nos Estados da BA, ES, GO, MG e RJ, sugerindo uma ampla disseminação desse vírus no Brasil.

Resumo em Inglês:

Tomato chlorosis virus (ToCV) is a species in the genus Crinivirus, transmitted by Bemisia tabaci biotype B, first detected in Brazil in 2006 in the county of Sumaré, State of São Paulo. During the period from 2007 to 2010, RT-PCR analyses followed by nested-PCR with specific primers for ToCV detection, and sequencing of the amplicons, confirmed the presence of this virus in samples of symptomatic tomato plants (Solanum lycopersicum) from crops in counties in the states of Bahia (BA), Espírito Santo (ES), Goiás (GO), Minas Gerais (MG), and Rio de Janeiro (RJ). This is the first ToCV report for the states of BA, ES, GO, MG, and RJ, suggesting that this virus is widely disseminated in Brazil.

Resumo em Português:

Visando estudar a interação Phytophthora palmivora x pupunheira (Bactris gasipaes Kunt.), foram efetuados cortes histológicos nos locais onde plântulas, com seis meses de idade, foram inoculadas na base do estipe, para serem examinados ao microscópio eletrônico de varredura (MEV). Os métodos de inoculação utilizados foram: i. Inoculação com gotas (5µL) de uma suspensão de 1 x 10(6) zoósporos/mL; ii. Irrigação com 5 mL da suspensão de 1 x 10(6) zoósporos/mL; e iii. Inoculação com discos de micélio de 0,7 cm de diâmetro. Os cortes foram realizados 6 e 12 horas após a inoculação seguindo-se as etapas de fixação, desidratação e metalização para a preparação do material para MEV. Zoósporos encistados e esporângios aderidos à epiderme das plantas foram observados 6 e 12 horas após a inoculação, com a fase de pré-infecção ocorrendo anteriormente a este período. Independentemente do método de inoculação utilizado foi observada a colonização dos tecidos do hospedeiro em todas as plantas inoculadas.

Resumo em Inglês:

Aiming to study the interaction Phytophthora palmivora and pejibaye palm (Bactris gasipaes Kunt.) with the aid of scanning electron microscope (SEM), sections were made of the stem base of pejibaye plants in the sites where six-month-old pejibaye seedlings were inoculated. The inoculation methods used were: i. inoculation with 5 µL drops of zoospore suspension (1x10(6) zoopores/mL); ii. irrigation around the stem base of seedlings, with 5 mL of a suspension of 1 x 10(6) zoospores/mL; and iii. inoculation with a 7-mm-diameter disk of mycelium. Tissue sections were made 6 and 12 hours after inoculation, following the conventional process of fixation, dehydration and metallization steps for SEM. Encysted zoospores and sporangia attached to host epidermis were seen 6 and 12 hours after inoculation, with the pre-infection phase occurring before that stage. Independently of the inoculation method employed, host tissue colonization could be observed in all inoculated plants.

Resumo em Inglês:

Disease severity evaluation is an important decision support for adoption of strategies and tactics for disease control. The most commonly used method to assess disease severity is visual, but the problem is repeatability, due to subjectivity and imprecision of estimates. For Puccinia sorghi, a threshold of action of 1% severity was determined, so high precision is required in disease quantification. The aim of this study was to compare different assessment methods and analyze their association. Two diagrammatic scales were used to estimate severity, the Peterson and Amorim scales. Pustules were counted with the naked eye and with a 20x magnification hand lens. Software for disease quantification, Assess 2.0, was used to determine actual percentage area and lesion count. No significant differences were found between naked-eyed count and with magnifier. Lesion count with Assess 2.0 gave an imprecise result. Significant differences were found between diagrammatic scales. Compared with Assess 2.0, severity using Peterson was 2% higher, showing widely scattered differences (R²=0.48). Overestimation with visual scales was suggested, especially at low severity levels. Counting pustules was more objective, precise and reproducible. Thus, a calibration curve was constructed (R²=0.79), which will allow calculation of severity from counting pustules.