No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Fusarium Species Isolated from Soil Samples Collected at Different Altitudes in the Transkei, Southern Africa
Mycologia
Abstract
Fusarium species were isolated from soil samples and soil debris obtained at altitudes of 1400, 1100, 800, 500, 250, and 0 m in the Republic of Transkei. Nineteen species of Fusarium were isolated representing sections Eupionnotes, Sporotrichiella, Discolor, Gibbosum, Arthrosporiella, Liseola, Elegans, Martiella, and Lateritium. Fusarium oxysporum, F. equiseti, F. semitectum, F. nygamai, and F. solani were isolated most frequently and F. oxysporum was the predominant species isolated from all samples. Other species recovered were F. chlamydosporum, F. merismoides, F. lateritium, F. culmorum, F. compactum, F. dlamini, F. poae, F. proliferatum, F. moniliforme, F. graminearum, F. sambucinum, F. napiforme, and three unknown populations. Using Simpson's index, the diversity indices calculated for Fusarium species from debris and soil from each sampling site indicate that overall debris was a greater source of species diversity than soil. Diversity indices calculated for each altitude sample and each isolation technique showed that the sea level site yielded the most diverse population.
... Chi square for goodness of fit was used to compare the distribution of the species in water and air samples throughout the year. To determine which pond, station, environment and sample yielded the greatest diversity of species, Simpson's Index modified by Pielou was calculated (Krebs, 1989; Jeschke et al., 1990). This index measures the probability of selecting two individuals of the same species at random from a given population—greater values indicate lower diversity. ...
... Efficient mechanisms of dispersal (wind action or rain splash) are needed for the spread to diverse habitats (Snyder and Toussoun, 1965; Ooka and Kommedahl, 1977; Burgess, 1981). Another factor determining the distribution of Fusarium is the abundance of vegetation, because many species are associated with aerial and subterranean parts of plants (Burgess, 1981; Jeschke et al., 1990). The effect of rain and wind in the total CFU of Fusarium spp. was observed in both water and air samples. ...
... More CFU/ 500 ml of Fusarium spp. were found at pond 1 (the abundance of each species is higher), but species richness was the same for both ponds, i.e., the index of species diversity is higher at pond 2. Jeschke et al. (1990) speculated that greater vegetation diversity may support a greater diversity of Fusarium species, but their results, as well as ours, do not support this hypothesis. The more frequent species in water and 1977). ...
A mycological survey of Fusarium species was conducted in two rearing ponds for M. rosenbergii in SW Puerto Rico, from October 1989 to September 1990. Six species of Fusarium were identified: F. chlamydosporum, F. equiseti, F. moniliforme, F. semitectum, F. solani and F. subglutinans. The more frequent species in water and air samples were F. semitectum and F. equiseti. During the rainy season the total colony forming units (CFU) of Fusarium spp. decreased in air samples and increased in water samples. During months of higher wind velocity the total CFU increased in air samples. -from Authors
... At each location, four collection sites were selected to represent major variations in landscape, elevation, and vegetation. Samples were collected from the upper 10 cm of the soil profile (Mandeel 2006) with a 15 × 15 m transect method (Jeschke et al. 1990) in a north-south and east-west direction. Soil was collected at the ends of the perpendicular transects and at the intersecting point and pooled to form composite samples. ...
... This study reports on the prevalence and genetic diversity of FOSC members isolated from South African grassland soils with low anthropogenic disturbance. Previous South African Fusarium surveys focused primarily on species associated with plant debris from agricultural and native soils (Jeschke et al. 1990;Marasas et al. 1988;Rheeder and Marasas 1998). Indeed, very few habitats and ecological niches in South Africa have been explored in terms of their fungal biodiversity and taxonomy (Crous et al. 2006). ...
The genetic diversity of pathogenic members of the Fusarium oxysporum species complex (FOSC) has been intensively studied worldwide, yet strains occurring from native soils with low anthropogenic disturbance remain poorly understood. This study focused on 355 F. oxysporum isolates from soils with low anthropogenic activity obtained from the grassland biome of South Africa. Analysis of the translation elongation factor 1-alpha (tef-1α) gene revealed high levels of sequence type (ST) diversity within the soil population in comparison to the global dataset. Phylogenetic relationships of the South African isolates revealed that only four nested within FOSC Clade 1. This is the first report of members of the basal clade recovered from ecosystems with low anthropogenic disturbance from Sub-Saharan Africa. The remaining strains nested within Clades 2 to 5. This study contributes significantly to our understanding of the distribution of the FOSC in natural systems as we show that FOSC populations in the South African grassland biome are genetically diverse. This fills in our knowledge gap as previous studies reported only on the occurrence and diversity of the FOSC isolated from plant debris in South Africa. This is the first comprehensive survey of fusaria from grassland soils with low anthropogenic disturbance in South Africa.
... Moreover, F. oxysporum is considered a cosmopolitan species (Edel et al., 1997). Jeschke et al. (1990) showed F. oxysporum as the principal Fusarium species obtained from different altitudinal zones in Southern Africa. The high density of F. oxysporum in agricultural soils is a matter of study, because this fungus develops pathogenic and non-pathogenic isolates (Burgess, 1981). ...
... In our study, F. merismoides was obtained only from 5-10 cm soil layer from the rotation of winter agriculture in soil with limitations (III) and from 10-20 cm soil layer of the traditional mixed rotation with annual forage (IV). Jeschke et al. (1990) observed low frequency of F. merismoides in soil samples collected at different altitudes in Southern Africa. Leslie & Summerell (2006) suggested that F. merismoides is a fungal saprophyte of soil, but it has the potential to cause some plant diseases if the environmental conditions are appropriate. ...
The presence of Fusarium species in cultivated soils is commonly associated with plant debris and plant roots. Fusarium species are also soil saprophytes. The aim of this study was to examine the occurrence and distribution of soil Fusarium spp. at different soil depths in a zero tillage system after the wheat was harvested. Soil samples were obtained at three depths (0-5 cm, 5-10 cm and 10-20 cm) from five crop rotations: I, conservationist agriculture (wheat-sorghum-soybean); II, mixed agriculture/livestock with pastures, without using winter or summer forages (wheat-sorghum-soybean-canola-pastures); III, winter agriculture in depth limited soils (wheat-canola-barley-late soybean); IV, mixed with annual forage (wheat-oat/Vicia-sunflower); V, intensive agriculture (wheat-barley-canola, with alternation of soybean or late soybean). One hundred twenty two isolates of Fusarium were obtained and identified as F. equiseti, merismoides, F. oxysporum, F. scirpi and F. solani. The most prevalent species was F. oxysporum, which was observed in all sequences and depths. The Tukey's test showed that the relative frequency of F. oxysporum under intensive agricultural management was higher than in mixed traditional ones. The first 5 cm of soil showed statistically significant differences (p = 0.05) with respect to 5-10 cm and 10-20 cm depths. The ANOVA test for the relative frequency of the other species as F. equiseti, F. merismoides, F scirpi and F solani, did not show statistically significant differences (p <= 0.05). We did not find significant differences (p <= 0.05) in the effect of crop rotations and depth on Shannon, Simpson indexes and species richness. Therefore we conclude that the different sequences and the sampling depth did not affect the alpha diversity of Fusarium community in this system.
... Moreover, F. oxysporum is considered a cosmopolitan species (Edel et al., 1997). Jeschke et al. (1990) showed F. oxysporum as the principal Fusarium species obtained from different altitudinal zones in Southern Africa. The high density of F. oxysporum in agricultural soils is a matter of study, because this fungus develops pathogenic and non-pathogenic isolates (Burgess, 1981). ...
... In our study, F. merismoides was obtained only from 5-10 cm soil layer from the rotation of winter agriculture in soil with limitations (III) and from 10-20 cm soil layer of the traditional mixed rotation with annual forage (IV). Jeschke et al. (1990) observed low frequency of F. merismoides in soil samples collected at different altitudes in Southern Africa. Leslie & Summerell (2006) suggested that F. merismoides is a fungal saprophyte of soil, but it has the potential to cause some plant diseases if the environmental conditions are appropriate. ...
... Moreover, specific species have been observed to inhabit desert, alpine, and arctic regions, thereby subjecting themselves to adverse climatic circumstances (Francis & Burgess, 1975). Jeschke et al. (1990) reported a significant discrepancy in the geographic spread of Fusarium species, wherein a greater occurrence was observed in agriculturally productive cultivated and rangeland soils compared to forest soils. Fusarium species are commonly recognized as fungi that predominantly inhabit soil, frequently in conjunction with plant roots, and exhibit parasitic or saprophytic lifestyles (Nelson et al., 1994). ...
Tomato (Lycopersicon esculentum), a widely cultivated vegetable rich in vitamins, minerals, and health-promoting antioxidants like lycopene and vitamin C, faces significant production challenges. Among these, Fusarium wilt, caused by the soilborne fungus Fusarium oxysporum f.sp. lycopersici (FOL), is a prevalent and destructive disease in tomato-growing regions worldwide. FOL, a highly damaging ascomycete fungus, poses a serious threat alongside the large populations of nonpathogenic F. oxysporum (NPF) residing in various ecological niches. The disease manifests initially with yellowing of lower leaves, followed by progressive wilting. FOL invades the tomato plant, colonizing the vascular tissue and causing its discoloration to a dark brown hue. This discoloration extends upwards, ultimately leading to wilting, collapse, and plant death. The wilting syndrome is attributed to a complex interplay of factors induced by the fungus, including xylem blockage by fungal mycelia, production of mycotoxins, suppression of host defense mechanisms, and formation of tyloses (cellular outgrowths).. Managing Fusarium wilt is challenging due to the extended survival of the pathogen and its existence in diverse pathogenic races. Conventional approaches, such as deployment of resistant cultivars and application of synthetic fungicides have shown limited efficacy. Additionally, the potential environmental hazards associated with fungicides necessitate a cautious approach. This review explores the use of both chemical and biological control agents in Fusarium wilt management, acknowledging the limitations of single-method strategies. To achieve sustainable and environmentally friendly disease control, an integrated approach is recommended. This review aims to equip farmers with a diverse toolbox of management methods that can be combined into a comprehensive package to combat Fusarium wilt and related soil borne diseases.
