New records of smut fungi from Venezuela : Anthracoidea uleana , Sporisorium panici-petrosi and Ustilago schroeteriana

Three smut fungi from Venezuela are described, illustrated and discussed based on newly studied collections. Ustilago schroeteriana Henn. is reported for the first time from the country. Anthracoidea uleana (Syd. & P. Syd.) Vánky is confirmed in Venezuela on Carex longii Mack., which is an accessory host for this smut. Sporisorium panici-petrosi (Syd. & P. Syd.) M. Piepenbr. is reported on Thrasya sp. from a second world locality in northern Venezuela, its description is slightly expanded and issues concerning typification of this name and the nomenclature of the host in the type collection are clarified and corrected.


INTRODUCTION
Neotropical smut fungi have been recently monographed by Piepenbring (2003) who listed 227 species from this part of North and South America.This number seems to be not final, and the author considers that many new species can be discovered in the area as well as numerous species can be found in particular countries as a new national records.Indeed several further new species have been subsequently described from different parts of Neotropics (Vánky 2004(Vánky , 2005(Vánky , 2006)).
Venezuela is the sixth largest country of South America, located at the northern coast of the continent, bordering with Colombia, Brazil, Guyana and the Caribbean Sea.The country has very diverse, tropical landscape, vegetation and vascular plant flora.As in most of neotropical countries, the of smut fungi of Venezuela are insufficiently known, and altogether 57 species have been reported from the country till now (Sydow and Sydow 1916;Jackson 1934;Dennis 1970;Nannfeldt 1977;Piepenbring 2003;Vánky 2005Vánky , 2006Vánky , 2007)).During ongoing studies focusing on biodiversity of tropical smut fungi, I examined three unidentified collections from Venezuela.They belonged to three species, Anthracoidea uleana (Syd.& P. Syd.) Vánky, Sporisorium panici-petrosi (Syd.& P. Syd.) M. Piepenbr.and Ustilago schroeteriana Henn.Of these, Ustilago schroeteriana is new to Venezuela, while two remaining species are reported for the second time from the country.These new collections are described, illustrated and discussed in the present contribution.

MATERIALS AND METHODS
Dried herbarium specimens were examined by light microscopy (LM) and scanning electron microscopy (SEM).For LM, small pieces of sori were mounted in heated lactophenol and examined under a NIKON Eclipse E600 light microscope.For SEM, spores were dusted onto carbon tabs and fixed to an aluminium stub with double-sided transparent tape.The stubs were sputter-coated with carbon using a CRESSINGTON sputter-coater and viewed with a Hitachi S-4700 scanning electron microscope, with a working distance of ca 12−13 mm.SEM micrographs were taken in the Laboratory of Field Emission Scanning Electron Microscopy and Microanalysis at the Institute of Geological Sciences, Jagiellonian University, Kraków (Poland).

