Resumo em Inglês:

The progress of charcoal root rot (CRR) disease in Pinus radiata seedlings caused by Macrophomina phaseolina was evaluated in greenhouse and field trials. In one greenhouse trial P. radiata was sown in a sandy soil with pathogen inoculum densities (ID) ranging from 25 to 1000 cfu.g-1. After two months, the seedlings were established under three soil moisture content (SMC) levels corresponding to 100%, 75% and 50% of field capacity (FC). In one field trial, P. radiata was sown on microplots infested with ID of 50 to 250 cfu.g-1. In the greenhouse trial the disease incidence was related with the pathogen ID and SMC. At 100% FC, the seedlings remained asymptomatic until the experiment ended, however M. phaseolina was able to infect the roots. In the field trial, the disease progress curves were similar to those of the greenhouse trial in response to ID and SMC but the plant mortality due to CRR incidence did not exceed 50%. The monomolecular model was the one that best fitted the disease progress curve data for both trials and most treatments. Knowledge of the existing ID of M. phaseolina in the soil, combined with information on SMC, may be important for predicting CRR epidemics in P. radiata nurseries.

Resumo em Inglês:

This work reports the in vitro expression of Citrus leprosis virus C (CiLV-C) putative coat protein (p29) and the production of a polyclonal antibody to be used as a tool for serological diagnosis of citrus leprosis. The ORF2/RNA1, corresponding to p29, was cloned in pET28a and transformed into Escherichia coli cells (BL21). Expression of p29 was induced in vitro and the protein was purified and used for immunization of rabbits to produce the polyclonal antibody. The anti p29 serum was shown to be highly specific to CiLV-C detection by immunological methods (Western blot, PTA-ELISA, tissue blot and in situ immunolocalization), without cross reaction with healthy citrus plants or other cytoplasmic and nuclear viruses transmitted by Brevipalpus mites. These results demonstrate that the antibody against CiLV-C p29 protein is highly specific for CiLV-C detection. In situ immunogold labeling assays on thin sections of sweet orange leaf cells infected by CiLV-C demonstrated that short, bacilliform particles present within cisternae of the endoplasmic reticulum were specifically labeled, confirming their viral nature. The dense cytoplasmic viroplasm was also heavily labeled indicating that it represents a site of p29 accumulation.

Resumo em Inglês:

A newly emerged disease, the Pyricularia blast caused by Pyricularia grisea, is commonly observed on wheat and black oats, since its discovery in 1985. Within a few years the disease spread to other species of Gramineae, but white oat cultivars remained resistant and were the only ones among cultivated cereals resistant to this disease. In 2012, one commercial field of white oat cultivar IAC 7 was found severely attacked by Pyricularia blast in Assis, in the state of São Paulo. The objective of the present investigation was to find out whether other white oat cultivars are also susceptible to the new P. grisea isolate from cv. IAC 7 and to determine the pathogenic variability, if any, among P. grisea isolates from black oats. Thirty-three white oat cultivars, along with some cultivars of black oat, barley, wheat, triticale, and rye were evaluated against the IAC 7 isolate. Results of disease severity analysis indicated that four white oat cultivars were resistant, seven were moderately resistant and the remaining were susceptible or highly susceptible. Five wheat cultivars were also resistant. Pathogenic variation among P. grisea isolates from black oats was observed.

Resumo em Inglês:

Elsinoë fawcettii causes citrus scab and E. australis causes sweet orange scab and there are different pathotypes of each species. Citrus scab is widely distributed, whereas sweet orange scab is limited mostly to southern South America. In 2010, E. australis was detected by PCR in Texas for the first time in the USA and subsequently found in commercial areas of Texas. In this study, cultures were obtained in Texas mostly from diseased fruit with symptoms similar to "late-season windscar" and identified as the Natsudaidai pathotype of E. australis by sequencing of the PCR amplification products and sequencing of the translation elongation factor and ITS regions. Inoculations of detached leaves and fruit of grapefruit, sweet orange, and tangerine produced scab-like symptoms on all organs and species. The fungus was re-isolated from the inoculated organs and PCR tests on re-isolated fungal colonies and lesions confirmed the presence of E. australis. The disease represents sweet orange scab of citrus with a new scab disease symptomatology, but the host range, ecology and epidemiology of this pathotype are still not completely understood. Thus far, Natsudaidai pathotype has been reported only from South Korea.

Resumo em Inglês:

This work was conducted to evaluate the effect of Fusarium verticillioides on the early stage development of maize seedling/plants, considering different inoculum potentials of this fungus in seeds, under controlled conditions. To obtain seeds with different inoculum potentials of that fungus, the osmo-priming technique as referred to in literature was used. By this technique, the non-germinated seeds of the same lot, exhibiting typical structures of F. verticillioides, were grouped into five categories according to a grading system that was established based on the visible area of the seeds covered by the fungal structures. Seeds of each category were sowed in soil substrate and plants were grown under controlled conditions, 25ºC and 16 h light/day, for 25 days. All variables used, plant population (stands), speed of seedling emergence, and height/weight of emerged plants, were negatively affected by the increase of the inoculum intensity of the fungus initially present in the seeds. The regression equation showed high values of correlation coefficient (>0.85) for all variables, except for plant height which presented correlation coefficient of 0.77. The most severe effect of the fungus in this study occurred on the root system of the emerged plants as determined by the highest inoculum intensity of the pathogen on the planted seeds.

