Dothideales: Cochliobolus Drechsler

September 9, 2010 By MBL

Cochliobolus Drechsler; anamorphs Bipolaris Shoemaker, Curvularia Boedijn.

Ascomata perithecial, unilocular, with little or no stromatic development, dark brown, thick-walled. Asci cylindrical to saccate, thick-walled, apparently with two discernible layers but not exhibiting the “jack-in-the-box” discharge of many “bitunicate” ascomycetes, usually 8-spored. Ascospores helically coiled within the ascus, filiform, multiseptate, sometimes surrounded by mucus.

Conidiomata absent. Conidiophores dark brown, more or less erect, thick-walled, the conidia being produced sequentially from a series of conidiogenous loci in the usually knobbly apical cells, the loci appearing as pale dots, conidial dispersal frequently being delayed so that clusters of conidia are visible at the tips of conidiophores. Conidia dark brown, slightly (in Bipolaris) or strongly (in Curvularia) curved, with many thick septa (Bipolaris) or relatively few thin septa (Curvularia).

These fungi are most prominent as plant pathogens, but may occasionally be encountered in industrial situations, from soil and air isolations, and acting as agents of biodeterioration of textiles etc. They are most frequently encountered in the tropics. In addition, there is interest in enzyme, metabolite and toxin production by some species of Cochliobolus and Pyrenophora (q.v.), and at least one isolate is subject to patent restrictions for this reason. Some species are also implicated as disease-causing organisms (McGinnis et al., 1986b)

The fungi are most frequently seen in their anamorphic (conidium-producing) condition, and at one time were merged with Drechslera (the anamorphic state of Pyrenophora) and several other form-genera as Helminthosporium Link. This assemblage was shown to be unnacceptably heterogeneous more than thirty years ago (Hughes, 1953), and the use of that last name since than has been restricted to a small group of saprobic fungi of no industrial interest. The fungi are in most cases more difficult to identify using teleomorphic rather than anamorphic characteristics.

Bipolaris and Curvularia are very similar, and share the same teleomorph genus. Curvularia species have conidia which are strongly curved and have relatively few, thin, septa, while those of Bipolaris in general are less strongly curved, and have larger numbers of thick (disto-) septa (Alcorn, I983a) . The two groups intergrade, and may be merged in the future (Sivanesan, 1987).

Most species produce only the anamorph in culture, and in many cases it is difficult to maintain even conidium production after successive subculturing.

Cochliobolus geniculatus Nelson; anamorph Curvularia geniculata (Tracy & Earle) Boedijn.

Conidia are 18-37 x 8-14µm in size in culture (often rather longer on natural substrata), strongly curved, and almost always 4-septate, with the end cells paler. It is heterothallic. The anamorphic state was formerly known as Helminthosporium geniculatum Tracy & Earle.

Cochliobolus lunatus Nelson & Haasis; anamorph Curvularia lunata (Wakker) Boedijn.

Conidia are 20-32 x 9-15µm in size, strongly curved, 3-septate, with the central cells dark brown and the apical ones much paler. It also is heterothallic.

Filed Under: Notes On Fungi Tagged With: Cochliobolus, Dothideales

Dothideales: Botryosphaeria

September 8, 2010 By MBL

Botryosphaeria Ces. & de Not.; anamorphs Diplodia Fr., Dothiorella Sacc., Lasiodiplodia Ellis & Everh., Sphaeropsis Sacc. etc. Botrosphaeria rhodina (Berk. & Curtis) von Arx is frequently encountered in its anamorphic state, to which the name Lasiodiplodia theobromae (Pat.) Griffon & Maublanc (syn. Botryodiplodia theobromae Pat.) is applied. B. rhodina is best-known as a ubiquitous plant pathogen in the tropics, and it frequently causes storage rots of fruits and vegetables (Brackett, 1991). Further information on the fungus may be found in Punithalingam (1976), Domsch et al. (1980) and Pitt & Hocking (1985a).

Filed Under: Notes On Fungi Tagged With: Botryosphaeria rhodina, Dothideales

Diaporthales

September 5, 2010 By MBL

Most Diaporthales species are plant parasites or occur on moribund or decaying woody and herbaceous tissues. Few species are of interest to industrial mycologists, but the well-known chestnut blight fungus Cryphonectria parasitica (Murrill) Barr (syn. Endothia parasitica (Murrill) P.J. Anderson & H.W. Anderson) has been used in commercial rennet production (Bigelis & Lasure, 1991; Blain, 1975; Sivanesan & Holliday, 1981). Some species produce toxins of medical and veterinary importance, such as Diaporthe woodii Punith. (anamorph Phomopsis leptostromiformis (Kühn) Bubak) which causes the chronic liver damage sometimes referred to as lupinosis in sheep (Butler, 1975; Punithalingam & Gibson, 1975). Other species of Diaporthe cause rots of stored foods (Brackett, 1991; Splittstoesser, 1991).

