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Molecular identification of a bronopol tolerant strain of Saprolegnia australis causing egg and fry mortality in farmed brown trout, Salmo trutta
Abstract
Some species of the genus Saprolegnia, such as Saprolegnia diclina and Saprolegnia ferax are responsible for devastating infections on salmonid eggs. Members of this group cause saprolegniasis, a disease resulting in considerable economic losses in aquaculture. Although both S. diclina and S. ferax have received much attention, the role of other Saprolegnia species in infecting fish eggs is less known. For this purpose, we have investigated the aetiology of chronic egg mortality events occurring in farmed brown trout, Salmo trutta. A total of 48 isolates were obtained from eggs with signs of infection as well as from water samples. A molecular analysis based on rnDNA internal transcribed spacer (ITS) operational taxonomic units indicated that the majority of the isolates correspond to Saprolegnia australis. All isolates of S. australis exhibited the same random amplified polymorphic DNA (RAPD) band patterns suggesting that a single strain is implicated in egg infections. The isolates followed Koch postulates using trout eggs and fry. Under standard concentrations of bronopol commonly used in farms, these isolates could grow, but not sporulate. However, both growth and sporulation were recovered when treatment was removed. This study shows that S. australis can infect and kill salmon eggs, and helps in defining oomycetes core pathogens.
... Saprolegnia, the largest genus of the Saprolegniaceae family, comprising approximately 25 species [13][14][15], is widely distributed throughout the world and possesses pathogenic species that attack the embryonic and adult stages of fishes [16][17][18] and amphibians [19][20][21]. In Korea, there have been few reports of infections associated with Saprolegnia parasitica in live fishes and their eggs [22,23] and S. ferax in the Asiatic toad (Bufo gargarizans) eggs [24]. ...
... Note: Isolates W353, W415, W420, W2043, W2044, and W2045 were identified as S. australis, which was first described in freshwater by Elliott [63]. Considering the high pathogenicity of crayfish [64,65], Prussian carp eggs (Carassius gibelio) [66], and trout [16,17,67,68] and the present finding that S. australis has been attributed to saprolegniosisinfected rice fish (Oryzias sinensis) and a freshwater snail in Korea, this species could adversely affect the Korean aquaculture industry. ...
... This species-specific seasonal distribution could be a crucial factor in determining the ecological patterns of the microbial community and may impact the entire aquatic ecosystem. It is particularly noteworthy that the WH season species obtained from this study are the pathogenic species of aquatic animals, such as fish [17,31,65], frogs [26,55], shellfish [56], and mosquitoes [57,58]. Recovering the WH season-species isolated in this study revealed the potential pathogenicity of Saprolegniaceae, which might impact warm freshwater ecosystems by infecting aquatic animals. ...
The fungal-like family Saprolegniaceae (Oomycota), also called “water mold,” includes mostly aquatic saprophytes as well as notorious aquatic animal pathogens. Most studies on Saprolegniaceae have been biased toward pathogenic species that are important to aquaculture rather than saprotrophic species, despite the latter’s crucial roles in carbon cycling of freshwater ecosystems. Few attempts have been made to study the diversity and ecology of Saprolegniaceae; thus, their ecological role is not well-known. During a survey of oomycetes between 2016 and 2021, we investigated the diversity and distribution of culturable Saprolegniaceae species in freshwater ecosystems of Korea. In the present study, members of Saprolegniaceae were isolated and identified at species level based on their cultural, morphological, and molecular phylogenetic analyses. Furthermore, substrate preference and seasonal dynamics for each were examined. Most of the species were previously reported as animal pathogens; however, in the present study, they were often isolated from other freshwater substrates, such as plant debris, algae, water, and soil sediment. The relative abundance of Saprolegniaceae was higher in the cold to cool season than that in the warm to hot season of Korea. This study enhances our understanding of the diversity and ecological attributes of Saprolegniaceae in freshwater ecosystems.
... Massive infections of eggs are common, and entire batches can be lost (Cao et al., 2012;Meyer, 1991;Rach et al., 2005;Thoen et al., 2011;van den Berg et al., 2013). This is a significant problem worldwide, commonly causing yearly economic losses of more than 10%, and occasionally up to 50% (Diéguez-Uribeondo et al., 2007;Rezinciuc et al., 2014;van den Berg et al., 2013;van West, 2006). Further, the primary existing disease control measure, malachite green, is banned in the European Union, due to its carcinogenicity and toxicity. ...
... This was probably because species were identified only based on the morphology of their sexual structures (Seymour, 1970), which was time-consuming and often unsuccessful (Diéguez-Uribeondo et al., 2007;Fregeneda-Grandes et al., 2007;van den Berg et al., 2013). Molecular diagnostic tools have been recently introduced in the identification of Saprolegnia spp., based on the sequence of internal transcribed spacer (ITS) region positioned between rRNA encoding genes (Cao et al., 2012;Diéguez-Uribeondo et al., 2007;Kozubíková-Balcarová et al., 2013;Rezinciuc et al., 2014;Sandoval-Sierra et al., 2014;Sarowar et al., 2019a;Tandel et al., 2020). However, the presence of many misassigned ITS sequences in DNA databases (e.g. ...
... A recent study on Saprolegnia molecular taxonomy resolved this issue and enabled the correct identification of Saprolegnia isolates to the species level, without the need for morphological characterization (Sandoval-Sierra et al., 2013). This allowed the recent accurate identification of Saprolegnia species in fish farms in Canada (Sarowar et al., 2019a), Chile , Spain (Rezinciuc et al., 2014), and elsewhere (Paul et al., 2015;Sakaguchi et al., 2019). ...
Oomycetes from the genus Saprolegnia are opportunistic pathogens that cause significant losses in salmonid aquaculture. Despite this, studies reporting dominant Saprolegnia species in different fish farming facilities, as well as analyses of their spreading to natural environments, are still scarce. In this study, we have for the first time identified oomycete species present in four different trout farms in Croatia. We have collected 220 oomycete isolates, both from affected tissue (46 in total: adult trout - 28, eggs - 13, and alevins - 5) and from water (174 in total: in the fish farm – 78, upstream – 50, and downstream - 46). We have used Bayesian inference to reconstruct phylogenetic relationship among the internal transcribed spacer (ITS) sequences of the collected isolates and referent strains, and determined that the isolates belonged to three different oomycete genera: Saprolegnia (64% of isolates), Pythium (35%), and Leptolegnia (1%). Saprolegnia isolates were classified into four species: S. parasitica with 53 isolates, S. australis - 52, S. delica – 25, and S. ferax – 11. Pythium and Leptolegnia isolates couldn't be identified to the species level and probably belong to so far undescribed species since their sequences didn't group with previously described species. Next, isolates from the affected tissue were mostly S. parasitica (32), while S. australis, S. delica, and S. ferax were less common (≤ 4 isolates per species). Furthermore, we used hempseed baits to capture oomycetes from water and positioned them inside the fish farms, as well as upstream (between 55 and 155 m) and downstream (between 95 and 140 m) of the fish farms. According to correspondence analysis, Saprolegnia species showed a strong association with fish farms and downstream locations, while upstream locations were associated with Pythium species, highlighting a possible role of trout farms as a source of spreading Saprolegnia species into the environment.
... This genus contains important pathogens that are reportedly responsible for high-profiled declines in animal wildlife and aquaculture populations [3,4]. In particular, the genus Saprolegnia possesses pathogenic species that attack the embryonic and adult stages of most fish worldwide, and as result of climate change are involved in the decline of amphibian populations [5][6][7][8]. In spite of the increasing need for a better understanding of the biology of these organisms, they lack of a robust taxonomy. ...
... The isolates were collected from diverse geographical freshwater aquatic habitats and hosts (S1 Table). All isolates were obtained as described in [5,6,12]. Briefly, in freshwater aquatic habitats, sampling was carried out by taking 300 mL of water using plastic bottles of 500 mL that contained rice seeds as bait. ...
... Rice seeds were incubated in the bottle at 20°C for 3 d until a superficial "cotton like" growth was observed. Then, the colonized rice seeds with a "cotton like" growth were place onto a peptone glucose agar plate (PGA) supplemented with antibiotics [5,6]. For isolation from diseased eggs and tissues of amphibian and fish, these were first washed with sterile distilled water supplemented with 100 mg/L penicillin C and placed onto PGA plates as described above. ...
The description, identification and classification of organisms are the pillar in biodiversity and evolutionary studies. The fungal-like organism Saprolegnia contains important animal pathogens. However, its taxonomy is weak, making it difficult to perform further studies. This problem mainly arises from the unavailability of suitable holotypes. We propose a standardized protocol for describing Saprolegnia spp. that includes good cultural practices and proper holotype preservation. In order to illustrate this new proposal, we describe two species, Saprolegnia aenigmatica sp. nov. and Saprolegnia racemosa sp. nov., based on the recently described molecular operational taxonomic units (MOTUs), phylogenetic relationships, and the analyses of morphological features. We show that they belong to two different MOTUs that are grouped into two sister clades. Morphologically, we find that S. racemosa exhibits a species-specific character, i.e., aggrupation of oogonia in racemes, while S. aenigmatica does not have any specific characters. Analyses of a combined set of characters, i.e., length and breadth of sporangia, length/breadth ratio (l/b) of oogonia, cyst and oospore diameter, and the number of oospores per oogomium, allow distinguishing these two species. To improve Saprolegnia taxonomy, we propose to incorporate into the protologue: (i) several isolates of the new species; (ii) the rDNA sequences to compare them to data-bases of Saprolegnia sequences of reference; (iii) a phylogenetic analysis to check relationships with other species; (iv) to preserve holotypes in absolute ethanol and to include lyophilized material from holotype; and (v) the ex-type as a pure culture from single-spore isolates stored in at least two different collections.