Resumo em Inglês:

The objective of this study was to identify fungi and bacteria associated with the post-harvest rot of ginger rhizomes (Zingiber officinale Roscoe) in the Serrana region of Espírito Santo, Brazil. Rhizomes with symptoms of rot were sampled in the packing-house and in the field soon after harvest. In the packing-house, we report positive pathogenicity tests for Acremonium murorum, Acrostalagmus luteo-albus, Fusarium sp., Fusarium oxysporum, Lasiodiplodia theobromae and Sclerotium rolfsii. For the rhizomes sampled during harvest, the mean incidence of pathogens was as follows: F. oxysporum, 74%; Fusarium sp., 31%; Fusarium solani, 21%; Nigrospora oryzae, 5%; Fusarium semitectum and Nigrospora sphaerica, 6%; Alternaria tenuissima, 4%; Penicillium commune, Verticillium sp.(1) and Verticillium sp.(2), 3%; A. luteo-albus, Aspergillus niger, Chaetomium sp. and Epicoccum sp., 2%; and Curvularia geniculata and Mucor hiemalis, 1%. The mean incidence of bacteria that cause soft rot was as follows: Enterobacter cloacae subsp. cloacae, 4%; and Pseudomonas fluorescens, 1%. The presence of Enterobacter cloacae subsp. cloacae indicated probable fecal contamination. This is the first record of ginger rhizome rot caused by P. fluorescens in the world and the first from A. murorum, A. luteo-albus, L. theobromae and E. cloacae subsp. cloacae causing ginger rhizome rot in Brazil.

Resumo em Inglês:

A new fungal species, Pestalotiopsis samarangensis, was isolated from fruit rot in Syzygium samarangense from markets in Chiang Mai and Chiang Rai provinces, Thailand. Initially small, circular, black, slightly sunken spots developed on fruits. Later, the spots enlarged rapidly, became sunken, and resulted in a soft decay of the fruit flesh. Molecular analysis of the ITS, β-tubulin, and tef1 combined gene sequences distinguish P. samarangensis from other species in the genus. Pathogenicity testing proved that wounding triggers the disease symptoms and thus careful handling of fruits during transport and storage helps to prevent the disease.

Resumo em Inglês:

This study aimed to characterize the resistance of 31 passion fruit (Passiflora sp.) genotypes to Fusarium oxysporum f. sp. passiflorae (FOP). About 20 seedlings of each genotype were inoculated by immersing the roots in a suspension of 10(6) macroconidia mL-1 for five minutes and then transplanting them into pots containing a mixture of soil and sterile substrate. They were evaluated daily for 120 days for the occurrence of wilt symptoms and death. These data were used to calculate the area under the disease progress curve, for survival analysis and grouping. The mortality rate ranged from 0 to 100% and the AUDPC ranged from 0 for genotypes without symptoms of the disease to 6,650.63 for the hybrid HFOP-01. Genotypes were classified into four subgroups: resistant, moderately resistant, susceptible and highly susceptible. The resistance was genotype dependent, but no significant variation was found between the purple and the yellow P. edulis.

Resumo em Espanhol:

La identificación del agente causal del amachamiento se llevó a cabo de diciembre de 2008 a noviembre de 2009 mediante cuatro pruebas: análisis para detectar ARN de doble cadena (dsRNA) de origen viral, DAS-ELISA, cumplimiento de los postulados de Koch y prueba de patogenicidad. El análisis para la detección de dsRNA reveló la presencia de dos bandas de aproximadamente 1100 y 3200 pb, coincidentes en tamaño para un miembro del género Bromovirus, aunque no se pudo establecer su asociación con el amachamiento debido a que ese patrón de bandas solo se presentó en el 55,5% de las muestras de plantas enfermas analizadas. Mediante la prueba de DAS-ELISA no se detectó el Cowpea chlorotic mottle virus (CCMV) en ninguna de las muestras de plantas con amachamiento analizadas lo que confirma que ese virus no es causante de la enfermedad. La aplicación de los postulados de Koch y la prueba de patogenicidad permitieron identificar al nematodo Aphelenchoides besseyi Christie como el agente causal del amachamiento; asimismo, descartar a otros organismos patógenos mencionados previamente como agentes causales del amachamiento (CCMV o fitoplasma).

