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Search Results: 1 - 10 of 658 matches for " pathogen "
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Presence of the Potato Late Blight Resistance Gene RB Does Not Promote Adaptive Parasitism of Phytophthora infestans  [PDF]
Dennis A. Halterman, Gail Middleton
American Journal of Plant Sciences (AJPS) , 2012, DOI: 10.4236/ajps.2012.33043
Abstract: The gene RB is derived from the wild potato species S. bulbocastanum and confers partial resistance to late blight, caused by the oomycete pathogen Phytophthora infestans. In order to investigate whether a single strain of P. infestans can adapt to overcome this partial resistance source, we subjected RB containing leaflets to multiple rounds of infection with P. infestans, with a culture isolated from a lesion used to infect the next leaflet (a passage). A parallel line of passages was done using susceptible leaflets as hosts. At the end of the experiment, P. infestans strains passaged through resistant or susceptible leaflets were compared for infection efficiency and lesion size. Variants of the P. infestans effector family IPI-O, some of which are recognized by the RB protein to elicit resistance, were cloned and sequenced to determine whether variation occurred during selection on the partially resistant host. Our results show that after 20 rounds of selection, no breakdown in RB resistance took place. In fact, the strain that was continually passaged through the partially resistant host produced smaller lesions on susceptible leaflets and had a lower infection frequency than the strain passaged through susceptible cultivar Katahdin. No changes within IPI-O coding regions were detected after selection on the hosts with RB. Our results indicate that individual strains of P. infestans are not capable of rapidly overcoming RB resistance even when it is the only host available.
Phylogenetic Identification of Pathogenic Fungi from Apple in Batu City, Malang, Indonesia  [PDF]
Fitria W. Lestari, Suharjono  , Estri L. Arumingtyas
Advances in Microbiology (AiM) , 2013, DOI: 10.4236/aim.2013.31011
Abstract:

Pathogenic fungi cause dying off of apple tree and giving negative impact to farmers. The objective of this study was to identify tree pathogenic fungi isolates from apple tree in the Batu City and to know phylogenetic relationship of the isolates based on the DNA sequences. The method in this study included subculture of three pathogenic fungi isolates (M1, M4, and MB1) using V8 Juice Agar medium for one to three days, continued with DNA isolation, amplification using ITS5/ITS4 primer, purification, sequencing, and sequence homology analysis of DNA amplicons of each isolates with reference isolates. The results showed similarity value of DNA sequence of the three isolates M1, M4, and MB1 of more than 99%. The three isolates M1, M4, and MB1 have a similarity value of DNA sequence with species of Pythium splendens of 99.84%, 99.67% and 99.83%, respectively. On the other hand similarity value between those isolates with Phytophthora was less than 76%. It was concluded that the three isolates are Py. splendens.

The Unexplored Role of Probiotics on the Parasitic Pathogens  [PDF]
Bratati Mukhopadhyay, Nirmal Kumar Ganguly
Food and Nutrition Sciences (FNS) , 2014, DOI: 10.4236/fns.2014.522230
Abstract: The beneficial bacteria coined as probiotics are used as therapeutics to the host and evidences are there to demonstrate to treat bacterial and viral respiratory infections, gastrointestinal diseases, eczema, inflammation, H. pylori infection, irritable bowel syndrome and allergic symptoms etc. In recent past, probiotics has been reported for the control of intestinal parasite infections as well as few non-gut infections spread among human and veterinary animals. Animal models and in vitro culture systems have been studied regarding cellular interactions between probiotics and pathogens or relevant host cells, though the underlying molecular mechanisms mediating the beneficial effects have not yet fully discovered. Hence, more evidence based studies are warranted to correlate whether probiotics through multiple mechanisms might indeed provide a strain-specific protection against parasites to use it as therapeutics. This article has described the effect of probiotics in some of the intestinal as well as non-gut parasites and suggested the scope of exploring the benefit for protozoan parasite Leishmania, as India is planning for the elimination of the disease.
Stem Histopathology of Sesame Seedlings Infected with Alternaria alternata  [PDF]
Maryam Ajmal, Abida Akram, Anum Ara, Shaista Akhund, Brian Gagosh Nayyar, Wajiha Seerat
Microscopy Research (MR) , 2016, DOI: 10.4236/mr.2016.42002
Abstract: In the present study, histopathology of three varieties of sesame TS 3, TS 5 and SG 27 infected with Alternaria alternata was carried out to understand the mechanism of fungal infection and penetration in sesame plant as well as to determine the histological manifestation in sesame cells by light microscopy. Fungus was identified in infected tissues as a dark bluish black with toluidine blue O staining. Light microscopic examination of sesame stem showed that the fungus was present in epidermis, hypodermis and cortical parenchyma tissue as the symptoms became visible by naked eye ten days after inoculation (DAI). As the disease progress, the fungus moved from cortical parenchyma to vascular bundle, xylem and phloem. Later on, it completely overlapped the vascular bundle and entered in pith. When necrotic lesion appeared, fungus was present abundantly in epidermis, hypodermis, cortical parenchyma, vascular bundles and in pith. Due to its excessive growth and complete overlapping of cells, disorganization or destruction of cells of sesame took place. It was concluded that the Alternaria alternata was not a tissue limited pathogen instead of this it spread in to all tissues of stem from epidermis to pith.