... F. lateritium occurs in soil worldwide [14] and has been reported in soil samples from different altitudes in the Transkei, Southern Africa [46], soil planted with millet and sorghum from Lesotho, Nigeria, and Zimbabwe [47], and from and in desert zones of Dead Sea Valley [48]. ...
Fusarium genus comprises important saprophytic and phytopathogenic fungi and is widespread in nature. The present study reports the occurrence of Fusarium spp. in soils from two mangrove forests in northern Peninsular Malaysia and analyzed physico-chemical properties of the mangrove soil. Based on TEF-1α sequences, nine Fusarium species were identified: Fusarium solani species complex (FSSC) (n = 77), Fusarium verticillioides (n = 20), Fusarium incarnatum (n = 10), Fusarium proliferatum (n = 7), Fusarium lateritium (n = 4), Fusarium oxysporum (n = 3), Fusarium rigidiuscula (n = 2), Fusarium chlamydosporum (n = 1), and Fusarium camptoceras (n = 1); FSSC isolates were the most prevalent. Phylogenetic analysis of the combined TEF-1α and ITS sequences revealed diverse phylogenetic affinities among the FSSC isolates and potentially new phylogenetic clades of FSSC. Soil analysis showed varied carbon content, pH, soil moisture, and salinity, but not nitrogen content, between sampling locations. Regardless of the physico-chemical properties, various Fusarium species were recovered from the mangrove soils. These were likely saprophytes; however, some were well-known plant pathogens and opportunistic human pathogens. Thus, mangrove soils might serve as inoculum sources for plant and human pathogenic Fusarium species. The present study demonstrates the occurrence of various Fusarium species in the extreme environment of mangrove soil, thereby contributing to the knowledge on species diversity in Fusarium.
... Similarly, the proportion of Fusarium in rhizosphere fungi in cotton flowering stage was as high as 11.48%. It had previously been observed that, in many cases, Fusarium was abundant in both the soil environment [43,44] and endophytically [45][46][47][48]. ...
This study aimed to investigate the fungal diversity and its temporal and spatial dynamics in the rhizosphere soil of healthy cotton by high-throughput sequencing. We studied species richness, composition, and distribution of cotton rhizosphere fungal community with respect to location (Alaer, Kuerle, Tumushuke, Hami, Shihezi, Wusu, and Jinghe) and plant growth period (seedling stage, bud stage, flowering stage, and boll-opening stage) using the methods of PCR-based high-throughput sequencing and real-time quantitative PCR. A total of 1,838,454 fungal nuclear ribosomal internal transcribed spacer region sequences (rRNA ITS) were obtained from all cotton plants sampled at different growth stages in the seven locations in Xinjiang. The most abundant fungal group in the cotton rhizosphere was the Ascomycota (78.72%), followed by the Zygomycota (9.56%) and Basidiomycota (2.77%). These sequences revealed an enormous number of operational taxonomic units (OTUs) in cotton (1802 unique OTUs), with 67–464 OTUs in a single cotton sample, at a 3% threshold and a sequencing depth of 30,000 sequences. We identified 33 classes and 389 genera from the resulting 1,800,714 sequences. Sordariomycetes was the most frequent class in all samples, followed by Leotiomycetes and Eurotiomycetes. There were some differences in OTUs among different growth stages, but the differences were not significant, with 382 OTUs (14.66%) being common to each of the stages. A marked difference in the diversity of fungi in the rhizosphere soil of cotton was evident among the different locations, with the highest number of OTUs being detected in Jinghe (1084 OTUs) and clusters of OTUs representative of northern and eastern Xinjiang being detected. There were significantly more tags of Mortierella in Jinghe and Wusu than in the other sampling sites. The dynamics of the rhizosphere fungal communities were influenced by sampling sites. To the best of our knowledge, the current study is the first application of PCR-based Illumina to characterize and compare the fungal biodiversity in multiple rhizosphere soil samples from cotton.
... Within the genus the following 16 sections have been recognized: Eupionnotes, Macroconia, Spirarioides, Submicrocera, Pseudomicrocera, Arachnites, Sporotrichiella, Roseum, Arthrosporiella, Gibbosum, Discolor, Lateritium, Liseola, Elegans, Martiella, and Ventricosum. However, many Fusarium species are abundant in fertile cultivated and rangeland soils rather than in forest soils [3]. Fusarium species are causal agents of various diseases affecting many economically important cereals, crops, etc. Airborne Fusarium species are rarely found in the cultures obtained from soil or the roots of plants. ...
... Although the level of recovery of Fusarium isolates varied little across the collection sites, the incidence of the species recorded was not equally important at all locations. These results are consistent with those obtained by Jeschke et al. (1990) following a study associated with Fusarium spp. in the Transkei region of South Africa. They reported a differential incidence in the occurrence of the Fusarium spp. that they isolated, suggesting for example that F. oxysporum was more abundant where F. equiseti had a low level of occurrence. ...
Cassava chips are transformed products obtained following the fermentation and drying of cassava fresh roots. Once produced, chips can be stored for more than 180 days in conditions conducive for the development of toxigenic moulds. In this study, the incidence of Fusarium spp. is assessed from a set of 72 home-stored samples of cassava chips collected from farmers, during a 2-month monitoring survey period. Results from this survey enabled the recovery of 298 isolates of Fusarium spp. The Fusarium taxa detected included: Fusarium chlamydosporum, Fusarium equiseti, Fusarium verticillioides, Fusarium oxysporum, Fusarium pallidoroseum and Fusarium solani. F. oxysporum was associated with the highest level of isolation frequency (25%), whereas F. solani isolated was scanty (5%). Their level of recovery was increasingly important as the moisture content of samples increased and/or the product was stored for longer periods. Specific associations were observed to exist between the most frequently isolated Fusarium spp. The level of fumonisins further assessed showed that only 5 samples hosted this mycotoxin at concentration levels ranging between 0.22 and 1.7 mg/kg. Among the parameters used to assess its incidence, only storage duration showed significant (P<0.05) relationships with fumonisins. The occurrence of fumonisins as natural contaminants of cassava-based products is reported here for the first time. This study shows that no known fumonisin producing-Fusarium species was related to toxin occurrence in the samples collected. It can be hypothesized that any species of Fusarium infesting the samples studied could have the potential capability of producing the toxin as a result of a possible horizontal transfer of functional fumonisin gene clusters from an ancestral gene. Consequently, the present study suggests both investigations on genes responsible for plausible fumonisin formation associated with the Fusarium spp. identified from the samples collected as well as the various factors allowing their expression.
... The hills and mountains are characterised by grasslands, as well as sporadic forests. This region experiences a sub-humid climatic conditions, with a summer dominant rainfall (Jeschke et al., 1990). The area receives an average annual rainfall ranging from 500 mm to 1400 mm (Madikizela, 2000). ...
Soil erosion is increasingly recognised as the principal cause of land degradation, loss of agricultural land area and siltation of surrounding water waterbodies. Accurate and up-to-date soil erosion mapping is key in understanding its severity if these negative impacts are to be minimised and affected areas rehabilitated. The aim of this work was to investigate map the severity of soil erosion, based on the 30-m Landsat series multispectral satellite data in the former South African homelands of Transkei between the year 1994 and 2010. Further, the study assessed if the observed soil erosion trends and morphology that existed in this area could be explained by biophysical factors (i.e. slope, stream erosivity, topographic wetness index) retrieved from the 30-m ASTER Digital Elevation Model (DEM). The results of this study indicate that the Transkei region experience varying erosion levels from moderate to very `severe. The large portion of the land area under the former homelands was largely affected by rill erosion with approximately 74% occurring in the year 1984 and 54% in 2010. The results also revealed specific thresholds of soil erosion drivers. These include steeper areas (≥30°), high stream power index greater than 2.0 (stream erosivity), relatively lower vegetation cover (≤15%) and low topographic wetness index (≤5%). The results of this work demonstrate the severity of soil erosion in the Southern African former homelands of Transkei for the year 1984 and 2010. Additionally, this work has demonstrated the significance of the 30-m Landsat multispectral sensor in examining soil erosion occurrence at a regional scale where in depth field work still remain a challenging task.
... They are found in desert, alpine, and arctic areas, where harsh climatic conditions prevail (Nelson et al., 1994). Many Fusarium species are abundant in fertile cultivated and rangeland soils but are relatively uncommon in forest soils (Jeschke et al., 1990). Fusarium species are often regarded as soil-borne fungi because of their abundance in soil and their frequent association with plant roots, as either parasites or saprophytes. ...
... Most of these studies focussed on 253 economically important genera, but the vast majority of fungi are 254 not pathogenic, and only a few studies have focussed on the fungal 255 communities in soils (Scott, 1968;Eicker, 1969Eicker, , 1970Eicker, , 1973Eicker, , 1976256 Papendorf, 1976;Eicker et al., 1982;Lundquist and Baxter, 1985; 257 Lundquist 1986Lundquist , 1987Visagie et al., 2009Visagie et al., , 2013Visagie et al., , 2014Visagie et al., , 2015a 258 Spruyt et al., 2014). 259 The main representative sample for a particular site (Jeschne et al., 1990;286 Zeller et al., 2003). In the case of taxonomic studies, point samples 287 are usually more than sufficient to provide adequate material for 288 study. ...
