POPULATION DIFFERENCES IN INDIGENOUS FUSARIUM SPECIES BY CORN CULTURE OF PRAIRIE SOIL

Six species of Fusarium were identified among approximately 7,000 cultures isolated from roots and soils collected from prairies and cornfields in southern Minnesota. In both soil sources, F. oxysporum and F. solani predominated, followed in order by F. roseum, F. episphaeria, F. tricinctum, and F. moniliforme. The same order was obtained for the 28 species of prairie grasses and forbs as for corn. From prairie plant and corn roots, respectively, F. oxysporum was isolated from 64 and 90%; F. solani, 26 and 80%; F. roseum, 8 and 35%; and F. tricinctum, 6 % each. In 10 of 17 companion soil pairs, populations of Fusarium species were higher in cornfield than in prairie soils. Populations of F. roseum and F. moniliforme especially, were higher in cornfield soils of sample pairs, but populations of F. solani were higher in prairie soils. Fusarium roseum ‘Equiseti’ was the predominant cultivar of this species in both prairie and cornfield soils. Thus all six species of Fusarium appeared to be indigenous to the prairie, and some, especially F. roseum, apparently had increased in prevalence in soil and roots by corn culture.     

Distribution of Fusarium in some British soils

Soil fusaria from various areas in and around Surrey were estimated on medium selective forFusarium. 4 species ofFusarium, F. episphaeria. F. oxysporum, F. roseum andF. solani were detected.F. roseum was the most widely distributed species and present in highest numbers. Among 3 cultivars of this species obtained, non-pathogenic clones of “Culmorum” was always present. The other 3 species ofFusarium were less widely distributed and occurred in lower numbers, withF. solani being the most restricted in distribution and present in very small populations. NoFusarium was recorded for soils from natural field vegetation (except grass areas) and forests.     

Contamination of freshly harvested maize kernels with<Emphasis Type="Underline">Fusarium</Emphasis> mycotoxins on Bihar state,India

Freshly harvested maize samples, collected from different fields of Bhagalpur during January-March, 1989, were analysed for the presence of Fusarium species and their toxins.F. moniliforme was most common followed byF. roseum,F. sporotrichioides,F. graminearum andF. equiseti. Different strains of these species produced zearalenone (11.2–28.2 μ/g), DON (0.3–2.9 μg/g) and T-2 (5.2–20.6 μg/g) toxins on mostrice medium. Fifteen per cent, out of 86 maize samples analysed, were found to be contaminated with various levels of above toxins, which occurred either alone or in groups. Toxin concentration in contaminated samples varied from 0.76–1.5 μg/g (ZEN), 0.41–202 μg/g (DON) and 0.55–2.92 μg/g (T-2).     

Diversity and infectivity of arbuscular mycorrhizal fungi in agricultural soils of the Sichuan Province of mainland China

Knowledge about the presence and diversity of arbuscular mycorrhizal fungi (AMF) in a specific area is an essential first step for utilizing these fungi in any application. The community composition of AMF in intensively managed agricultural soil in the Sichuan Province of southwest China currently is unknown. In one set of samples, AMF were trapped in pot cultures from 40 fields growing legumes in the Panxi region, southeast Sichuan. In a second set of samples, the MPN method with four-fold dilutions and maize as host was used to estimate infective propagules in soil from another 50 agricultural sites throughout the province. Soil types were heterogeneous and were classified as purple, yellow, paddy and red. Crops at each site were either maize, wheat or sweet orange. From this set of soil, AMF spores were also extracted and identified. Including all ninety soils, thirty glomeromycotan species in Glomus (20 species), Acaulospora (four species), Scutellospora (three species), Ambispora (one species), Archaeospora (one species) and Paraglomus (one species) were identified. Yellow, red and purple soils yielded similar numbers of AMF species, while AMF species diversity was clearly lower in paddy soil. In trap culture soils, the most frequent species were Glomus aggregatum or Glomus intraradices, Glomus claroideum and Glomus etunicatum. The species Acaulospora capsicula, Acaulospora delicata, G. aggregatum (or intraradices), G. claroideum, Glomus epigaeum, G. etunicatum, Glomus luteum, Glomus monosporum, Glomus mosseae and Glomus proliferum were successfully cultured as single-species pot cultures in Plantago lanceolata. The three most frequent species in field soils were G. mosseae, Glomus caledonium and Glomus constrictum. MPN values varied between 17 and 3334 propagules 100 g soil⁻¹ among the fifty field sites sampled. Regression analysis, including host&soil, log(P) and pH as explanatory variables explained 59% of the variation in log(MPN). The highest MPN estimates were found in purple soil cropped with maize and citrus, 324 and 278 propagules 100 g soil⁻¹, respectively. The lowest MPN value, 54 propagules 100 g soil⁻¹, was measured in wheat in purple and yellow soil. Despite intensive agricultural management that can include often repeated tillage, our examination of 90 agricultural sites revealed that soils of the Sichuan region have moderate to high numbers of infective AMF propagules as well as a high AMF species diversity. This opens possibilities for further studies and utilization of AMF in agriculture and horticulture in the Sichuan province, People’s Republic of China.     

