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Fungal Population (fungal + population)
Selected AbstractsAnalysis of the Italian Dutch Elm Disease Fungal PopulationJOURNAL OF PHYTOPATHOLOGY, Issue 2 2005A. Santini Abstract Sixty-two Ophiostoma ulmi sensu lato strains have been collected from symptomatic trees in seven areas of Central Italy. Isolates were compared with 10 reference strains, belonging to the species O. ulmi and to the two subspecies of O. novo-ulmi, in order to establish the genetic variability within the Italian population of this fungal pathogen. The structure of the population has been analysed by means of morpho-physiological features and of the direct amplification of minisatellite-region DNA polymerase chain reaction (DAMD-PCR) by using the M13 core sequence. The DNA profiles have been compared with taxonomic parameters (growth rate, culture aspect and fertility barriers). Taxa could thus be well separated. None of the isolates collected was recognized as O. ulmi. Isolates assigned to the two subspecies of O. novo-ulmi (novo ulmi and americana) by means of the fertility test, showed short genetic distances with the respective reference strains and they constituted subgroups according to their geographical origin. The high level of variation detected indicates a postepidemic situation in Italy. Some inconsistency was found within the subspecies clusters. Several isolates, assigned to subspecies americana using fertility test, were in the novo-ulmi cluster and vice versa. A possible explanation is that these isolates are americana,novo-ulmi hybrids. [source] Fungal pathogens associated with melon collapse in Spain,EPPO BULLETIN, Issue 2 2000J. García-Jiménez Spain produces 43 200 ha of melons with a considerable export to European markets. In the last 10 years, melon cultivation in Spain has decreased more than 40% due mainly to collapse of the vines caused by soil-borne diseases. Serious economic losses have resulted. In order better to understand the aetiology of this disease, a survey of 217 melon fields throughout the melon production areas of Spain was conducted from 1987 to 1996 to analyse the fungal population associated with roots. In addition, the presence of melon necrotic spot carmovirus (MNSV) was studied in 93 fields. This virus is present mainly in southeastern Spain. The predominant fungal species isolated from 82.5% of sampled fields with symptoms of collapse was Acremonium cucurbitacearum. Roots affected by this fungus show corky brown areas soon after transplanting. Small secondary roots and root hairs become necrotic, although there is continuous production of new rootlets. This process continues until the late stages of the disease. As the fruits approach maturity, the entire plant wilts and dies. Other fungal species associated with melon collapse are: Monosporascus cannonballus (isolated from 29.5% of sampled fields), Macrophomina phaseolina (32.7%) and Rhizoctonia solani (31.8%). Of these, the incidence of M. cannonballus isolated from diseased melons has increased substantially over the past 10 years. Melon collapse in Spain is complex because several fungi capable of causing collapse of the vines are prevalent and often isolated from roots in the same field. In addition, other minor pathogens, such as Rhizopycnis vagum and Plectosporium tabacinum, are frequently isolated from symptomatic vines and may also contribute to the death of the plants. [source] FUNGI AND PATULIN IN APPLES AND THE ROLE OF PROCESSING ON PATULIN LEVELS IN JUICES: A STUDY ON NATURALLY CONTAMINATED APPLESJOURNAL OF FOOD SAFETY, Issue 2 2010JULIANE ELISA WELKE ABSTRACT The purpose of this study was to determine the predominant fungal species, including toxigenic strains, patulin levels in apples used for juice production and in produced juices. The possibility of use of apple highly contaminated with patulin to produce juice with lower patulin levels than the limit permitted by Codex Alimentarius was also checked. Sixteen lots of apples and juices were analyzed. The most prevalent fungal population was Penicillium spp. (93%) followed by the Aspergillus spp. (3.5%) and the Rhizopus spp. (3.5%). The mycoflora of apples was composed mainly of species that produce patulin. P. expansum was identified as the most frequently isolated species (66%). Species able to produce patulin were P. expansum and P. griseofulvum. Patulin levels in apples from cold storage ranged from 254.6 to 653.4 µg/kg. Apple juice processing caused average reduction of 95% in patulin levels. Patulin levels ranged from 14.3 to 46.7 µg/L in apple juices. In all samples were found patulin levels lower than the limit of 50 µg/L considered acceptable by the Codex Alimentarius Commission. PRACTICAL APPLICATIONS This study was performed to define the mycoflora of apples and patulin levels in apples that were used for juice production. This approach is useful to evaluate the quality of apples and the effect of processing on patulin to determine if the toxin level can be managed through postharvest procedures. Besides, information about patulin levels in juices is important to contribute for establishing national regulation. [source] Analysis of Mycelial Growth Rates and RAPD-PCR Profiles in a Population of Gaeumannomyces graminis var. tritici Originating from Wheat Plants Grown from Fungicide-treated SeedJOURNAL OF PHYTOPATHOLOGY, Issue 6 2005Z. Weber Abstract Linear mycelial growth rates of 70 isolates of Gaeumannomyces graminis var. tritici on agar medium amended or unamended with the fungicide silthiofam were not correlated. Mycelial growth rate was not influenced by the fungicide applied to the seed of the plants from, which the isolates originated. DNA polymorphism determined by randomly amplified polymorphic DNA (RAPD) polymerase chain reaction was used to assess genetic variation among isolates. Thirty RAPD markers generated with five arbitrary 10-mer primers revealed DNA polymorphism suitable for assessing variability in this fungal population. Cluster analysis of RAPD data identified two groups at the 54% similarity level. There was a significant relationship between the presence of 11 markers and sensitivity to silthiofam. [source] Detection and monitoring of anaerobic rumen fungi using an ARISA methodLETTERS IN APPLIED MICROBIOLOGY, Issue 6 