... Some species of Fusarium are restricted to the tropics, some are predominant in the temperate zones, while others are found in desert, alpine, and arctic areas, where harsh climatic conditions prevail (Francis and Burgess, 1975). Many Fusarium species are abundant in fertile cultivated and rangeland soils but are relatively uncommon in forest soils (Jeschke et al., 1990). Fusarium species are often regarded as soil-borne fungi because of their abundance in soil and their frequent association with plant roots, as either parasites or saprophytes (Nelson et al., 1994). ...
Fusarium species are soil borne vascular wilt pathogens, which are among the most important phytopathogenic and toxigenic fungi. They are filamentous and belong to the Class Ascomycetes and Family Hypocreaceae. Fusarium species typically produce macroconidia and microconidia, as well as mycelia and chlamydospores that serve as propagules in infecting host plants. The life cycle can be divided into dormant, parasitic and saprophytic stages. Most species are harmless saprobes; some species are parasitic, with some producing mycotoxins on plants. The pathogenic strains have high level of host specificity which has led to the development of the "formae specialis" concept. Each formae specialis can be further sub divided into races, on the basis of virulence in a set of differential cultivars within the same plant species. Fusarium wilt is a major concern in agriculture as it causes great economical losses in a wide variety of crops. The symptoms of Fusarium wilt range from stunted growth, yellowing and wilting of the leaves, reddish discolouration of the xylem vessels (visible inside the stem as lines or dots in cross section) and white, pink or orange fungal growth on the outside of affected stems (particularly in wet conditions), to root or stem decay. There is remarkably little knowledge available about the molecular mechanism and/or pathogenicity genes required by Fusarium species to cause disease and how hosts combat or tolerate the pathogen. The genomes of some Fusarium species have been sequenced and comparative genomic analyses have shown that pathogenic Fusarium species consist of a larger number of proteins in the pathogenicity related protein families such as transcription factors, hydrolytic enzymes, and transmembrane transporters which play significant roles in pathogenicity, compared to non pathogenic species. In general, the disease is difficult to control, as physical,chemical and cultural methods of control are not only ineffective but also expensive. The best method of control is breeding for resistant cultivars. Also, rhizosphere fungi such as Trichoderma harzianum, T. asperellum, T. koningii, Penicillium spp. and Streptomyces griseoviridis have been used to control the disease. This present review gives a general overview of some common Fusarium wilts.
... Although the level of recovery of Fusarium isolates varied little across the collection sites, the incidence of the species recorded was not equally important at all locations. These results are consistent with those obtained by Jeschke et al. (1990) following a study associated with Fusarium spp. in the Transkei region of South Africa. They reported a differential incidence in the occurrence of the Fusarium spp. that they isolated, suggesting for example that F. oxysporum was more abundant where F. equiseti had a low level of occurrence. ...
... The climate changes gradually from the coast to the westerly plateau. On the other hand, the greater part of the Transkei is characterised by a sub-humid warm climate with summer-dominant rainfall (Jeschke et al., 1990). Annual rainfall varies between 500 and 1400 mm, with a mean temperature of 20 • C (Madikizela, 2000). ...
Erosion on roadcuts is a concern due to the potential of causing environmental
degradation, which has significant economic costs. It is therefore critical
to understand the relationship between roadcut characteristics and soil
erosion for designing roadcuts that are less vulnerable to erosion and to
help road rehabilitation works. This study investigated the characteristics
(i.e. gradient, length, percentage of vegetation cover and soil texture) of
degraded (i.e. with rills) and non-degraded roadcuts (i.e. without rills)
and explored the relationship of the roadcut characteristics with the
dimensions (widths and depths) of the rills. Degraded roadcuts were steep
(52.21°), long (10.70 m) and had a low percentage of vegetation
cover (24.12) when compared to non-degraded roadcuts which had a gradient of
28.24°, length of 6.38 m and 91.7% of vegetation cover.
Moreover, the gradient and percentage of vegetation cover of the roadcut
significantly determine the rill dimensions. The widths and depths of the
rills increase with the increase in slope gradient and decrease with an
increase in percentage of vegetation cover. Moreover, the widths and
depths of the rills decreased downslope of the roadcuts. Based on these
results, re-vegetation of roadcuts as well as construction of gentle
gradients could minimise rill erosion and hence the negative on-site and
off-site effects.
... characterized by a sub-humid warm climate with summer dominant rainfall (Jeschke et al. 1990). Rainfall patterns fluctuate between 750 and 1400 mm in the coastal areas and 500 and 1400 mm in the interior (Madikizela 2000). ...
The increased demand and abstraction of groundwater resources is a cause for concern in sub-Saharan Africa. Timely mapping and monitoring of the quantity and annual abstraction levels of groundwater resources are critical if sustainable groundwater resources management is to be fully achieved. Conventionally, groundwater mapping has been conducted based on field surveys that depend on geomorphic interpretation expertise and ancillary data analysis. Considering that these methods are costly, laborious and time-consuming makes remote sensing a better alternative for mapping groundwater resources, given the imminent need of knowledge on the status of this resource. It is therefore essential to adopt methods that would provide timely and spatially explicit information on the distribution and magnitude of groundwater for informed and restoration strategies, particularly in resource constrained Africa. This study, therefore, sought to review literature on the use of remote sensing in monitoring groundwater across sub-Saharan Africa.
... This area is characterised by undulating terrain that consists of a series of dissected steps that rise from a relatively flat coastal plain in the east of South Africa, to the Drakensberg mountains which are approximately over 3000 m above sea level (Beckedahl 1996). The south-eastern part of South Africa is characterized by a sub-humid warm climate with summer dominant rainfall (Jeschke et al. 1990). Rainfall patterns fluctuate between 750 and 1400 mm in the coastal areas and 500 and 1400 mm in the interior (Madikizela 2000). ...
An assessment of gully erosion along road drainage-release sites is critical for understanding the contribution of roads to soil loss and for informed land management practices. Considering that road-related gully erosion has traditionally been measured using field methods that are expensive, tedious and limited spatially as well as temporally, it is important to identify affordable, timely and robust methods that can be used to effectively map and estimate the volume of gullies along the road networks. In this study, gullies along major roads were identified from remotely sensed datasets and their volumes were estimated in a Geographic Information Systems environment. Also, the biophysical and climatic factors such as vegetation cover, the road contributing surface area, the gradient of the discharge hillslope and rainfall were derived from remotely sensed datasets using Geographic Information Systems techniques to find out if they could explain the morphology of gullies that existed in this area. The results of this study indicate that hillslope gradient (R2 = 0.69, α = 0.00) and road contributing surface area (R2 = 0.63, α = 0.00) have a strong influence on the volume of gullies along the major roads in the south-eastern region of South Africa, as might have been expected. However, other factors such as vegetation cover (R2 =0.52 α = 0.00) and rainfall (R2=0.41 and α = 0.58) have a moderately weaker influence on the overall volume of gullies. Overall, the findings of this study highlight the importance of using remote sensing and Geographic Information Systems technologies in investigating gully erosion occurrence along major roads where detailed field work remains a challenge.
... The climate changes gradually from the coast to the westerly plateau. On the other hand, the greater part of the Transkei is characterised by a sub-humid warm climate with summer dominant rainfall (Jeschke et al., 1990). Annual rainfall varies between 500 and 1400 mm, with mean temperatures of 20 • (Madik- 20 izela, 2000). ...
Erosion on roadcuts is a concern due to potential to cause environmental degradation which has significant economic costs. It is therefore critical to understand the relationship between roadcut characteristics and soil erosion for designing roadcuts that are less vulnerable to erosion and to help road rehabilitation works. This study investigated the characteristics (i.e. gradient, length and percentage of vegetation cover) of degraded (i.e. with rills) and non-degraded roadcuts (i.e. without rills) and explored the relationship of the roadcut characteristics with the dimensions (widths and depths) of the rills. Degraded roadcuts were steep (52.21°), long (10.70 m), and had a low percentage of vegetation cover (24.12) when compared to non-degraded roadcuts which had a gradient of 28.24°, length of 6.38 m and 91.7% of vegetation cover. Moreover, the gradient and percentage of vegetation cover of the roadcuts significantly determined the rill dimensions. The widths and depths of the rills increased with the increase in slope gradient and decreased with an increase in percentage of the vegetation cover. Moreover, the widths and depths of the rills decreased downslope of the roadcuts. Based on these results, re-vegetation of roadcuts as well as construction of gentle gradients could minimise rill erosion and hence the negative onsite and offsite effects.
... Fusarium nygamai Burgess and Trimboli is distributed widely in Australia (3,4) and several countries in southern Africa (12,17,19). It is usually found in or on soil, where it exists as a colonizer of living plant parts or plant debris in field soils (3,4,6,7,8,12,20). This fungus is also associated with millet (14,18) and sorghum (19) grains. ...
Isolates of Fusarium nygamai were mated and produced fertile perithecia of Gibberella nygamai sp. nov., on carrot agar. Female-fertile tester strains were recovered from random ascospore progeny and two were identified as more reliable female parents in the detection of other members of this population. The formation of microconidia in short chains and the formation of chlamydospores in anamorph progeny cultures are suitable characters for species identification of F. nypamai. Fusarium nygamai is predominantly soilborne.
... are usually isolated from soil, where they are saprophytic, but they also infect economically important plants such as wheat, rye, oat, barley, triticale, maize and potatoes. [8] Another important issue is the asymptomatic colonization of plants, during which the fungus retrieves nutrients necessary for its growth directly from the host tissues. Endophytic form of the pathogen is entirely hidden in the host organism, only after some time its presence is manifested by the decline in plant growth, followed by wilt, chlorosis and premature plant dieback. ...
