The occurrence of Microsporon gypseum (Bodin,Guiart & Grigorakis) in soil nematodes

Summary The author gives a brief survey on the prevailing statements of today's soil biology on the occurrence of nematodes in soils, further on their conditions of living and on those of the rapacious fungi as well. On the basis of his own investigations carried out mainly in garden soils of the Hungarian Plain being dressed and undressed with manure, he comes to the conclusion that the occurrence ofM. gypseum cultured by means of the To-Ka-Va method, and on the presence of the nematodes in the soil admit the assumption that the frequent infection of persons engaged in gardening which is generally caused byM. gypseum, is likely to be in correlation with the abundance of nematodes in these soils.     

Ecology of nematophagous fungi: Effect of the soil nutrients N,P and K,and seven major metals on distribution

The effects of the major soil nutrients and seven common metals on the distribution of nematophagous fungi were evaluated by comparing the concentration of the elements in soils with and without nematophagous fungi. Mineral nutrients, which were all positively correlated with nematode density, were the most important elements determining the presence of such fungi. Endoparasites producing adhesive conidia were independent of all the elements tested, while those species forming ingested conidia were isolated from soils high in nutrients, indicating a strong dependence on nematode density. Knob forming predators which rely on their ability to spontaneously produce traps to obtain nutrients were isolated from soils with low concentrations of mineral nutrients, while species with constricting rings were isolated from richer soils containing a greater density of nematodes. Net-forming species were largely independent of soil fertility, although generally they were isolated from soils with limited nutrientsd, especially K. Like other fungi, nematophagous fungi are generally not found in soils containing elevated concentrations of heavy metals. The results indicate that even concentrations of heavy metals which naturally occur in Irish soils can restrict the distribution of this fungal group. However the endoparasiteMeria coniospora is tolerant to all metals and to Cu in particular.     

Generalist entomopathogens as biological indicators of deforestation and agricultural land use impacts on Waikato soils

The relative abundance of entomopathogenic nematodes and fungi was estimated for 10 sites in each of indigenous forest, pasture, and cropland habitats by baiting soil samples with Galleria larvae. The steinernematid Steinernema feltiae (Filip) was the dominant nematode, occurring in soils from all three habitat types. The heterorhabditid Heterorhabditis zelandica Poinar was recovered only from soils of podocarp (Dacrycarpus dacrydioides (A. Rich.)) forests. Galleria infection by nematodes was higher in soils from forest habitat than in soils from pasture and cropland. Among the sampled forests, nematode infection was higher in soils from podocarp stands than those from broadleaf stands. The deuteromycete fungi Beauveria bassiana (Balsamo) Vuillemin, Metarhizium anisopliae (Metschnikoff) Sorokin, and Paecilomyces cf. cicadae (Miquel) Samson, and a Entomophthorales zygomycete, tentatively identified as a Tarchium species, were recovered from the Galleria baits. Infection of Galleria by B. bassiana and M. anisopliae occurred in soils from all habitat types, while that by P. cicadae occurred only in soils from forest habitats. Tarchium was recovered from a single pasture site. The frequency of Galleria infection by these entomopathogenic fungi collectively, and by B. bassiana alone, was higher in pasture soils than in soils from either forest or cropland. These results are discussed in relation to disturbance effects of land use changes and the potential role of generalist entomopathogens as biological indicators of soil health.     

Effects of Nematophagous Fungi on Numbers and Death Rates of Bacterivorous Nematodes in Arable Soil

In a series of microcosm experiments with an arable, sandy loam soil amended with sugarbeet leaf, the short-term (8 weeks) dynamics of numbers of nematodes were measured in untreated soil and in γ-irradiated soil inoculated with either a field population of soil microorganisms and nematodes or a mixed population of laboratory-propagated bacterivorous nematode species. Sugarbeet leaf stimulated an increase in bacterivorous Rhabditidae, Cephalobidae, and a lab-cultivated Panagrolaimus sp. Differences were observed between the growth rates of the nematode population in untreated and γ-irradiated soils, which were caused by two nematophagous fungi, Arthrobotrys oligospora and Dactylaria sp. These fungi lowered the increase in nematode numbers due to the organic enrichment in the untreated soil. We estimated the annually produced bacterivous nematodes to consume 50 kg carbon and 10 kg nitrogen per ha, per year, in the upper, plowed 25 cm of arable soil.     

