Failure of a Mycelial Formulation of the Nematophagous FungusHirsutella rhossiliensisto Suppress the NematodeHeterodera schachtii

Jaffee, B. A.; Muldoon, A. E.; Westerdahl, B. B.

doi:10.1006/bcon.1996.0043

Cited by 18 publications

(12 citation statements)

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“…Although feeding preferences of enchytraeids are not well understood (Didden 1993;Mothes-Wagner et al 1996), these segmented worms ingest fungal spores and hyphae (Standen and Latter 1977), have been associated with fungi in the ®eld (Dash and Cragg 1972;Standen and Latter 1977;Dash et al 1980;Jaee et al 1996;Jaee and Muldoon 1997), and have suppressed nematophagous fungi in soil microcosms (Jaee et al, in press). We therefore hypothesized that exclusion of enchytraeids would increase persistence of nematophagous fungi in ®eld plots, and that hypothesis was supported by three cage experiments in this study.…”

Section: Discussionmentioning

confidence: 99%

“…This could be caused by a¯ush of nutrients released by soil heat treatment, but the hyphae in the pellets contain abundant nutrients that support extensive growth. We therefore suspect that heat treatment reduced numbers of antagonistic microorganisms and protozoa (Mankau 1962;Cooke and Satchuthananthavale 1968;Guima and Cooke 1974;Jaee et al 1996;Jager and Velvis 1996). Separating the eects of nutrition, microorganisms, microfauna, and mesofauna is not easy, however, and will require additional research.…”

Section: Discussionmentioning

confidence: 99%

“…When placed in a moist and warm environment, the fungus in the dried pellet uses stored assimilate in the hyphae to produce new structures, including those that adhere to and infect nematodes. Enchytraeids seemed to feed on pellets in soil, and Jaee et al (1996) and Jaee and Muldoon (1997) therefore suspected that they reduced the ecacy of the fungi as biological control agents.…”

Section: Introductionmentioning

confidence: 99%

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Suppression of nematophagous fungi by enchytraeid worms: a field exclosure experiment

Jaffee

Santos²,

Muldoon³

1997

Oecologia

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The feeding biology of Enchytraeus crypticus and other enchytraeids is poorly understood as is their effect on nematophagous fungi. Because enchytraeids had been associated with nematophagous fungi in the field and had suppressed these fungi in soil microcosms, we tested the hypothesis that exclusion of enchytraeids, largely E. crypticus, would improve establishment of certain nematophagous fungi in field plots. The fungi, Hirsutella rhossiliensis and Monacrosporium gephyropagum, are being studied as potential control agents of plant-parasitic nematodes and were formulated as hyphae in alginate pellets. The pellets were mixed into soil without enchytraeids and placed in cages (PVC pipe, 80 cm volume) with fine (20 μm) or coarse (480 μm) mesh; cages were buried 15 cm deep in field plots and then recovered after 6-52 days. When fine mesh was used, enchytraeids were excluded and the fungi increased to large numbers. When coarse mesh was used, enchytraeid numbers in cages increased rapidly and the fungi did poorly. Although mesh also affected other potential fungivores, including collembolans and large dorylaimid nematodes, we suspect that enchytraeids were more important because large numbers were consistently found in cages with coarse mesh soon after the cages were placed in soil. Organisms smaller than enchytraeids (bacteria, fungi, and protozoa) also appeared to be important because the fungi did better in heat-treated soil than in non-heat-treated soil, regardless of mesh size. The rapid increase in enchytraeid numbers in cages with hyphal pellets and coarse mesh was probably caused by movement of enchytraeids toward the pellets with hyphae: increase in enchytraeid numbers was minimal when movement into cages was blocked (or when cages contained pellets without hyphae). Overall, the data were consistent with the hypothesis that enchytraeids, or other meso- or macrofauna, contributed to suppression of nematophagous fungi in our field plots.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Suppression of nematophagous fungi by enchytraeid worms: a field exclosure experiment

Jaffee

Santos²,

Muldoon³

1997

Oecologia

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“…Once the fungus penetrates the nematode, it proliferates in the nematode body and produces new conidia within a few days (Lackey et al, 1992); these conidia then initiate a new round of infection. Although H. rhossiliensis significantly suppressed plant-parasitic nematodes in greenhouse and laboratory assays (Velvis and Kamp, 1996;Amin, 2000;Liu and Chen, 2001;Chen and Liu, 2005), the fungus did not reduce population densities of cyst and root-knot nematodes in some field trials Jaffee et al, 1996;Chen et al, unpublished data). Because the fungus provided inconsistent nematode suppression in different studies, we suspect that a better understanding of its ecology after being introduced into soil is critical for its successful use as an inundative commercial biocontrol agent.…”

