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Somavilla L.,Federal University of Pelotas | Gomes C.B.,Laboratorio Of Fitopatologia | Carbonari J.J.,Ministerio da Agricultura | Carneiro R.M.D.G.,Embrapa Recursos Geneticos e Biotecnologia
Tropical Plant Pathology | Year: 2011

Forty-four populations of Meloidogyne spp. obtained from a root-knot nematode survey on kiwi (Actinidia deliciosa) orchards and nurseries in Rio Grande do Sul State were characterized biochemically using esterase isoenzyme (Est). Meloiodgyne arenaria Est A2 (Rm: 1.20, 1.28) was the most frequent species detected in this survey, occurring in 66.65% of the samples. Meloiodgyne ethiopica, with the phenotype E3 (Rm: 0.92, 1.10, 1.30) was detected in 16.66% of the samples in association with other Meloidogyne species. Other species found were M. javanica Est J3 (Rm: 1.00, 1.21, 1.35), M. hapla Est H1 (Rm: 1.17), M. incognita I1 (Rm: 1.03) and I2 (Rm: 1.03, 1.10) identified in 29.9%, 16.66%, 3.33% and 9.79% of the samples, respectively. Only one atypical population presenting the phenotype L3 (Rm: 1.00, 1.10, 1.30) occurred in one orchard (3.33%) but its identification was not possible even through the examination of the perineal patterns of females.© by the Brazilian Phytopathological Society.


PubMed | National Institute of Amazonian Research, Laboratorio Of Biologia Molecular, Laboratorio Of Fitopatologia and Embrapa Cocais
Type: Journal Article | Journal: Genetics and molecular research : GMR | Year: 2016

Black sigatoka, caused by the fungus Mycosphaerella fijiensis (anamorphic stage: Paracercospora fijiensis), was first detected in Brazil in early 1998 in the Benjamin Constant and Tabatinga municipalities in the State of Amazonas, near to where the borders of Brazil, Colombia, and Peru converge. Understanding how cultivars react to the pathogen, and characterizing the genetic variability of isolates from two distant and distinct banana-producing regions, are important for determining the virulence of M. fijiensis. In the present study, the genetic diversity of 22 M. fijiensis isolates was assessed using simple sequence repeats (SSR) markers, and their virulence was determined following inoculation on three different banana tree cultivars. All 22 isolates caused symptoms of the disease in the Ma and Prata Comum cultivars 45 days after inoculation, and at least two virulence groups were identified for the Ma and Prata Comum cultivars. For the DAngola cultivars, two virulence groups were observed only after 60 days post-inoculation, and three of the isolates were not virulent. Using SSR markers, the isolates from two different regions of Brazil were placed into two genetic groups, both genetically distant from the Mf 138 isolate collected in Leticia, Colombia. There was no evidence of correlation between the virulence groups and the genetic diversity groups. These results demonstrate variability in virulence between isolates as measured by the severity of black sigatoka in the analyzed cultivars.


Gonzalez-Varela G.,Laboratorio Of Fitopatologia | Gonzalez A.J.,Laboratorio Of Fitopatologia | Milgroom M.G.,Cornell University
European Journal of Plant Pathology | Year: 2011

To understand the history of introductions of the chestnut blight fungus, Cryphonectria parasitica, in the Principality of Asturias in northern Spain, we conducted an extensive survey of chestnut blight and collected C. parasitica from 216 sites. All 778 isolates were assayed for vegetative compatibility (vc) type, whereas a subsample of 301 isolates was assayed for mating type, and 189 isolates were genotyped at 16 microsatellite markers. We found low diversity for all markers. Nearly all isolates (95%) were compatible with vc type EU-1 and had the same microsatellite multilocus haplotype, or differed from the most common type by mutation at one locus. Approximately 5% of the isolates were vegetatively compatible with EU-13 and only two isolates (< 1%) were compatible with EU-3; five different microsatellite haplotypes were found among isolates in these latter two vc types. The overall mating-type ratio was 218 MAT-1: 81 MAT-2, with both mating types represented in each of the three vc types. Microsatellite haplotypes based on ten markers used in France showed that most isolates in Asturias were either identical to or only one marker different from one of the seven most common genotypes in France, RE103. Based on these ten markers alone, the population of C. parasitica in Asturias, would appear to have been founded by a single genotype from the C1 lineage (to which RE103 belongs) found in eastern France and northern Italy. However, additional genotyping by vc types suggests the introduction of multiple genotypes, with different vc types. The exact source for introduction into Asturias cannot be determined without additional genotyping of isolates from other locations. Regardless of their origin, the low diversity of vc types makes this population ideal for deploying hypovirulence because there will be few barriers for virus transmission between individuals. © 2011 KNPV.