Studies on the relation between density of Longidorus elongatus and growth of sugar beet, with supplementary observations on Trichodorus spp

Longidorus elongatus attacks sugar beet on light sandy soils in the West Midlands. Severely damaged plants may die or recover, producing fanged roots. Up to 335 L. elongatus/200 g of soil were found around attacked seedling plants and were often visible to the unaided eye on the roots of freshly lifted plants. Five experiments were made and regressions computed of yield of beet, total numbers of plants and numbers of normal and fanged beet on L. elongatus numbers. Between 24% and 50% of roots per 100 L. elongatus/ 200 g were killed or became fanged. Corresponding figures for loss of plant were between 7.5% and 33%. Estimated loss of yield varied between 0.8 and 7.3 tons (2.0–18.3 t/ha)/acre/100 L. elongatus/200 g, the former where the potential yield was high and the latter where poor growing conditions hindered recovery. Large numbers of Trichodorus occurred in two trial sites and there is some evidence of competition between the two genera. Significant negative regressions for Trichodorus spp. were obtained in one trial suggesting a loss of 12% total and 17% normal roots per 100 Trichodorus spp./200 g.     

Mycoecology of willow and cottonwood lowland communities in Southern Wisconsin I. Soil microfungi in the willow-cottonwood forests

Summary A survey of the soil microfungi in 5Salix nigra-Populus deltoides forests in southern Wisconsin was conducted. The dilution plate method was employed to obtain 500 isolates per stand. The species present and their frequencies of occurrence were determined. The dominant forms,Trichoderma viride, Cladosporium cladosporioides, Gliocladium roseum, Mucor hiemalis, Coniothyrium sp. 5154,Mortierella minutissima, andPenicillium thomii, accounted for 41 % of the 2,500 isolates but only 4.5 % of the 154 species. They were followed at a second level of prevalence byPenicillium janthinellum P. multicolor, Mortierella alpina, andPhoma sp. 5157. The distribution of these taxa and others in the willow-cottonwood community was found to be correlated with an organic matter gradient. The Dematiaceae and the Sphaerioidaceae characterized populations obtained from the dry pioneer sites; the Mucorales and Moniliaceae became increasingly abundant as the percentage of organic matter increased. The number of fungal propagules ranged from 3,000 to 234,000 per gram of dry soil, the highest numbers occurring in soils with greater organic matter. The willow-cottonwood microfungal population was most similar to one obtained from soils of the closely related southern Wisconsin wet-mesic forests and least similar to ones isolated from the northern Wisconsin bogs and spruce-tamarack swamps.     

A study of spatial distribution and population dynamics of two sympatric species of trichodorid nematodes