This study aimed to determine the susceptibility of Fusarium spp. strains isolated from cereals to selected heavy metals, fungicides and silver nanoparticles. The experiments were conducted using 50 Fusarium strains belonging to five species: F. graminearum, F. culmorum, F. oxysporum, F. sporotrichioides and F. avenaceum. The strains were found to be highly resistant to Pb2+ and Zn2+. Medium resistance to Cu2+ and Mn2+ and low resistance to Cd2+ and Fe3+ was also observed. Among the tested fungicides, formulations containing azoxystrobin, prochloraz and tebuconazole proved to be the most effective in inhibiting the growth of fungi, as they affected fungal growth in each of the applied doses. Susceptibility of Fusarium spp. to nanosilver, demonstrated in this study, shows the legitimacy of using nanostructures as fungicidal agents. The results confirm high diversity of the analyzed fungal species in terms of susceptibility to the tested substances, and encourage to continue research on the resistance of Fusarium spp. to various fungicidal agents.
... They are commonly found in soils, and persist as chlamydospores or as hyphae in plant residues and organic matter (Burgess, 1981). However, many Fusarium species are abundant in fertile cultivated and rangeland soils, rather than in forest soils (Burgess et al., 1988;Jeschke et al., 1990). Keeping in view, the importance of root rot of okra and the losses it causes, this research study was designed to find out the variability in growth rate of different isolates of Fusarium solani in district Peshawar. ...
Fusarium solani is a phytopathogenic fungus and is an important causal agent of several crop diseases, such as root and fruit rot of Cucurbita spp., root and stem rot of pea, root rot of okra. The objective of current research was to determine the growth rate of different isolates of Fusarium solani, the cause of root rot of okra, in Peshawar. Five isolates of Fusarium solani collected from five different places and were investigated for growth rate of the colonies. Highest colony growth rate (86.3 mm) was recorded for isolate collected from Achini payan and lowest (60 mm) for isolate collected from Palosi. Under In vitro.
... obecnoae kajakowato-lub bananowato-kszta³tnych zarodników konidialnych [43]. Zgodnie z najnowsz¹ systematyk¹ [43] grzyby z rodzaju Fusarium zosta³y zaliczone do: Gromady: Eumycota Grzyby w³aciwe Podgromady: Fungi imperfecti Grzyby niedoskona³e Klasy: Hyphomycetes Strzêpczaki Rzêdu: Moniliades Moniliowce Rodziny: Tuberculariaceae Gruze³kowate Grzyby z rodzaju Fusarium s¹ szeroko rozpowszechnione w glebie, szczególnie zasiedlaj¹ ¿yzne, urodzajne gleby, za stosunkowo rzadko lene [33]. Mog¹ rozwijaae siê równie¿ na ró¿nych czêciach rolin, resztkach rolinnych i innych zwi¹zkach organicznych [12]. ...
Fungi belonging to the genus Fusarium are recognized as one of the most dangerous pathogens causing serious plant, human and animal diseases. In addition, they are able to produce very toxic compounds knows as mycotoxins. Mycotoxins have various toxic effects on microorganisms, plants, animals and humans. The most common mycotoxins found in the natural environment are zearalenone and trochothecenes, including deoxynivalenol. These compounds cause disorders and deformations during plant growth. They also cause human and animal diseases connected with digestive, reproductive and immune system. Lots of genes are recognized in the biosynthesis of these mycotoxins. Essential genes in trichothecenes synthesis are Tri5 and Tri7 genes, and in zearalenone synthesis another two genes PKS4 and PKS14. Molecular methods based on PCR allow to evaluation of mycotoxicity of filamentous fungi. The easiest and most frequently used method is SCAR. Other molecular analyses like RT-PCR and Real-Time PCR are very expensive methods but are also very sensitive and less and less labour-intensive and thus are used in this kind of tests as well.
1. Introduction. 2. Characterization of Fusarium genus. 2.1. Morfology. 2.2. Characterization of important Fusarium species. 2.2.1. Fusarium culmorum. 2.2.2. Fusarium graminearum. 2.2.3. Fusarium poae. 2.3. Diseases caused by Fusarium sp. 3. Mycotoxins. 4. Fusarium mycotoxins. 4.1. Beauvericins, moniliformin, fumonisins. 4.2. Zearalenone. 4.3. Trichothecenes. 4.3.1 Type B trichothecenes. 4.3.2. Type A trichothecenes. 5. Occurence of fusarium mycotoxins worldwide and in Poland. 6. The most important factors involved in mycotoxins synthesis. 7. Genes involved in the biosynthesis of zearalenone and trichothecenes. 7.1. Characterization of Tri5, Tri7, Tr3 and Tri13. 7.2. Characterization of PKS4 and PKS13. 8. Molecular methods. 8.1. Detection and identification methods based on PCR. 8.1.1 SCAR. 8.1.2. RT-PCR. 8.1.3. Real-Time PCR. 9. Summary
... There are some Fusarium species which appear to be limited in certain climatic region while some species were not influenced by climatic factor Summerell et al. 1993). F. compactum had only been recovered in warmer areas while F. solani and F. oxysporum can be found in all climatic regions, and these two species are commonly found in the soil Kommedahl et al. 1988;Jeschke et al. 1990;Leslie et al. 1990). Sangalang et al. (1995b) also reported that climate contributes to the distribution of many Fusarium species but the mechanism is unknown. ...
Fusarium is a cosmopolitan and highly diversified genus of saprophytic, phytopathogenic and toxigenic fungi. However, the existence and diversity of a few species of Fusarium are restricted to a certain area or climatic condition. The present study was conducted to determine the occurrence and diversity of Fusarium species in tropical highland areas in Malaysia and to compare with those in temperate and subtropical regions. A series of sampling was carried out in 2005 to 2009 at several tropical highland areas in Malaysia that is: Cameron Highlands, Fraser Hills and Genting Highlands in Pahang; Penang Hill in Penang; Gunung Jerai in Kedah; Kundasang and Kinabalu Park in Sabah; Kubah National Park and Begunan Hill in Sarawak. Sampling was done randomly from various hosts and substrates. Isolation of Fusarium isolates was done by using pentachloronitrobenzene (PCNB) agar and 1449 isolates of Fusarium were successfully recovered. Based on morphological characteristics, 20 species of Fusarium were identified. The most prevalent species occurring on the highlands areas was F. solani (66.1%) followed by F. graminearum (8.5%), F. oxysporum (7.8%), F. semitectum (5.7%), F. subglutinans (3.5%) and F. proliferatum (3.4%). Other Fusarium species, namely F. avenaceum, F. camptoceras, F. chlamydosporum, F. compactum, F. crookwellense, F. culmorum, F. decemcellulare, F. equiseti, F. nygamai, F. poae, F. proliferatum, F. sacchari, F. sporotrichioides, F. sterilihyphosum and F. verticillioides accounted for 1% recoveries. The present study was the first report on the occurrences of Fusarium species on highland areas in Malaysia.
... The distribution of F. solani is cosmopolitan, and it can be found in native soils worldwide (Joffe & Palti 1977;Marasas et al. 1988;Leslie et al. 1990;Jeschke et al. 1990;Burgess & Summerell 1992). Therefore, it is not surprising that F. solani was the most prevalent species recovered from the mangrove soil samples. ...
A total of 33 isolates of Fusarium sp. were isolated from soil samples collected from a mangrove forest in an area in Kampung Pantai Acheh, Balik Pulau, Pulau Pinang, Malaysia. The isolates were isolated using soil dilution, direct isolation and debris isolation techniques. The debris isolation technique yielded the most isolates, with a total of 22 Fusarium isolates. Based on identification using morphological characteristics, three Fusarium species were identified: F. solani, F. oxysporum and F. verticillioides. F. solani (91%) was the most common species recovered from the mangrove soil samples, followed by F. oxysporum (6%) and F. verticillioides (3%).
... Fusarium acuminatum Ellis & Everh., was restricted to the temperate locations of southern and south-eastern parts of Australia . Several authors have also suggested that the composition of communities of Fusarium species in soil vary along climatic gradients (Jeschke et al. 1990; Burgess and Summerell 1992). Investigating the distribution pattern of Fusarium species between regions is an important process which can provide useful information of the species growth conditions (Burgess 1981). ...
Understanding the distribution pattern of the Fusarium species can help prevent crop diseases and large yield losses. While several approaches have been used to control soil-borne pathogens, soil solarisation has shown promising results in managing these pathogens. The main objectives of this study were to: (i) describe the biogeography of Fusarium species in four different climatic zones in Iran and (ii) explain the effect of soil solarisation on main pathogenic Fusarium species in wheat grains, beans and date palms. A total of 12 sub-samples were collected from four different climatic zones including, Rasht (humid), Zanjan (semi-arid), Isfahan (extra-arid) and Ahwaz (arid). For precise identification, molecular-phylogenetic analyses of the species were also performed. From these four sites 17 Fusarium species were recovered. F. solani complex, F. oxysporum and F. equiseti were the only species found in all four regions; whereas F. compactum, F. sambucinum and F. fujikuroi were restricted to Ahwaz, Zanjan and Rasht, respectively. Furthermore, soil solarisation treatments were applied to F. pseudograminearum, F. solani and F. oxysporum, as the main cause of root rot pathogens and wilt disease of wheat, bean and date palm, respectively. After 6 weeks of soil solarisation application, the population densities of these species were decreased from 900 to 100 CFU g−1 in F. solani, from 600 to 50 CFU g−1 in F. oxysporum and from 550 to 0 CFU g−1 in F. pseudograminearum showing a promising result in controlling soil-borne pathogens. Mycogeography of Fusarium species and the effect of soil solarisation can help improve the management control strategies of these soil-borne fungi.