Section: Introductionmentioning

confidence: 99%

Population dynamics and biocontrol efficacy of the nematophagous fungus Hirsutella rhossiliensis as affected by stage of the soybean cyst nematode

et al. 2008

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a b s t r a c tMonitoring the population dynamics of a biocontrol agent in soil is important for understanding, predicting and increasing its efficacy. In this study, the population dynamics and the efficacy of a promising biocontrol agent against nematode, the fungus Hirsutella rhossiliensis, were investigated in greenhouse experiments with quantitative real-time polymerase chain reaction (PCR) and bioassay. To explore the effects of the fungus on nematode inoculum, soil infested with eggs or second-stage juveniles (J2) of Heterodera glycines was used. The results showed that the quantity of H. rhossiliensis DNA based on real-time PCR decreased over time, regardless of eggs or J2 as inoculum. The quantity of H. rhossiliensis DNA [femtogram (fg)/g soil] was highest (3.83 ± 1.96 Â 10 8 fg/g soil) when the fungus was first added to soil and then decreased rapidly to 3.24 ± 1.22 Â 10 7 fg/g in egg-infested soil and 7.34 ± 2.94 Â 10 7 fg/g in J2-infested soil 17 days after planting, and then declined gradually between 17 and 59 days after planting. The data based on the bioassay showed that the percentage of J2 parasitized by H. rhossiliensis decreased throughout the experiment in both egg-and J2-infested soils. H. rhossiliensis controlled H. glycines more effectively in J2-infested soil than in egg-infested soil. At the end of the experiments (59 days after planting), nematode suppression and plant growth promotion in J2-infested soil were 79% and 55%, respectively, which were higher than the 34% and 2% in egg-infested soil. In soil that was not inoculated with the fungus, the number of H. glycines was 10 times higher in J2-infested soil than in egg-infested soil, indicating the greater nematode inoculum potential in soil infested with J2. DNA yield of H. rhossiliensis was statistically higher in J2-infested soil than in egg-infested soil in earlier period (prior to day 31) (p < 0.05), which is consistent with the hypothesis that the numbers of J2 present during and soon after fungal inoculation are critical for maintaining the population density and biocontrol efficiency of the fungus.

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“…The pellets, however, did poorly in field microplots (16,18). Because performance improved if the pellets were added to 60°C-treated rather than to non-heattreated microplot soil, poor performance was attributed to antagonistic organisms.…”

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confidence: 98%

Soil pH and the Activity of a Pelletized Nematophagous Fungus

Jaffee¹,

Zasoski²

2001

Phytopathology®

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When formulated as assimilative hyphae in alginate pellets, the nematophagous fungus Hirsutella rhossiliensis was more active (i.e., parasitized more assay nematodes) in an acidic vineyard soil than in a neutral vineyard soil. To determine whether soil pH explained the difference, fungus activity was measured in soil from the neutral site that had been acidified (by adding sulfuric acid) and in soil from the acidic site that had been neutralized (by adding calcium hydroxide). As hypothesized, the activity of pelletized Hirsutella rhossiliensis was negatively correlated with soil pH. Maximum activity occurred at pH(calcium chloride) 4.5, and activity gradually declined to near zero as the pH increased to 6.5 and rapidly declined to near zero as the pH dropped below 4.0. Assays performed on leached soil samples indicated that the effects of sulfuric acid and calcium hydroxide were largely due to pH rather than to specific ions or osmotic potential. The effect of pH, however, was indirect. Heating the neutral soil to 60 degrees C for 2 h did not alter soil pH or electrical conductivity but increased fungus activity to levels equivalent to those in acidified soil. We conclude that, in these two soils, heat treatment or low soil pH suppresses soil organisms that otherwise interfere with growth of Hirsutella rhossiliensis from alginate pellets.

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Failure of a Mycelial Formulation of the Nematophagous FungusHirsutella rhossiliensisto Suppress the NematodeHeterodera schachtii

Cited by 18 publications

References 0 publications

Suppression of nematophagous fungi by enchytraeid worms: a field exclosure experiment

Suppression of nematophagous fungi by enchytraeid worms: a field exclosure experiment

Population dynamics and biocontrol efficacy of the nematophagous fungus Hirsutella rhossiliensis as affected by stage of the soybean cyst nematode

Soil pH and the Activity of a Pelletized Nematophagous Fungus

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