The origins of the trypanosome genome strains Trypanosoma brucei brucei TREU 927, T. b. gambiense DAL 972, T. vivax Y486 and T. congolense IL3000
Wendy Gibson
Parasites & Vectors , 2012, DOI: 10.1186/1756-3305-5-71
Abstract: The genome sequence of Trypanosoma brucei brucei TREU 927/4 was published in 2005 [1] and that of T. b. gambiense Dal 972 clone 1 in 2010 [2]. Genome sequencing projects for T. vivax Y486 and T. congolense IL3000 are also complete [3]. The trypanosome strains chosen for sequencing were selected because they had been well characterised in the laboratory, but all were isolated several decades ago (Table 1). The purpose of this short review is to provide some background information on the origins and biological characterisation of these strains as a source of reference for future users of the genome data. The history of the discovery of these trypanosome species has been recently reviewed [4].Trypanosoma brucei brucei clone TREU 927/4 was chosen as the representative T. brucei for the genome project, because it displays the full range of known phenotypes for T. brucei, barring human infectivity. TREU 927/4 is capable of complete cyclical development within the tsetse fly, including mating [5] and produces short stumpy forms during bloodstream infection in the mammalian host [6]. TREU 927/4 is a clone derived from the isolate GPAL/KE/70/EATRO 1534 [5] that originates from Kiboko, Kenya, an area where human trypanosomiasis is unknown [7]. Nevertheless, there is some doubt about the status of TREU 927/4 with regard to human infectivity, since it has a degree of resistance to human serum [8], though it lacks the SRA gene that is characteristic of the human infective subspecies T. b. rhodesiense from East Africa [9].The isolate GPAL/KE/70/EATRO 1534 was one of a collection of 15 T. brucei subgroup isolates obtained from wild caught tsetse flies of the species Glossina pallidipes from Kiboko, Kenya [7,10,11]. Each isolate was derived from the metacyclic population of a single infected fly by inoculation of macerated salivary glands into rodents; the bloodstream forms were subsequently used to study the antigenic types circulating in wild-caught flies [11]. Like other pleomor
Niveles de esporulación experimentales y naturales de Nosema locustae (Microsporidia) en especies de tucuras y langostas (Orthoptera: Acridoidea) de la Argentina
Lange,Carlos E.;
Revista de la Sociedad Entomol?3gica Argentina , 2003,
Abstract: nosema locustae canning, an intracellular sporogenic pathogen of the fat body of orthopterans used for the biological control of grasshoppers, became established in some grasshopper communities of argentina after its introduction more than 20 years ago. following standard methods for counting spores per individual insect affected, the levels of spore production by n. locustae was measured for three species of grasshoppers naturally infected [ dichroplus elongatus giglio-tos, dichroplus pratensis bruner, baeacris punctulatus (thunberg)], and for six species experimentally infected [ dichroplus maculipennis blanchard, dichroplus schulzi bruner, d. elongatus, b. punctulatus, ronderosia bergi stal, schistocerca cancellata (serville)]. the levels of sporulation were relatively high in all species of the subfamily melanoplinae (mean values varied from 2 x 108 to 3,2 x 109), while the production of spores was rare (9,5 % of the infected individuals) and low (maximum of 9,6 x 106) in s. cancellata. there was no infection development in the romaleidae grasshopper elaeochlora viridicata (serville). the values of sporulation reached by the melanoplines agree with the establishment of n. locustae in communities of grasshoppers in argentina because a high availability of infective transmissible units (propagules) is a central factor for the transmission and persistence of a disease in a population of susceptible insects. although the highest sporulation levels were reached in d. maculipennis, r. bergi appears to be, among the species used in this study, the best choice for in vivo production of n. locustae, because there is no obligatory embrionic diapause in its cycle, and its less reactive behaviour makes the handling of colony easier.