... agar (PDA; Himedia, Mumbai, India) and Czapek Dox agar (Himedia) and further purified by single-spore culture through serial dilutions (Choi et al. 1999). Fusarium was isolated from soils following the method of Jeschke et al. (1990). Three 5-mm-diameter discs were cut from cultures of each isolate grown on PDA using a sterile cork borer and inoculated aseptically into conical flasks containing 100 ml of potato dextrose broth (PDB) and incubated at 28 AE 2°C with shaking at 120 rpm. ...
Sissoo (Dalbergia sissoo), commonly known as shisham, is amongst the finest woods of South Asia, but ‘wilt’ disease has caused a rapid decline in this species. The cause of the disease remains uncertain. The aim of this study is to identify the causal agent of the disease and characterize isolates made from diseased trees, based on genomic data and variations in virulence. Samples of infected roots, stems and of the ooze exuded from infected trees were obtained from plants showing symptoms in different geographical regions of India for the isolation of microorganisms. Isolates were used to inoculate healthy plants. Based on morphological characteristics, genus- and species-specific PCR, and in silico analysis of 5.8S rDNA-ITS regions, out of 38 fungal isolates, 24 and 14 were identified as Fusarium solani and Fusarium sp., respectively. In a pathotyping study, eighteen F. solani isolates, isolated from roots and stem parts of symptomatic plants, induced typical wilt symptoms when inoculated through soil and roots on D. sissoo seedlings of 1 - 15 months in age. The population of F. solani was highest in infected roots and the lower parts of stems, gradually decreasing with height and was isolated constantly up to approximately 40% height of the seedling. F. solani isolates used in inoculations were successfully re-isolated from the rhizosphere, infected roots and wilted stems, as confirmed using isolate specific DNA fingerprints. Molecular phylogenies based on rDNA-ITS sequences showed that the 38 isolates fell into 2 groups. Group I comprised F. solani isolates from D. sissoo, and F. solani sequences in the NCBI GenBank database, whereas group II included Fusarium isolates other than F. solani. These results are helpful in developing integrated control measures for this highly variable pathogen and to establish a base for future population studies.
... ESTUDIO PRELIMINAR DE LA PRESENCIA DE ESPECIES DE FUSARIUM et al., 1988; JESCHKE et al., 1990; TELLO et al., 1990b; BACKHOUSE y BURGES, 1995; BACKHOUSE et al., 2001) En las muestras tomadas en la desembocadura del río Albuñol se aislaron F. oxysporum y F solani a 4,5 y 1,5 m de profundidad, F. moniliforme y F. proliferatum a 4,5 m de profundidad y F. equiseti a 1,5 m de profundidad. Ambas situaciones de muestreo están próximas a zonas antrópicas con gran e intensa actividad agrícola, donde los vientos marinos son frecuentes y fuertes. ...
En este trabajo se presenta los resultados analíticos preliminares para el género Fusarium de muestras de aguas litorales del mar Mediterráneo y de aguas del cauce del río Andarax en las provincias de Granada y Almería (Sureste de España).
Un total de 18 muestras de agua del río Andarax fueron analizadas. De ellas se aislaron 10 especies de Fusarium: F. anthophilum, F. acuminatum, F. chlamydosporum, F. culmorum, F. equiseti, F. moniliforme, F. oxysporum, F. proliferatum, F. solani y F. sambucinum. De las 33 muestras de aguas del mar Mediterráneo se aislaron 5 especies: F. equiseti, F. moniliforme, F. oxysporum, F. proliferatum y F. solani. Sobre el total de
muestras analizadas, un 27,45% de las muestras de aguas del río y un 29,41% de muestras de agua marina presentaron como mínimo una especie de Fusarium a lo largo de casi 12 meses de muestreo. Considerando las muestras según sus orígenes se encuentra que en las de origen aguas del río un 77,77% presentaron alguna especie de Fusarium; en el caso de las agua marinas un 45,45% de las muestras presentó alguna especies de Fusarium. La mayor presencia de especies en las aguas del río puede ser debida a los contenidos en el agua de partículas de suelo y materia orgánica, después de
los arrastres producidos en las orillas por las lluvias. La presencia de especies encontradas en el mar pueden ser la consecuencia de las aguas de los cauces que desembocan en este. Sin embargo, no pueden excluirse otras vías. de Granada y Almería (Sureste de España). Un total de 18 muestras de agua del río Andarax fueron analizadas. De ellas se aislaron 10 especies de Fusarium: F. anthophilum, F. acuminatum, F. chlamydosporum, F. culmorum, F. equiseti, F. moniliforme, F. oxysporum, F. proliferatum, F. solani y F. sambucinum. De las 33 muestras de aguas del mar Mediterráneo se aislaron 5 especies: F. equiseti, F. moniliforme, F. oxysporum, F. proliferatum y F. solani. Sobre el total de muestras analizadas, un 27,45% de las muestras de aguas del río y un 29,41% de muestras de agua marina presentaron como mínimo una especie de Fusarium a lo largo de casi 12 meses de muestreo. Considerando las muestras según sus orígenes se encuentra que en las de origen aguas del río un 77,77% presentaron alguna especie de Fusarium; en el caso de las agua marinas un 45,45% de las muestras presentó alguna especies de Fusarium. La mayor presencia de especies en las aguas del río puede ser debida a los contenidos en el agua de partículas de suelo y materia orgánica, después de los arrastres producidos en las orillas por las lluvias. La presencia de especies encontradas en el mar pueden ser la consecuencia de las aguas de los cauces que desembocan en este. Sin embargo, no pueden excluirse otras vías.
... Los autores anteriormente mencionados no publicaron resultados que pusieran de manifiesto que las especies de Fusarium aisladas de dichos hábitats fuesen patógenas sobre los cultivos de las zonas muestreadas. Este hecho es bastante común en las publicaciones que estudian la presencia de especies de Fusarium, donde los autores presentan inventarios que relacionan con aspectos del clima (temperatura, pluviometría) o con la producción de micotoxinas, pero no muestran datos sobre su poder patógeno (BURGESS, 1981; STONER, 1981; KOMMEDAHL et al., 1988; JESCHKE et al., 1990; BACKHOUSE et al., 2001;). seguido fue el mismo, añadiéndose el contenido de una placa de Petri de PDA sin hongo. ...
En este artículo se estudia la patogenicidad de los aislados de Fusarium solani aislados de muestras de fondos marinos del Mediterráneo en las provincias de Granada y Almería (Sureste de España) sobre plántulas de cebada, colirrábano, melón y tomate. La evaluación del poder patógeno se hizo para 8 aislados de Fusarium solani. Todos los aislados mostraron patogenicidad tanto en preemergencia como en postemergencia de plántulas para los cultivos de melón y tomate. En colirrábano la patogenicidad ha sido mínima, solo significativa en el caso del aislado Fso2. No se encontraron evidencias de patogenicidad de ninguno de los aislados en cebada. Palabras clave: cebada, melón, tomate, colirrábano, hábitat acuático INTRODUCCIÓN TELLO y LACASA (1990) estudiaron la presencia de especies de Fusarium en terrenos incultos, encontrando una elevada proporción de F. solani y F. oxysporum. Estos autores se preguntaron sobre la relación entre las especies aisladas y las que producían enfermedades en los cultivos circundantes a los suelos incultos muestreados, especialmente para el caso de F. oxysporum. En los cultivos de clavel de la zona muestreada F. oxysporum f. sp. dianthi origina una micosis que es limitante para el cultivo. En los cultivos de tomate encontraron dos micosis importantes, una causada por F. oxysporum f. sp. lycopersici (Fusarium wilt) y otra causada por F. oxysporum f. sp.radicis-lycopersici (Fusarium foot rot). TELLO et al. (1990) y NÚÑEZ et al. (2006) estudiaron la presencia de especies de Fusarium en las arenas de playas y fondos marinos del litoral español del mar Mediterráneo. El estudio se justificó para buscar posibles fuentes de inóculo patógeno para las diferentes fusariosis vasculares que se expresan en los cultivos enarenados de Almería.
... Later, it was also isolated from poultry feed in Argentina 33 and from soil in Africa and Australia. 34,35 In the literature, only three studies have reported that this species can cause hyalohyphomycosis and pneumonitis in humans. [36][37][38] This species was also identified by us among the examined isolates from human ocular infections. ...
Seventy Fusarium isolates derived from human keratomycosis were identified based on partial sequences of the β-tubulin (β-TUB) and translation elongation factor 1α (EF-1α) genes. Most of the isolates were confirmed as members of the F. solani species complex (75.71%), followed by the F. dimerum species complex (8.57%), the F. fujikuroi species complex (8.57%), the F. oxysporum species complex (4.29%) and the F. incarnatum-equiseti species complex (2.86%). A combined phylogenetic tree was estimated including all the 70 isolates. Isolates belonging to different species complexes formed separate clades. In this study, we also report the first isolation of F. napiforme from human keratomycosis. A new method based on a specific EcoRI restriction site in the EF-1α gene was developed for the rapid identification of F. solani. In vitro antifungal susceptibilities of the isolates to seven antifungals were determined by broth microdilution method. Terbinafine, natamycin and amphotericin B proved to be the most effective drugs, followed by voriconazole. The minimal inhibitory concentrations of clotrimazole, econazole and itraconazole were generally high (≥64 μg ml(-1) ). The interactions between the two most effective antifungals (natamycin and terbinafine) were determined by checkerboard microdilution method. Synergism (71.8%) or no interaction (28.2%) was revealed between the two compounds.
