Molecular and morphological characterization of rice phylloplane fungi and determination of the antagonistic activity against rice pathogens.

Cladosporium spp. is a cosmopolitan fungal genus. In the literature, it has been reported as a biological agent for controlling several plant diseases, but its mechanism of action has never been clarified. The present study aims to identify Cladosporium spp. based on the DNA phylogeny of nine isolates obtained from the phylloplane of rice and their potential antagonistic activity against the main fungal pathogens that affect rice crop. Nine isolates of Cladosporium spp. were identified based on DNA phylogeny, molecular and morphological characterization, and their antagonistic effects with the rice pathogens C. miyabeanus, M. oryzae, M. albescens and S. oryzae. Four isolates were selected to study lytic enzymes such as ß-1,3-glucanase, chitinase and protease, and only one isolate was selected for a conidial germination and appressoria formation assay. The nine isolates were identified as C. cladosporioides, C. tenuissimum and C. subuliforme. Four isolates, identified as C. cladosporioides, inhibited the mycelial growth of rice pathogens such as C1H (68.59%) of S. oryzae, C5 G (74.32%) of C. miyabeanus, C11 G (75.97%) of M. oryzae and C24 G (77.39%) of M. albescens. C24 G showed a high activity of lytic enzymes, was tested against C. miyabeanus and M. oryzae, and inhibited conidial germination and appressorium formation by more than 59.36%. The characterization of C. cladosporioides suggested this species as a potential bioagent for the management of several rice diseases, especially rice blast. This is the first time that a potential biological agent from the genus Cladosporium identified at the species level was isolated from the rice phylloplane, and some of its mechanisms of action were demonstrated, such as increasing lytic enzyme activity against rice pathogens.

A new parasite that infects eggs of the mud crab, Scylla serrata, in Australia.

The mud crab, Scylla serrata, is currently being evaluated for its feasibility for mass aquaculture in Australia. As part of the evaluation process, pathogens that can affect this species need to be identified. This research note describes a possible new parasite that infects the eggs of S. serrata. The parasite was discovered in two separate cases (three months apart) in a broodstock research program and appears to cause 100% egg mortality. The parasite consists of a cluster of cells with rhizoids that appear to function as an anchorage and a feeding organ. The individual cells range from 3 to 6 microm with a single nucleus. The parasite could not be classified to a phylum by morphology alone. However, BLAST analysis of the DNA sequence from a PCR amplicon generated using universal 18S ribosomal RNA gene primers indicated similarity to pathogenic thraustochytrids, Dermocystidium sp. and Rhinosporidium seeberi. All except R. seeberi are protistan parasites of fish and crustaceans. A neighbour-joining phylogenetic tree confirmed the homology with the thraustochytrids; however, further molecular techniques need to be exploited for absolute classification of this new parasite.

First report of Basidiolum fimbriatum since 1861, with comments on its development, occurrence, distribution and relationship with other fungi.

An obscure parasitic fungus, Basidiolum fimbriatum, was found on Amoebidium parasiticum (Amoebidiales) associated with Caenis sp. (mayfly) nymphs, during a survey of gut fungi (Trichomycetes) from a small stream in northeastern Kansas, USA. The hindguts of the nymphs harboured a species of Legeriomycetaceae and Paramoebidium sp. This is the first report of the ectocommensal protozoan, A. parasiticum, associated with the gills of Caenidae (Ephemeroptera), and of B. fimbriatum in the 142 years since its original documentation from Wiesbaden, Germany. B. fimbriatum is recorded from two midwestern USA states (Kansas and Iowa) and the morphological and developmental features of the parasite on its host are compared with Cienkowski's original observations and interpretation. B. fimbriatum is characterized as a parasitic fungus possessing merosporangia that from on a simple pyriform thallus that penetrates and consumes its host via a haustorial network. The hypothesis that B. fimbriatum is most closely related to members of the order Zoopagales sensu Benjamin (1979) is proposed. The importance of future collections and molecular-based phylogenetic approaches to place this parasitic fungus within a current system of classification are highlighted.

Sooty moulds from European tertiary amber, with notes on the systematic position of Rosaria ('Cyanobacteria').

Sooty moulds are described and illustrated from European amber dating back to 22-54 Myr. All the fossils are fragments of superficial subicula composed of brown moniliform hyphae with markedly tapering distal ends. The subglobose cells are identical to those of extant Metacapnodium (Metacapnodiaceae, Capnodiales) species. Also other preserved features, like the type of apical growth, wide-angled branching and the production of two distinctive conidial states, supports a placement in this genus. The fossils demonstrate that Metacapnodium hyphae have remained unchanged for tens of millions of years. This confirms that hyphal morphology and conidial states should be accorded considerable classificatory significance in this group of fungi. The following nomenclatural change is made: Metacapnodium succinum comb. nov. (syn. Rosaria succina). The type specimen was initially described as a filamentous cyanobacterium, due to similarities with Rosaria ramosa. Also the systematic position of this attribute is shortly discussed.