Gomez D.E.,Instituto Nacional de Tecnologia Agropecuaria | Reis E.M.,Laboratorio Of Fitopatologia
Summa Phytopathologica | Year: 2013

Fungi require special substrates for their isolation, vegetative growth and sporulation. In experiments conducted in the laboratory, the influence of substrates, light, filter paper and pH on the sporulation of Cercospora sojina conidia, the causal agent of soybean frogeye leaf spot, was assessed. The media potato sucrose agar, V-8 agar, tomato extract agar, soybean leaf extract agar, soybean seed extract agar, soybean meal agar, soybean flour agar and wheat flour agar were tested, added on the surface, with and without filter paper and under two light regimes, with 12 h light at 25°± 2°C and in the dark. A triple factorial 8x2x2 (substrates x light/dark x with/without filter paper) design with four replicates was used. V-8 agar medium was employed and the pH was adjusted with HCl 0.1N or NaOH 0.1N before autoclaving to the values: 3, 4, 5, 6, 7 and 8, and the pH of V-8 agar medium is 6.7. The evaluation was done on the seventh day of incubation. Data underwent regression analysis. Sporulation was maximized on the agar media V-8, seed extract, oat flour, tomato extract, and potato sucrose in the presence of filter paper and 12h light. On V-8 medium, maximal sporulation was obtained with pH 6.7.


Araujo E.R.,University of Brasilia | Araujo E.R.,Laboratorio Of Fitopatologia | Ferreira M.A.S.V.,University of Brasilia | Quezado-Duval A.M.,Laboratorio Of Fitopatologia
European Journal of Plant Pathology | Year: 2013

Xanthomonas vesicatoria is a member of the species complex associated with tomato bacterial spot. New and specific primers for X. vesicatoria were developed and validated. The primers were highly specific and detection was positive using purified bacterial DNA, bacterial suspensions and foliar lesions. These primers represent an additional tool for detection and identification of one of the species involved in this important disease complex. © 2013 KNPV.


Cysne A.Q.,Laboratorio Of Fitopatologia | Cardoso J.E.,Laboratorio Of Fitopatologia | Maia A.D.H.N.,Embrapa Meio Ambiente | Farias F.C.,Laboratorio Of Fitopatologia
Journal of Phytopathology | Year: 2010

The cashew gummosis caused by the fungus Lasiodiplodia theobromae is one of the most important disease of cashew in the northeast of Brazil. The lack of studies about method of early detection, pathogen dissemination, host predisposition, mechanisms of attack and defence and efficient control measures assures this disease as a limiting factor as to growing of cashew under semi-arid conditions. Therefore, the characterization of spatial patterns of gummosis development under commercial orchards may provide important insights into the mechanisms involving in dissemination and disease progress of this disease, as well as in the understanding of dynamic of host, pathogen and environmental interactions for this pathossystem. This work aimed to characterize gummosis temporal and special dynamics in three commercial orchards of cashew clones of cashew with different levels of susceptibility by studying the special arrangement of diseased plants. Disease incidence and severity, quantified determined by a descriptive scale in clones BRS 226 (resistant), Embrapa 51 (slightly resistant) and Faga 11 (susceptible) in a commercial orchard located in Pio IX district (Piaui state, Brazil), were monitored and mapped. Data were collected within three blocks of 90 plants for each clone. Indices of dispersion were estimated to study the spatial dynamic. The dynamics and structure of gummosis foci were also analysed. As expected, data showed different degrees of gummosis incidence and severity for the three clones. Even under different levels of disease, a random dispersion pattern model of dispersion could be observed at the beginning of epidemic for all clones. However, as disease develops, a clustered model is likely to fit. The increase in disease incidence resulted from the increasing in both focus number and size. © 2010 Blackwell Verlag GmbH.


