Fumosoroseus Isolates Research Articles

Influence of culture media in viability test of conidia of entomopathogenic fungi

This work aimed at investigatimg whether the culture medium used in viability tests affects the conidial germination of Lecanicillium lecanii, Beauveria bassiana and Paecilomyces fumosoroseus isolates. The tests were performed on microscope slides containing one of the culture media: agar-water (AW), minimal medium (MM), potato-dextrose agar (PDA), potato-dextrose-1% yeast extract agar (PDAY), Sabouraud-dextrose-yeast extract agar (SDAY), and complete medium (CM). Three areas per slide were delimited and 0.05ml of a 5.5 x 105 conidia ml-1 suspension was applied to each area. One bioassay was performed for each isolate. Germination was determined after 15 hours of incubation at 26±0.5°C. The culture media influenced the germination of the species studied, verifying within and inter specific variations. CM and PDA provided the highest germination of L. lecanii isolates and the lowest was obtained on SDAY and AW. The germination of B. bassiana isolates was favoured by CM, PDA and PDAY media, a fact not observed in AW and MM. P. fumosoroseus isolates showed the highest germination on CM and PDA media and the lowest on SDAY. However, some isolates presented high germination on nutrient-poor media (AW and MM).

Isolation and characterization of microsatellite loci from the entomopathogenic hyphomycete, Paecilomyces fumosoroseus

AbstractNine microsatellite markers were isolated from the entomopathogenic haploid fungus Paecilomyces fumosoroseus. Genetic diversity was assessed in 26 P. fumosoroseus isolates originated from the whitefly Bemisia tabaci collected in various geoclimatic areas. Eight loci were polymorphic with an observed number of alleles ranging from two to six. The loci differentiated some isolates and group of isolates according to their geographical location, showing promise for the study of gene flow. All loci failed to give clear amplifications in P. fumosoroseus isolates from hosts other than B. tabaci. These microsatellite markers provide powerful tools for ecological, epidemiological, and population genetic studies.

Relationship between thermotolerance and hydrophobin-like proteins in aerial conidia of Beauveria bassiana and Paecilomyces fumosoroseus as fungal biocontrol agents.

This study was to illustrate the relationship between the thermotolerance and the contents of hydrophobin-like or formic-acid-extractable (FAE) proteins in aerial conidia of Beauveria bassiana and Paecilomyces fumosoroseus produced on rice-based substrate. Survival indices of 11 isolates were separately assessed as a ratio of the viability of conidia after 3-150 min thermal stress at 48 degrees C over that of unstressed conidia and fitted well to a survival model (r(2) >/= 0.97). For a given isolate, the fitted model generated an LT(50), the time for 50% viability loss under the stress. The LT(50)s of six B. bassiana isolates (10.1-61.9 min) and five P. fumosoroseus isolates (2.8-6.2 min) were correlated (r(2) = 0.81) with FAE protein contents (6.9-23.4 microg mg(-1)). The survival indices of a fixed B. bassiana isolate after 45-min thermal stress at 48 degrees C were also correlated to the FAE protein contents from conidia produced on glucose-, sucrose-, or starch-based substrate (0.79 </= r(2) </= 0.86). Three bands of 12.0, 15.0 and 17.5 kDa were recognized from SDS-PAGE profiles of protein extracts from different isolates or from the fixed isolate grown on the three carbon sources, but the 12 kDa was less likely related to the thermotolerance. Approximately 80% of variability in conidial thermotolerance was attributed to either 15.0- or 17.5-kDa FAE protein or both. The relationship between conidial thermotolerance and FAE protein contents implicates a new way to search for fungal biocontrol agents with more thermotolerance and environmental persistence.

Genetic variability among Paecilomyces fumosoroseus isolates from various geographical and host insect origins based on the rDNA-ITS regions

The entomopathogenic hyphomycete Paecilomyces fumosoroseus is a promising candidate for biocontrol of economically important agricultural pests. Assessment of genetic relatedness of this species appears to be essential to gain insight into the monitoring of such biocontrol products. Intraspecific variation within the internal transcribed spacer region of the ribosomal RNA gene (rDNA-ITS) was studied in 48 isolates of P. fumosoroseus. These strains were isolated from different geographical and biological origins, more particularly from the silverleaf whitefly, Bemisia tabaci-argentifolii (Homoptera: Aleyrodidae), a major insect pest in field and greenhouse crops. PCR amplification of the ITS1–5.8S-ITS2 rDNA region followed by restriction analysis of the PCR products underlined the overall highly variable nature of this region. Digestion with the six endonucleases AluI, HaeIII, Hin6I, HpaII, NdeII, and SmaI allowed the separation of the isolates into three distinct groups. The group 1, representing 25 isolates, is composed of strains isolated only from the host B. tabaci-argentifolii. By contrast, the group 3 is more diffuse as it included strains from various insect host and geographical origins. Phylogenetic analysis of rDNA-ITS sequence data strongly supported the conclusions of the PCR-RFLP analysis and recognized three monophyletic groups within the P. fumosoroseus complex. The high level of polymorphism within the P. fumosoroseus species is discussed in the light of their biological origin.