... For example, over 15 000 cultures of Fusarium species have been isolated and identified from the region around Alice Springs, central Australia (11,12,27) and these large numbers give considerable confidence in conclusions drawn about the presence or absence of species of Fusarium in this region. Similar intensive surveying has been done in southern Africa (13,17,23,36), with more limited surveys in North America (16) and Europe (1,15). The remainder of the world is poorly surveyed. ...
... Fusarium solani is an important soilborne pathogen with worldwide distribution (Joffe & Palti, 1977;Samac & Leong, 1989;Jeschke et al., 1990;Leslie et al., 1990;Ploetz, 1991;Pegg et al., 2002;Chen et al., 2006). Based on host specificity, Suga et al. (2000) divided F. solani into 10 'formae speciales' (f. ...
The pathogenicity of 35 Fusarium solani isolates obtained from diseased leaves of greenhouse-grown Phalaenopsis plants in Taiwan was tested on different orchids, including Phalaenopsis sp., Cymbidium spp., Oncidium sp., Dendrobium sp. and Cattleya sp., plus pea (Pisum sativum), chrysanthemum (Chrysanthemum indicum) and cucurbit [melon (Cucumis melo) and cucmber (C. sativus)] plants. Isolates of F. solani from Phalaenopsis spp. caused severe leaf yellowing on Phalaenopsis and mild symptoms on Cymbidium spp., but no visual symptoms on Oncidium sp., Dendrobium sp., Cattleya sp., pea, chrysanthemum or melon. Fusarium solani isolates collected from Phalaenopsis, pea and cucurbits were molecularly characterized by internal transcribed spacer (ITS), intergenic spacer (IGS) and β-tubulin gene analyses. Phylogenetic trees constructed by distance and parsimony methods indicated that isolates from Phalaenopsis were grouped into one type based on ITS, IGS and β-tubulin sequences with high bootstrap value (> 84%) support, compared to ‘formae speciales’ of F. solani from the other hosts. These analyses show that isolates of F. solani from Phalaenopsis are distinct from F. solani isolates from other hosts in Taiwan. Therefore, it is proposed that F. solani isolates that incite Phalaenopsis leaf yellowing be designated F. solani f. sp. phalaenopsis.
... Several recent mycogeographic studies, using a consistent taxonomic system, have shown that species of Fusariumdiffer in their geographic distribution (Burgess, Nelson et al., 1988; Marasas ef a!. 1988;Jeschke, Nelson & Marasas, 1990;Burgess & SummerelL 1992;Sangalang ef a!', 1995). Climate, especially temperature and the seasonal distribution and abundance of rainfall, has been proposed as the dominant influence on the distribution of Fusarium species in these studies. ...
Comparison of survival and growth in culture of Fusarium acuminatum, F. compactum, F. equiseti and F. sambucinum at constant and fluctuating temperatures showed that F. compactum, abundant in hot arid regions, grew better and had higher survival rates at high temperatures than the other species. Fusarium acuminatum and F. sambucinum, which originated from temperate areas, had survival rates lower than the other two species when grown at elevated temperatures. Fusarium equiseti, a cosmopolitan species, was affected less by elevated temperature than were F. acuminatum and F. sambucinum, but was not as well adapted to hot arid regions as F. compactum.
... obecnoae kajakowato-lub bananowato-kszta³tnych zarodników konidialnych [43]. Zgodnie z najnowsz¹ systematyk¹ [43] grzyby z rodzaju Fusarium zosta³y zaliczone do: Gromady: Eumycota Grzyby w³aciwe Podgromady: Fungi imperfecti Grzyby niedoskona³e Klasy: Hyphomycetes Strzêpczaki Rzêdu: Moniliades Moniliowce Rodziny: Tuberculariaceae Gruze³kowate Grzyby z rodzaju Fusarium s¹ szeroko rozpowszechnione w glebie, szczególnie zasiedlaj¹ ¿yzne, urodzajne gleby, za stosunkowo rzadko lene [33] . Mog¹ rozwijaae siê równie¿ na ró¿nych czêciach rolin, resztkach rolinnych i innych zwi¹zkach organicznych [12]. ...
Grzyby z rodzaju Fusarium nale¿¹ do najczêciej izolowanych patogenów upraw rolniczych na wiecie [28]. S¹ one przyczyn¹ olbrzymich strat gospodar-czych, które wynikaj¹ z wysokiej patogennoci i tok-synotwórczoci, dlatego te¿ uznano je za jedne z naj-groniejszych grzybów strzêpkowych. Fusaria infekuj¹ uprawy rolinne o podstawowym znaczeniu gospodar-czym dla cz³owieka [15]. Posiadaj¹ tak¿e zdolnoae do syntezy wysoce niebezpiecznych i toksycznych metabolitów, zwanych mikotoksynami [47]. Mikotoksyny tworzone przez Fusaria okrelono mianem mikotoksyn fuzaryjnych. Uwa¿a siê, i¿ ode-gra³y one istotn¹ rolê w historii, pocz¹wszy od rednio-wiecznej Europy, przez czasy kolonialne obu Ameryk, a¿ do czasów obecnych. Dodatkowo wysuwano liczne hipotezy, i¿ mikotoksyny produkowane przez Fusaria mog³y byae przyczyn¹ wyginiêcia Etrusków czy pomo-ru w Atenach w V w p.n.e. [15, 60]. W rodowisku naturalnym wykrywa siê obecnoae kilku klas mikotoksyn fuzaryjnych: zearalenonu, tricho-tecenów, fumonizyn, moniliforminy oraz bowerycyny. Wykazuj¹ one dzia³anie toksyczne w stosunku do mikroorganizmów, rolin, a tak¿e ludzi i zwierz¹t [57]. Zwi¹zki te wytwarzane s¹ przewa¿nie przez: F. cul-morum, F. graminearum, F. nivale, F.avenaceum, F. sporotrichioides, F. poae, F. oxysporum, F. verti-cillioides [49, 52, 58]. Na terenie Polski dominuj¹ F. culmorum, F. graminearum [3, 38]. Problemy wynikaj¹ce z patogennoci i zdolnoci do syntezy mikotoksyn przez grzyby z rodzaju Fusarium Trichoteceny z grupy B. 4.3.2. Trichoteceny z grupy A. 5. Wystêpowanie mikotoksyn fuzaryjnych w Polsce i na wiecie. 6. Najwa¿niejsze czynniki rodowiska zwi¹zane z tworzeniem mikotoksyn. 7. Geny warunkuj¹ce formowanie zearalenonu i tricho-tecenów. 7.1. Charakterystyka Tri5, Tri7, Tri3 i Tri13. 7.2. Charakterystyka PKS4 i PKS13. 8. Metody molekularne. 8.1. Metody detekcji i identyfikacji oparte na procedurze PCR. 8.1.1 SCAR. 8.1.2. RT-PCR. 8.1.3. Real-Time PCR. 9. Podsumowanie Mycotoxigenic phythopathogenic fungi of Fusarium genus and their identification by PCR techniques Abstract: Fungi belonging to the genus Fusarium are recognized as one of the most dangerous pathogens causing serious plant, human and animal diseases. In addition, they are able to produce very toxic compounds knows as mycotoxins. Mycotoxins have various toxic effects on microorganisms, plants, animals and humans. The most common mycotoxins found in the natural environ-ment are zearalenone and trochothecenes, including deoxynivalenol. These compounds cause disorders and deformations during plant growth. They also cause human and animal diseases connected with digestive, reproductive and immune system. Lots of genes are recognized in the biosynthesis of these mycotoxins. Essential genes in trichothecenes synthesis are Tri5 and Tri7 genes, and in zearalenone synthesis another two genes PKS4 and PKS14. Molecular methods based on PCR allow to evaluation of mycotoxicity of filamentous fungi. The easiest and most frequently used method is SCAR. Other molecular analyses like RT-PCR and Real-Time PCR are very expensive methods but are also very sensitive and less and less labour-intensive and thus are used in this kind of tests as well.
In this study, eighty isolates of Fusarium were obtained from the uncultivated soils and roots of chickpea plants showing typical black root rot symptoms from different areas of Kermanshah province, west Iran during 2015 to 2017. Based on colony morphology, growth pattern, and micromorphological characteristics, the most prevalent Fusarium species recovered from uncultivated soil were F. redolens, 38 isolates (64%), followed by F. oxysporum, 12 isolates (20%), F. solani, seven isolates (11%) and Neocosmospora vasinfecta, three isolates (5%). All isolates recovered from chickpea plants with black root rot symptom were identified as F. redolens according to macro-micromorphological and molecular characteristics. After grouping, 27 isolates were selected for molecular confirmation by phylogeny of DNA sequence data for the internal transcribed spacer (ITS) rDNA and translation EF1α intergenic regions. The results of the pathogenicity test under greenhouse condition revealed that all isolates of F. redolens obtained from chickpea plants with black root rot symptoms in this study and N. vasinfecta from uncultivated soil are pathogenic to chickpea cultivar Bivanij. Two weeks after inoculation with F. redolens and N. vasinfecta, symptoms developed as black cankers that extended upward and downward of roots of all emerged seedlings. Re-isolation from all inoculated plants after observation of symptoms were performed, and isolates were compared to original cultures thus fulfilling Koch’s postulates. According to the results of canonical correspondence analysis, soil texture, altitude, CaCO3, EC, carbon, organic matter and pH in descending order were recognized as the most important environmental variables for the distribution of Fusarium species in soil. Fusarium redolens reflected a soil with very low sand, carbon, organic matter and intermediate pH, EC and CaCO3. Results of this study suggest that previously reported F. oxysporum in western Iran on chickpea might have been mistaken. This is the first report of pathogenicity of F. redolens and N. vasinfecta on chickpea from Iran.