The spatial distribution and population dynamics of Trichodorus primitivus and Paratrichodorus pachydermus were studied at a Scottish nursery site in replicated plots. Each plot was split and half was fumigated with dichloropropene. The numbers of males, females and juveniles under Scots pine (Pinus sylvestris), grass/clover (Lolium perenne/Trifolium repens) and fallow in non-fumigated and fumigated subplots were recorded at 10 cm intervals to a depth of 50 cm every 4 months for 3 years. In the non-fumigated subplots the population densities of T. primitivus under each crop and the fallow soil were similar at the beginning and end of the experiment but P. pachydermus responded differentially, decreasing in fallow soils and increasing under pine. The ratios of adult: juvenile and male: female for the two species were not significantly affected by crop or sampling depth. T. primitivus was the more numerous species except under pine where P. pachydermus gradually became dominant during the study. Both species were present in all the depth samples but showed an aggregated distribution with different modal depths. The depth at which most P. pachydermus were found was shallower than for T. primitivus. Differences in the distribution and behaviour of the two species were found indicating how the two species could co-exist or succeed each other. Fumigation with dichloropropene decreased the trichodorid populations to < 1 per 200 g soil to a depth of 50 cm. The relative development of the populations under the different crops and fallow soil were similar to those in non-fumigated soils.     

Emergence of cabbage seedlots in field soils with different cropping histories

In three non-sterilised soils with different long-term cropping histories of continuous mixed vegetables, continuous brassicas and continuous grassland, emergence of cabbage seedlots was lower than values obtained in laboratory germination tests. The greatest reductions occurred in soil (mixed vegetables) infested with Pythium ultimum. The presence of Pythium irregulare in the continuous brassicas soil had less effect on emergence, but the ranking for emergence of four of the seedlots was identical in the two soils. When the soils were sterilised and re-inoculated with their respective Pythium isolate emergence was less than that in non-sterilised soil but the rankings were similar. The pre-emergence, and post-emergence losses which occurred in these two soils, were controlled by seed treatment with 1 g metalaxyl/kg seed. In the continuous grassland soil although Pythium irregulare was present, emergence from most of the seedlots was high.     

The influence of harvester and Messor capensis nest-mounds on the productivity and distribution of some plant species in the southern Karoo,South Africa

Nest-mounds of the harvester ant Messor capensis occur on and around nutrient-rich patches, along minor drainage lines in nutrient-rich soils, and on the plains, generally in nutrient-poor soils. Nest-site selection is related to the presence of suitable deep soils, the presence of stones and the distance from the nearest neighbouring nest. Two plant species, Galenia fruticosa and Pteronia pallens, were significantly associated with Messor capensis nest-mounds, both in numbers of mounds occupied and in numbers of individuals. A third species, Drosanthemum montaguense, was also more common in numbers of individuals, while a fourth species, Rhinephyllum macradenium was negatively associated with these mounds. The analysis of species guilds by soil type shows that significantly more species of nutrient-rich soils are present on M. capensis nest-mounds. Also, significantly more taller, woody species occurred on nest-mounds than in inter-mound spaces. Two species, Pteronia pallens and Osteospermum sinuatum, growing on ant nest-mounds had significantly longer inter-nodes than the same species growing off mounds. However, two other species, Pteronia cf. empetrifolia and Galenia fruticosa showed no difference in inter-node lengths between plants growing on and off mounds. Six of the nine species of plants sampled on ant nest-mounds had significantly higher seed production than plants of the same species growing in inter-mound spaces. The other three species showed a tendency towards more seeds per plant on ant nest-mounds. The proportions of live and dead plants on mounds differed between species. Only Ruschia spinosa showed a significant difference between the numbers of dead plants in the population on and off mounds, with more dead plants occurring on mounds. Significantly more seeds set on individuals of Pteronia pallens growing on ant nest-mounds than those growing off nest-mounds, but no such difference occurred in P. cf. empetrifolia. There was no significant difference in the proportion of seeds parasitized by the tephritid fly Desmella anceps for individuals of P. pallens and P. cf. empetrifolia growing on and off mounds.     

Populations in Saskatchewan soils of spore-perforating amoebae and an amoeba (Thecamoeba granifera s.sp.minor) which feeds on hyphae ofCochliobolus sativus

Summary Thecamoeba granifera s.sp.minor was the predominant species of hyphal feeding amoeba in Saskatchewan soils. The average number per gram dry weight in soil was 66.2 in 1983 and 76.2 in 1984 with a range of 2 to 429 individuals. This population was 10 times greater than that of spore perforating amoebae which occurred in average numbers of 5.9 in 1983 to 4.5 in 1984. The populations of both the hyphal-feeding amoeba and the sporeperforating type, varied over the growing season with low numbers in summer and a peak population in fall. The data suggest that the number ofT. granifera s.sp.minor remains similar in a field from year to year regardless of cropping practice. Contribution no. 895.     

