Some zoosporic fungi of New Zealand

Summary In further studies of the zoosporic fungi of New Zealand nine additional species were isolated on various substrata from soil. These include Rhizophydium pythii de Wildemann, R. condylosum Karling, Rhizophlyctis oceanis Karling, R. ingoldii Sparrow, R. boneysi Sparrow, Rhizophlyctis sp., Rhizidium reniformis sp. nov., Chytriomyces rotoruaensis sp. nov., Sparrowia parasitica Willoughby, and Aphanomycopsis punctatus Karling. Rhizidium reniformis is characterized by predominantly reniform, appendiculate zoosporangia and small zoospores which emerge slowly in a columnar mass. This usually floats away from the zoosporangium and explands, and after a while the zoospores swarm collectively in a vesicle. Chytriomyces rotoruaensis resembles R. reniformis by the structure and appearance of its thallus and behavior of the zoospores after discharge, but differs by the presence of a thin inconspicuous operculum and the development of smooth hyaline resting spores with coarsely granular content. Rhizophlyctis ingoldii, Sparrowia parasitica, and R. boneysi, known previously only from England and Hawaii, respectively, occurred abundantly in New Zealand.This study has been supported by a grant from the National Science Foundation, Washington, D.C.     

Monocentric fungi on species of rhizosolenia from saline habitats

Summary Eight monocentric fungi are reported in two provisionally identified species ofRhizosolenia from sea-water. Only two species are assigned specific names. These areRhizophydium planktonicum Canter andR. fragilariae Canter. A fungus with depressed-globose sporangia is included as a form ofR. fragilariae. Two unidentified species ofChytridium are reported. A fungus tentatively assigned toZygorhizidium and a form provisionally assigned toPetersenia are also reported and described insofar as their characteristics are known.     

In vitro studies on the mechanisms of endospore release by Rhinosporidium seeberi

Studies of Rhinosporidium seeberi have demonstrated that this organism has a complex life cycle in infected tissues. Its in vivo life cycle is initiated with the release of endospores into a host's tissues from its spherical sporangia. However, little is known about the mechanisms of sporangium formation and endospore release since this pathogen is intractable to culture. We have studied the in vitro mechanisms of endospore release from viable R. seeberi's sporangia. It was found that watery substances visibly stimulates the mature sporangia of R. seeberi to the point of endospore discharge. The internal rearrangement of the endospores within the mature sporangia, the opening of an apical pore in R. seeberi's cell wall, and the active release of the endospores were the main features of this process. Only one pore per sporangium was observed. The finding of early stages of pore development in juvenile and intermediate sporangia suggested that its formation is genetically programed and that it is not a random process. The stimulation of R. seeberi's sporangia by water supports the epidemiological studies that had linked this pathogen with wet environments. It also explains, in part, its affinities for mucous membranes in infected hosts. The microscopic features of endospore discharge suggest a connection with organisms classified in the Kingdom Protoctista. This study strongly supports a recent finding that placed R. seeberi with organisms in the protoctistan Mesomycetozoa clade. This revised version was published online in June 2006 with corrections to the Cover Date.     

A RHIZOPHYDIUM AND ITS HYPERPARASITE ON POLYSIPHONIA

Rhizophydium distinction Petersen and its hyperparasite are reported from Polysiphonia nigrescens in North Carolina. The planonts of R. discinctum, undescribed previously, are posteriorly uniflagellate. Olpidiopsis paradoxus (Petersen) Johnson is proposed as a new combination for the holocarpic, endobiotic fungus parasitizing the Rhizophydium. Early infection stages are evidenced by the accumulation of oil deposits in the host cytoplasm. Resting spores are unknown.     