Effects of nematodes,fungi and bacteria on the growth of young apple trees grown in apple replant disease soil

Growth, dry root weight of seedlings and root score of apple seedlings cv. McIntosh were reduced when soils were inoculated with Pratylenchus penetrans, Penicillium janthinellum, Constantinella terrestris, Trichoderma sp., and 4 strains of Bacillus subtilis. Trichoderma sp., and B-1 and B-26 strains of B. subtilis alone reduced plant growth but the combination of Trichoderma sp. + B. subtilis (B-1) and Trichoderma sp. + B. subtilis (B-26) increased plant height. Plant height, root weight and root score were significantly reduced when P. penetrans plus B. subtilis or P. penetrans plus fungi plus bacteria were present in the soil. It is suggested that fungi, bacteria, nematodes alone or their combinations such as nematodes plus bacteria or nematodes plus fungi plus bacteria may contribute towards the occurrence of apple replant disease.Contribution number 700.Contribution number 700.     

华东地区根结线虫寄生真菌调查*

通过对5种分离根结线虫寄生真菌的方法的比较,发现通过雌成虫平板分离法和卵平板分离法有较高的成功率,其他三种自幼虫上或土壤中分离的方法很少取得成功。从华东地区104个根结线虫样品中分离得到根结线虫寄生真菌638个菌株, 鉴定为14个属22个种,其中Cylindrocarpon destructans, C.heteronema, Fusarium equiseti, F.lateritium, F.proliferatum, Gliocladium virens, Humicola fuscoatra, Idriella lunata, Trichoderma hamatum, T.harzianum, Verticillium catenulatum, Volutella ciliata 为首次报道在根结线虫上寄生。通过种群分析发现Fusarium solani出现频率最高, F. oxysporum, Paceilomyces lilacinus 和 Acremonium strictum为常见种,这些种在根结线虫上广泛分布。同时还发现卵和成虫寄生真菌有所不同,Gliocladium virens 和Trichoderma harzianum仅在卵上分离到,而Volutella ciliata, Trichoderma hamatum 和Idriella lunata仅在雌成虫分离到,从幼虫上仅分离一次Paecilomyces lilacinus。其它真菌在卵和成虫上均可分离得到,真菌种类在三种根结线虫上和在不同地区有所不同。     

Citrus replant problem in Iraq I. Possible role of soil fungi and nematodes

The role of soil fungi and nematodes in citrus replant problems was investigated. Several pathogenic and non-pathogenic fungi and the nematodeTylenchulus semipenetrans were isolated in about equal abundance from soils which displayed or did not display replant problems. However, in almost all trees showing evidence of decline, infection by the fungusPhytophthora citrophthora had advanced through the roots until it had reached the tree crown. Fumigation of old citrus soil with methyl bromide greatly increased the growth of sour organe. The application of Nemacure, Benomyl and Ridomil 5G confirmed the important role of pathogenic and non-pathogenic fungi and nematodes in the citrus replant problem. Inoculation of methyl bromide-treated soil with the pathogenic and non-pathogenic fungi separately or in combination further confirmed the previous experiments and also revealed an important role ofP. citrophthora andFusarium solani when replanting citrus in old citrus orchards.     

First record of Clonostachys rosea (Ascomycota: Hypocreales) as an entomopathogenic fungus of Oncometopia tucumana and Sonesimia grossa (Hemiptera: Cicadellidae) in Argentina

Clonostachys rosea (Link: Fries) Schroers, Samuels, Seifert, and Gams (Ascomycota: Hypocreales) has been reported as a mycoparasite of fungi and nematodes and as saprobe in soils, but this fungus has not been reported previously to be entomopathogenic. Many species of cicadellid leafhoppers cause economic damage to crops as vectors of plant pathogens. In the present work, we report the first record of C. rosea as an entomopathogenic fungus of two leafhoppers pest, Oncometopia tucumana and Sonesimia grossa (Hemiptera: Cicadellidae), in Argentina and evaluate the pathogenicity of C. rosea against them.     