Pathogenicity of entomopathogenic fungi to different developmental stages of Rhipicephalus sanguineus (Acari: Ixodidae).

The pathogenicity of 4 species of entomopathogenic fungi (Hyphomycetes species: Beauveria bassiana, Metarhizium anisopliae, Metarhizium flavoviride, and Paecilomyces fumosoroseus) to various developmental stages of Rhipicephalus sanguineus (Acari: Ixodidae) ticks was compared under laboratory conditions. The most virulent isolate, M. anisopliae-108, caused 92-96% mortality to unfed larvae and nymphs on day 7 postinfection (PI) and 100% mortality to unfed adults and engorged females on day 21 PI. The pathogenicity of M. anisopliae-108 to engorged larvae and nymphs was lower--82.6 and 60%, respectively. All tested B. bassiana, M. flavoviride, and P. fumosoroseus isolates were significantly less virulent (P < 0.05) or avirulent toward most life stages of R. sanguineus. The M. anisopliae and M. flavoviride isolates also prevented or reduced the ability of the ticks to lay eggs several days before their deaths. Female ticks infected by the fungi achieved only 11.3-60.8% of their egg-laying capacity compared with the controls.

Penetration of Cuticle and Proliferation in Hemolymph by Paecilomyces fumosoroseus Isolates That Differ in Virulence against Lepidopteran Larvae

Frequencies of cuticular penetration and speed of proliferation in hemolymph were demonstrated for two isolates of Paecilomyces fumosoroseus that differ in virulence against diamondback moth, Plutella xylostella. Penetrant hyphae of virulent isolate 4461 were visible in larval cuticle cross-sections of diamondback moth and fall armyworm, Spodoptera frugiperda, within 22 h after inoculation. Virtually no penetration was observed for isolate 1576 for up to 52 h after inoculation. Isolate 4461 also proliferated more quickly than isolate 1576 in the hemolymph of fall armyworm when the isolates were injected as blastospores.

Standardized Bioassay and Screening of Beauveria bassiana and Paecilomyces fumosoroseus Against the Russian Wheat Aphid (Homoptera: Aphididae)

Two hyphomycetous fungi with potential as biocontrol agents were used in Bioassays against the Russian wheat aphid, Diuraphis noxia (Kurdjumov). Dose-response assays were done using 5-7 concentrations of 2 isolates each of Beauveria bassiana (Balsamo) Vuillemin and Paecilomyces fumosomseus (Wize) Brown & Smith. A sensitive assay technique was developed in which adult aphids, 0-2 d of age, were sprayed with fungal spore suspensions on cut barley leaf sections. LC50 estimates were 91 and 282 spores per square centimeter for two B. bassiana isolates and 46 and 56 spores per square centimeter for two P. fumosoroseus isolates. Slopes ranged from 1.43 to 1.76. Aphids were significantly less susceptible to B. bassiana than to P. fumosoroseus , indicated by the lack of overlap among fiducial limits. LT50s varied inversely with dose for all 4 isolates and ranged from 4.6 d to 12.2 d for B. bassiana , and from 3.3 d to 12.2 d for P. fumosoroseus , depending on isolate and dose. In standardized screening assays, relative potencies ranged from 0.2 to 2.1 among 23 isolates of B. bassiuna , and from 0.3 to 3.7 among 14 isolates of P. fumosoroseus . Use of this assay method will facilitate studies of biotic and abiotic factors that influence Russian wheat aphid susceptibility to fungal infection in the laboratory and in the field.

Microbial Control of Cabbage Maggot-Preliminary Screenings of Fungal Isolates, 1995