RESULTS AND DISCUSSION
Anthracoidea uleana (Syd. & P. Syd.)For further synonyms see Piepenbring (2003: 46).Sori in ovaries, as black, globose, hard bodies around the ovaries, about 1-1.5 mm in diameter, partly hidden by the scales, composed of agglutinated spores, powdery on the surface.-Spores very variable in shape, rounded, bluntly polyhedral, 12-19 × 10-17 μm, olive-brown to dark brown, with 3-5 light, thin-walled, rounded areas that are collapsed and often form characteristic mamillate depressions, which are especially well visible on the SEM micrographs; wall uneven, 1-3 μm thick, thickest at the angles, internal swellings and light refractive spots absent, surface as seen by LM finely punctate to verruculose, warts not affecting the spore profile, surface as seen by SEM finely verruculose.
specimens Anthracoidea uleana is easy to identify because of unusual spores, which are quite small and possess 3-5 light, thin-walled, rounded areas.These areas are collapsed and often form mamillate depressions, which are especially well visible on the SEM micrographs.The host plants of A. uleana belong to Carex subgen.Vigna sect.Ovales.The only other neotropical Anthracoidea Bref.with similar appearance of spores is Anthracoidea altiphila Vánky & M. Piepenbr., which however differs by some small morphological characters and host plants belonging to Carex subgen.Carex sect.Fecundae (Vánky 1994).
Anthracoidea uleana is one of the four species of Anthracoidea known from the Neotropics (Piepenbring 2003).The small number of species in this floral kingdom Sporisorium panici-petrosi (Syd.Sori usually replacing the whole inflorescence, long, elongated, up to 5 mm wide and up to 10 mm long, sometimes partly concealed by leaf sheaths, at first covered by thick, pale brown peridium, which ruptures irregularly exposing dark brown powdery mass of spores surrounding numerous filiform columellae that are sometimes connected with each other.Sori rarely restricted to spikelets, replacing flowers with dusty mass of spores, enclosed by a pale brown peridium and surrounding filiform columellae, partly concealed by glumes.-Spores yellowish-brown, on one side lighter coloured, pale yellowish or almost hyaline, globose, subglobose to slightly irregular, 9-13(-15) × (7-)8.5-12μm; wall ca.0.5 μm thick, thinner on the lighter coloured side, surface as seen by LM finely verruculose, spore profile smooth, surface as seen by SEM moderately verruculose.-Sterile cells absent.
Sporisorium panici-petrosi was so far known only from the type locality in southern Venezuela.The collection from northern Venezuela reported here represents the second record of this smut (Fig. 6).
The presence of unusual columellae that are connected with each other as well as characteristic spores that are lighter coloured on one side makes this species easy to identify.According to the descriptions (Piepenbring 2003;Vánky 2005) of the type collection, the smut destroys whole inflorescences; in the new collection from northern Venezuela, however, the sori are restricted only to individual spikelets in some plants while they destroy whole inflorescences in others.
The smut was originally described in the genus Ustilago (Pers.)Roussel as U. panici-petrosi Syd.& P. Syd., but because of the presence of the peridium and columellae, Piepenbring (2003) transferred it to Sporisorium Ehrenb.ex Link.Vánky (2005) did not accept this proposal, since in his opinion the manner of spore formation in this species is rather of the Ustilago-type, and the spores with a thinner wall on one side are typical of numerous species of Ustilago.However, sporogenesis was analysed in detail only in some species of Sporisorium and Ustilago (e.g., Langdon andFullerton 1975, 1978), and it is not clear whether the way of spore formation is a constant character of taxonomic importance.This is particularly essential in light of recent molecular analyses (Stoll et al. 2005) in which Sporisorium appeared to be a polyphyletic genus.Therefore, the taxonomic value of spore formation in delimiting the genera Ustilago and Sporisorium should be checked by careful studies of ontogeny and sporogenesis in numerous species, preferably based on freshly collected specimens.In contrast to the statement of Vánky (2005), the spores with a thinner wall on one side are known not only in the genus Ustilago, but also in several species of Sporisorium, for instance in S. clandestinum R.G. Shivas, Vánky & P. Athipunyakom (Vánky et al. 2006), S. sphacelatum Vánky (Vánky 2003), S. wynaadense (Sundaram) Vánky & R.G. Shivas (Vánky and Shivas 2001).Therefore, this character is not useful in delimiting the genera Ustilago and Sporisorium.In conclusion, I follow the proposal of Piepenbring (2003), who placed Ustilago panici-petrosi in Sporisorium, also because the general appearance of this smut is similar to the species included in this genus.
The host plant of Sporisorium panici-petrosi was originally named Panicum petrosum Trin., and for that reason this smut was analysed in the monograph of smut fungi infecting Panicum species (Vánky 2005).However, Panicum petrosum is currently placed in the genus Thrasya, as T. petrosa (Trin.)Chase, which is phylogenetically more closely related to Paspalum than to Panicum (Giussani et al. 2001).The new collection from northern Venezuela reported here is on unidentified species of Thrasya.In addition, in the same collection there are some plants infected by Ustilago schroeteriana, which is a typical Paspalum smut.Therefore, Sporisorium panicipetrosi must be excluded from Panicum smuts.
The holotype of Ustilago panici-petrosi was destroyed in 1943 by Berlin fire along with a greater part of the Berlin herbarium.Fortunately, a duplicate of this collection is preserved in Stockholm (herb.S).Piepenbring (2003) considered the latter specimen as holotype, which is, however, incorrect as the main collection of the Sydows was housed in Berlin.Vánky (2005) designated the specimen preserved in Stockholm (herb.S) as neotype.That denoting is also incorrect, because a neotype can be selected only when all the original material is lost, which is not the case here.Therefore, Vánky's denoting is treated as an error (Art.9.8 of ICBN), and the specimen in herb.S must be treated as the lectotype of Ustilago panici-petrosi.For further synonyms and types see Piepenbring (2003: 184) and Vánky (2007: 5).
Sori destroying all spikeletes and peripheral axial tissues of an inflorescence, retaining the shape of affected organs, with shredded remnants of host plant tissue attached to them, spore mass dark brown, powdery.The morphology of sori and spores of the present collection matches well with those given in descriptions of Ustilago schroeteriana (Piepenbring 2003;Vánky 2007), but the spore sizes are closer to these given by Piepenbring (2003): (13-)14-17(-20) × (11-)12-15(-17) μm, than by Vánky (2007): 13.5-20 × 12-18.5 μm.The former author pointed out that the spore sizes in different collections of U. schroeteriana are fairly variable, but the most measurements are about 15-17 μm.Vánky (2007) in his description gives only extreme values and does not specify which measurements are most common.
Ustilago schroeteriana is widespread in the Neotropics on different species of Paspalum, being known from Belize, Brazil, Colombia, Costa Rica, Cuba, Granada, Honduras, Mexico, Nicaragua, Panama, Peru and Puerto Rico (Piepenbring 2003;Pérez and Minter 2005).The present record is new to Venezuela (Fig. 7) on the new host plant genus Thrasya.The molecular phylogenetic studies (Giussani et al. 2001) showed that Thrasya is closely related to Paspalum and the presence of the same smut fungus on these two host genera additionally supports this close relationship.

Fig. 7 .
Fig. 7. Distribution of Ustilago schroeteriana Henn. in South America (black dots) with new locality in northern Venezuela marked by triangle (modified from Piepenbring 2003).