... The most common sign of saprolegniosis in adult fish is a superficial "cotton like" growth with a white growth of mycelia on the fish skin, especially around the head, dorsal and caudal fins, gills, and in the muscular layer and internal organs (Fregeneda-Grandes et al., 2001;Hussein et al., 2001). In the embryonic stage, the typical symptom is the outgrowth of "cotton like" mycelium (Fernández-Benéitez et al., 2008;Rezinciuc et al., 2014). Currently, the lack of an effective chemical control has resulted in a rapid increase in the number of reported cases of saprolegniosis in fish farms (Cao et al., 2012;Fregeneda-Grandes et al., 2007;Ghiasi et al., 2010;Rezinciuc et al., 2014;Thoen et al., 2011;Vega-Ramírez et al., 2013). ...
... In the embryonic stage, the typical symptom is the outgrowth of "cotton like" mycelium (Fernández-Benéitez et al., 2008;Rezinciuc et al., 2014). Currently, the lack of an effective chemical control has resulted in a rapid increase in the number of reported cases of saprolegniosis in fish farms (Cao et al., 2012;Fregeneda-Grandes et al., 2007;Ghiasi et al., 2010;Rezinciuc et al., 2014;Thoen et al., 2011;Vega-Ramírez et al., 2013). In the past the consequence of this disease was generally discounted because it was easily controlled with malachite green (Bailey, 1984;Robertson et al., 2009;van West, 2006). ...
... Saprolegnia infections seem to be mainly caused by the species: Saprolegnia parasitica, Saprolegnia diclina, and Saprolegnia australis (Diéguez-Uribeondo et al., 1996;Rezinciuc et al., 2014;van West, 2006;Willoughby, 1978). While S. parasitica is often reported in infections of adult fish (Diéguez-Uribeondo et al., 2007;Fregeneda-Grandes et al., 2007;Songe et al., 2013;Tiffney, 1939;Willoughby, 1978), other species such as S. diclina are more often found in eggs (Diéguez-Uribeondo et al., 2007;Fregeneda-Grandes et al., 2007;. ...
... The total annual production losses in freshwater aquaculture due to saprolegniosis remain consistently high, with losses of 50% having been reported for over two decades, and with Saprolegnia responsible for at least 10% of all annual salmonid economic loss worldwide [1][2][3][4][5][6]. Past publications have identified species within the genus Saprolegnia as the cause of these infections [3][4][5][7][8][9][10]; however, the taxonomic classification of Saprolegnia spp., and oomycetes in general, has often been ambiguous. ...
... Saprolegniosis is caused by several species within the genus Saprolegnia, in particular, the species S. australis, S. diclina, and S. parasitica [3,5,[7][8][9][10]14]; however, only a few published studies have investigated the range of Saprolegnia species within Atlantic salmon fish farms. Across farms in Chile and Canada, differences were reported in the species diversity of Saprolegnia, with S. parasitica making up the overall majority of isolated species [4,15]. ...
Saprolegniosis is a major destructive disease in freshwater aquaculture. The destructive economic impact of saprolegniosis on freshwater aquaculture necessitates further study on the range of Saprolegnia species within Atlantic salmon fish farms. This study undertook a thorough analysis of a total of 412 oomycete and fungal isolates that were successfully cultured and sequenced from 14 aquaculture sites in Scotland across a two-year sampling period. An ITS phylogenetic analysis of all isolates was performed according to whether they were isolated from fish or water samples and during enzootic or epizootic periods. Several genera of oomycetes were isolated from sampling sites, including Achlya, Leptolegnia, Phytophthora, and Pythium, but by far the most prevalent was Saprolegnia, accounting for 66% of all oomycetes isolated. An analysis of the ITS region of Saprolegnia parasitica showed five distinct phylotypes (S2–S6); S1 was not isolated from any site. Phylotype S2 was the most common and most widely distributed phylotype, being found at 12 of the 14 sampling sites. S2 was overwhelmingly sampled from fish (93.5%) and made up 91.1% of all S. parasitica phylotypes sampled during epizootics, as well as 67.2% of all Saprolegnia. This study indicates that a single phylotype may be responsible for Saprolegnia outbreaks in Atlantic salmon fish farms, and that water sampling and spore counts alone may be insufficient to predict Saprolegnia outbreaks in freshwater aquaculture.
... During the winter months, S. richardsonii, in early as well as in advance stages, are susceptible to Saprolegnia infections (Jen, 2008). Knowledge of the pathogen aetiology is the first few steps for the development of control strategies (Rezinciuc et al., 2014;Sarowar et al., 2019). Nevertheless, so far, no study has been performed concerning the identification and characterization of different Saprolegnia spp. ...
... S. australis has been isolated from infected eggs of salmonids in earlier studies, and the species is reported to be pathogenic in opportunistic conditions (Sandoval-Sierra et al., 2014a). Outbreaks of S. australis were also reported from eggs and juveniles of brown trout, Salmo trutta (Rezinciuc et al., 2014;Sandoval-Sierra et al., 2014b); embryonic stages of chum salmon, O.keta (Sandoval-Sierra et al., 2014a), eggs of crucian carp, Carassius carassius and Nile tilapia, Oreochromis niloticus (Lei et al., 2015;Zahran et al., 2017). In this study, we have chosen two different regions of Central Himalayan; Bhimtal and Champawat for our sample collection sites. ...
Snow trout, Schizothorax richardsonii, in early as well as in advance life stages are highly susceptible to Saprolegnia spp. infections. In the present study, we aimed to identify the Saprolegnia spp. from different life stages of infected snow trout eggs, juveniles, and adults from two geographic regions, Bhimtal and Champawat of Central Himalaya, India. Morphological identification was carried out by microscopic observation of life stages of Saprolegnia. For the molecular characterization, the internal transcribed spacer region (ITS) was amplified using universal primers ITS 1 and ITS 4. On the basis of the morphological and molecular findings, we have identified two Saprolegnia species from snow trout, i.e., Saprolegnia parasitica from eggs and adults; and S. australis from eggs and juveniles. In particular, S. parasitica was isolated from both geographical regions and S. australis only from Bhimtal, where a comparatively higher temperature regime prevails. An in-vitro experiment was conducted to study the growth of Saprolegnia spp. in varying incubation temperatures. The results confirmed that S. australis could not thrive at or below 7 °C, whereas S. parasitica could grow within the temperature range of 4–20 °C.
... n. was isolated from water sample, thus we cannot draw any conclusions regarding its pathogenicity yet. The most common fish pathogen species, S. parasitica, or the known saprotrophs damaging fish eggs, such as S. australis and S. ferax are often found in water samples [7,20,[34][35][36], thus the new species could be still considered potential pathogen. Nevertheless, further in vivo experiments are required to understand if S. velencensis sp. ...
Here, we describe a novel water mold species, Saprolegnia velencensis sp. n. from Lake Velence, in Hungary. Two strains (SAP239 and SAP241) were isolated from lake water, and characterized using morphological and molecular markers. In addition, phylogenetic analyses based on ITS–rDNA regions and on the RNA polymerase II B subunit (RPB2) gene complemented the study. The ITS–rDNA of the two strains was 100% identical, showed the highest similarity to that of S . ferax (with 94.4% identity), and they formed a separate cluster in both the ITS–rDNA and RPB2-based maximum likelihood phylogenetic trees with high bootstrap support. Although mature oogonia and antheridia were not seen under in vitro conditions, the S . velencensis sp. n. could be clearly distinguished from its closest relative, S . ferax , by the length and width of sporangia, as the new species had shorter and narrower sporangia (163.33±70.07 and 36.69±8.27 μm, respectively) than those of S . ferax . The two species also differed in the size of the secondary cysts (11.63±1.77 μm), which were slightly smaller in S . ferax . Our results showed that S . velencensis sp. n. could not be identified with any of the previously described water mold species, justifying its description as a new species.
... S. australis are the most common Saprolegnia species associated with the occurrence of saprolegniasis in salmonid aquaculture in Japan and that these species can cause disease as a primary pathogen or as an opportunistic one in both adult fish and eggs (Hussein et al., 2001;Hussein & Hatai, 2002;Sakaguchi et al., 2019). S. australis is known infecting eggs and fry of Salmo trutta in Spain and Croatia (Pavić et al., 2021;Rezinciuc et al., 2014) and also crayfish Astacus astacus alkaline water conditions, with a pH 7-10 ( Koeypudsa et al., 2005;Tedesco et al., 2021;Van West, 2006;Willoughby, 1986). Notably, in vitro experiments combination of lower temperature (about +10°C) and acidic water conditions (pH 4.8) also tend to favour both mycelial growth and zoospores production among S. parasitica and S. diclina isolates . ...
The present work is the first comprehensive study of fungus‐like stramenopilous organisms (Oomycota) diversity in Lithuanian fish farms aimed at proper identification of saprolegniasis pathogens, which is important for water quality control, monitoring infection levels and choosing more effective treatments for this disease in aquaculture. Pathogenic to fish, Saprolegnia and other potentially pathogenic water moulds were isolated from adult fish, their eggs, fry and from water samples. All detected isolates were examined morphologically and confirmed by sequence‐based molecular methods. A total of eight species belonging to the genera Saprolegnia , Achlya , Newbya and Pythium were identified. Four species ( S. parasitica , S. ferax , S. australis and S. diclina ) were found to be the main causative agents of saprolegniasis in Lithuania. S. parasitica and S. ferax dominated both in hatcheries and open fishponds, accounting for 66.2% of all isolates. S. parasitica was isolated from all farmed salmonid fish species as well as from the skin of Cyprinus carpio , Carassius carassius and Perca fluviatilis . S. australis was isolated from water and once from the skin of Oncorhynchus mykiss , and S. diclina was detected only once on the skin of Salmo salar fish. In addition, Achlya ambisexualis , Saprolegnia anisospora and Newbia oligocantha isolated during this study are noted as a possible source of saprolegniasis. The results of this study are relevant for assessing the risk of potential outbreaks of saprolegniasis or other saprolegnia‐like infection in Lithuanian freshwater aquaculture.
... (Saprolegnia parasitica and Saprolegnia diclina), belonging to family Saprolegniaceae (Table 1). These two species are most commonly associated with saprolegniasis infection and, hence often written as S. parasitica-diclina complex (Rezinciuc et al. 2014). Saprolegnia is a filamentous fungus with branched and aseptate mycelium. ...