Zoosporic fungi of Oceania. IV. Additional monocentric chytrids

Summary Several monocentric chytrid species of the generaPhlyctochytrium,Rhizidium,Chytridium,Chytriomyces andKarlingia were isolated on various substrata from soils of Oceania. Among these are two new species,Phlyctochytrium megastomum andRhizidium endosporangiatum. The former species is characterized chiefly by sporangia with an usually large apical, subapical, or a lateral exit orifice, the persistence of remnants of the pailla wall at the edge of the exit orifice, and by small zoospores. Rhizidium endosporangiatum is characterized at first primarily by predominantly spherical sporangia which develop 1 to 8 broad papillae. At maturity these papillae give them an angular shape. The exit papillae deliquesce at the tip, and through them protrude prominent arms of an endosporangium which expands and in which the zoospores usually swarm briefly. Willoughby's Chytridium parasiticum occurred abundantly as a parasite ofNowakowskiella sp.,Pythium sp., andPhytophthora sp. and developed epibiotic resting spores like those ofChytriomyces. Accordingly, this parasite is transferred to this genus and renamedChytriomyces willoughbyii because the nameparasiticum is preempted by the author's previously describedChytriomyces parasiticus.This study has been supported by a grant from the National Science Foundation, Washington, D.C.     

Rhizophydium brooksianum sp. nov., a multipored chytrid from soil

Rhizophydium136 was isolated from pollen bait placed in a water culture containing garden soil from Penobscot County, Maine. It is an important isolate because its entire mitochondrial genome has been sequenced and it is the representative member of the Chytridiales in a fungal phylogeny based on mitochondrial protein sequences. Also, this isolate is included in an 18S rDNA, chytrid phylogeny. On nutrient agar, many inflated rhizoidal axes extend from the base of the zoosporangium, zoosporangia mature in 3 d and zoospores discharge through numerous, lenticular, discharge pores. Smooth-walled resting spores form in crowded cultures. Zoospores are a variation of the Rhizophydium subtype. This chytrid differs from R. sphaerotheca sensu Barr and because it cannot be placed in a described species it herein is described as Rhizophydium brooksianum sp. nov. Many of the differences between Rhizophydium brooksianum and other multipored Rhizophydium isolates were observed only in pure culture. Attributing a spherical, multipored Rhizophydium to a species that was described without developmental information from pure culture is untenable. Epitypes or neotypes for inadequately characterized species need to be selected, and cultures made available.     

SPORE MORPHOLOGY IN THE CYATHEACEAE. I. THE PERINE AND SPORANGIAL CAPACITY: GENERAL CONSIDERATIONS

The literature on cyatheaceous spore morphology relative to the presence of a perine layer is reviewed, and evidence based on a sodium-hydroxide assay is presented indicating that the outer scultpine layer in certain cyatheaceous spores is perine. Perine so defined characterizes Metaxya, paleotropical and certain neotropical species of Sphaeropteris, nearly all species of Alsophila, all species of Nephelea, and certain species of Trichipteris and Cyathea. It is lacking in Lophosoria, many species of Trichipteris and Cyathea, and all species of Cnemidaria. Two major patterns of spore number per sporangium in the family are reported. Lophosoria, Sphaeropteris, Trichipteris, Cyathea, Cnemidaria, and probably Metaxya are characterized by 64-spored sporangia, whereas most species of Alsophila and all species of Nephelea are characterized by 16-spored sporangia. The congruence of this generic distribution of sporangial-capacity types with Tryon's phyletic arrangement of cyatheaceous genera supports the naturalness of his system. The intrasporangial germination of spores retained in dehisced and dispersed sporangia supports the suggestion that decreased spore number per sporangium in Alsophila and Nephelea may relate to the role of the sporangia as dispersal units. The decreased number of spores per sporangium is associated with a trend toward increase in the number of sporangia per sores, with the highest known count approaching 1000 sporangia per sorus. The Alsophila-Nephelea evolutionary line has probably not been ancestral in the phylogeny of the more advanced groups of ferns.     