Biological Control of Fusarium spp. in Cotton, Wheat and Muskmelon by Trichoderma harzianum

A new isolate of Trichoderma harzianum (T-35) was isolated from the rhizosphere of cotton plants from a field infested with Fusarium. Under glasshouse conditions, the antagonist was applied to soil growing in a bran/peat mixture (1:1, v/v) or as a conidial suspension or used as a seed coating. When T. harzianum was tested against Fusarium oxysporum f. sp. vasinfectum, F. oxysporum f. sp. melonis or F. roseum‘Culmorum”, a significant disease reduction, was obtained in cotton, melon and wheat, respectively. Biological control of Fusarium wilt of cotton was achieved when tested at two inoculum levels of the pathogen (2 × 10⁷ and 2 × 10⁸ microconidia/kg soil), decreasing the Fusarium spp. soil population. The long term effect of T. harzianum on Fusarium wilt of cotton was studied using successive plantings. The antagonist persisted in soil throughout three consecutive plantings, reducing the Fusarium, wilt incidence in each growth cycle. At the first planting the largest amount of preparation was found superior, whereas at the third planting, no significant difference could be observed between the four rates of Trichoderma preparation. T. harzianum (T-35) controlled Fusarium wilt in cotton and muskmelon when applied in both naturally or artificially infested alluvial vertisol and sandy-loam soils, respectively. Soil or seed treatments with the antagonist provided a similar disease control of F. roseum‘Culmorum’ and of F. oxysporum f. sp. melonis.     

Fungicides and some biological controller agents effects on the growth of fusarium oxysporum causing paprika wilt: Wirkung von fungiziden und einigen biologischen kontrollwirkstoffen auf das wachstum des paprikawelke verursachenden fusarium oxysporum

Soil samples from both healthy and diseased paprika roots were tested to identify their mycoflora. Thirty-one species belonging to 16 genera were collected from rhizosphere and rhizoplane samples. The most frequently isolated fungi were Aspergillus flavus, A. niger, A. terreus, Fusarium oxysporum, Penicillium jensenii and Trichoderma harzianum. Fusarium oxysporum was the most common Fusarium species in the rhizoplane samples of diseased roots and identification was confirmed by RAPD-PCR technique. Trichoderma harzianum, T. pseudokoningii and Glioclaium roseum were chosen to study their biological control efficiency against Fusarium oxysporum. These fungal species reduced the percentage of seedling infection to 25, 40 and 50%, respectively. With the increasing of fungicide (Folicur and Ridomil) doses the dry weight of F. oxysporum decreased. Also, the increasing of fungicide dose lead to a slight decrease in the dry weight of T. harzianum, T. pseudokoningii and Glioclaium roseum.     

Occurrence and distribution of Fusarium species in maize fields in New Zealand

Fusarium populations were investigated in maize grains and their husks about six weeks before harvest in three maize fields in the Manawatu region of New Zealand. The role of litter and soil as reservoirs for these fungi was also examined. Two techniques were used to examine populations, dilution plating and direct plating. Using the dilution plating technique the highest overall populations were found in husks (mean 2.2 × 10⁵/g) and litter (mean 1.4 × 10⁵/g), while similar lower numbers of viable propagules were obtained from grain (mean 2.1 × 10³/g) and soil (2.8 × 10³/g). With this technique five Fusarium spp. were commonly isolated; F. graminearum (Gibberella zeae), F. culmorum, F. subglutinans, F. oxysporum and F. acuminatum, of which F. graminearum was the most abundant. With the direct plating technique 87% of grains were infected with Fusarium spp., with some grains being infected with more than one species. Segments from husks and litter, 70% and 43% respectively, were colonised by Fusarium spp. F. graminearum was the most frequent species isolated from maize grain and husk segments(48.3 and 37.7% colonisation respectively). Other species, particularly F. culmorum and F. acuminatum, were also found to be common contaminants. A total of 15 Fusarium spp. was recovered from all material examined by both techniques. Cultures with characteristics resembling those of F. moniliforme were rarely observed.This revised version was published online in October 2005 with corrections to the Cover Date.     