Fisheries and aquaculture are the most important sources
of animal protein and this sector provides employment to
around 31.1 million people globally (Gozlan and Britton
2014). Disease outbreaks in animals, including fish, result in
significant economic losses. Many infectious agents like
bacteria, virus, fungi and parasites cause diseases in fish.
Bacterial and fungal diseases are two top reasons for
economic losses in aquaculture (Gonçalves and Gagnon
2011). Fungal diseases are becoming one of the most
important emerging problems with increasing incidences,
mainly because of their wide geographic range and increase
in virulence (Loo 2009; Peeler et al. 2010). Many infectious
fungi have now been discovered and many of them have
found new hosts (Kim and Harvell 2004; Frick et al. 2010)
... The pathogen was introduced into Europe along with North American non-indigenous invasive crayfish species which now act as its carriers, being mostly resistant to infection due to a long co-evolution with the pathogen [13,14]. Members of the genus Saprolegnia cause saprolegniosis, which is responsible for significant economic losses in salmonid farms and hatcheries [15][16][17][18]. Among them, Saprolegnia parasitica is highly virulent and widespread [4,7,19,20], and recent studies suggest that aquaculture facilities can act as the sources of its spread into the natural environment [21,22]. ...
Oomycete pathogens in freshwaters, such as Saprolegnia parasitica and Aphanomyces astaci, are responsible for fish/crayfish population declines in the wild and disease outbreaks in aquaculture. Although the formation of infectious zoospores in the laboratory can be triggered by washing their mycelium with natural water samples, the physico-chemical properties of the water that might promote sporulation are still unexplored. We washed the mycelia of A. astaci and S. parasitica with a range of natural water samples and observed differences in sporulation efficiency. The results of Partial Least Squares Regression (PLS-R) multivariate analysis showed that SAC (spectral absorption coefficient measured at 254 nm), DOC (dissolved organic carbon), ammonium-N and fluoride had the strongest positive effect on sporulation of S. parasitica, while sporulation of A. astaci was not significantly correlated with any of the analyzed parameters. In agreement with this, the addition of environmentally relevant concentrations of humic acid, an important contributor to SAC and DOC, to the water induced sporulation of S. parasitica but not of A. astaci. Overall, our results point to the differences in ecological requirements of these pathogens, but also present a starting point for optimizing laboratory protocols for the induction of sporulation.
... For example, although prolonged salt immersion is effective to inhibit S. parasitica, this treatment is impractical in large freshwater systems (11). Bronopol is effective against saprolegniosis (7), but tolerance to this product has been reported (12). Powerful oxidants such as ozone and hydrogen peroxide can reduce Saprolegnia spp., but these may also damage the gills of fish (13,14). ...
Copper-based fungicides have a long history of usage in agriculture and aquaculture. With the rapid development of metal-based nanoparticles, copper-based nanoparticles have attracted attention as a potential material for prevention and control of Saprolegnia parasitica. The present study investigated the effectiveness of copper/carbon core/shell nanoparticles (CCCSNs) and a commercial CCCSNs filter product (COPPERWARE®) against S. parasitica in a recirculating system. Results showed that the growth of agar plugs with mycelium was significantly suppressed after exposure to both CCCSNs powder and COPPERWARE® filters. Even the lowest concentration of CCCSNs used in our study (i.e., 100 mg/mL) exhibited significant inhibitory effects on S. parasitica. The smallest quantity of the filter product COPPERWARE® (3.75 × 3.7 × 1.2 cm, 2.58 g) used in our aquarium study also demonstrated significant inhibition compared with the control group. However, we observed leaching of copper into the water especially when larger quantities of COPPERWARE® were used. Water turbidity issues were also observed in tanks with the filter material. Besides these issues, which should be further investigated if the product is to be used on aquatic species sensitive to copper, CCCSNs has promising potential for water disinfection.
... Infections with oomycetes of the genus Saprolegnia represent one of the main parasitic diseases affecting freshwater-farmed salmonids. Saprolegnia parasitica is of primary importance with respect to infections in fish, while other Saprolegnia species such as S. diclina and S. australis infect fish and their eggs [10][11][12][13]. Saprolegnia species can cause heavy losses in salmonid farming [10,14] and are responsible for the 'winter kill' in catfish aquaculture [15]. ...
Saprolegnia infections are among the main parasitic diseases affecting farmed salmonids. The distribution and potential transfer of Saprolegnia spp. between farms and the natural environment has been scarcely investigated. Therefore, this work aimed to study the diversity and abundance of oomycete species in salmonid farms, tributary water, and effluent water systems. Four trout farms in Italy and two Atlantic salmon farms in Scotland were considered. In Italian farms, 532 isolates of oomycetes were obtained from fish and water, at upstream, inside, and downstream the farms. In Scottish farms, 201 oomycetes isolates were obtained from water outside the farm and from fish and water inside the farming units. Isolates were identified to the species level through amplification and sequencing of the ITS rDNA region. In Italy, S. parasitica was significantly more present in farmed than in wild fish, while in water it was more frequently isolated from the wild, particularly in effluent systems, not associated with more frequent isolation of S. parasitica in wild fish downstream the farm. In Scotland, S. parasitica was the most prevalent species isolated from fish, while isolates from water were mostly Pythium spp. with few S. parasitica isolates from upstream and downstream the farms.
... do not compromise the survival and hatching success of the larvae, but there are no studies that indicate the long-term effects. Rezinciuc et al. (2014) identified a strain of S. australis resistant to treatment with bronopol in the recommended doses. Moreover, Tišler et al. (2004) observed acute effects of bronopol and its degradation products in tannery wastewater on the microcrustacean Daphnia magna in low concentrations (0.70 × 10 −5 v/v%), causing immobility of 50% of the cladocerans. ...
In fish farming, high losses occur during egg incubation and larviculture due to diseases caused by oomycetes. This study aimed to identify the oomycete species that occurs in zebrafish Danio rerio eggs and to evaluate the oomyceticidal effect of copper sulfate, bronopol and methylene blue on the mycelial growth of this organism, as well as to determine the lethal and sublethal toxicity of these compounds in embryos of D. rerio . The isolates were cultivated in yeast-starch medium to determine the concentration necessary to inhibit mycelial growth by 50% (IC50) and 100% (minimum oomyceticidal concentration) after a 96 h exposure to these compounds. In addition, tests with D. rerio eggs were conducted to determine the lethal concentrations for 50% of the organisms (96h-LC50), and the concentrations that inhibited 17% of the eggs hatching (96h-IC17) after 96 h. The organism responsible for the mortality of D. rerio eggs was classified by classical and molecular methods as Aphanomyces brasiliensis , representing the first report of this pathogen in zebrafish eggs. IC50 values could be determined for both bronopol and copper sulfate, whereas methylene blue had low effectiveness against the oomycete. Copper showed high toxicity to D. rerio eggs at low concentrations, while methylene blue and bronopol toxicity was low and similar to each other. The use of bronopol at a concentration of 4.8 mg l ⁻¹ for the treatment of zebrafish eggs allows controlling the pathology without causing deleterious effects to the treated organisms.
... Вместе с тем S. asterophora в качестве субстрата не только использует останки ракообразных (Czeczuga et al., 2002), но способна колонизировать перья водоплавающих птиц (Czeczuga et al., 2004) и является паразитом водорослей рода Spirogyra (Пыстина, 2005). S. parasitica, S. ferax и S. australis часто рассматриваются не как сапротрофы, а как паразиты различных видов ракообразных (Hirsch et al., 2008;Wolinska et al., 2008;Kestrup et al., 2010), моллюсков (Czeczuga, 2000) и рыб (Noga, 1993;Phillips et al., 2008;van den Berg et al., 2013;Cao et al., 2014;Rezinciuc et al., 2014). Вызванные ими заболевания наносят эко-номический ущерб аквакультуре и способствуют снижению численности диких популяций лососевых (Phillips et al., 2008). ...
Впервые проведены молекулярная идентификация и сравнение спектра представителей порядка
Saprolegniales (Oomycota) в байкальских губках и на внешних покровах рыб в нативных условиях оз.
Байкал и в условиях аквариумной экспозиции. Установлен сходный спектр видов водных плесеней
у рыб и байкальских губок в аквариумной экспозиции и наличие у губок из оз. Байкал вида, близкого к Leptolegnia chapmanii, паразитирующего на личинках насекомых. Проанализированы результаты детекции представителей порядка Saprolegniales и факторы, влияющие на частоту их встречаемости в образцах губок из оз. Байкал.
... For example, bronopol (2-bromo-2-nitropropane-1,3-diol) and its methyl derivative 2-methyl-4-isothiazolin-3-one oxidize thiol groups in proteins and are, as such, inhibitors of dehydrogenases. These chemicals have been identified as promising compounds for the control of Saprolegnia infections in ova and adult fish (Branson, 2002;Oono and Hatai, 2007), although tolerant strains of Saprolegnia have been reported (Rezinciuc et al., 2014). Further chemicals of the oxyalkylchalcone class have been developed to overcome bronopol resistance. ...
Many Stramenopile species belonging to oomycetes from the genus Saprolegnia infect fish, amphibians, and crustaceans in aquaculture farms and natural ecosystems. Saprolegnia parasitica is one of the most severe fish pathogens, responsible for high losses in the aquaculture industry worldwide. Most of the molecules reported to date for the control of Saprolegnia infections either are inefficient or have negative impacts on the health of the fish hosts or the environment resulting in substantial economic losses. Until now, the whole proteome of S. parasitica has not been explored for a systematic screening of novel inhibitors against the pathogen. The present study was designed to develop a consensus computational framework for the identification of potential target proteins and their inhibitors and subsequent experimental validation of selected compounds. Comparative analysis between the proteomes of Saprolegnia, humans and fish species identified proteins that are specific and essential for the survival of the pathogen. The DrugBank database was exploited to select food and drug administration (FDA)-approved inhibitors whose high binding affinity to their respective protein targets was confirmed by computational modeling. At least six of the identified compounds significantly inhibited the growth of S. parasitica in vitro. Triclosan was found to be most effective with a minimum inhibitory concentration (MIC100) of 4 μg/ml. Optical microscopy showed that the inhibitors affect the morphology of hyphal cells, with hyper-branching being commonly observed. The inhibitory effects of the compounds identified in this study on Saprolegnia’s mycelial growth indicate that they are potentially usable for disease control against this class of oomycete pathogens. Similar approaches can be easily adopted for the identification of potential inhibitors against other plant and animal pathogenic oomycete infections.