TWO NEW MEMBERS OF THE BLASTOCLADIACEAE. I. TAXONOMY,WITH AN EVALUATION OF GENERA AND INTERRELATIONSHIPS IN THE FAMILY

Two new fungi in a small family of zoosporic phycomycetes, the Blastocladiaceae, are described. Both are included in the Brachyallomyces category, as sexuality has not been found in either one thus far. Microallomyces dendroideus from Costa Rica represents a new genus distinguished by its occurrence on animal or plant substrata rich in protein, its branched thallus in which pseudosepta are entirely lacking but growth is renewed by sympodially formed hyphal tips, and its small size. Allomyces reticulatus from California is the first species in this well-known genus to exhibit reticulately sculptured resistant sporangia. Its robust thallus is also unusual in that, despite the presence of the characteristic pseudosepta and branching with sympodially renewed hyphal tips, growth is ordinarily not unlimited as it is in all other species of the genus. The addition of these two new water molds to the Blastocladiaceae poses some basic questions regarding generic distinctions in the family. These problems are discussed and a working key to the genera is provided.     

Phytophthora austrocedrae sp. nov., a new species associated with Austrocedrus chilensis mortality in Patagonia (Argentina)

Phytophthora austrocedrae is a new species isolated from necrotic lesions of stem and roots of Austrocedrus chilensis. It is a homothallic species characterized by semipapillate sporangia, oogonia with amphigynous antheridia, and very slow growth (1–2 mm d⁻¹ on V-8 agar at 17.5 °C optimum temperature). Phylogenetic analysis of ITS rDNA sequence indicates that its closest relative is Phytophthora syringae, another species frequently isolated from soil and streams in A. chilensis forests.     

Pythium dimorphum from rhododendron

A pythiaceous phycomycete was isolated from diseased roots of rhododendron in New York. It was characterized by fast growth, preference for high temperature for growth, ovoid to elongate, non-papillate, internally proliferating sporangia and large spherical, pigmented chlamydospores, but failed to produce sex organs in single or dual cultures. It was identified as Pythium dimorphum Hendrix & Campbell. This appears to be the second report of its occurrence since its first isolation from lolly pine roots in Louisiana in 1971.     

Some Observation on the Alga Fragilaria crotonensis Kitton and its Parasitism by Two Chytridiaceous Fungi

It has been shown by experimentation that two morphologicallydistinct clones of Fragilaria crotonensis Kitton, isolated fromthe plankton of Windermere at approximately the same time, wereaffected quite differently by the chytrid Rhizophydium fragilariaeCanter. In one case the diatom filaments became heavily parasitizedand could be used for the maintenance of the fungus. In theother case infection was negligible. Additional clones, representative of these two morphologicalforms, from other bodies of water in the Windermere drainagebasin were tested. The same pattern of infection or relativenon-infection again ensued in direct accordance with the particulartype of filament used. Some preliminary experiments undertaken with a second, as yetlittle known chytrid parasite of F. crotonensis are reported.In this instance the fungus appeared to find its natural hoston cells belonging to the morphological form which failed tosupport the continued increase of R. fragilariae. The parasitism of morphological variants of F. crotonensis bythese fungi in the wild from Britain and else where is discussed. Fragilaria crotonensis Kitton, Rhizophydium fragilariae Canter, chytrid, diatom, parasitism, culture     

Development of the zoosporangia ofSynchytrium endobioticum,the causal agent of potato wart disease

Summary An ultrastructural study of zoosporangium development ofSynchytrium, endobioticum (Schilb.) Perc. is presented. Emphasis is placed on the location of the parasitic fungal thallus in the potato host cell, on the specific location of organelles in relation to the developing zoosporangial wall, and on the host cell reaction to the fungal infection. The cytoplasmic organization of the individual sporangia after division of the zoosporangium into a sorus of sporangia is characterized by numerous similarly sized nuclei, well developed dictyosomes, and the presence of many lipid bodies of variable size. Cytoplasmic microtubules are observed to flare out from the functional kinetosome both before and after zoospore cleavage.The ultrastructural details of zoosporangium development are used to revaluate the life cycle ofS. endobioticum as described from light microscopic observations made early in the century (Curtis 1921;Köhler 1923, 1932;Percival 1910).     