Filed Under: Notes On Fungi Tagged With: Cryphonectria parasitica, Diaporthales, Diaporthe woodii

Clavicipitales: Verticillium Nees

September 4, 2010 By MBL

Colonies moderately rapidly growing. Conidiophores fairly well differentiated from the usually hyaline vegetative hyphae, erect or prostrate, hyaline or pigmented, verticillately branched over most of their length, with successive whorls of conidiogenous cells. Conidiogenous cells slender, gradually tapering, producing conidia successively from single apical conidiogenous loci. Conidia small, hyaline, usually aseptate, in most species aggregating into spherical slimy heads but formed in chains in a few taxa.

Verticillium is clearly an unnatural form-genus, with links both to the Clavicipitales and to the Hypocreales. Many of the species of interest to the industrial mycologist have links with the Clavicipitales, so the form-genus is treated here. However, the type species V. tenerum Nees has links with the Hypocreales, and a few other species of Nectria have since been reported with Verticillium anamorphs, but the anamorph has such a simple structure that it is likely that convergent evolution has taken place.

The latest taxonomic work on Verticillium is the study by Jun et al. (1991), which compared isolates of V. lecanii from insect and fungal hosts. Further information may be found in Domsch et al. (1980), Ellis (1971), Evans & Samson (1986), Gams (1971, 1988) , and Gams & van Zaayen (1982). Verticillium species are widespread in soil, and are pathogens of other fungi, insects and plants. Recently, they have become important in biological control programmes.

Verticillium albo-atrum Reinke & Berthold

Colonies white at first, then turning black in patches. Conidiophores usually only with one order of branching, hyaline though sometimes with a darkened base. Conidiogenous cells in whorls of 2-4, narrow, gradually tapering. Conidia 3.5-10.5 x 2-5µm, ellipsoidal to cylindrical, hyaline, occasionally septate. This species is a serious parasite, causing wilt diseases of many plants. Verticillium dahliae Kleb. is also a serious pathogen, which has dark multicellular resting structures sometimes referred to as microsclerotia, hyaline conidiophores, and slightly smaller conidia.

Verticillium fungicola (Preuss) Hassebrauk

Colonies white to cream, powdery to velvety. Conidiophores erect, with a single order of branching. Conidiogenous cells in whorls of 3-9, narrow, gradually tapering. Conidia 3-8.5 x 1-2.5µm, ellipsoidal to cylindrical, sometimes curved in older colonies, aseptate. Resting spores not produced.

This species, also referred to in some circles as Verticillium malthousei Ware, causes the diseases of commercial mushroom beds known as “dry bubble” and “brown spot”. It can cause serious losses.

Verticillium psalliotae Treschow is similar to V. fungicola, but has less-branched conidiophores which are usually prostrate, purple pigments at the edge of the colonies, Conidiogenous cells usually in groups of 2-3, and conidia which are crescent-shaped in young cultures and cylindrical to ellipsoidal in older colonies. V. lamellicola (F.E.V. Sm.) W. Gams is similar to V. psalliotae, but has conidia which are not curved. It also causes diseases of mushroom beds.

Verticillium lecanii (Zimmermann) Viegas

Col0nies white to pale yellow, cottony. Conidiophores not well-developed, erect or prostrate, with a single order of branching. Conidiogenous cells in whorls of 3-5, narrow, gradually tapering. Conidia variable in size (dependent on the host), ranging between 2.3-10µm in length and 1-2.6µm in width, cylindrical to ellipsoidal.

Interest in Verticillium lecanii as an agent of biological control is considerable. The fungus is pathogenic on a number of economically important insects, and strains are also parasitic on rust and other fungi. Jun et al. identified a number of taxonomic groups within the species aggregate largely based on host preference. The fungus also produces antiviral agents (Bucknall et al., 1973).