... Вместе с тем S. asterophora в качестве субстрата не только использует останки ракообразных (Czeczuga et al., 2002), но способна колонизировать перья водоплавающих птиц (Czeczuga et al., 2004) и является паразитом водорослей рода Spirogyra (Пыстина, 2005). S. parasitica, S. ferax и S. australis часто рассматриваются не как сапротрофы, а как паразиты различных видов ракообразных (Hirsch et al., 2008;Wolinska et al., 2008;Kestrup et al., 2010), моллюсков (Czeczuga, 2000) и рыб (Noga, 1993;Phillips et al., 2008;van den Berg et al., 2013;Cao et al., 2014;Rezinciuc et al., 2014). Вызванные ими заболевания наносят эко-номический ущерб аквакультуре и способствуют снижению численности диких популяций лососевых (Phillips et al., 2008). ...
We performed first molecular identification and comparison of the spectrum of representatives of the order Saprolegniales (Oomycota) in Baikalian sponges and on investments of fishes under native conditions of Lake Baikal and under the conditions of aquarium exposition. We found out similar spectrum of water molds in fishes and Baikalian sponges in aquarium exposition and presence in Baikalian sponges of a species close to Leptolegnia chapmanii, which is parasite in insects larvae. We analyzed the results of detection of representatives of the order Saprolegniales and factors influencing the frequency of their occurrence in the samples of sponges from Lake Baikal.
... The few parasitic species are aggressive and economically important pathogens of aquatic invertebrates and their eggs including fish, frogs and toads in both wildlife populations and commercial aquaculture (fish farm) systems (Nechwatal et al. 2008, van den Berg et al. 2013, Singer et al. 2016. Saprolegnia parasitica, S. ferax, S. diclina and S. mixta were reported as causal agents of cotton wool disease (saprolegniasis) in embryonic and different other life stages of sea animals , Rezinciuc et al. 2014. Saprolegnia parasitica is clearly one of the most devastating fish pathogen that causes huge economic losses in fish industry and extensive decline in population of several fish species (Sarowar et al. 2014). ...
Eight new species presented are Calostoma areolatum collected in Wuyishan National Park (China), Crinipellis bidens from Hubei Province (China), Lactifluus sainii from Himalayan India, Inocybe elata from Yunnan (China), Inocybe himalayensis from Pakistan. Specimens previously identified as Massalongia carnosa represent a new species, namely M. patagonica restricted to southern South America. Saprolegnia maragheica is a new oomycete species of fresh water in Maraghe (Iran). Uncispora wuzhishanensis is a new aquatic hyphomycete species. A type specimen of Raddetes turkestanicus was studied and based on this the new combination Conocybe turkestanica, is proposed. Argyranthemum frutescens is a new host for Alternaria alternata and Syzygium cumini for Phyllosticta capitalensis in India. Crepidotus ehrendorferi is confirmed for Hungary and Pluteus leucoborealis for Central Europe, and for the phytogeographical region of Carpaticum. Pseudopithomyces palmicola is shown to occur on grapevine and it is validated by adding a unique identifier. Terfezia fanfani is reported first from Algeria.
... Several molecular methods are used for identification of pathogens 4,5 . Restriction fragment length polymorphism (RFLP) which analyzes the polymorphism of digested genomic fragments as the specific fingerprint of microbial by pulsed-field gel electrophoresis (PFGE), is the gold standard for microbial typing 6 . ...
Rapid and accurate identification of pathogen is a major quarantine strategy for outbreak prevention. We used capillary electrophoresis-random amplified polymorphic DNA (CE-RAPD) to generate highly discriminatory pathogen profiles, reduced batch effects between profiles by novel normalization procedure and pattern of technical repeats, followed by target similarity evaluation using target identification score (TIS). A full target signature contains several patterns. TIS system was optimized by training set isolates that included three species, and validated using two hundred clinical Klebsiella pneumoniae isolates. Hierarchical clustering analysis showed CE-RAPD profiles arrange clusters according to the species or the source. Moreover, samples with similar profile may display similar antibiotic susceptibility. By using a signature of four patterns, the TIS system could accurately identify target among different isolates. The variation between isolates may be caused by small change in genome. TIS system provides a standardized tool for building of outbreak firewall and facilitate data exchange.
... The members of this genus are known to be saprophytes, parasites and under some circumstances opportunistic pathogens as well. The majority of the species are responsible for causing diseases on aquatic animals (Blaustein et al. 1994, Fernández-Benéitez et al. 2008, Berger et al. 2009, Ruthig 2009, Perotti et al. 2013, Rezinciuc et al. 2014, Sandoval-Sierra et al. 2014). There are reports suggesting that some species of Saprolegnia causes high mortality rate in wildlife and aquaculture populations (van West 2006, van den Berg et al. 2013. ...
Saprolegnia ferax is isolated from polluted water sample collected from Mula River, Pune, Maharashtra, India. The isolated taxon is illustrated and compared with the morphotaxonomy based first record of Indian S. ferax isolated by Wani et al. (2017). The present study deals with the re-description of the isolated taxon S. ferax based on detail morphological features, sequence analysis and phylogeny of ITS and LSU regions of rDNA.
... The members of this genus are known to be saprophytes, parasites and under some circumstances opportunistic pathogens as well. The majority of the species are responsible for causing diseases on aquatic animals (Blaustein et al. 1994, Fernández-Benéitez et al. 2008, Berger et al. 2009, Ruthig 2009, Perotti et al. 2013, Rezinciuc et al. 2014, Sandoval-Sierra et al. 2014). There are reports suggesting that some species of Saprolegnia causes high mortality rate in wildlife and aquaculture populations (van West 2006, van den Berg et al. 2013. ...
Saprolegnia ferax is isolated from polluted water sample collected from Mula River, Pune, Maharashtra, India. The isolated taxon is illustrated and compared with the morphotaxonomy based first record of Indian S. ferax isolated by Wani et al. (2017). The present study deals with the re-description of the isolated taxon S. ferax based on detail morphological features, sequence analysis and phylogeny of ITS and LSU regions of rDNA.
... As examples, Aphanomyces euteiches is a known pathogen of legumes (Gaulin et al. 2007, Madoui et al. 2009), and Aphanomyces astaci is responsible for the crayfish plague (Unestan 1965, Söderhäll and Cerenius 1999, Diéguez-Uribeondo et al. 2006, Kozubíková et al. 2009, Strand et al. 2012, Rezinciuc et al. 2016. Saprolegnia is one of the bestknown pathogens of fish and their eggs (Noga 2010, Kiziewicz et al. 2013, Van Den Berg et al. 2013, Rezinciuc et al. 2014, Sandoval-Sierra et al. 2014a, Sarowar et al. 2014, Mastan 2015 and, together with Achlya, are reported as parasites in amphibians (Fernández-Benéitez et al. 2007, Romansic et al. 2009, Ault et al. 2012, Urban et al. 2015. ...
Saprolegniales is a complex and monophyletic order of oomycetes. Their members inhabit terrestrial, freshwater, and marine ecosystems and have a worldwide distribution. In these ecosystems, they are found as saprobes, parasites, or even pathogens of animals and plants of economic importance. In this study, a concatenate phylogeny of the partial LSU and complete ITS rDNA regions is presented, including isolates from Brazil and Argentina, which were sequenced after a detailed morphological analysis. Among the sequenced species, Achlya orion, Leptolegnia eccentrica, Phragmosporangium uniseriatum, and Pythiopsis irregularis are included for the first time in a phylogeny. Our results are in agreement with the recent informal proposals outlined in taxonomic overviews of the Oomycota of G.W. Beakes and collaborators, who placed the family Verrucalvaceae into the Saprolegniales and introduced the family Achlyaceae to group Achlya s.s., Brevilegnia, Dictyuchus, and Thraustotheca. These results also support the transference of Achlya androgyna to Newbya. Leptolegnia appears as paraphyletic, with the separation of L. eccentrica from the other species of this genus. In addition, Phragmosporangium, which is herein sequenced for the first time, clustered as sister to some species of Aphanomyces, including the type species, A. stellatus.
... In recent years, the global increased aquaculture production combined with the banning of chemicals used to control Saprolegnia infections, including the carcinogenic compound malachite green, have led to the spread of Saprolegnia populations worldwide (van West, 2006). Although other chemicals are being trialed for their potential to control Saprolegnia species (Pottinger and Day, 1999;Gieseker et al., 2006;Rezinciuc et al., 2014;Warrilow et al., 2014), there are currently no effective and safe chemical treatments that give sufficient protection against Saprolegniasis. Therefore, alternative measures for disease control are urgently needed in order to manage the spread of the infection. ...
Several water mold species from the Saprolegnia genus infect fish, amphibians and crustaceans in natural ecosystems and aquaculture farms. Saprolegnia parasitica is one of the most severe fish pathogens. It is responsible for millions of dollars of losses to the aquaculture industry worldwide. Here, we have performed a proteomic analysis, using gel-based and solution (iTRAQ) approaches, of four defined developmental stages of S. parasitica grown in vitro, i.e., the mycelium, primary cysts, secondary cysts and germinated cysts, to gain greater insight into the types of proteins linked to the different stages. A relatively high number of kinases as well as virulence proteins, including the ricin B lectin, disintegrins and proteases were identified in the S. parasitica proteome. Many proteins associated with various biological processes were significantly enriched in different life cycle stages of S. parasitica. Compared to the mycelium, most of the proteins in the different cyst stages showed similar enrichment patterns and were mainly related to energy metabolism, signal transduction, protein synthesis and post-translational modifications. The proteins most enriched in the mycelium compared to the cyst stages were associated with amino acid metabolism, carbohydrate metabolism and mitochondrial energy production. The data presented expand our knowledge of metabolic pathways specifically linked to each developmental stage of this pathogen.