Development of Dactylaria eudermata Drechsler a predaceous fungi in Meloidogyne incognita

Dactylaria eudermata Drechsler is one of the important predaceous fungi occurring widely in different soils. The fungus produces hyphal bails and network compound in which nematodes are entangled. This hyphal nets as trapping structure which may be single dimensional to two or three dimensional and are formed through repeated hyphal anastomosis, which capture nematodes either through the adhesive material present on the surface of hyphal nets or due to physical entanglement. In the experiment it was observed that inflation of hyphal bails takes 30 to 50 minutes and capturing and killing the nematode by a single conidia in water takes 35–55 hours, were as time required for inflation of hyphal bails and real trapping and killing of a nematode in maize meal (MMA: water (1:10) medium) takes one minute and 30–50 hours respectively.     

食线虫真菌资源研究概况

食线虫真菌是指寄生、捕捉、定殖和毒害线虫的一类真菌,这类真菌是自然界中线虫种群控制的重要因子,也是动植物病害生物防治的重要研究材料,具有特殊的研究意义和经济价值。目前全世界共报道700余种食线虫真菌,包括捕食线虫真菌380余种,线虫内寄生真菌120余种,产毒真菌270余种和大量机会真菌。针对丰富的食线虫真菌资源,近年来世界各国尤其是中国科学家对其进行了广泛研究,在捕食线虫真菌资源的分类、系统进化、生态分布、有性无性联系等方面的研究取得了重要进展,在线虫内寄生真菌侵染宿主的方式及产毒真菌的次生代谢产物挖掘等方面也进行了广泛研究,文章综述了以上研究进展并简述了食线虫真菌资源的生物防治应用概况。     

The living strategy of nematophagous fungi

The infection structures, trophism, and ecological character of nematophagous fungi are reviewed in this article on the basis of data extracted from the literature and the most recent experiments conducted in this area. Traditionally, nematophagous fungi are classified into four groups according to their modes of attacking nematodes: nematode-trapping fungi using adhesive or mechanical hyphal traps, endoparasitic fungi using their spores, eggparasitic fungi invading nematode eggs or females with their hyphal tips, and toxin-producing fungi immobilizing nematodes before invasion. In the present review, we focus on the first two groups. The living strategies of these nematophagous fungi depend on the diversity of their infection structures, such as different traps and spore types, which determine the modes of infecting nematodes. The diversity of trophic modes of nematophagous fungi is an important prerequisite for fungal survival and activity in soil. The abundance and activity of Hirsutella rhossiliensis and H. minnesotensis, representatives of endoparasites and potential biocontrol agents against nematodes, are highly dependent on environmental factors. Comprehensive understanding of the survival and activity of nematophagous fungi in soil is fundamental for the exploitation of these fungi as successful biocontrol agents.     

Ecology of nematophagous fungi: vertical distribution in a deciduous woodland

Summary The distribution of nematophagous fungi in soil collected from a deciduous woodland is compared to various biotic and abiotic soil factors. The microfungi are isolated at all depths down to a maximum of 35 cm. Predators forming constricting rings, adhesive branches and adhesive knobs are restricted to the upper litter and humus layers. The net forming predators and endoparasites are isolated at all depths, although they are significantly more abundant in the lower mineral rich soils. A much greater species diversity of nematophagous fungi is recorded in the upper organic zones.Preliminary soil analysis indicates thatCephalosporium balanoides is independent of all soil variables, while predators able to form traps spontaneously are restricted to the organic soils which are rich in nematodes. Non-spontaneous trap forming predators, which are excellent saprophytes, are isolated from the deeper soils which are low in nutrients. The ecological significance of these results is discussed.     