The mycoflora of groundnut rhizosphere,soil and geocarposphere on light,medium and heavy soils and its relations to aspergillus flavus

Summary A comparative study was carried out in groundnut fields in Israel of the mycoflora of rhizosphere (R) and soil adhering to geocarps (G) and of the soil (S).Of a total of 157 fungal species isolated and listed, 133 occurred in R, 96 in S, and 86 in G. Ten species considered rare or worthy of special note are briefly discussed.Species ofAspergillus were most numerous in heavy soil, species ofPenicillium in light soil, and species ofFusarium in medium soil.Penicillium funiculosum andP. rubrum were the species occurring with greatest frequency, and these were equally common in R, S, and G of light and medium soil. Soil inoculation withA. flavus depressed the number of species in the mycoflora of R and S.Quantitative comparison of R, S, and G on the three soils showed that numbers for R exceeded those for S and G, forP. funiculosum andP. rubrum on all soils, and for several Aspergilli on heavy soil. Among fungi more prevalent in S than in R and G wasA. flavus on medium and heavy soil. No special affinity of any one of the 3 major groups (Aspergillus, Penicillium, Fusarium) for the mycoflorae of R or S or G has been found. The relative number of colonies of all fungi in R and S (R/S ratio) was in almost all cases in excess of 1 on all soil types.This research is supported by grant number FG-161 of the United States Department of Agriculture, to whom the author is indebted.     

THE OCCURRENCE AND DISTRIBUTION OF ACRASIEAE IN FORESTS OF SUBTROPICAL AND TROPICAL AMERICA

Forests of the subtropical and tropical regions of North America harbor cellular slime molds not found in the soils of temperate deciduous forests investigated previously. However, most species found in the temperate forest are common in the tropics. Although the diversity of forms is greater in the soils of tropical forests the numbers of Acrasieae per unit of soil are comparable. Characteristic of tropical and subtropical forest soils are Acrasieae bearing crampon bases, of which four new species of Dictyostelium are presently known. Also present, but less frequently isolated, are two other new species of the genus Dictyostelium and two still undescribed species of the Guttulinaceae. Occasional isolates of D. purpureum and D. discoideum were found that produce macrocysts, which seem, also, to be confined to tropical and subtropical areas. Macro-cysts were previously known only in D. mucoroides and D. minutum isolated from temperate forest soils. The occurrence and distribution of Acrasieae in warm temperate desert and mesquite-scrub, in subtropical hammock, and in tropical thorn, deciduous, seasonal evergreen, rain, and cloud forests were investigated. Acrasieae were well represented in all of these forests except desert. The number of species and the total populations were largest in seasonal evergreen forests. The composition of the cellular slime mold populations and the dominant species within these populations could be related to the soil environment as expressed by the dominant vegetation.     

Identification of a mycorrhizal fungus in Epipogium roseum (Orchidaceae) from morphological characteristics of basidiomata

A mycorrhizal fungus, ME1-1, isolated from an achlorophyllous orchid, Epipogium roseum, was identified as Coprinellus disseminatus (≡ Coprinus disseminatus) based on characteristics of basidiomata that were artificially induced. Spawn of ME1-1 cultivated on a medium that consisted of sawdust and wheat, sandwiched between two mats of volcanic soils, which was incubated at 20.0° ± 0.5°C in 80.0% ± 0.5% relative humidity in the dark. The basidiomata were formed on the soil after 2 months. Morphological and anatomical characteristics of the basidioma mostly accorded with those of Coprinellus disseminatus. We therefore concluded that C. disseminatus is one of the mycobionts of E. roseum.     

Soil water potential as a factor in the ecology ofFusarium roseum f. sp.cerealis ‘Culmorum’