... [14]; however, there are growing concerns regarding its use within the industry, due to its acute toxicity to several fish species and its potentially harmful effects to human health [15]. Furthermore, it has been reported that prolonged use of this product has caused Saprolegnia to develop multiresistance mechanisms to the action of this compound [16]. Tests of the antioomycete activities of natural compound 1 and oxyalkylchalcones 2-11 were performed, and the results compared to commercial antifungal "Bronopol"; the minimum inhibitory concentrations (MIC) ( Table 1) and the minimum oomycidal concentrations (MOC) ( Table 2) for 1-11 were determined. ...
A series of novel oxyalkylchalcones substituted with alkyl groups were designed and synthesized, and the antioomycete activity of the series was evaluated in vitro against Saprolegnia strains. All tested O-alkylchalcones were synthesized by means of nucleophilic substitution from the natural compound 2′,4′-dihydroxychalcone (1) and the respective alkyl bromide. The natural chalcone (1) and 10 synthetic oxyalkylchalcones (2–11) were tested against Saprolegnia parasitica and Saprolegnia australis. Among synthetic analogs, 2-hydroxy,4-farnesyloxychalcone (11) showed the most potent activity against Saprolegnia sp., with MIC and MOC values of 125 µg/mL (similar to bronopol at 150 µg/mL) and 175 µg/mL, respectively; however, 2′,4′-dihydroxychalcone (1) was the strongest and most active molecule, with MIC and MOC values of 6.25 µg/mL and 12.5 µg/mL.
... In addition to plant pathogens, the oomycetes also comprise important animal parasitic species (Phillips et al. 2008). For example, some species of the genus Saprolegnia can cause severe losses in aquaculture and fi sheries (van den Berg et al. 2013, Rezinciuc et al. 2014b, and in wildlife affecting amphibian populations (Blaustein et al. 1994, Kiesecker and Blaustein 1997, Romansic et al. 2009). Other species such as Lagenidium giganteum Couch can infect the larval stage of many mosquito species Söderhäll 1985, Kamoun 2003), and spore formulations of this organism have been used for biocontrol of mosquitoes Söderhäll 1985, Kamoun 2003). ...
... Although the present study only yielded S. parasitica and S. diclina from the infected Atlantic salmon eggs from the commercial hatchery, other researchers have shown that other species may also be involved in infecting fish eggs. Rezinciuc and coworkers (Rezinciuc, Sandoval-Sierra & Dieguez-Uribeondo 2014) investigated the aetiology of chronic egg mortality events occurring in farmed brown trout, Salmo trutta, and identified the causative agent as Saprolegnia australis. Yet another study (Cao et al. 2012) isolated Saprolegnia ferax from infected fish eggs, showing the diversity of species infecting eggs of different fish species. ...
Here, we address the morphological changes of eyed eggs of Atlantic salmon, Salmo salar L. infected with Saprolegnia from a commercial hatchery and after experimental infection. Eyed eggs infected with Saprolegnia spp. from 10 Atlantic salmon females were obtained. Egg pathology was investigated by light and scanning electron microscopy. Eggs from six of ten females were infected with S. parasitica, and two females had infections with S. diclina clade IIIA; two Saprolegnia isolates remained unidentified. Light microscopy showed S. diclina infection resulted in the chorion in some areas being completely destroyed, whereas eggs infected with S. parasitica had an apparently intact chorion with hyphae growing within or beneath the chorion. The same contrasting pathology was found in experimentally infected eggs. Scanning electron microscopy revealed that S. parasitica grew on the egg surface and hyphae were found penetrating the chorion of the egg, and re-emerging on the surface away from the infection site. The two Saprolegnia species employ different infection strategies when colonizing salmon eggs. Saprolegnia diclina infection results in chorion destruction, while S. parasitica penetrates intact chorion. We discuss the possibility these infection mechanisms representing a necrotrophic (S. diclina) vs. a facultative biotrophic strategy (S. parasitica).
© 2015 John Wiley & Sons Ltd.
Global harvest of aquatic biota which includes flora and fauna both, through capture fisheries has already reached its maximum potential, or has shown offshoot in some cases. Capture fisheries is now stagnant, and therefore, in order to fulfil the need for growing worldwide population, culture fisheries have come up with a promising way. To further increase the production and sustainability of culture fisheries, various tools and techniques of biotechnology can be used. Aquatic biotechnology, which has both basic and spin-off applications, can help aquaculture producers increase output, efficiency, profitability, and sustainability. Genomic and proteomic research such as whole genome sequence (WGS) and marker-assisted selection (MAS) of economically important cultured fish could have an impact on fish genetic resource development and management as well. In genetically modified (GM) and gene knockout (GKO) fishes, economically important features such as improved growth, enhanced muscle mass, cold tolerance and disease resistance can be further improved. Cryopreservation of gametes (sperms and eggs) and embryos could open up new commercial possibilities for endless seed and fry production, as well as healthier and better-conditioned fish and brood stock management. It could also help with ex situ genome conservation in threatened and endangered species. Biotechnological interventions in intensive aquaculture have shown a considerable potential in using bioremediation and probiotics to regulate effluents, toxicants, and pathogens in the environment. Therefore, molecular tools can be used to minimize the impact of intensive aquaculture in environmental pollution.KeywordsAquatic biotechnologyBiotechnological interventionsGene knockoutBrood stock genetic managementProteomeMarker-assisted selection
One of the emerging oomycete pathogens of rainbow trout and other salmonids is designated as Saprolegnia spp. Rainbow trout and other cold-water fish are most susceptible to Saprolegnia infections in early and advanced life stages. Saprolegnia has a complicated and well-characterized life cycle that includes both sexual and asexual stages. It has been traditionally identified and distinguished, using patterns of asexual and sexual characteristics, while the sexual characteristics, oospore and lipid droplet position in the oospore, and the asexual characteristics, such as mycelium and germinating cyst, have been most frequently used in identifications. This chapter highlights the morphological and molecular identification of Saprolegnia spp., symptoms of Saprolegnia infections and control measures, including biocontrol methods.KeywordsSaprolegniasisMorphological identificationMolecular characterizationControl measures
This study aims to determine the Calotropis gigantea extract against hatchability of Barbonymus gonionotus eggs infected with pathogenic fungi. The research was conducted at Fish Seeds Center Krueng Batee, Aceh Barat Daya district, from July to August 2020. Statistical analysis used a completely randomized design (CRD) method with 6 treatment and 3 replications for each treatment. The treatments were carried out by immersing the Barbonymus gonionotus eggs into C. gigantea leaf extrcact. Namely Control (without extract), A (400 ppm extract), B (800 ppm extract), C (1200 ppm extract), D (1600 ppm extract), and E (2000 ppm extract). ANOVA test results showed that the addition of C. gigantea leaf extract had asignificant effect (P<0.05) on hatchability and survival of B. gonionotus larvae. The best treatment was achieved at the C treatment (800 ppm extract) with 88 % hatching rate and 92,54 % survival rate. From the results of this study, it is known that using C. gigantea leaf extract can increase the hatchability of B. gonionotus fish eggs infected with the Saprolegnia sp. pathogen, which means it can also increase the production of fish seeds.
This study explored the pharmacokinetic characteristics of bronopol in grass carp (Ctenopharyngodon idella) under different temperatures. The concentrations of bronopol in the plasma and tissues (kidney, liver and muscle) of grass carp after soaking in bronopol (6.75 µg/ml) at 15 and 20°C were determined using liquid chromatography–mass spectrometry. The concentrations of bronopol in both plasma and tissue first increased and then decreased with soaking time at both tested temperatures. The peak bronopol concentrations at 15°C (plasma: 8.934 µg/ml; kidney: 9.23 µg/g; liver: 9.47 µg/g; and muscle: 7.98 µg/g) were slightly lower than those at 20°C (plasma: 9.654 µg/ml; kidney: 10.83 µg/g; liver: 13.40 µg/g; and muscle: 8.68 µg/g). In an analysis of pharmacokinetic parameters, the bronopol concentration–time profiles for plasma were best described by a two‐compartment, open pharmacokinetic model with first‐order absorption. The t1/2β for plasma at 15 and 20°C was 82.933 and 92.041 hr, respectively, indicating that the elimination of bronopol was faster at 15°C than at 20°C. In addition, AUC0‐t and AUC0‐∞ values of bronopol were 477.892 and 495.809 µg/L hr at 15°C and 495.809 and 589.859 µg/L hr at 20°C, indicating that the content of bronopol in the organism was higher at higher temperature.
To identify the pathogens causing saprolegniosis among farmed fish in Nova Scotia, 172 infected tissues and 23 water samples were collected from six species of teleosts: Atlantic salmon (Salmo salar), brown trout (Salmo trutta), Arctic charr (Salvelinus alpinus), brook trout (Salvelinus fontinalis), striped bass (Morone saxatilis) and rainbow trout (Oncorhynchus mykiss) at nine facilities over a 600 km range. Following laboratory culture, 132 isolates were recovered. Six species of oomycetes were identified from analysis of the internal transcribed spacer (ITS) sequence of the nrDNA: Saprolegnia parasitica, Saprolegnia ferax, Saprolegnia diclina, Saprolegnia aenigmatica, Saprolegnia torulosa, Saprolegnia sp. and Pythiopsis cymosa. Further phylogenetic analyses of the ITS and cytochrome c oxidase subunit 1 (Cox1) regions revealed four strains of Saprolegnia parasitica (named here as S1, S2, S3 and S4), of which S1 and S2 were common (37% and 42% of the isolates), and two strains of S. ferax. Among S. parasitica, S2 and S3 are more closely related to each other than to S1 based on the phylogenetic analyses and predicted RNA secondary structure of the ITS region. Sexual structures with a similar morphology were formed by S1 and S3 in vitro, but were not formed by S2.
The potential use of RAPDs for taxonomic studies were investigated using Brassica, Sinapis and Raphanus taxa. Principal coordinate analysis of 284 RAPD bands revealed the classical U triangle relationship between diploid and amphidiploid Brassica taxa. Raphanus sativus and S. alba were distinct from the Brassica taxa. It appears that at least ten primers with approximately 100 total bands are needed to adequately portray these relationships. Cultivars of cabbage and cauliflower were separated by RAPDs. Analysis of RAPDs from individual plants of B. carinata cv. dodola resulted in 69 RAPDs, with 91.7% monomorphic and 8.3% polymorphic bands. RAPDs appear to be useful for taxonomic studies at levels ranging from populations to species and perhaps genera.