Abstract Adult CM were exposed to dry conidia of isolates of Beauvaria bassiana (Bb), Metarhizium anisopilae (Ma) or Paeciomyces fumosoroseus (Pf). Two B. bassiana isolates were from Cornell University (P89, L90) isolated from Musca domestica (Diptera: Muscidae), one was from Mycoteh Corp., Butte, MT (Myc 726) originally isolated from southern corn rootworm, Diabrotica undecimpuntata (Coleoptera: Chrysomelidae), re-isolated from a grasshopper, Melanoplus sp. (Orthoptera:Acrididae), and then re-isolated from silverleaf whitefly, Bemesia argentiflora (Homoptera: Aleyrodidae). The other isolates were from the USDA-ARS Collection of Entomophagous Fungal Cultures. One B. bassiana isolate, 4012, was isolated from Delia radicum (Diptera: Anthomyiidae). The P. fumosoroseus isolates were number 1626 from M. autumnalis (Diptera: Muscidae), 1644, 1645, 1867 and 1868 from M. domestica, 1646 from Calliphora spp. (Diptera: Calliphoridae), and 887 from unidentified Diptera. The M. anisopilae isolates were 2521 from Deois spp. (Homoptera: Cercopidae), 3540 from Gelleria mellonella (Lepidoptera: Pyralidae) and 4862 and 4865 from soil. Flies from rearings at the New York State Agricultural Experiment Station, Geneva, NY, were exposed to the fungi by placing 5 flies in a centrifuge tube containing conidia scraped directly from culture plates. The flies were then released into small screened plastic cages, which were placed in chambers with constant temperature of 21° C and L:D 15: 9. There were 3 replicates. Mortality was assessed after 48, 120 and 160h. Dead flies were placed in petri dishes with moistened filter paper to assess infection.

Genetic Variability of Paecilomyces fumosoroseus Isolates Revealed by Molecular Markers

Paecilomyces fumosoroseus (Deuteromycotina:Hyphomycetes) is a fungus that is potentially useful for the biocontrol of economically important agricultural pests, such as whitefly (Bemisia tabaci). Arbitrarily primed PCR and PCR with tRNA consensus primers were used to analyze genetic variability among 27 P. fumosoroseus isolates, 15 of which came from the same host, B. tabaci, one P. lilacinus isolate, used as an outgroup, 9 previously unidentified Paecilomyces isolates. Fifteen 10-mer oligonucleotide primers of arbitrary sequence revealed 322 scorable binary characters. Principal coordinates and cluster analysis of characters showed that most of the P. fumosoroseus and Paecilomyces sp. isolates were in three phenetic groups with >65% internal similarity. Two of the three arbitrary phenetic groups were closely related (76% similarity) with the third group quite different (only 14% similarity) from the first two. The phenetic groups did not correlate with geographical origin or host species. Genetic variability of isolates infecting whitefly in Florida was detected. Isolates from B. tabaci were represented in two of the three groups, and different genotypes were identified even when they were isolated from an epizootic population in India and Pakistan. There was no evidence of host-specific selection of genotypes, as has been shown in other entomopathogenic fungi. Three isolates morphologically classified as P. fumosoroseus were clustered in a phenetic group which displayed only 14% similarity to the other isolates of this species. Seven isolates that presented problems for morphological classification were found to be similar or, in three cases, identical to other P. fumosoroseus isolates that did not present problems for morphological classification. Two of the three difficult-to-classify isolates clearly belonged to other species, based on their low degree (< 13%) of similarity in relation to the three main phenetic groups of P. fumosoroseus and to each other. This level of divergence suggests that what is morphologically classified as P. fumosoroseus likely represents a species aggregate, in agreement with studies of other entomopathogenic fungi. Phenetic analysis using arbitrarily primed PCR polymorphisms was concordant with a phylogenetic analysis of 107 amplified products (53 informative) obtained by PCR with four pairs of consensus tRNA gene primers. Molecular data suggested that a morphologically based taxonomy provides little insight to species, and perhaps, in some cases, even genera within imperfect fungi. Both the arbitrarily primed PCR and the tRNA fingerprinting were found to be powerful tools for improving the taxonomy of the genus Paecilomyces and other imperfect fungi.

Susceptibility of the Fall Armyworm, Spodoptera frugiperda, to the Fungal Pathogens Paecilomyces fumoso-roseus and Nomuraea rileyi

Laboratory bioassays determined the susceptibility of the fall armyworm Spodoptera frugiperda Smith to 6 isolates of Nomuraea rileyi (F.) Samson and to 10 isolates of Paecilomyces fumoso-roseus (Wize) Brown and Smith. Significant differences in first-instar mortality and in time-mortality response were found to exist between the different strains of the 2 fungi. Calculated LT 50 values varied between 2 and 3.7 days for 7 P. fumoso-roseus isolates as compared to 5 and 10 days for the N. rileyi isolates. S. frugiperda caterpillars were highly susceptible to 4 strains of P. fumoso-roseus. The most active pathotype, P. fumoso-roseus n@* 32 had a LT 50 value of 2.6 days at the concentration of 3000 conidia/mm^2 of leaf surface and its LD 50 was 40 conidia/mm^2 of leaf surface (mortality recorded at 6 days post-exposure). In contrast, the best N. rileyi isolate (n@* 5) had a LD 50 value of 400 conidia/mm^2 of leaf surface. This study demonstrated that P. fumoso-roseus might also have potential as microbial control agent against the fall armyworm.