Araujo E.R.,University of Brasilia | Araujo E.R.,Laboratorio Of Fitopatologia | Costa J.R.,Laboratorio Of Fitopatologia | Ferreira M.A.S.V.,University of Brasilia | Quezado-Duval A.M.,Laboratorio Of Fitopatologia
Journal of Applied Microbiology | Year: 2012

Aims: To establish protocols for the simultaneous detection and identification of Xanthomonas species causing tomato bacterial spot. Methods and Results: We verified the specificity and sensitivity of the previously reported sets of primers designed for strains of the four species of Brazilian tomato bacterial spot xanthomonads, consisting of 30 of Xanthomonas euvesicatoria, 30 of X. vesicatoria, 50 of X. perforans and 50 of X. gardneri. Furthermore, we tested a multiplex PCR protocol for the purpose of concurrent species identification. The possibility of direct detection of the pathogens in diseased leaf samples was also verified. The primers were highly specific, amplifying only target DNA. The sensitivity of the primers in conventional PCR was 50 pg μl-1 for purified DNA and ranged from 5 × 102 to 5 × 104 CFU ml-1 when bacterial suspensions were analysed. The multiplex PCR was suitable for the detection of all four species and showed similar sensitivity to conventional PCR when tested on purified DNA. When using bacterial suspensions, its sensitivity was similar to conventional PCR only when a biological amplification step (Bio-PCR) was included. Both methods were able to detect the pathogens in symptomatic tomato leaves. Conclusions: Brazilian Xanthomonas strains causing tomato bacterial spot can be differentiated and identified at species level by a PCR-based method and by a multiplex PCR. Significance and Impact of the Study: This protocol may be a feasible alternative tool for the identification and detection of these pathogens in plant material and may be used for routine diagnostic purposes in plant pathology laboratories. © 2012 The Society for Applied Microbiology.


Gonzalez A.J.,Laboratorio Of Fitopatologia | Fernandez A.M.,Laboratorio Of Fitopatologia | Jose M.S.,University of Oviedo | Gonzalez-Varela G.,Laboratorio Of Fitopatologia | Rodicio M.R.,University of Oviedo
Applied and Environmental Microbiology | Year: 2012

A virulent Pseudomonas viridiflava-related bacterium has been identified as a new pathogen of soybean, one of the most important crops worldwide. The bacterium was recovered from forage soybean leaves with dark-reddish spots, and damage on petioles and pods was also observed. In contrast, common bean was not affected. © 2012, American Society for Microbiology.


Trapiello E.,Laboratorio Of Fitopatologia | Gonzalez A.J.,Laboratorio Of Fitopatologia
Genetic Resources and Crop Evolution | Year: 2012

The preservation of plant genetic resources involves the conservation of the microbial biota associated with them. The presence of culturable bacteria in a series of 16 bean seed batches, corresponding to nine local bean varieties, stored in a germplasm bank was studied by amplifying and sequencing the 16S rDNA. Microorganisms identified in seed lots were classified into three groups: environmental biota (present in all samples), biota characteristic of humans and animals (present in 53 % of samples) and phytopathogenic biota (present in 19 % of samples). Genus diversity ranged between 0.6931 and 2.0942 according to the Shannon-Weaver Index (H'), the sample presenting the highest number of plant pathogenic bacteria being the most diverse. This result suggests that contrary to common practice in diagnostic laboratories, it is necessary to identify all culturable bacteria isolates from each sample. In addition, the fact that potentially phytopathogenic bacteria have been preserved in a genebank should emphasize the importance of rigorous sanitary controls for plant genetic resources. © 2012 Springer Science+Business Media Dordrecht.


de Carvalho C.,Laboratorio Of Fitopatologia | Fernandes C.D.,Laboratorio Of Fitopatologia | dos Santos J.M.,São Paulo State University | Macedo M.C.M.,Laboratorio Of Fitopatologia
Revista Ceres | Year: 2013

The aim of this work was to evaluate the population density of Pratylenchus brachyurus and Pratylenchus zeae associated with Brachiaria brizantha, B. decumbens and B. humidicola and their influence on forage availability and quality. The experiment was conducte in the Hisaeda Farm, Terenos, MS, Brazil. Soil, roots and plant aerial part were harvest with ten replications each, in one square meter randomized sets encompassing three treatments: Good, Intermediary and Bad, visually characterized, considering the percentage of green material. P. brachyurus and P. zeae density were evaluated in soil and plant roots. Dry matter of green, dead and re-growth materials, plant nutritional status and forage quality were assessed in the aerial plant part. Soil fertility was determined in all harvested samples. Both nematode species were identified from all samples, with a larger numbe in the roots (between 87-311 P. brachyurus and 1-61 P. zeae.10 g-1) than in the soil (0-8 P. brachyurus and 1-39 P. zeae.200 cm-3), however, no significant differences were found in the number of specimens between treatments. Considering that these forage species are perennial and host Pratylenchus spp, there is a tendency to increase the population of these pathogens over time, becoming a serious phytosanitary problem.

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