Resistance of soil biota and plant growth to disturbance increases with plant diversity

Plant diversity is critical to the functioning of ecosystems, potentially mediated in part by interactions with soil biota. Here, we characterised multiple groups of soil biota across a plant diversity gradient in a long‐term experiment. We then subjected soil samples taken along this gradient to drought, freezing and a mechanical disturbance to test how plant diversity affects the responses of soil biota and growth of a focal plant to these disturbances. High plant diversity resulted in soils that were dominated by fungi and associated soil biota, including increased arbuscular mycorrhizal fungi and reduced plant‐feeding nematodes. Disturbance effects on the soil biota were reduced when plant diversity was high, resulting in higher growth of the focal plant in all but the frozen soils. These results highlight the importance of plant diversity for soil communities and their resistance to disturbance, with potential feedback effects on plant productivity.     

Soil microbiota in two annual grasslands: responses to elevated atmospheric CO2

We measured soil bacteria, fungi, protozoa, nematodes, and biological activity in serpentine and sandstone annual grasslands after 4 years of exposure to elevated atmospheric CO₂. Measurements were made during the early part of the season, when plants were in vegetative growth, and later in the season, when plants were approaching their maximum biomass. In general, under ambient CO₂, bacterial biomass, total protozoan numbers, and numbers of bactivorous nematodes were similar in the two grasslands. Active and total fungal biomasses were higher on the more productive sandstone grassland compared to the serpentine. However, serpentine soils contained nearly twice the number of fungivorous nematodes compared to the sandstone, perhaps explaining the lower standing crop of fungal biomass in the serpentine and suggesting higher rates of energy flow through the fungal-based soil food web. Furthermore, root biomass in the surface soils of these grasslands is comparable, but the serpentine contains 6 times more phytophagous nematodes compared to the sandstone, indicating greater below-ground grazing pressure on plants in stressful serpentine soils. Elevated CO₂ increased the biomass of active fungi and the numbers of flagellates in both grasslands during the early part of the season and increased the number of phytophagous nematodes in the serpentine. Elevated CO₂ had no effect on the total numbers of bactivorous or fungivorous nematodes, but decreased the diversity of the nematode assemblage in the serpentine at both sampling dates. Excepting this reduction in nematode diversity, the effects of elevated CO₂ disappeared later in the season as plants approached their maximum biomass. Elevated CO₂ had no effect on total and active bacterial biomass, total fungal biomass, or the total numbers of amoebae and ciliates in either grassland during either sampling period. However, soil metabolic activity was higher in the sandstone grassland in the early season under elevated CO₂, and elevated CO₂ altered the patterns of use of individual carbon substrates in both grasslands at this time. Rates of substrate use were also significantly higher in the sandstone, indicating increased bacterial metabolic activity. These changes in soil microbiota are likely due to an increase in the flux of carbon from roots to soil in elevated CO₂, as has been previously reported for these grasslands. Results presented here suggest that some of the carbon distributed below ground in response to elevated CO₂ affects the soil microbial food web, but that these effects may be more pronounced during the early part of the growing season.     

Nematophagous fungi of Toxocara canis eggs in a public park of La Plata, Argentina

Fungi have showed a great potential for the biological control of nematodes. However, they have not been evaluated for the control of animal and/or human parasites transmitted by egg contaminated soils. Environmental contamination with Toxocara spp. eggs is a public health problem. Accidental swallowing of Toxocara canis eggs (a nematode of dogs) usually results on a zoonotic infection (toxocarosis). The objectives of this research were: 1) To test the presence of antagonistic fungi against T. canis in the soil in public places of La Plata city, Argentina, infected with eggs of this parasite, 2) To determine the possible association between biotic and abiotic factors of the soil with the presence of fungal parasites of egg nematodes. Soil samples were tested for: textural type, organic matter (%), pH, presence of egg-parasite fungi, of larvae and of nematode eggs, in particular of Toxocara spp. The studied area showed the following characteristics: pH: 6.6-8.0, organic matter: 1.2-70%, with a predominantly loam texture. The following antagonistic fungal genera were identified: Acremonium, Aspergillus, Chrysosporium, Fusarium, Humicola, Mortierella, Paecilomyces and Penicillium. A prevalence of 70% was detected for nematode eggs, of 33% for Toxocara spp. eggs and of 90% for larvae. No association between the presence of egg-parasite fungi and the considered factors was found. More studies are necessary to know the natural antagonism factors to T. canis eggs for its in situ biological control.     