Resumo em Inglês:

Identification of the causal agent of the disease "amachamiento" of common bean was carried out using four tests: analysis of double strand RNA (dsRNA) of viral origin, DAS-ELISA technique, applying Koch's postulates and the pathogenicity test. The analysis to detect dsRNA brought about two bands of approximately 1100 and 3200 bp, a similar pattern of bands for a member of genus Bromovirus. However, those bands were present only in 55.5% of the diseased plant samples analyzed; consequently, it was not possible to establish an association of a virus with the disease. The DAS-ELISA test did not detected Cowpea chlorotic mottle virus (CCMV) in any samples of diseased plants, confirming that the causal agent of the disease is not this virus. By using both Koch's postulates and the pathogenicity test, the nematode Aphelenchoides besseyi Christie was identified as the real causal agent of the bean disease "amachamiento" and we were able to discard other pathogen organisms previously proposed as responsible for the disease (CCMV and phytoplasm).

Resumo em Inglês:

The predicted atmospheric carbon dioxide concentration's increases are likely to alter plant-pathogen interactions. To assess the effects on rice blast, during three years (2007, 2008 and 2009), three rice cultivars (Agulha Precoce, Shao Tiao Tsao and Caloro) were exposed to elevated CO2 air concentration (approximately 100 - 300 µmol mol-1 higher than ambient) in open-top chamber facility. The disease was more severe under high CO2 concentration. Area under disease progress curve was 35.43 under high CO2 concentration and 17.48 for the current concentration. Leaves of treated plants tended to contain less silicon. In 2009, plant height of two cultivars was greater in high CO2. Understanding and predicting the climate-driven changes in the agroecosystem may allow the development of adaptation strategies in order to minimize crop losses.

Resumo em Inglês:

The supply of silicon (Si) to wheat plants may potentiate their resistance against infection by Bipolaris sorokiniana. Considering that there is no information regarding how Si affects the infectious process of this fungus on wheat leaves, this study intended to investigate, using light and scanning electron microscopy, the effects of Si supply on the infection process of B. sorokiniana on wheat leaves at tissue level. For that, leaf segments of -Si and +Si plants were prepared. The number of necrotic brown cells and the degree of browning of necrotic cells were determined for each infection site. As results, it was found that the number of brown epidermal cells and the frequency of infection sites showing browning were significantly lower on leaves of +Si plants. On the leaves of -Si plants, an intense dissolution of the wax layer also occurred and hyphae were found inside the disorganized epidermal cells. On leaves of +Si plants, degradation of the wax layer was observed only in areas close to conidia. Within 96 hours after inoculation, a dense network of hyphae had colonized the leaf surface of -Si plants, in striking contrast to +Si plants, for which only sparse hyphae were found.

Resumo em Português:

Avaliou-se o potencial de oito isolados de rizobactérias que eficientemente controlam doenças fúngicas em arroz [DFs185 (Pseudomonas synxantha), DFs223 (P. fluorescens), DFs306 (não identificado), DFs416, DFs418 e DFs419 (Bacillus sp.), DFs422 (Bacillus subtilis), DFs471 (Stenotrophomonas malthophilia)] no controle de Meloidogyne graminicola, in vitro, e em arroz irrigado em casa de vegetação. As rizobactérias DFs185, DFs223, DFs306 e DFs416 se destacaram na redução da eclosão e no aumento da mortalidade de J2 de M. graminicola. Todas as rizobactérias foram capazes de produzir pelo menos um composto associado ao biocontrole de nematoides (quitinases, fosfatases, lipases, proteinases e sideróforos). O número de galhas e de ovos de M. graminicola em plantas de arroz foi reduzido em relação às plantas vindas de sementes não microbiolizadas. O fator de reprodução do nematoide foi reduzido, em média, em 29%, com destaque para as rizobactérias DFs185 e DFs223 que proporcionaram redução de 35%. Esse resultado é significativo, porque são rizobactérias que também controlam doenças fúngicas.

Resumo em Inglês:

The potential of eight rhizobacteria that effectively control fungal diseases in rice [DFs185 (Pseudomonas synxantha), DFs223 (P. fluorescens), DFs306 (not identified), DFs416, DFs418 e DFs419 (Bacillus sp.), DFs422 (Bacillus subtilis), DFs471 (Stenotrophomonas malthophilia)] was evaluated for the control of Meloidogyne graminicola in vitro and in irrigated rice in the greenhouse. The rhizobacteria DFs185, DFs223, DFs306, DFs416 and DFs419 exceeded in reducing hatching and in increasing the mortality of M. graminicola J2. All rhizobacteria were able to produce at least one compound associated with the biocontrol of nematodes (chitinasis, phosphatases, lipases, proteinasis and siderophores). The number of eggs and galls of M. graminicola in rice plants was reduced compared to plants from seeds not microbiolized. The nematode reproduction factor was reduced on average by 29%, highlighting rhizobacteria DFs185 and DFs223 that reduced 35%. This result is significant because the rhizobacteria also control fungal diseases.