Paecilomyces

Taxobox
name = "Paecilomyces"


image_width =
image_caption =
regnum = Fungi
phylum = Ascomycota
classis = Eurotiomycetes
ordo = Eurotiales
familia = Trichocomaceae
genus = "Paecilomyces"
genus_authority = Samson 1974
subdivision_ranks = Species
subdivision ="Paecilomyces lilacinus"
"Paecilomyces ramosus "
"Paecilomyces viridis "
and others

"Paecilomyces" is a nematophagous fungus which kills (harmful) nematodes by pathogenesis, or causing disease in the nematodes. Therefore the fungus can be used as a bio-nematicide to control nematodes by applying it to soil. Nematodes are crop pests.

"Paecilomyces lilacinus"

"Paecilomyces lilacinus (Thom) Samson" is a common fungus which has frequently been isolated from plant-parasitic nematode eggs and from soil in many parts of the world. It has been isolated from a wide range of habitats including cultivated and uncultivated soils, forests, grassland, deserts, estuarine sediments and sewage sludge as well as from nematode eggs and occasionally from females of root-knot and cyst nematodes. In addition, it has frequently been isolated from the rhizosphere of many crops. The species can grow at a wide range of temperatures – from 8°C to 38°C for a few isolates, with optimal growth in the range 26–30°C. It also has a wide pH tolerance and can grow on a variety of substrates.cite journal| last =Samson | first =RA | authorlink = | coauthors = | title =Paecilomyces and some allied hyphomycetes | journal =Studies in Mycology | volume =6 | issue = | pages =119 | publisher =Centralbureau voor Schimmelcultures | location =Baarn | date =1974 | url = | doi = | id = | accessdate = ] cite book| last =Domsch | first =KH | authorlink = | coauthors =Gams W and Anderson T | title =Compendium of Soil Fungi | publisher =Academic Press | date =1980 | location =London | pages =529–532 | url = | doi = | id = | isbn = ]

Taxonomy of "Paecilomyces"

"P. lilacinus" was classified with the Fungi Imperfecti or Deuteromycetes, fungi for which perfect (i.e. sexually reproducing) states have rarely been found. The last major revision of the genus "Paecilomyces" was in 1974 by Samson."Paecilomyces lilacinus" is classified in the section "Isarioidea", for which perfect states have not been found. Many isolates of "P. lilacinus" have been identified from around the world and it is accepted that variation exists within the species. "P. lilacinus" forms a dense mycelium which gives rise to conidiophores. These bear phialides from the ends of which spores are formed in long chains. Spores germinate when suitable moisture and nutrients are available. Colonies on malt agar grow rather fast, attaining a diameter of 5–7 cm within 14 days at 25°C, consisting of a basal felt with a floccose overgrowth of aerial mycelium; at first white, but when sporulating changing to vinaceous near Light Vinaceous Drab and Light Brownish Drab. Reverse sometimes uncoloured but usually in vinaceous shades near Daphne Red to Verona Purple. Vegetative hyphae smooth-walled, hyaline, 2.5–4.0 m wide. Conidiophores arising from submerged hyphae, 400–600 m in length, or arising from aerial hyphae and half as long. Phialides consisting of a swollen basal part, tapering into a thin distinct neck. Conidia in divergent chains, ellipsoid to fusiform, smooth walled to slightly roughened. Chlamydospores absent.