Isolates of Fusarium nygamai were mated and produced fertile perithecia of Gibberella nygamai sp. nov., on carrot agar. Female-fertile tester strains were recovered from random ascospore progeny and two were identified as more reliable female parents in the detection of other members of this population. The formation of microconidia in short chains and the formation of chlamydospores in anamorph progeny cultures are suitable characters for species identification of F. nygamai. Fusarium nygamai is predominantly soilborne.
The genus Fusarium hosts a large number of economically significant phytopathogens with a global distribution. Surprisingly, only a limited number of studies have tried to identify the natural distribution of members of this genus in undisturbed soils. Members of the Fusarium incarnatum-equiseti species complex (FIESC) are increasingly associated with plant disease, and human and animal health problems. Recently, an outbreak of kikuyu poisoning of cattle was attributed to the F. incarnatum-equiseti species complex. Thus, it is of importance to identify the natural distribution of members of the FIESC from the environment. The aim of this study was to use the phylogenetic signal within the TEF 1α gene region to characterise 54 F. incarnatum-equiseti isolates obtained from undisturbed soils from the grassland biome of South Africa. These isolates were further compared with members of the FIESC previously associated with kikuyu poisoning of cattle. The phylogenetic analysis indicated a high level of variation within this species complex. Several members were closely related to isolates implicated in the death of cattle from infected kikuyu grass.
A survey was conducted in the Windward Islands of Dominica, St Lucia, and St Vincent to obtain information on the characteristics of banana farms, cultural practices adopted, the thriftiness of the crops, the health of the roots, and the abundance of root-parasitic nematodes and fungi. Most farms appeared to be thrifty, irrespective of farm size and duration under cultivation, and apparently received proper crop care. Leaf spot disease control, weed control, and the condition of the drains needed improvement on some farms. Farmers perceived the unavailability of chemicals, leaf spot disease, and drought as the main production constraints. Other perceived constraints were various pests, heavy rainfall, soil texture, slope of land, and lack of labour. Necrotic roots parasitized by micro-organisms occurred on all farms. The most abundant root-parasitic nematode was Radopholus similis and the most frequently detected fungus was Fusarium oxysporum f. sp. cubense. All species of root-inhabiting nematodes and fungi were detected at high and low altitudes. Helicotylenchus sp. and Trichoderma spp occurred more frequently at altitudes less than 229 m above sea level (asl) than at higher altitudes and the percentage occurrence of Fusarium spp and the degree of root necrosis were significantly higher in farms at altitudes higher than 229 m asl than at the lower altitudes. The nematode population densities in roots were positively correlated with the degree of necrosis in roots of suckers at high altitudes in St Lucia. The information gained from these studies will be useful in the development of integrated control measures.
Date palm (Phoenix dactylifera) as an indigenous halophytic tree was selected as a target host to evaluate biodiversity of the genus Fusarium in the north-west transect of the main island of Bahrain. A total of 27 villages were thoroughly surveyed and 81 samples of roots, plant debris and soil were collected from the rhizosphere soil of small, medium and large plants. Soils samples were found mostly saline, high in soluble salts, calcareous, gypsiferous, poor in organic matter and sandy to coarse in texture. Data assessment for recovery of Fusarium species was based on colony identification and plate counts by direct plating of roots, plant debris and soil on selective media. A sum of 2107 isolates, fluctuating between 1 to 345 per sample, were encountered among all transects, plant heights, media and isolation type. Jid Ali village yielded the highest colony counts (162.56). Mean recovery of Fusarium isolates was highest in plant debris (723) followed by roots (540) and lowest in soil samples (410). A gradual increase in colony counts from root samples were observed proportionally related to growth in plant height from small to large. A total of thirteen species were recovered representing eight sections, twelve from roots and six from plant debris and soil samples each. The isolated species were F. avenaceum, F. chlamydosporum, F. equiseti, F. illudens, F. lateritium, F. moniliforme. var. subglutinans, F. oxysporum, F. pallidoroseum, F. poae, F. sambucinum, F. solani, F. sporotrichioides and F. tricinctum. Three species, F. avenaceum, F. illudens, and F. poae are reported for the first time from Bahrain. F. solani and F. oxysporum were the most dominant and frequently encountered species, a finding confirm previously reported data and validated by chi-square contingency analysis. Northern transect resulted in higher species assemblage and isolate counts compared to west and principally isolation from root samples was superior than other isolation types. Analysis of data supported by diversity indices revealed that roots of small plants were the most diverse (0.588) followed by large plant (0.544). Overall, variations related to locations were much greater than differences attributed to isolation type or plant height. Large-medium plants combinations exhibited the highest species similarity composition (0.80) as determined by Sorensen community coefficient. Species richness among samples fluctuated between 2-10 for soil of medium plants and root of small plants. Overall, that predominance of F. solani and F. oxysporum in the rhizosphere of date palm is consistent with the hypothesis that these fungi have broad ecological tolerances and tend to be illustrative of hot arid habitats. The influence of soil biotic factors on Fusarium diversity and spectra is discussed.
For the first time in over 20 years, a comprehensive collection of photographs and descriptions of species in the fungal genus Fusarium is available. This laboratory manual provides an overview of the biology of Fusarium and the techniques involved in the isolation, identification and characterization of individual species and the populations in which they occur. It is the first time that genetic, morphological and molecular approaches have been incorporated into a volume devoted to Fusarium identification. The authors include descriptions of species, both new and old, and provide protocols for genetic, morphological and molecular identification techniques. The Fusarium Laboratory Manual also includes some of the evolutionary biology and population genetics thinking that has begun to inform the understanding of agriculturally important fungal pathogens. In addition to practical how-to protocols it also provides guidance in formulating questions and obtaining answers about this very important group of fungi. The need for as many different techniques as possible to be used in the identification and characterization process has never been greater. These approaches have applications to fungi other than those in the genus Fusarium. This volume presents an introduction to the genus Fusarium, the toxins these fungi produce and the diseases they can cause. The Fusarium Laboratory Manual is a milestone in the study of the genus Fusarium and will help bridge the gap between morphological and phylogenetic taxonomy. It will be used by everybody dealing with Fusarium in the Third Millenium. -W.F.O. Marasas, Medical Research Council, South Africa.
The commercial tomato, Lycopersicon esculentum is one of the most popular vegetables in the world. It is cultivated for its culinary, industrial and ornamental values. It has also served as a model plant for various scientific studies. Tomato is affected by several economically important plant diseases, notably vascular wilt caused by Fusarium oxysporum f. sp. lycopersici (Fol). Fusarium is a soil borne fungus which infects the plant root and colonises the xylem vessels, resulting in wilting, stunting and death. Fusarium wilt of tomato continues to be a major cause of yield losses in endemic regions. As a result of its growth within the confinement of the vascular tissues of the host plant, chemical and cultural attempts at protecting tomato against Fusarium wilt have been rendered ineffective or impractical. The most effective method of control is breeding for resistant cultivars. Resistance is mediated by the I, I-2 and I-3 resistance genes in tomato against Fol. There is remarkably little knowledge available about the molecular mechanism or/and pathogenicity genes required by Fol to cause disease and how hosts combat or tolerate the pathogen. Understanding the process by which Fol infects, colonises and interacts with tomato host plant could lead to more efficient ways of controlling it. More so, the interaction between Fol and tomato, which has become a model system for the study of the molecular mechanism of disease susceptibility and resistance, could give a better insight into the control of wilt in many agriculturally important crops caused by other species of Fusarium. This present review highlights the nature and molecular basis of Fusarium wilt in tomato, as well as disease management.
Grzyby z rodzaju Fusarium od wielu
lat pozostają w kręgu zainteresowania
mikrobiologów z całego świata. Mimo iż
są bardzo dobrze poznanymi i opisanymi
mikroorganizmami, a na ich temat powstało
wiele opracowań i publikacji naukowych, w
dalszym ciągu w wielu ośrodkach naukowych
trwają badania nad lepszym poznaniem Fusarium
spp. W początkowym okresie badań
nad tym rodzajem jego przedstawicielom
przypisywano rolę fitopatogenów, porażających
rośliny uprawne, co skutkowało zmniejszeniem
plonu. Następnie zauważono, że
grzyby z rodzaju Fusarium posiadają zdolności
do produkcji toksycznych substancji, będących
zagrożeniem nie tylko dla roślin, ale
także dla ludzi i zwierząt. Ponadto, stwierdzano
coraz częściej występujące u ludzi zakażenia
wywoływane przez Fusarium spp., co
spowodowało konieczność ustalenia metod
racjonalnej antybiotykoterapii możliwej do
zastosowania w leczeniu fuzarioz. Obecnie
prowadzone są badania nad zróżnicowaniem
genetycznym Fusarium w ramach rodzaju,
jak i zróżnicowania wewnątrzgatunkowego.
Ponadto, prowadzone są analizy pod kątem
obecności genów odpowiedzialnych za produkcję
wybranych mykotoksyn oraz oceny
patogeniczności konkretnych izolatów względem
odmian i gatunków roślin. Niezwykle
ciekawym zagadnieniem jest także hodowla
odpornościowa mająca na celu selekcję
i produkcję roślin posiadających naturalne
mechanizmy chroniące je przed porażeniem
grzybami. Jeszcze innym kierunkiem aktualnie
prowadzonych badań jest ocena skażenia
ziarna zbóż oraz pasz mykotoksynami. Tutaj
zastosowanie znajdują chromatograficzne
metody analityczne coraz powszechniej stosowane
w laboratoriach na całym świecie.