Verticillium tenerum Nees

Colonies growing rapidly, velvety, brick-red to orange-brown. Conidiophores erect, stiff, strongly pigmented, often branched several times. Conidogenous cells 12-23 x 2-4µm, flask-shaped. Conidia 3.5-5 x 2-2.5µm, pale reddish brown in mass. Resting structures not produced. This fungus is better-known under the name Verticillium lateritium (Ehrenb.) Rabenh, and the synonym Acrostalagmus cinnabarinus Corda may also be familiar to some. It has been reported to be the anamorph of Nectria inventa Pethybridge, but that fungus is poorly-known, and is certainly not a typical Nectria. The evidence of connexion is based solely on a single early report (Pethybridge, 1919), and the teleomorph has not recently been found. V. tenerum is a common and cosmopolitan soil fungus. It has also been found on paper, cloth, cotton fibres in conveyor belts, and rotting vegetables, and been isolated from milk, cheese, giner, wheat and salami (Domsch et al., 1980; Pitt & Hocking, 1985a).

Filed Under: Notes On Fungi Tagged With: clavicipitales, Hypocreales, Nectria, Verticillium

Clavicipitales: Paecilomyces Bainier

September 2, 2010 By MBL

Paecilomyces is a form-genus with connexions to various teleomorph genera, belonging to the Clavicipitales and Eurotiales. Paecilomyces section Paecilomyces (the type subgroup of the form-genus which contains the original described species) has links to the Eurotiales. Paecilomyces section Isarioidea Samson on the other hand, belongs to the Clavicipitales, and the following description refers to this group. Several species in this group are important as agents of biological control. See Samson (1974) and Domsch et al. (1980) for comprehensive descriptions, keys to the genus, and further information.

Colonies often brightly coloured. Hyphae hyaline to slightly pigmented. Conidiophores with several verticillate branches, sometimes aggregated into synnemata. Conidiogenous cells in whorls of 2-7 at the apex of branches and often inserted laterally also, flask-shaped, usually rather less elongated than in Paecilomyces section Paecilomyces, producing conidia successively from apical loci. Conidia formed in chains with the oldest one at the apex, smooth or ornamented, hyaline or brightly coloured, rarely septate. Resting-spores present in some species.

Paecilomyces carneus (Duche & Heim) A.H.S. Brown & G. Smith

Colonies growing slowly, matted, sometimes powdery, at first pure white but becoming pale pink with a green reverse. Conidiophores hardly differentiated, with a few usually verticillate branches. Conidiogenous cells in whorls of 2-4, 9-18 x 1.5-2.5µm, flask-shaped with a distinct neck. Conidia 3-4 x 2-2.5µm, ± globose to ellipsoidal, roughened with tiny spines.

Paecilomyces carneus is found on a wide range of substrates, and especially from soil. It is sometimes isolated from insects, though it appears not to be strongly pathogenic. Several metabolites of the antibiotic group cephalosporins are produced by some isolates (Kitano et al., 1974).

Paecilomyces farinosus (Holm) A.H.S. Brown & G. Smith

Colonies growing quite rapidly, felty or powdery, at first white but often eventually becoming yellowish. Conidiophores verticillately or irregularly branched, sometimes aggregating into synnemata. Conidiogenous cells 5-15 x 1.5-2.5µm, the basal part swollen, tapering towards the apex. Conidia 2-3 x l-2µm, ellipsoidal to fusiform, smooth-walled, hyaline. Resting-spores not produced.

Paecilomyces farinosus is a well-known insect pathogen, and there has been interest in its use as an agent of biological control. The species is polyphagous, but isolates are commonly restricted in their host preferences. P. farinosus is also commonly isolated from soil.
Domsch et al. (1980) state the teleomorph of this fungus to be Cordyceps memorabilis CBS., but the anamorph species as currently recognized is morphologically simple but polymorphic, and in practice the name P. farinosus would probably cover the anamorphs of a range of species of the Clavicipitales (Samson, 1974) . Teleomorphs are not as a rule produced in culture.

Paecilomyces fumosoroseus (Wize) A.H.S. Brown & G. Smith

Colonies growing fairly rapidly, deeply floccose, white at first but becoming dull pink, the reverse pale yellow. Conidiophores erect, sometimes aggregated into pale pink synnemata, with often closely-spaced verticillate branches. Conidiogenous cells in whorls of 4-6, 5.5-8 x 1-2µm, the basal part globose to ellipsoidal and with a distinct neck. Conidia 3-4 x 1-2µm, cylindrical to fusiform, hyaline to pale pink. Resting-spores not produced.

Paecilomyces fumosoroseus is an insect parasite, causing economic damage to silkwork production in eastern Asia (Samson, 1974), and has also been investigated for biological control. It has also been isolated from soil, butter and gelatin.