2008S.E. Denman Abstract Aim:, To develop an automated ribosomal intergenic spacer region analysis (ARISA) method for the detection of anaerobic rumen fungi and also to demonstrate utility of the technique to monitor colonization and persistence of fungi, and diet-induced changes in community structure. Methods and Results:, The method could discriminate between three genera of anaerobic rumen fungal isolates, representing Orpinomyces, Piromyces and Neocallimastix species. Changes in anaerobic fungal composition were observed between animals fed a high-fibre diet compared with a grain-based diet. ARISA analysis of rumen samples from animals on grain showed a decrease in fungal diversity with a dominance of Orpinomyces and Piromyces spp. Clustering analysis of ARISA profile patterns grouped animals based on diet. A single strain of Orpinomyces was dosed into a cow and was detectable within the rumen fungal population for several weeks afterwards. Conclusions:, The ARISA technique was capable of discriminating between pure cultures at the genus level. Diet composition has a significant influence on the diversity of anaerobic fungi in the rumen and the method can be used to monitor introduced strains. Significance and Impact of the Study:, Through the use of ARISA analysis, a better understanding of the effect of diets on rumen anaerobic fungi populations is provided. [source] Clonal variability among oral Candida albicans assessed by allozyme electrophoresis analysisMOLECULAR ORAL MICROBIOLOGY, Issue 6 2000A. L. Mata A total of 49 Candida albicans strains were isolated from the saliva of 11 healthy children in Piracicaba, Brazil and were analyzed according to their alloenzymatic patterns. Among eight loci assayed, seven were polymorphic and allowed to determine allelic and genotype frequencies, in order to establish the genetic variables for this fungal population. Some children showed just one genetic type, whereas other harbored two or more clones of such yeast, in a multiclonal manner of colonization by C. albicans. [source] Coordinated Development of Yeast Colonies: An Experimental Analysis of the Adaptation to Different Nutrient Concentrations , Part 1ENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 2 2005T. Walther Abstract The development of yeast colonies on solid agar substrates served as a model system to investigate the growth of higher fungi in a heterogeneous environment. Applying a new analytical technique , which was based on the estimation of the intensity of transmitted light from microscopic images taken along the colony radius , cell-density distributions inside fungal mycelia were measured at an extremely high spatial resolution. Using this method, the adaptation of yeast colonies to the limitation of different nutrients was investigated. Under conditions of carbon or nitrogen limitation, populations of the dimorphic model yeasts Yarrowia lipolytica and Candida boidinii underwent a transition in their morphology from solid colony to mycelial colony patterns. When grown under conditions that induced the mycelial morphology, colonies extended linearly at a constant rate irrespective of the initial nutrient concentration. In general, the cell density within the population declined at higher degrees of limitation. Nitrogen-limited colonies of both model yeasts, as well as carbon-limited Y.,lipolytica colonies proceeded to extend until the growth field was finally covered by the population. Under these conditions, areas of fairly constant cell densities were formed during the growth process. Only carbon-limited C.,boidinii colonies stopped extending at a final diameter which was small when compared to the size of the growth field, and formed a cell-density profile which was monotonically declining. The observed differences in the final colony diameter, and in the cell-density profile morphology indicated the presence of different regulatory mechanisms that ruled the colony development of the model yeasts. The presented monitoring technique for the biomass distribution inside fungal populations provided the basis for a quantitative and non-invasive description of mycelial development. [source] DOMESTICATION OF MAIZE, SORGHUM, AND SUGARCANE DID NOT DRIVE THE DIVERGENCE OF THEIR SMUT PATHOGENSEVOLUTION, Issue 2 2007Andrew B. Munkacsi We investigated two alternative hypotheses for the origin of crop pathogen species: that human-mediated agricultural practices drove the divergence of many crop plant pathogen species or that coevolutionary processes in natural populations of the crops' ancestors drove divergence of pathogen species. We distinguished between these two hypotheses by constructing a robust multigene phylogeny and estimating the dates of divergence among four, monophyletic species of smut fungi (Ustilago maydis, U. scitaminea, Sporisorium reilianum, S. sorghi) known to specifically infect maize, sorghum, sugarcane, and their wild ancestors. Without a fossil record for smut fungi, we calibrated the pathogen species' divergence times to their plant host divergence times. Specifically, a calibration date of 10,000 years was employed to test the hypothesis that the fungal species originated at the time of domestication of their current hosts and a calibration date of 50 million years was employed to test the hypothesis that the fungal species originated on wild ancestors of their domesticated hosts. Substitution rates at five protein coding genes were calculated and rates obtained for the 10,000 year calibration date were orders of magnitude faster than those commonly reported for eukaryotes, thus rejecting the hypothesis that these smut pathogen species diverged at the time of domestication. In contrast, substitution rates obtained for the 50 million year calibration were comparable to eukaryotic substitution rates. We used the 50 million year calibration to estimate divergence times of taxa in two datasets, one comprised solely the focal species and one comprised the focal species and additional related taxa. Both datasets indicate that all taxa diverged millions of years ago, strongly supporting the hypothesis that smut species diverged before the time of domestication and modern agriculture. Thus, smut species diverged in the ecological context of natural host plant and fungal populations. [source] | ||||||||||