Distribui??o espacial de Phytophthora nicotianae e rea??o de cultivares de cebola ao fungo
Almeida, F.A.;Barreto, M.;Barbosa, J.C.;Costa, F.M.;
Summa Phytopathologica , 2011, DOI: 10.1590/S0100-54052011000100002
Abstract: onion culture has demonstrated to be highly susceptible to phytophthora nicotianae with economic damages and high crop costs due to the excessive use of chemical products. the present work has as objective to evaluate the spatial dependence of pathogen by geostatistic and after that, to test the resistance of onion cultivars to this disease under conventional crop. the experiments were conducted at fcav/unesp. soil samples were collected and processed at the laboratory in relation to pathogen, presence through the count of disks of sicilian lemon infected of the solution of the soil. immediately after that, at the same experimental unit, thirteen onion cultivars (dom victor, bz 21; princesa, taiko, óptima, bz 50, mercedes, sunset, duquesa, gobi, sirius, colina e superex) were analysed in a randomized blocks design with four repetitions. weekly evaluations were effectuated, from transplanting to harvest. by spherical isotropic semivariogram model, results demonstrated no spatial dependence, revealing that the area presented uniform distribution of the pathogen. with the mapping incidence by krigage method in blocks, it was verified higher incidence of fungi between the first three patches of lower place, being sequenced reduced with area declivity. no cultivar evaluated presented resistance to the pathogen. it's detached that - mercedes, princesa and duquesa cultivars are highly susceptible, and the others demonstrated low susceptibility to the pathogen in that first field evaluation.
Preserva??o do inóculo de Plasmodiophora brassicae utilizando o método de congelamento
Cruz, Juliana Cristina Sodário;Souza, Nilton Luiz de;Padovani, Carlos Roberto;Furtado, Edson Luiz;
Summa Phytopathologica , 2009, DOI: 10.1590/S0100-54052009000100010
Abstract: the preservation of plasmodiophora brassicae resistance structures under laboratory conditions is difficult since this is an obligate parasite. the freezing method using an ordinary household freezer was tested to ensure the pathogen's survival and the preservation of its infective traits. roots of different brassica species naturally infected by p. brassicae, showing typical clubroot symptoms, sampled in the same farm, located in the pardinho county, state of s?o paulo, were collected during different seasons and were immediately frozen at approximately 20oc. the treatments were divided as follows: t1: clubroots frozen for 389 days (arugula); t2: clubroots frozen for 242 days (broccoli); t3: clubroots frozen for 21 days (chinese cabbage), and t4: control (without inoculum). the pathogenicity tests were conducted under greenhouse conditions (25±2oc). each plant of the susceptible variety of chinese cabbage (pak choi) was inoculated with 2ml of a spore suspension of each treatment at a concentration of 107 spores.ml-1. each treatment consisted of six replicates distributed in random blocks. the roots of plants were washed and evaluated five weeks after inoculation. there were significant differences between treatments. the frozen materials preserved their infective traits over a period of 21 to 242 days, demonstrating that the freezing method could be an option to preserve the resistance structures of this pathogen.
Patogenicidade de Sphaeropsis sapinea em árvores jovens de Araucaria angustifolia
Corrêa, Paula Rachel Rabelo;Auer, Celso Garcia;Santos, álvaro Figueredo dos;
Summa Phytopathologica , 2012, DOI: 10.1590/S0100-54052012000100014
Abstract: sphaeropsis sapinea is a pathogen that causes dieback and death of trees in commercial conifer crops around the world. in brazil, the literature remarks this fungus on seedlings and logs of araucaria angustifolia after harvesting, without reports of branch death or dieback. this study aimed to verify the pathogenicity of s. sapinea in a. angustifolia. koch postulates were performed for 25 years-old trees. mycelium-agar disks of an aggressive isolate obtained from pinus taeda, collected from 10 days-old cultures, were inoculated into injured branches. each plant had three branches inoculated with the fungus and one branch remained as control plant. all plants were kept in a greenhouse for 30 days. branches with and without symptoms were incubated in humid chamber, under light, to reisolate the pathogen. eight of the inoculated trees showed symptoms similar to those caused by s. sapinea in pines. the fungus was reisolated from 68 % inoculated trees. the branch death caused by s. sapinea was confirmed in young araucaria trees.
Efeito da temperatura sobre a severidade de Plasmodiophora brassicae
Rosa, Daniel Dias;Basseto, Marco Antonio;Furtado, Edson Luiz;
Summa Phytopathologica , 2010, DOI: 10.1590/S0100-54052010000300010
Abstract: temperature is an important parameter for infection and plant desease development. in order to determine the influence of temperature on the severity of clubroot caused by plasmodiophora brassicae in pak choi chinese cabbage plants, infection tests were carried out under temperatures set at 5oc increments, from 10 to 40oc. a reduction in severity of the disease was observed during the analysis of results in 28-day-old seedlings, at temperatures above 30oc. the optimal temperature for disease development and crop growth were from 20 to 25oc. it was observed that at this temperature range inoculated seedling presented 26% less dry matter than noninoculated seedlings, thus demonstrating a direct effect of clubroot on plant dry matter accumulation.
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