Phaeosphaeria deschampsii (Ascomycota): A new parasite species of Deschampsia antarctica (Poaceae) described to Antarctica

This study presents the description of Phaeosphaeria deschampsii, which was found in plant communities from Half Moon Island, South Shetland Archipelago, Antarctica, in February 2014. Many patches of Deschampsia antarctica (Poaceae), the only indigenous Poaceae specie in Antarctic, were found dead, parasitized by a fungi pathogen. Based on the shape of its perithecia, with oblique neck, erumpent in the grass tissues, ascospore form and septation, the specie was identified as new to science.


INTRODUCTION
Plant pathogens are little known from the Antarctic region, generally reported from lichens and mosses more than from angiosperms. The fanerogams are restricted to only two species in this continent: Colobanthus quitensis Kunth (Caryophyllaceae) and Deschampsia antarctica Desv. (Poaceae) (Putzke and Pereira 1996). World climatic change is occurring and pathogens usually restricted to some areas are now being found in new sites as saprophytes or sometimes as pathogens.
Phaeosphaeria is a fungus genus restricted as parasitic of Poaceae and some other grass-like monocot plants. Some species are very specialized while others have a large host spectrum (Stchigel et al. 2004).
During field work done in the Antarctic (Half Moon Island), we collected many samples of dead D. antarctica presenting well-developed symptoms that is the fungi peritecia present on the plant lives. The pathogen was compared to all known taxa from Antarctica (Pegler et al. 1980) and all around the world and was found as a new species to science.
The main purpose of this work is to describe this pathogen, contributing with the knowledge of pathogens distribution and their impact over native plant communities in Antarctica.
The MycoBank is deposit this one new taxon: (MB 817663).

MATERIALS AND METHODS
Halfmoon Island (62°36'S, 59°53'W) is located between Livingston and Greenwich Islands, in the South Shetland Archipelago. The small island is about 3 km long and its name is derived from its halfmoon-like contour, whose concavity opens toward the north-west. The D. antarctica small cespitose especimes found in this island were revised for symptoms of diseases and all the suspected material was carried to the laboratory settled at the Camara Base (Argentine). The samples were examined in stereoscopic microscope and lots of perithecia were found. Cuts were done and slides were prepared for microscopic observation. Photographs were taken (Camera Canon EOS 550) directly from an Olympus microscope.

RESULTS
The samples collected were found parasitized by a Phaeosphaeria deschampsii J. Putzke & A.B. Pereira fungus, which is considered new to science. The description is presented below: Phaeosphaeria deschampsii J. Putzke & A.B. Pereira sp. nov.
Our collection was found occurring on D. antarctica, killing branches among healthy

Phaeosphaeria mounceae Shoemaker and Babcock
is the closest one in this genus, but the erumpent obliquely necked perithecia and ascospores with 8 septa differentiated it very well (Shoemaker and Babcock 1988).