The use of "P. lilacinus" to control plant-parasitic nematodes

"P. lilacinus" was first observed in in association with nematode eggs in 1966cite journal| last =Lysek | first =H | authorlink = | coauthors = | title =Study of biology of geohelminths. II. The importance of some soil microorganisms for the viability of geohelminth eggs in the soil | journal =Acta Universitatis Palackianae Olomucensis | volume =40 | issue = | pages =83–90 | publisher = | location = | date = | url = | doi = | id = | accessdate = ] and the fungus was subsequently found parasitising eggs of "Meloidogyne incognita" in Peru.cite journal| last =Jatala | first =P | authorlink = | coauthors =Kaltenbach R and Bocangel M | title =Biological control of Meloidogyne incognita acrita and Globodera pallida on potatoes | journal =Journal of Nematology | volume =11 | issue = | pages =303 | publisher = | location = | date = | url = | doi = | id = | accessdate = ] It has now been isolated from many cyst and root-knot nematodes and from soil in many locations.cite book| last =Stirling | first =GR | authorlink = | coauthors = | title =Biological Control of Plant Parasitic Nematodes | publisher =CABI Publishing | date =1991 | location =UK | pages =282 | url = | doi = | id = | isbn = ] cite journal| last =Stirling | first =GR | authorlink = | coauthors =West LM | title =Fungal parasites of root-knot nematode eggs from tropical and sub-tropical regions of Australia | journal =Australasian Plant Pathology | volume =20 | issue = | pages =149–154 | publisher = | location = | date = | url = | doi = 10.1071/APP9910149| id = | accessdate = ] Several successful field trials using "P. lilacinus" against pest nematodes were conducted in Peru. The Peruvian isolate was then sent to nematologists in 46 countries for testing, as part of the International Meloidogyne project, resulting in many more field trials on a range of crops in many soil types and climates.cite journal| last =Jatala | first =P | authorlink = | coauthors = | title =Biological control of plant-parasitic nematodes | journal =Annual Review of Phytopathology | volume = 24| issue = | pages =453–489 | publisher = | location = | date =1986 | url = | doi = 10.1146/annurev.py.24.090186.002321| id = | accessdate = ] Field trials, glasshouse trials and in vitro testing of "P. lilacinus" continues and more isolates have been collected from soil, nematodes and occasionally from insects. Isolates vary in their pathogenicity to plant-parasitic nematodes. Some isolates are aggressive parasites while other, though morphologically indistinguishable, are less or non-pathogenic. Sometimes isolates which looked promising "in vitro" or in glasshouse trials have failed to provide control in the field.cite journal| last =Gomes Carniero | first =RMD | authorlink = | coauthors =Cayrol J | title =Relationship between inoculum density of the nematophagous fungus Paecilomyces lilacinus and control of Meloidogyne arenaria on tomato | journal =Revue Nématologique | volume =14 | issue =4 | pages =629–634 | publisher = | location = | date = | url = | doi = | id = | accessdate = ]

Enzymes

Many of the enzymes produced by "P. lilacinus" have been studied. A basic serine protease from "P. lilacinus" with biological activity against "Meloidogyne hapla" eggs has been identified. [cite journal| last =Bonants | first =PJM | authorlink = | coauthors =Fitters PFL, Thijs H, den Belder E, Waalwijk C and Henfling J W DM | title =A basic serine protease from Paecilomyces lilacinus with biological activity against Meloidogyne hapla eggs | journal =Microbiology | volume =141 | issue = | pages =775–784 | publisher = | location = | date =1995 | url = | doi = | id = | accessdate = ] One strain of "P. lilacinus" has been shown to produce proteases and a chitinase, enzymes could therefore break down the egg shell to enable a narrow infection peg to push through.cite journal| last =Khan | first =A | authorlink = | coauthors =Williams KL, and Nevalainen HKM | title =Effects of Paecilomyces lilacinus protease and chitinase on the eggshell structures and hatching of Meloidogyne javanica juveniles | journal =Biological Control | volume = 31| issue = | pages =346–352 | publisher = | location = | date =2004 | url = | doi = 10.1016/j.biocontrol.2004.07.011| id = | accessdate = ]

Egg infection

Before infecting a nematode egg, "P. lilacinus" flattens against the egg surface and becomes closely appressed to it. "P. lilacinus" produces simple appressoria anywhere on the nematode egg shell either after a few hyphae grow along the egg surface, or after a network of hyphae form on the egg. The presence of appressoria appears to indicate that the egg is, or is about to be, infected. In either case, the appressorium appears the same, as a simple swelling at the end of a hypha, closely appressed to the eggshell. Adhesion between the appressorium and nematode egg surface must be strong enough to withstand the opposing force produced by the extending tip of a penetration hypha.cite book| last =Money | first =NP | authorlink = | coauthors = | title =Mechanics of invasive fungal growth and the significance of turgor in plant infection. In: Molecular genetics of host-specific toxins in plant disease | publisher =Kluwer Academic Publishers | date =1998 | location =Netherlands | pages =261–271 | url = | doi = | id = | isbn = ] When the hypha has penetrated the egg, it rapidly destroys the juvenile within, before growing out of the now empty egg shell to produce conidiophores and to grow towards adjacent eggs.

See also

* Entomopathogenic fungus
* Cordyceps
* Tarsonemidae

References

External links

* [http://www.mycology.adelaide.edu.au/Fungal_Descriptions/Hyphomycetes_(hyaline)/Paecilomyces/ University of Adelaide entry 1]
* [http://www.mycology.adelaide.edu.au/gallery/photos/paecilomyces1.html/ University of Adelaide entry 2]
* [http://www.denniskunkel.com/DK/DK/Fungi_and_Slime_Molds/24282A.html/ Dennis Kunkel Microscopy]
* [http://www.mold-help.org/content/view/423/ Mold-Help]
* [http://www.doctorfungus.org/thefungi/paecilomyces.htm/ Doctor Fungi]