Paecilomyces lilacinus (Thorn) Samson

Colonies growing rapidly, floccose, at first white but becoming purplish or greyish violet, with a light to dark purple reverse. Conidiophores variably developed, often rather thick-walled, yellowish or purple at the base, sometimes aggregated into synnemata, verticillately branched. Conidiogenous cells in whorls of 2-4, 7.5-9 x 2.5-3µm, flask-shaped. Conidia 2.5-3 x 2-2.5µm, ellipsoidal to fusiform, hyaline but purple in mass. Resting-spores not produced.

Paecilomyces lilacinus has been found on insects on numerous occasions, but is most commonly encountered in isolations from soil. It has also been implicated as a human and animal pathogen, is found on various organic substrates including plastic contact lenses, synthetic rubber and polyurethane, and is used in fungus resistance testing. Strains produce the antibiotics leucostatin and lilacin (Arai et al., 1973). P. lilacinus was originally described as Penicillium lilacinum Thorn, but its colonies lack the characteristic green colour of Penicillium species, its Conidiogenous cells have distinct necks, and its Conidiophores are not divaricately branched (Samson, 1974),.

Paecilomyces marquandii (Massee) S. Hughes is very similar to P. lilacinus, but has colonies with a yellow reverse, smooth-walled hyaline conidiophores, and small globose to ellipsoidal resting-spores are often present.

Paecilomyces tenuipes (Peck) Samson

Colonies rather slow-growing, floccose or powdery, at first white but becoming cream or pinkish buff. Conidiophores erect, hyaline, sometimes aggregated into synnemata, with short branches arranged verticillately or irregularly. Conidiogenous cells in whorls of 2-6, 4.5-6.5 x 2.5-3.5µm, the basal part globose and with a ditinct neck. Conidia 3-7.5 x 2-2.5µm, ± cylindrical, often curved, smooth-walled, hyaline, sometimes septate, the septate conidia significantly longer.

Paecilomyces tenuipes is similar to P. farinosus, especially on the insect host rather than in culture, but its colonies lack yellow pigments, the conidiophore branches and conidiogenous cells are shorter and more swollen, and the conidia are larger and cylindrical. Early reports linked P. tenuipes with the teleomorph Cordyceps polyarthra Moller, but these may not be reliable (Samson, 1974).

Filed Under: Notes On Fungi Tagged With: clavicipitales, Eurotiales, Paecilomyces

Clavicipitales: Nomuraea Maubl.

August 29, 2010 By MBL

Colonies slow-growing, hyaline to slightly pigmented. Conidiophores erect, verticillately branched, sometimes aggregated into synnemata. Conidiogenous cells in compact whorls, the basal part often swollen, the apex slightly attenauted. Conidia developing in succession from single apical loci, forming dry chains with the oldest at the apex, ellipsoidal to cylindrical, smooth, hyaline or slightly coloured. No teleomorphs are known, but similarities with other anamorphs of the Clavicipitales suggest that the genus belongs to that order. Only one species is well-known.

Nomuraea rileyi (Farlow) Samson

Colonies slow-growing, dense, dusty green. Conidiophores with compact clusters of branches. Conidiogenous cells 4-6 x 2.5-3.5µm, usually short, cylindrical, occasionally with a swollen base, the neck absent or very short. Conidia in dry divergent chains, 3-4 x 2-2.5µm, ellipsoidal, rarely cylindrical, hyaline but green in mass. Nomuraea rileyi is an insect pathogen, attacking larvae and pupae of Lepidoptera and Coleoptera. There has been interest in the use of this fungus as an agent of biological control, though its slow, growth in culture is disadvantageous. See Samson (1974) and Onions (1979) for further information.

Filed Under: Notes On Fungi Tagged With: clavicipitales, Nomuraea

Clavicipitales: Mycogone

July 18, 2010 By MBL

Mycogone Link

Colonies growing rapidly, cream to pinkish or red-brown. Conidiophores ± erect, verticillately branched. Conidiogenous cells in clusters of up to 5, narrow, tapering, producing conidia successively from single apical conidiogenous loci. Conidia ellipsoidal to cylindrical, hyaline, aseptate. Resting spores produced from the ends of vegetative hyphae, two-celled, the basal cell ± hyaline and smooth-walled, the apical cell large, ± globose, thick-walled, pigmented, warty.

No teleomorphs are known for Mycogone, but the form-genus has clear links to the Clavicipitales, some species producing Verticillium-like conidiophores as well as thick-walled resting spores.