Se estudiaron 35 cepas de Saprolegnia, aisladas de Salmón y Trucha, provenientes de dos laboratorios ictiopatológicos de Castro y Puerto Montt, de Chile. Las cepas fueron obtenidas de ovas, branquias y aletas de alevines y smolt, de distintas especies de salmonídeos: salmón del Atlántico, salmón coho y trucha arco iris. Se reaislaron las cepas y se purificaron en agar Sabouraud, agar Lactrimel y agar MAO, con antimicrobianos. Saprolegnia fue cultivada en agua destilada y semillas de cáñamo, para la producción de estructuras sexuales y posterior identificación morfológica, según Dick (1973) y Seymour (1970). De las cepas estudiadas, las 35 correspondieron a Saprolegnia parasitica, única especie aislada, conformando el 100 % del total. El 34% de las cepas presentó estructuras sexuadas y el 100% se desarrolló a 30ºC.
We report a major update of the MAFFT multiple sequence alignment program. This version has several new features, including
options for adding unaligned sequences into an existing alignment, adjustment of direction in nucleotide alignment, constrained
alignment and parallel processing, which were implemented after the previous major update. This report shows actual examples
to explain how these features work, alone and in combination. Some examples incorrectly aligned by MAFFT are also shown to
clarify its limitations. We discuss how to avoid misalignments, and our ongoing efforts to overcome such limitations.
The aquatic fungi cultured from eggs, alevins and broodfish of brown trout Salmo trutta belonged to the genus Saprolegnia and were identified as S. diclina, S. australis, S. ferax, S. furcata, S. hypogyna, S. unispora and S. parasitica. The species obtained from infected eggs and alevins were different to those from infected fish. Several Saprolegnia species were isolated from eggs and alevins, whereas all the isolates obtained from broodfish were the pathogenic S. parasitica. (c) 2007 The Authors Journal compilation (c) 2007 The Fisheries Society of the British Isles.
Population losses and extinctions of species are occurring at unprecedented rates, as exemplified by declines and extinctions of amphibians worldwide. However, studies of amphibian population declines generally do not address the complexity of the phenomenon or its implications for ecological communities, focusing instead on single factors affecting particular amphibian species. We argue that the causes for amphibian population declines are complex; may differ among species, populations, and life stages within a population; and are context dependent with multiple stressors interacting to drive declines. Because amphibians are key components of communities, we emphasize the importance of investigating amphibian declines at the community level. Selection pressures over evolutionary time have molded amphibian life history characteristics, such that they may remain static even in the face of strong, recent human-induced selection pressures.
Phylogenetic inference is considered to be one of the grand challenges in Bioinformatics due to the immense computational requirements. RAxML is currently among the fastest and most accurate programs
for phylogenetic tree inference under the Maximum Likelihood (ML) criterion. First, we introduce new tree search heuristics
that accelerate RAxML by a factor of 2.43 while returning equally good trees. The performance of the new search algorithm
has been assessed on 18 real-world datasets comprising 148 up to 4,843 DNA sequences. We then present the implementation,
optimization, and evaluation of RAxML on the IBM Cell Broadband Engine. We address the problems and provide solutions pertaining
to the optimization of floating point code, control flow, communication, and scheduling of multi-level parallelism on the
Cell.
With the increasing availability of molecular data, maximum likelihood approaches have gained a new central role in phylogenetic reconstructions. Extremely fast tree-search algorithms have been developed to handle data sets of ample size in reasonable time. In the past few years, RAxML has achieved great relevance in this field and obtained wide distribution among evolutionary biologists and taxonomists because of its high computational performance and accuracy. However, there are certain drawbacks with regard to its usability, since the program is exclusively command-line based. To overcome this problem, we developed raxmlGUI, a graphical user interface that makes the use of RAxML easier and highly intuitive, enabling the user to perform phylogenetic analyses of varying complexity. The GUI includes all main options of RAxML, and a number of functions are automated
or simplified. In addition, some features extend the standard use of RAxML, like assembling concatenated alignments with automatic partitioning. RaxmlGUI is an open source Python program, available in a cross-platform package that incorporates RAxML executables for the main operating systems. It can be downloaded from http://sourceforge.net/projects/raxmlgui/.
Keywords: Rapid bootstrap; Graphical user interface; Maximum likelihood; Phylogenetic analyses; Python; RAxML
Summary: The two main functions of bioinformatics are the organization and analysis of biological data using computational resources. Geneious Basic has been designed to be an easy-to-use and flexible desktop software application framework for the organization and analysis of biological data, with a focus on molecular sequences and related data types. It integrates numerous industry-standard discovery analysis tools, with interactive visualizations to generate publication-ready images. One key contribution to researchers in the life sciences is the Geneious public application programming interface (API) that affords the ability to leverage the existing framework of the Geneious Basic software platform for virtually unlimited extension and customization. The result is an increase in the speed and quality of development of computation tools for the life sciences, due to the functionality and graphical user interface available to the developer through the public API. Geneious Basic represents an ideal platform for the bioinformatics community to leverage existing components and to integrate their own specific requirements for the discovery, analysis and visualization of biological data.Availability and implementation: Binaries and public API freely available for download at http://www.geneious.com/basic, implemented in Java and supported on Linux, Apple OSX and MS Windows. The software is also available from the Bio-Linux package repository at http://nebc.nerc.ac.uk/news/geneiousonbl.Contact:
peter@biomatters.com
Proper disease control is very important to minimize yield losses caused by oomycetes in many crops. Today, oomycete control is partially achieved by breeding for resistance, but mainly by application of single-site mode of action fungicides including the carboxylic acid amides (CAAs). Despite having mostly specific targets, fungicidal activity can differ even in species belonging to the same phylum but the underlying mechanisms are often poorly understood. In an attempt to elucidate the phylogenetic basis and underlying molecular mechanism of sensitivity and tolerance to CAAs, the cellulose synthase 3 (CesA3) gene was isolated and characterized, encoding the target site of this fungicide class. The CesA3 gene was present in all 25 species included in this study representing the orders Albuginales, Leptomitales, Peronosporales, Pythiales, Rhipidiales and Saprolegniales, and based on phylogenetic analyses, enabled good resolution of all the different taxonomic orders. Sensitivity assays using the CAA fungicide mandipropamid (MPD) demonstrated that only species belonging to the Peronosporales were inhibited by the fungicide. Molecular data provided evidence, that the observed difference in sensitivity to CAAs between Peronosporales and CAA tolerant species is most likely caused by an inherent amino acid configuration at position 1109 in CesA3 possibly affecting fungicide binding. The present study not only succeeded in linking CAA sensitivity of various oomycetes to the inherent CesA3 target site configuration, but could also relate it to the broader phylogenetic context.
Since its introduction in 2001, MrBayes has grown in popularity as a software package for Bayesian phylogenetic inference using Markov chain Monte Carlo (MCMC) methods. With this note, we announce the release of version 3.2, a major upgrade to the latest official release presented in 2003. The new version provides convergence diagnostics and allows multiple analyses to be run in parallel with convergence progress monitored on the fly. The introduction of new proposals and automatic optimization of tuning parameters has improved convergence for many problems. The new version also sports significantly faster likelihood calculations through streaming single-instruction-multiple-data extensions (SSE) and support of the BEAGLE library, allowing likelihood calculations to be delegated to graphics processing units (GPUs) on compatible hardware. Speedup factors range from around 2 with SSE code to more than 50 with BEAGLE for codon problems. Checkpointing across all models allows long runs to be completed even when an analysis is prematurely terminated. New models include relaxed clocks, dating, model averaging across time-reversible substitution models, and support for hard, negative, and partial (backbone) tree constraints. Inference of species trees from gene trees is supported by full incorporation of the Bayesian estimation of species trees (BEST) algorithms. Marginal model likelihoods for Bayes factor tests can be estimated accurately across the entire model space using the stepping stone method. The new version provides more output options than previously, including samples of ancestral states, site rates, site d(N)/d(S) rations, branch rates, and node dates. A wide range of statistics on tree parameters can also be output for visualization in FigTree and compatible software.
The 18S rRNA gene sequences from the bitunicate ascomycetes Ceramothyrium linnaeae (Chaetothyriaceae) and Coccodinium bartschii (Coccodiniaceae) were determined and aligned with the corresponding sequences from 33 other ascomycetes and one basidiomycete, Boletus satanas. Phylogenetic analyses of these sequences supported previous reports that the Herpotrichiellaceae (Capronia, black yeasts, etc.) are distant from Dothideales and Pleosporales. A new sequence of Ceramothyrium linnaeae, representing the family Chaetothyriaceae, is monophyletic with representatives of the Herpotrichiellaceae, suggesting that both families can be accommodated in the order Chaetothyriales. The concept of Chaetothyriales can not be based on the presence of periphysoids, since Coccodinium bartschii, which also has periphysoids, clustered with members of the Dothideaceae. The Chaetothyriales are not closely related to other bitunicates, but are the sister group of either Eurotiales or Lecanorales/Peltigerales.
Disease agents and pests associated with freshwater crayfish fall into six main categories—viruses, bacteria, rickettsia-like organisms (RLOs), fungi, protists, and metazoans. Data and information on specific disease agents and pests from each of these categories are presented in this synopsis. Each agent or group of agents is considered under the following headings—condition, causative agent(s), life cycle/life history, epizootiology, pathology, pathogen viability. Information for the synopsis was obtained from the published literature and from personal contact with internationally recognized experts in freshwater crayfish aquaculture, biology, and disease. Data of relevance for import risk analysis are summarized. Import risk analysis is the process by which the risks associated with importation of animals and plants, and products derived from animals and plants, are assessed and managed. Hazard identification is essential and is the first component of an import risk analysis. In 1996, the Australian Quarantine and Inspection Service (AQIS) commenced a review of policy relating to the importation of nonviable freshwater crayfish products, along with a suite of other aquatic animal products. AQIS commissioned a synopsis of freshwater crayfish pests and pathogens for use as a resource document for hazard identification in the formal IRA process.