Weeds are alternative hosts of plant pathogens and when colonized may not exhibit disease symptoms. In 2008 and 2009, samples of weeds and plant debris were collected from 12 locations in eastern Croatia, and 300 Fusarium isolates colonizing them were identified. Strains were grouped and identified based on morphology and amplified fragment length polymorphism (AFLP) patterns. Portions of the β‐tubulin and translocation elongation factor 1‐α genes were sequenced from representative strains of each group to confirm the identifications. Fourteen Fusarium species were identified with F. graminearum (20%), F. verticillioides (18%), F. oxysporum (16%), F. subglutinans (13%) and F. proliferatum (11%) all present as more than 10% of the population. Fusarium acuminatum, F. avenaceum, F. concolor, F. crookwellense (F. cerealis), F. equiseti, F. semitectum, F. solani, F. sporotrichioides and F. venenatum, were all present at frequencies Fusarium spp. may be isolated from numerous alternative hosts during the off season and that weeds and plant debris can serve as a reservoir of genetically diverse inoculum.
The purposes of the present study were to search for antagonistic fungi to control seed-borne diseases of cereals caused by Fusarium culmorum (W.G.Sm) Sacc. and to use these results to compare the distribution of non-pathogenic Fusarium spp. and other fungi antagonistic to Fusarium culmorum in soil and on straw particles in an organically and a conventionally cultivated field. The organic farm had been cultivated according to the principles of Steiner (1963) since 1952. The sites were similar with respect to climatic conditions, soil type and vegetation. There was no difference in the total number of antagonistic fungi isolated from the two differently cultivated fields, but the results for Fusarium spp. showed effects of the actual crop as well as the cropping system. Soil sampling over a three year period at the organically cultivated farm in two crops—winter wheat or a mixture of grass and clover—showed almost twice as many species of Fusarium in the mixed crop compared to monoculture. In mixed crop fields, the percentage of F. culmorum in relation to total isolations of fusaria was 20% in the organically cultivated field compared with 45% in the conventionally cultivated field. These results indicate that pathogenic fusaria may be suppressed by antagonistic fusaria to a larger extent in the organically cultivated field than in the conventionally cultivated field. In accordance with this, a higher number of antagonistic fusaria was found in the organically farmed field (14) compared to three in the conventionally farmed field. This was partly a result of a higher number of isolated fusaria and a higher number of different species of Fusarium in the organically cultivated soil (total number of non-pathogenic fusaria was 10 in the conventionally cultivated field and 56 in the organically cultivated field). However, it also seems to reflect an enrichment of fusaria with antagonistic properties towards F. culmorum. Thus, the occurrence of F. culmorum was 1.7 times higher in the organically cultivated field while the occurrence of its antagonists was 4.6 times higher in the organically compared with the conventionally cultivated field.
Soil samples were collected along two transects in relatively undisturbed forest and woodland areas in north-eastern Queensland, Australia. One transact was between Cairns (on the east coast) and Chillagoe (approximately 200 km inland), and the other between Mossman (on the east coast) and Mt. Lewis, (approximately 18 km inland). Fusarium species were isolated using the soil dilution plate technique and by plating soil debris, predominantly root material.
Thirteen species, F. beomiforme, F. chlamydosporum, F. compactum, F. equiseti, F. longipes, F. moniliforme, F. nygamai, F. oxysporum, F. proliferatum, F. scirpi, F. semitectum, F. solani and F. subglutinans and one undescribed population of Fusarium were isolated. There was no marked difference between the Fusarium species recovered by the two isolation techniques. F. semitectum and F. moniliforme were only recovered from sites having high rainfall. F. oxysporum and F. solani were isolated from the majority of the soils being most abundant in sites having higher rainfall. Fusarium species in the section Gibbosum and F. nygamai were isolated only in those areas with relatively lower rainfall.
Populations of Fusarium spp. from plots growing continuous winter wheat were estimated by dilution plating of soil samples taken in February, April and July 1993. The plots, from two sections of Broadbalk field, Rothamsted, either had the straw removed, or chopped and incorporated into the soil after every harvest since 1986; the plots also had different fertilizer treatments. Most species were more abundant in July than in February or April. Estimated propagule numbers of F. culmorum, the only cereal pathogen found frequently, were less than in a survey of the same plots in 1964. It occurred in greatest numbers in plots treated with farmyard manure and, in July, with the largest inorganic nitrogen applications. F. oxysporum and F. solani, non-pathogenic on cereals, were most frequent in plots treated with phosphorus, potassium and magnesium but without added nitrogen. Other non-pathogenic species, of which the most abundant was F. merismoides, showed no consistent response to any of the fertilizer treatments. The method of straw disposal had no consistent effects. The results are discussed in relation to perceived changes in fusarium disease in the U.K. and changing cereal husbandry practices.
Fungi were first collected for scientific study in southern Africa only in the late 1700s. In the monumental catalogue: “South African Fungi and Lichens to the end of 1945”, Doidge summarised the earliest mycological history of this country. To supplement her work Gorter compiled a bibliography of South African mycological publications for the period 1946 to 1977. The present paper briefly summarises developments since 1977 in terms of the taxonomy, nomenclature and mycobiotic surveys of all groups of fungi, including human and animal pathogens. It pays particular attention to specific habitats such as soil, fresh water, composts and animal dung as well as mycorrhizas. Although we have amassed valuable information about fungi that have an obvious economic impact, the majority remains undiscovered. Non-morphological taxonomy, including molecular and biochemical characters, will help us to expand our knowledge and understanding of the local mycobiota.
To test the hypothesis that climate is a major factor controlling the distribution of Fusarium species in soil, the effect of temperature on propagule density in soil and colonization of roots was determined experimentally. Five Fusarium species were inoculated together into untreated field soil in pots sown with perennial ryegrass. Changes in the density of propagules in soil recoverable by dilution plating and the proportion of roots colonized by each species were monitored over 12 months at three temperature ranges (13–18, 19–24 and 25–30°C). Propagule density of, and colonization of roots by, F. compactum and F. solani was greatest at higher temperatures (25–30°C). Fusarium torulosum demonstrated greatest colonization ability and propagule density in soil at lower temperatures (13–18°C). The propagule density of the cosmopolitan species F. equiseti remained high at all temperatures and this fungus successfully colonized plant roots under all conditions. While F. acuminatum did not compete well against the other species, the propagule density of this fungus was greatest at low temperatures. The differences in community structure resulting from differences in temperature in this model system mimicked those found when natural communities of Fusarium species are compared along climatic gradients.
The climate analysis and prediction system BIOCLIM proved useful for collating distribution records, defining climate profiles for known distributions and predicting potential distributions within Australia of Fusarium spp. from soil. The potential range of F. acuminatum ssp. acuminatum was southern and eastern Australia, with its distribution limited by high temperatures. Fusarium acuminatum ssp. armeniacum was predicted to occur only in a limited higher rainfall, temperate area in south-eastern Australia, but climate may be only a secondary factor in determining its distribution. The potential range of F. compactum was most of mainland Australia except the southern coastal fringe and south-east highlands from which it was excluded by low temperatures. No significant climatic limits to the distribution of F. equiseti were found and its potential range was the whole of Australia. Fusarium longipes had a potential range in the higher rainfall areas of the tropics and subtropics, and it was excluded from other areas by low summer rainfall or low temperatures in the wet season. Fusarium scirpi had a potential range over most of temperate and arid Australia, but was excluded from areas that were too cold, where winter rainfall was more than twice the summer rainfall, and from the hot summer rainfall areas of the tropics.
Este trabajo es continuación de una serie de estudios sobre la biogeografía de Fusa-rium que se están realizando desde hace 5 años en España (NUÑEZ et al, 2006). En él se presentan los resultados analíticos para el género Fusarium de muestras de aguas del cauce del río Andarax y de fondos del mar Mediterráneo en las provincias de Granada y Almería (Sureste de España). Se analizaron un total de 18 muestras de agua del río Andarax. De ellas se aislaron 10 especies de Fusarium: F y F. sambucinum. De las 23 muestras del mar Mediterráneo se aislaron 5 especies: F. equiseti, F. monili-forme, F. oxysporum, F. proliferatum y F. solani. Sobre el total de muestras analizadas, un 27,45% de las muestras de aguas del río y un 29,41% de muestras de procedencia marina presentaron como mínimo una especie de Fusarium a lo largo de casi 12 meses de muestreo. Considerando las muestras según sus orígenes se encuentra que en las de origen aguas del río un 77,77% presentaron alguna especie de Fusarium; en el caso de los fondos marinos un 45,45% de las muestras presentó alguna especie de Fusarium. La mayor presencia de especies en las aguas del río puede ser debida a los contenidos en el agua de partículas de suelo y materia orgánica, después de los arrastres producidos en las orillas por las lluvias. La presencia de especies encontradas en el mar puede ser conse-cuencia de las aguas de los cauces que desembocan en éste. Sin embargo, no pueden excluirse otras vías.
Microconidial chains in three Fusarium species of the Section Liseola that produce them (F. moniliforme, F. proliferatum and F. annulatum) increased in abundance and length as the water potential of the medium decreased. An optimal enhancing effect was obtained with water agar containing 4-8 g/l of KCl (0.053 to 0.107 M). At KCl concentrations of 32 g/l (0.427 M) and higher, growth as well as microconidial chain formation was inhibited. Isolates representing the "short-chained" type of F. moniliforme (=F. fujikuroi) were indistinguishable from F. moniliforme on water agar containing 8 g/l of KCl. The formation of microconidial chains was not induced in two species of the Section Liseola that are known not to produce them (F. subglutinans and F. anthophilum). The presence or absence of microconidial chains is, therefore, a reliable taxonomic criterion in Fusarium Section Liseola. Carnation leaf agar containing 4-8 g/l of KCl is recommended for the identification of these Fusarium species.
