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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. Source

Rueda-Hernandez K.R.,National University of Colombia | Cardona A.S.,Laboratorio Of Fitopatologia | Cadavid-Restrepo G.E.,National University of Colombia | Benjumea C.I.S.,National University of Colombia | Isaza R.E.A.,National University of Colombia
Journal of Phytopathology | Year: 2013

Blackberry anthracnose, caused by Colletotrichum spp., is an important disease of cultivated blackberry in the world. In Colombia, it is the number one limiting factor for commercial production. This study was conducted to determine the species of Colletotrichum infecting blackberry plants as well as the organ distribution, pathogenicity and response to benomyl of the isolated strains. Sixty isolates from stems (n = 20), thorns (n = 20) and inflorescences (n = 20) were identified as Colletotrichum acutatum and Colletotrichum gloeosporioides by a species-specific polymerase chain reaction (PCR). Both Colletotrichum species were found in the same plant but on different organs. Colletotrichum gloeosporioides species predominated in thorn lesions (n = 16) and C. acutatum in stems (n = 15) and inflorescence (n = 15). Pathogenicity assays on detached blackberry organs demonstrated differences between the two species with an average period of lesion development of 8.7 days for C. gloeosporioides and 10.3 days for C. acutatum. Wound inoculated organs had 90% disease development compared to 17.5% in non-wounded. All C. acutatum isolates (n = 34) were benomyl tolerant, whereas C. gloeosporioides isolates (n = 26) were 30.7% sensitive and 69.2% moderately tolerant. Phylogenetic analysis with ITS sequences of a subset of 18 strains showed that strains classified as C. gloeosporioides had 100% identity to Colletotrichum kahawae, which belongs to the C. gloeosporioides species complex, whereas C. acutatum strains clustered into two different groups, with high similarity to the A2 and the A4 molecular groups. These data demonstrate for the first time the differential distribution of both species complexes in blackberry plant organs and further clarifies the taxonomy of the strains. © 2012 Blackwell Verlag GmbH. Source

Martins M.V.V.,Laboratorio Of Fitopatologia | da Silveira S.F.,State University of Norte Fluminense | Maffia L.A.,Federal University of Vicosa
Summa Phytopathologica | Year: 2014

The aim of this paper was to estimate the loss caused by rust (Puccinia psidii) to 'Paluma' guava production in orchards located in Rio de Janeiro State. The disease intensity on the reproductive organs of plants was observed during two chemical control experiments carried out in 2003 and 2004. The loss was estimated based on simple linear regression and the production reduction (fruit number and weight ha-1) on the incidence of diseased buds and fruits. In the first experiment, no relationship was established between incidence of diseased buds and loss since there was a delay in spraying and the incidence of buds showing rust was high (mean of 47%) at the beginning of flowering. In the second experiment (2003-2004), spraying occurred at the beginning of the epidemics and there was a linear relationship between incidence of diseased buds and loss, justifying fungicide intervention at this stage. For the fruiting stage, a significant relationship was found between incidence of diseased fruits and loss in both experiments. In the absence of chemical control, rust reduced fruit production by around 90%. Source

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. Source

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. Source

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