Thirty five strains of Saprolegnia were isolated from salmon and trout, obtained from the IX, X and XII regions in southern Chile. The strains were obtained from eggs, gills and fins of alevins and smolt phase of different species of salmonids: Salmo salar (Atlantic salmon); Oncorhynchus kisutch (Coho salmon) and Oncorhynchus mykiss (rainbow trout). The strains were re-isolated and purified in Sabouraud agar, Lactrimel and MAO agar, supplemented with antibiotics. The strains were cultured in distilled water and hemp seeds, for the production of sexual structures, and for their morphological identification. All strains collected, were identified as Saprolegnia parasitica. This species was the only one isolated of its genus.
Water moulds in the genera Achlya and Saprolegnia were isolated from eggs of the Mekong giant catfish (Pangasianodon gigas) and from the water in the hatching tank at the Inland Aquaculture Research Institute, Phra Nakhon Sriayutthaya province, from 2008 to 2010. The optimal temperature of almost all isolates was 30 °C. The Achlya spp. and Saprolegnia spp. could tolerate an NaCl medium at 10 and 25 parts per trillion (ppt), respectively. An exception was Saprolegnia sp. (E3/52-P2) which could tolerate NaCl up to 30 ppt. The isolates could grow in broth at pH 4-11, while the optimal pH for Achlya spp. and Saprolegnia spp. was pH 5 and pH6, respectively. The study on pathogenicity of the water moulds isolated in the laboratory showed that the isolates Achlya spp. (T.MCF1-02, E.MCF 2-001 and E4/52-10) and Saprolegnia sp. (E1/53-12) were pathogenic to the catfish eggs.
The 18S rRNA gene sequences from the bitunicate ascomycetes Ceramothyrium linnaeae (Chaetothyriaceae) and Coccodinium bartschii (Coccodiniaceae) were determined and aligned with the corresponding sequences from 33 other ascomycetes and one basidiomycete, Boletus satanas. Phylogenetic analyses of these sequences supported previous reports that the Herpotrichiellaceae (Capronia, black yeasts, etc.) are distant from Dothideales and Pleosporales. A new sequence of Ceramothyrium linnaeae, representing the family Chaetothyriaceae, is mono-phyletic with representatives of the Herpotrichiellaceae, suggesting that both families can be accommodated in the order Chaetothyriales. The concept of Chaetothyriales can not be based on the presence of periphysoids, since Coccodinium bartschii, which also has periphysoids, clustered with members of the Dothideaceae. The Chaetothyriales are not closely related to other bitunicates, but are the sister group of either Eurotiales or Lecanorales/Peltigerales.
— We studied sequence variation in 16S rDNA in 204 individuals from 37 populations of the land snail Candidula unifasciata (Poiret 1801) across the core species range in France, Switzerland, and Germany. Phylogeographic, nested clade, and coalescence analyses were used to elucidate the species evolutionary history. The study revealed the presence of two major evolutionary lineages that evolved in separate refuges in southeast France as result of previous fragmentation during the Pleistocene. Applying a recent extension of the nested clade analysis (Templeton 2001), we inferred that range expansions along river valleys in independent corridors to the north led eventually to a secondary contact zone of the major clades around the Geneva Basin. There is evidence supporting the idea that the formation of the secondary contact zone and the colonization of Germany might be postglacial events. The phylogeographic history inferred for C. unifasciata differs from general biogeographic patterns of postglacial colonization previously identified for other taxa, and it might represent a common model for species with restricted dispersal.
A saprolegniasis occurred in a group of rainbow trout fingerlings of about 1.2 g in body weight at the Koide branch of the Niigata Prefectural Freshwater Fisheries Experimental Station. The initial sigh of the disease was an appearance of fin rot. Saprolegnia sp. was thought to infect secondarily on the area of fin rot.Six strains of the fungus were isolated from the base of the dorsal fin of 6 diseased fish. Inoculation experiments using moon fish showed that these six strains differed to some extent in pathogenicity from each other (Table 2.). Among the 6 strains strain N7619 was most virulent.All the strains were classified into Saprolegnia sp. according to SPARROW (1960) and DICK (1973) from the characteristics of the asexual organs on hemp seeds. Of the 6 strains, only strain N7619 formed sex organs. In this strain diclinous antheridial branches were predominantly produced, and the oogonial wall were pitted. The type of internal structure of oospores was subcentric. From these structures the strain was identified as S. australis according to SEYMOUR (1970). The characteristics of the sex organs of the strain also agreed with those of S. australis described originally by ELLIOTT (Table 3.).
Disease agents and pests associated with freshwater crayfish fall into six main categories-viruses, bacteria, rickettsia-like organisms (RLOs), fungi, protists and metazoans. Data and information on specific disease agents and pests from each of these categories are presented in this synopsis. Each agent or group of agents is considered under the following headings-condition, causative agent(s), life cycle/life history, epizootiology, pathology, pathogen viability. Information for the synopsis was obtained from the published literature and from personal contact with internationally recognised experts in freshwater crayfish aquaculture, biology and disease. Data of relevance for import risk analysis are summarised. Import risk analysis is the process by which the risks associated with importation of animals and plants, and products derived from animals and plants, are assessed and managed. Hazard identification is essential and is the first component of an import risk analysis. In 1996, the Australian Quarantine and Inspection Service (AQIS) commenced a review of policy relating to the importation of non-viable freshwater crayfish products, along with a suite of other aquatic animal products. AQIS commissioned a synopsis of freshwater crayfish pests and pathogens for use as a resource document for hazard identification in the formal IRA process.
Saprolegnia parasitica has caused large mortalities in brown trout, Salmo trutta, in Spain. Several strains of Saprolegnia parasitica have been isolated from these epizootics and characterized regarding their physiological adaptation and genetic diversity. These isolates exhibit similar physiological characteristics, i.e. radial growth, zoospore mobility and germination after encystment and differ substantially from other strains of the Saprolegnia diclina-parasitica complex tested. Random amplification of polymorphic DNA polymerase chain reaction (RAPD-PCR) of total DNA revealed a genetic similarity of about 85-100% between Spanish trout isolates whereas only 20-45% similarity to other strains of the Saprolegnia diclina-parasitica complex was found. The results suggest that the Spanish isolates are closely related strains and that they might have originated from one clone.
The lack of a robust taxonomy in the genus Saprolegnia (Oomycetes) is leading to the presence of incorrectly named isolates in culture collections and of an increasing number of misassigned named sequences in DNA databases. Accurate species delimitation is critical for most biological disciplines. A recently proposed approach to solve species delimitation (taxon diagnosis system) of difficult organisms is the definition of molecular operational taxonomic units (MOTUs) using molecular data.
In this study, we have analyzed 961 sequences of internal transcribed spacer from main culture collection of Saprolegniales (461 sequences) and GenBank (500 sequences). For this purpose, we have used two phylogenetic analyses, i.e, Maximum Parsimony and Bayesian inference, and also a clustering optimization analysis using arbitrary options regarding the distance threshold values and the clustering algorithm. Thus, we have identified 29 DNA-based MOTUs in agreement with phylogenetic analyses of species. The molecular clusters support the validity of 18 species of Saprolegnia and identify 11 potential new species. Based on this system, we have listed a number of incorrectly named isolates from culture collections, misassigned species names to GenBank sequences, and type sequences for species. We conclude that GenBank represents the main source of errors for identifying species since it possesses a high number of misassigned sequences, and the presence of sequences with sequencing errors. The presented taxonomic diagnosis system might help setting the basis for a suitable identification of species in this economically important genus.
A very large number of diseases in agriculture and aquaculture are caused by fungal-like micro-organisms, classified as Oomycetes or water moulds. Collectively, oomycetes represent a huge threat to global food security. In addition, several oomycetes can cause environmental disasters, by wiping out native species of trees, crustacians and amphibians. The group representing the aquatic oomycetes are relatively understudied in contrast to their terrestrial counterparts that predominantly infect plants (e.g. Phytophthora, Pythium and Bremia spp.). This review focuses on the unique characteristics of two aquatic Oomycetes, Saprolegnia parasitica and Saprolegnia diclina with respect to their impact on aquaculture, animal health and the surrounding environment. The species characteristics, ecology, biology, infectivity and identification methods are described and the latest research insights are discussed.
Ecological studies of exotic species focus primarily on how invaders directly affect particular resident species. In contrast, little is known about the indirect effects of introduced species on native communities, including how pathogens may be spread by introduced species. We provide evidence suggesting that introduced fish may serve as a vector for a pathogenic oomycete, Saprolegnia ferax, that has been associated with embryonic mortality of amphibians in the Cascade Mountains of Oregon, U.S.A. In laboratory experiments, mortality induced by S. ferax was greater in western toad ( Bufo boreas) embryos exposed directly to hatchery-reared rainbow trout (Oncorhynchus mykiss) experimentally infected with S. ferax and hatchery-reared trout not experimentally infected than in control embryos. Embryos also developed significant S. ferax infections when raised on soil that was exposed to trout experimentally infected with S. ferax. Furthermore, toad embryos exposed to S. ferax isolated from sites where Saprolegnia outbreaks are common experienced higher mortality than embryos exposed to S. ferax isolated from sites where Saprolegnia outbreaks have not occurred. Given the widespread practice of introducing hatchery-reared fishes, we suggest that fish used in stocking programs could be an important vector for diseases responsible for amphibian losses.
Morphological variation in isolates assigned to Saprolegnia terrestris Cookson and to a new species, S. australis, is described. These species are separated from each other by the structure and mode of origin of their antheridial hyphae and from other species by their subcentric oospore. When single-spore isolates, one from each species, were grown on hemp seed in liquid media, differences in size of culture vessel, incubation temperature, and age of cultures, but not in the amount of hemp seed added, induced small but sometimes significant changes in the morthology of sex organs. However, induced differences were not of an order to separate isolates at the spccies level, nor did they cover a range as great as the differences among isolates from the same species. The size of oogonia and the corresponding number of oospheres per oogonium tended to increase with increase in incubation temperature and age of culture, and to decrease with an increase in size of culture vessel.