Summary The soil water potential (inferred from vapor pressure measurements by thermocouple psychrometry) influenced both chlamydospore germination and continuing growth of germlings ofFusarium roseum f. sp.cerealis ‘Culmorum’ the same way in two different soils. Chlamydospore germination in both Ritzville silt loam (RSL) and Palouse silt loam (PSL) amended with about 2,500 ppm C (as glucose) and 250 ppm N (as ammonium sulfate) was 40–50 per cent in 24 hours at water potentials down to −50 to −60 bars. Some germination occurred by 72 hours at −80 to −85 bars in both soils but not at lower potentials. At a potential of −10 bars or higher, germ tubes lysed or converted into new chlamydospores within 48–72 hours after germination, whereas at lower potentials germlings branched and appeared to grow for at least 6 days. Bacterial numbers/g of RSL, 24 and 72 hours after adding nutrients, were 200 to 300 times greater in soil at water potentials of −5 bars or more than in comparably treated soil at about −14 to −17 bars or less. Markedly reduced bacterial activity appeared to coincide with a water potential of about −9 to −10 bars. When streptomycin and neomycin (300 ppm each) were mixed into the soil in addition to nutrients, the survival of germlings of Culmorum was greatly enhanced, even in soil at potentials of less than −1 bar. Indications were that soil water potentials of −10 bars or more favored bacterial activity, and that this in turn repressed growth of germlings of Culmorum. Culmorum infections of below-ground parts of wheat are serious primarily in drier soils, possibly because the fungus escapes bacterial antagonism but can still extract water for growth. Cooperative investigations, Crops Research and the Water and Soil Conservation Research Divisions, Agricultural Research Service, U.S. Department of Agriculture and the Agricultural Experiment Stations of Idaho, Montana, Oregon, Utah, and Washington. Scientific Paper No.3152, College of Agriculture, Washington State University, Pullman.     

Arbuscular mycorrhizal fungi associated with common pteridophytes in Dujiangyan,southwest China

The colonization and diversity of arbuscular mycorrhizal (AM) fungi associated with common pteridophytes were investigated in Dujiangyan, southwest China. Of the 34 species of ferns from 16 families collected, 31 were colonized by AM fungi. The mean percentage root length colonized was 15%, ranging from 0 to 47%. Nineteen species formed Paris-type and 10 intermediate-type AM. In two ferns, only rare intercellular non-septate hyphae or vesicles were observed in the roots and AM type could not be determined. Of the 40 AM fungal taxa belonging to five genera isolated from rooting-zone soils, 32 belonged to Glomus, five to Acaulospora, one to Archaeospora, one to Entrophospora, and one to Gigaspora. Acaulospora and Glomus were the dominant genera and Glomus versiforme was the most common species. The average AM spore density was 213 per 100 g air-dried soil and the average species richness was 3.7 AM species per soil sample. There was no correlation between spore density and percentage root length colonized by AM fungi.     

The distribution ofFusarium species in soils planted to millet and sorghum in Lesotho,Nigeria and Zimbabwe

Samples from soils planted to millet and sorghum from Lesotho, Nigeria, and Zimbabwe were processed and a total of 3,291Fusarium cultures were recovered. Of these 1,296 cultures were isolated from plant debris and 1,995 cultures were recovered from soil dilutions. The most prevalent species recovered wereF. oxysporum (37%),F. equiset (30%),F. solani (14%),F. moniliforme (6%),F. compactum (5%),F. nygamai (4%), andF. chlamydosporum (2%). OtherFusarium species isolated wereF. merismoides, F. polyphialidicum, F. graminearum, F. subglutinans, F. sambucinum, F. longipes, F. semitectum, F. dimerum, F. lateritium, and a group of cultures designated as population A which resembleF. camptoceras. Fusarium equiseti was the predominant species in soil samples from Nigeria and Zimbabwe, whileF. oxysporum was the predominant species recovered from soil from Lesotho.Contribution No. 1881, Fusarium Research Center, Department of Plant Pathology, The Pennsylvania State University.     

Occurrence of Zearalenols (Diastereomeric Mixture) in Corn Stalk Rot and Their Production by Associated Fusarium Species

Zearalenol was extracted from Fusarium-infected stems of corn from southern Italy. The toxin, which appeared as a single compound in various thin-layer chromatography systems, was resolved by high-pressure liquid chromatography into two components. A gas chromatography-mass spectrometry examination of a purified fraction confirmed the natural occurrence of zearalenol as a diastereomeric mixture and led to the identification of alpha (56 ng/g) and beta (27 ng/g) isomers. Among nine Fusarium species found associated with stalk rot in corn, only Fusarium culmorum (F. roseum `Culmorum') and F. equiseti (F. roseum `Gibbosum') produced zearalenol and always produced it in a diastereomeric mixture of alpha and beta isomers.