Mycogone perniciosa (Magn.) Delacr. and Mycogone rosea Link cause the “wet bubble” diseases of cultivated mushrooms (Brady & Gibson, 1976 b, c). Mycogone perniciosa has pinkish colonies, pale brown resting-spores, and produces Verticillium-like conidiophores and conidia. Mycone rosea has reddish brown colonies, strongly pigmented resting spores and lacks a Verticillium-like morph.

Filed Under: Notes On Fungi Tagged With: Mycogone perniciosa, Mycogone rosea

Clavicipitales: Hypomyces

July 10, 2010 By MBL

Hypomyces Tul.; anamorph Cladobotryum Nees

Hypomyces species, especially H. rosellus (Alb. & Schw.) Tul. (anamorph Cladobotryum dendroides (Bull.) W. Gams & Hoozemans) cause the economically significant cobweb disease of cultivated mushrooms, attacking Pleurotus as well as Agaricus culture (van de Geijn, 1982; Gray & Morgan-Jones, 1981). A useful review of the older literature is given by Arnold (1976), and modern taxonomic treatments are given by Gams & Hoozemans (1970) and de Hoog (1978).

Filed Under: Notes On Fungi Tagged With: Cladobotryum dendroides, Hypomyces, hypomyces rosellus

Clavicipitales: Beauveria

July 10, 2010 By MBL

Beauveria Vuill.

Vegetative growth white or pale, with hyaline trailing hyphae or forming simple loose masses on the host, with whorls or dense clusters of conidiogenous cells forming balls of dry and powdery conidia.

Conidia produced singly and separately, from short globose or flask-shaped conidiogenous cells which have an apical denticulate rhachis with a distinctly zig-zag appearance. Conidia one-celled, hyaline, thin-walled, smooth, globose to ellipsoidal, sometimes with an apiculate base.

Beauveria species are ubiquitous and well-known as insect pathogens, but have been recorded from other sources, mostly of animal origin. They can also be isolated from the soil in which their hosts overwinter. No teleomorphs are known.

There is much early literature on the genus, but more recently it has been discussed by de Hoog (1972) and Samson & Evans (1982). The most up-to-date taxonomic treatment is by Mugnai et al. (1989), who recognized seven species, almost all from diseased arthropods. Brady (1979) has provided descriptions of two of the most important species. Their industrial interest lies in the field of biological control.

Beauveria bassiana (Bals.) Vuill. is the best-known species. It has closely clustered conidiogenous cells and globose to broadly ellipsoidal, occasionally apiculate conidia 2-3 x 2-2.5µm in size. B. bassiana was first recorded as the “white muscardine” disease of silk worms.

Beauveria brongniartii (Sacc.) Fetch is less common, is also referred to as “white muscardine” and is also used in biological control. It often has slightly less closely clustered conidiogenous cells, and conidia (2-) 2.5-4 (-6)µm in length which are always cylindrical or ellipsoidal rather than globose.

Filed Under: Notes On Fungi Tagged With: Beauveria, Beauveria bassiana, Beauveria brongniartii, insect pathogens

Clavicipitales: Hypocrella

July 4, 2010 By MBL

Hypocrella Sacc.; anamorph Aschersonia Montagne, nom. cons.

Stromata superficial, fleshy, usually brightly coloured, discoid or pulvinate (cushion-shaped). Ascomata globose to pyriform. Asci cylindrical, narrow, thin-walled, with a conspicuously thickened apex penetrated by a narrow canal; not blueing in iodine. Ascospores filiform, multiseptate, fragmenting into part-spores.

Conidiomata usually multilocular, the locules tubular, flask-shaped, ovoid or globose, without clearly-defined walls, releasing conidia though irregular splits. Conidiophores branched irregularly. Conidiogenous cells mostly arising as irregular lateral branches, ± cylindrical, producing conidia successively though, a single apical conidiogenous locus. Conidia usually ellipsoidal to fusiform, hyaline, aseptate.

Considering the interest in these fungi as agents of biological control, it is surprising that there has been no comprehensive monograph of Hypocrella and Aschersonia for seventy years (Fetch, 1921). Useful work on classification of the fungi has been contributed by Mains (1960). The book by Samson et al. (1988) is a useful modern source reference for this and other entomogenous fungi.

The best-known species is the common Aschersonia aleyrodis Webber, which is not known to have a teleomorph. It exerts a natural control over scale insects in the tropics, and is used as a biological control agent of the citrus whitefly Dialeurodes citri and the common greenhouse whitefly Trialeurodes vaporariorum. A. aleyrodis is described more fully by Brady (1984) and Sutton (1980).

Filed Under: Notes On Fungi Tagged With: Aschersonia, clavicipitales, Hypocrella