Aquatic fungi isolated from salmonid eggs incubated at six fishery stations in Japan belonged to the genera Saprolegnia, Achlya, Aphanomyces, Leptolegnia, and Pythium. The species diversity of the fungi varied according to the site studied.
Water moulds (oomycetes) of the order Saprolegniales, such as Saprolegnia and Aphanomyces species, are responsible for devastating infections on fish in aquaculture, fish farms and hobby fish tanks. Members of the genus Saprolegnia cause Saprolegniosis, a disease that is characterised by visible white or grey patches of filamentous mycelium on the body or fins of freshwater fish. Up till 2002, Saprolegnia infections in aquaculture were kept under control with malachite green, an organic dye that is very efficient at killing the pathogen. However, the use of malachite green has been banned worldwide due to its carcinogenic and toxicological effects and this has resulted in a dramatic re-emergence of Saprolegnia infections in aquaculture. As a consequence Saprolegnia parasitica is now, economically, a very important fish pathogen, especially on catfish, salmon and trout species, and warrants further investigation to develop new alternative control strategies.
A method of determining the number of phases of repeated zoospore emergence in vitro in the water mould Saprolegnia parasitica was developed. Using vortexing to encyst zoospores it was possible, in a synchronous manner, to achieve up to six consecutive generations of cysts and laterally biflagellated zoospores. It was found that the length of time the zoospores were allowed to swim influenced the number of zoospore generations which could be produced. After zoospore encystment the spores can be triggered to either germinate or release a new zoospore depending upon the addition of external nutrients. Germination of cysts could only be triggered within 45 min of mechanically induced encystment. Thus, it is now possible in this species to study in detail the two alternative developmental pathways which follow after encystment: either repeated zoospore emergence or germ tube formation.
The recently-developed statistical method known as the "bootstrap" can be used to place confidence intervals on phylogenies. It involves resampling points from one's own data, with replacement, to create a series of bootstrap samples of the same size as the original data. Each of these is analyzed, and the variation among the resulting estimates taken to indicate the size of the error involved in making estimates from the original data, In the case of phylogenies, it is argued that the proper method of resampling is to keep all of the original species while sampling characters with replacement, under the assumption that the characters have been independently drawn by the systematist and have evolved independently. Majority-rule consensus trees can be used to construct a phylogeny showing all of the inferred monophyletic groups that occurred in a majority of the bootstrap samples. If a group shows up 95% of the time or more, the evidence for it is taken to be statistically significant. Existing computer programs can be used to analyze different bootstrap samples by using weights on the characters, the weight of a character being how many times it was drawn in bootstrap sampling. When all characters are perfectly compatible, as envisioned by Hennig, bootstrap sampling becomes unnecessary; the bootstrap method would show significant evidence for a group if it is defined by three or more characters.
This study determines whether zoospores of two strains of the fish-pathogenic fungus Saprolegnia diclina are positively chemotactic toward concentration gradients of chorionic membrane extracts from live eggs of brook trout Salvelinus fontinalis, and seven amino acids and five simple sugars, under experimental conditions. Zoospores of both strains exhibited significant positive chemotaxis toward higher concentrations of chorionic membrane extracts, and arginine and alanine, but not toward the other amino acids or any of the sugars used in the assays. The results indicate that chemotaxis may have an important role in attracting zoospores of S. diclina toward live salmonid eggs. They also suggest that chemoattractants might be used in the development of strategies to control or eliminate saprolegniaceous infestations among salmonid eggs raised in hatcheries.
Fungal cultures attributed to the Saprolegnia parasitica-diclina complex isolated from diseased salmonids, diseased coarse fish and natural water samples, are compared critically. The two species concept is not sustained and only S. diclina Humphrey is conserved. This results in a more flexible framework for comparing isolates within this species and three groups are distinguished here, based on growth characteristics and length/breadth (L/B) ratio of the oogonium. Oospore size is also considered in this connection. In Windermere (English Lake District) only Saprolegnia diclina Type 1 (L/B ratio ≥2≥13%) occurs as a parasite on salmonid fish. Only S. diclina Type 2 (L/B ratio ≥2 ≤12%) occurs as a parasite on perch Perca fluviatilis L. Saprolegnia diclina Type 3 (L/B ratio ≥2≤10%) is purely saprophytic. An attempt is made to fit S. parasitica-diclina isolates from natural water samples into this scheme so that the potential infectivity for a particular kind of fish could be assessed.
Saprolegnia parasitica has caused large mortalities in brown trout, Salmo trutta, in Spain. Several strains of Saprolegnia parasitica have been isolated from these epizootics and characterized regarding their physiological adaptation and genetic diversity. These isolates exhibit similar physiological characteristics, i.e. radial growth, zoospore mobility and germination after encystment and differ substantially from other strains of the Saprolegnia diclina-parasitica complex tested. Random amplification of polymorphic DNA polymerase chain reaction (RAPD-PCR) of total DNA revealed a genetic similarity of about 85–100% between Spanish trout isolates whereas only 20–45% similarity to other strains of the Saprolegnia diclina-parasitica complex was found. The results suggest that the Spanish isolates are closely related strains and that they might have originated from one clone.
Physiological, epidemiological and genetical properties of an Aphanomyces astaci strain (Pc) isolated from the warm water crayfish, Procambarus clarkii, were compared to other A. astaci strains isolated from the cold water crayfish Astacus astacus, Astacus leptodactylus and Pacifastacus leniusculus. Morphology, virulence at 10 °C and several physiological characters were similar to the rest of A. astaci strains used for comparison. However, the strain Pc was able to grow faster and release zoospores at higher temperatures. This means that the Pc strain is virulent towards crayfish at higher temperatures than any previously investigated strains. The application of RAPD-PCR demonstrated that this isolate is genetically separated from all other described strains.
A detailed review of malachite green and its chemical and physical properties as they relate to fisheries interests. Many of the confusions and misconceptions about malachite green are discussed. Its mode of action, toxicity and fate are considered.
In germinating spores of the parasitic fungus, Aphanomyces astaci, chitinase was first demonstrated shortly before the germ-tube began to branch, in contrast to protease which was present in both ungerminated and germinated spores. The time at which chitinase would be required when this fungus penetrates the crayfish cuticle is correlated with that of the in vitro production of chitinase.
One hundred and fifty-seven isolates of Aphanomyces euteiches were collected for comparison of morphology and pathogenicity. Pea, alfalfa or snapbean were used as baits for 140 isolates, 17 were collected using other crop and weed species. Isolates were tested for pathogenicity to seedlings of pea, alfalfa, snapbean, red clover and sugarbeet, and disease severity was rated with the aid of a five-class scale (1–5). Half of the isolates caused disease severity < 1·5 on pea, most of which were less pathogenic on pea than reference isolates of A. cochlioides. Ninety-five per cent of the isolates caused disease severity > 2·5 on alfalfa. Five per cent of the isolates were weakly virulent to both pea and alfalfa, but were morphologically similar to A. euteiches. Only one isolate was observed in the collection which matched the description of A. euteiches f.sp. phaseoli, and two isolates were highly virulent to red clover. Somatic segregation for virulence was also observed among cultures recovered from single zoospores of a broad host-range isolate. Such cultures differed from the parent isolate in virulence to every host except alfalfa. A relationship was found between the cropping history of agricultural soils and host specialization of isolates baited from such soils. Only 20% of the isolates baited from alfalfa root-rot soils were virulent to both pea and alfalfa, whereas 80–100% of the isolates from pea root-rot soils, and pea/alfalfa root-rot soils were moderately to highly virulent to both hosts.
Oomycetes cause destructive diseases on both animals and plants. The epidemic spread of oomycete diseases is primarily based on rapid dispersal from host to host by free swimming zoospores. These single-nucleated spores are formed in sporangia and are only released in aqueous environments. Oomycetes are classified in the Kingdom of the Stramenopiles or Chromista, which is comprised of several organisms, including the golden brown algae. The unique shared attribute found in most Stramenopiles is the morphology of the zoospores and especially the structure of their two flagella. They have one tinsel flagellum, and one whiplash flagellum. Only the tinsel flagellum has distinctive flagellar hairs. Zoospore formation can occur within minutes and it is considered one of the fastest developmental processes in any biological system. Once released from the sporangium they are able to exhibit chemotactic responses, electrotaxis, and autotaxis or autoaggregation to target new hosts for infection. Here we discuss the latest discoveries in the development and biology of the oomycete zoospore.
Arbitrary primers and the DNA polymerase chain reaction (PCR) technique were applied to study genetic variation between different strains of the crayfish plague fungus, Aphanomyces astaci. Eight different primers among 15 tested were chosen for a comparative analysis of the different A. astaci strains. On average, each primer gave rise to 5–8 bands and a majority of the bands was polymorphic for at least some strains. Two main groups among the different Swedish isolates were clearly discernible. One group included isolates from the indigenous crayfish species Astacus astacus and one isolate from As. leptodactylus originating from Turkey. The other main group included fungal isolates from both As. astacus and the introduced North American crayfish Pacifastacus leniusculus. In this latter case it seems likely that the introduced American signal crayfish has served as a vector and transmitted the pathogen to the indigenous crayfish.
Worldwide declines in amphibian populations have been the subject of numerous recent reports, and numerous hypotheses have been constructed to address the causes. There is no evidence for a single cause for the declines. We identify and describe the spread of a pathogenic fungus that appears to be largely responsible for egg mortality in one population of western toad Bufo boreas. This is the first study documenting contemporary mortality in an amphibian population with identification of the attributed pathogenic species. The fungus we identify is circumglobally distributed and we suggest that this fungal infection could also be a major contributor to other amphibian populations declines.
Members of the oomycete genus Phytophthora are the most devastating pathogens of dicot plants. Recent developments in the study of these organisms have led to improved understanding of their phylogenetic relationships and trends in their evolution. Molecular analyses of nonhost (species-level) resistance offer exciting prospects for disease management. A model that evokes a complex interplay of several layers of specific resistance, mediated by a set of ancient broad-spectrum R-gene loci, is sufficient to explain existing cellular and molecular data on nonhost resistance to Phytophthora.