BOTRYOPTERIS PINNULES WITH ABAXIAL SPORANGIA

Small sporangia borne abaxially on pinnules attached to Botryopteris foliar members are described from coal ball petrifactions of Early Pennsylvanian age. This is the first report of laminar sporangia in this genus. Sporangia are stalked and borne singly near lateral veins on Sphenopteris-like pinnules. Individual sporangia are of the leptosporangiate type, with a lateral annulus and a dehiscence zone of thin-walled cells immediately adjacent to the annulus. Spores are small, trilete, triangular in outline, typically have blunt spines covering the exine, and correspond to the dispersed spore genera Acanthotriletes, Leiotriletes, or Lophotriletes. These sporangia and their spores are unlike previously described globose Botryopteris fructifications from the Middle and Upper Pennsylvanian, but are similar to sporangia produced by modern members of the Osmundaceae.     

Neoleptonema yongpilii E.-Y. Lee & I.K. Lee,gen. et sp. nov. (Phaeophyceae), based on morphological characters and RuBisCO spacer sequences

An elachistacean epiphyte, Neoleptonema yongpilii E.-Y. Lee & I.K. Lee, gen. et sp. nov., is reported from Korean coasts. The plants are distinguished by having unbranched assimilatory filaments with intercalary plurilocular sporangia as well as lateral plurilocular sporangia from the cortex. The new genus differs from the genera Leptonematella P. Silva and Halothrix Reinke by having pod-shaped plurilocular sporangia on the medulla, and from Elachista Duby and Proselachista Y.P. Lee & Garbary by having intercalary plurilocular sporangia and a poorly developed medulla. The phylogenetic relationships of Neoleptonema yongpilii were inferred from the spacer sequences between the genes coding for the large and small subunits of the RuBisCO gene. The new genus is a member of a poorly resolved clade consisting of several genera within the Elachistaceae, within which it is more closely related to Halothrix and Elachista nipponica than to Leptonematella.     

ACAULANGIUM GEN. N., A FERTILE MARATTIALEAN FROM THE UPPER PENNSYLVANIAN OF ILLINOIS

Material described by Graham as Cyathotrachus bulbaceus is believed to represent a new genus that is a common constituent of Upper Pennsylvanian coal balls. The sessile synangia of Acaulangium gen. n. are borne in a row on either side of the pinnule midrib and are composed of four to six short, tapering, laterally appressed sporangia. The sporangia have extended tips which curve over the inside of the synangium distally and delimit a small open area inside the synangium. The outer facing walls of the sporangia are two to three cells thick throughout while the inner facing walls are uniseriate. During dehiscence the sporangia separate laterally and spore release results from the rupture of a row of elongate cells along the inner sporangium midline. Among species of Scolecopteris the new genus resembles S. illinoensis and S. minor var. parvifolia but differs in its sessile synangial attachment. The additional parenchyma present between sporangial cavities in the synangia of Acaulangium, and the tendency toward bilateral symmetry suggests an early stage in the evolution of a bivalve synangium such as is present in Marattia.     

<Emphasis Type="Italic">Pythium montanum</Emphasis> sp. nov., a new species from a spruce stand in the Bavarian Alps

During a study on soilborne Pythiaceae in the Bavarian Alps, 3 isolates of a papillate Pythium species with aplerotic oospores were found in rhizosphere soil from a declining spruce stand. The isolates showed a unique combination of sporangial and gametangial characters, and could not be assigned to any known species of the genus. They were characterised by a relatively low growth rate, internally proliferating sporangia and extremely variable, monoclinous, sessile or shortly stalked antheridia. Direct germination of sporangia frequently occurred in water culture. Internal transcribed spacer (ITS) regions of the ribosomal DNA showed very low levels of similarity to those of all known species of Pythium. This paper describes the isolates as Pythium montanum sp. nov., gives details on its morphology and provides preliminary information on its pathogenicity. Additional molecular evidence for its status as a new species is also provided. Phylogenetic analyses with a set of Pythium spp. showed that P. montanum groups in a clade together with P. vexans, a species whose taxonomical status still remains unclear, and that is considered a ‘border species’ between Pythium and Phytophthora.