High infectivity of an endoparasitic fungus strain, <Emphasis Type="Italic">Esteya vermicola</Emphasis>, against nematodes

Esteya vermicola, as the first recorded endoparasitic fungus of pinewood nematodes, exhibits great potential as a biological agent against nematodes. However, only two strains of this species have been described so far. In this study, we identified a novel endoparasitic fungal strain, CNU 120806, isolated from infected nematodes in forest soil samples during a survey of nematophagous fungi in Korea. This strain showed similar morphological characteristics and infection mode with the two previously described strains of E. vermicola. All strains are characterized by the ability to produce two types of conidiogenous cells and conidia, and to parasitize nematodes with lunate adhesive conidia. Moreover, the CNU 120806 strain showed 100% identity with E. vermicola CBS 115803 when their partial sequences of 28S rRNA gene were compared. Molecular phylogenetic analysis further identified CNU 120806 as a strain of E. vermicola, by clustering CNU 120806 and E. vermicola CBS 115803 into a single subclade. Culture medium influenced the proportion of dimorphic CNU 120806 conidia, and further changed the adhesive and mortality rates of nematodes. The CNU 120806 strain exhibits high infection activity against nematodes on nutrient-rich PDA medium. Almost all tested nematodes were killed within 8 approximately 10 days after inoculation. This study provides justification for further research of E. vermicola, and the application and formulation of this fungus as a bio-control agent against nematodes.     

Interaction of nematodes with nematophagus fungi: induction of trap formation, attraction and detection of attractants

Induction of trap formation in Arthrobotrys oligospora, A. conoides and Monacrosporium cystosporum was studied during a 24 h period in the presence of the free-living nematodes Panagrellus redivivus on various nutrient media. A definite pattern of trap formation was observed in these fungi. Low nutrient mineral salt medium had the most pronounced effect on trap formation. Attraction and repulsion of P. redivivus towards these three nematophagous and three non-nematophagous fungi was studied. The nematodes were attracted towards three nematophagous and one non-nematophagous fungi, the other two repelled them. Attractants of the nematophagous fungi were determined by thin-layer chromatography. In the case of A. oligospora and M. cystosporum, four spots were traced, whereas in A. conoides, five spots were detected.     

Effects of introduced and indigenous VA mycorrhizal fungi on nodulation,growth and nutrition ofMedicago sativa in phosphate-fixing soils as affected by P fertilizers

Summary The legumeMedicago sativa was grown in two phosphate-fixing soils which received soluble or rock phosphate. The effects of the inoculation withGlomus mosseae on plant nutrition and nodulation were studied. The introduced VA fungi became successfully established and improved the degree of infection over level achieved by native endophytes. In all experimental conditions tested, plant dry weight, the total uptake of N and P and nodulation byRhizobium meliloti were increased by mycorrhizal inoculation. The size of the increase was inversely correlated with soluble P content in the soil. Mycorrhization, enhanced by introduction of suitable VA fungi, had similar effects to that of the dose of soluble phosphate tested. Indigenous and native endophytes cooperated in these effects. Results are discussed in terms of reducing the input of soluble P fertilizer to phosphate-fixing soils and the possibility of restoring the phosphate stock using a more rational supply of soluble P, that allows cooperation with VA fungi, or by the use of less soluble and expensive forms of P fertilizers.     

Nematode-Capturing Hyphomycetes from Soils over Xerophytic Calcareous Rock in Upper Bavaria*

Nematode-capturing hyphomycetes were isolated from soil and plant debris on the south slope of a hill in the Jurassic of Upper Bavaria. The following species were found: Arthrobotrys arthrobotryoides, A. dactyloides, A. oligospora, A. superba, Dactylella astenopaga, Monacrosporium cionopagum, M. psychrophilum. Endozoic fungal parasites of nematodes were not isolated. With one fungal propagule of nematode-destroying fungi in 1.7 g soil, the density is only slightly lower than values given for agricultural soils.