Diethylene glycol removal by Echinodorus cordifolius (L.): the role of plant-microbe interactions.

This work presents the use of the plant Echinodorus cordifolius for remediating diethylene glycol (DEG) contaminated waters. The potential of this plant for treating DEG wastewater in a remediation system was observed. We found that E. cordifolius was able to remove DEG from wastewater, decrease the pH to neutral and remove approximately 95% of the chemical oxygen demand within 12 days. The plants can grow well in DEG wastewater, as indicated by their root and leaf biomass, which was found to be statistically similar to control. Wilting, chlorosis and necrosis were observed in DEG-treated plants, but the relative water content was not significantly different between control and treated plants, suggesting that the plants were able to take up and tolerate DEG present in the wastewater. Plant roots changed to black colour during experimental period. The fluorescence in situ hybridisation and bacterial enrichment confirmed that 4.30 × 10(5) cells/g of sulphate reducing bacteria and 9.30 × 10(8) cells/g of acid-producing bacteria were found associated with the plant roots. Furthermore, volatile fatty acids were found in non-sterile soil treatments, indicating that soil microorganisms are associated with DEG remediation. These results demonstrated that plants and bacteria have the ability to form a relationship to remove the organic contaminant DEG.

Doassansiopsis caldesiae sp. nov. and Doassansiopsis tomasii: two remarkable smut fungi from Cameroon.

Three recent collections of Doassansiopsis from western Cameroon are assessed taxonomically. Doassansiopsis caldesiae M. Piatek & Vánky is described as a new species from infected leaves of Caldesia reniformis (D. Don) Makino. Its diagnostic characters are flat, nonthickened sori with spore balls as blackish, slightly elevated dots, more or less globoid spores, conspicuous cortical sterile cells and parasitism on Caldesia reniformis of family Alismataceae. The species is compared to another Doassansiopsis species on host plants belonging to family Alismataceae. Doassansiopsis tomasii Vánky is described from two localities on Nymphaea nouchali Burm.f. var. caerulea (Savigny) Verdc. (Nymphaeaceae), which represents the first report of this smut from Cameroon and western Africa. Similarities between this species and Doassansiopsis nymphaeae (Syd. & P. Syd.) Thirum. and D. ticonis M. Piepenbr. are outlined and the global distribution of the three taxa is mapped. The species concept in the genus Doassansiopsis is discussed, and a key to all known species of the genus is provided.

Plectosporium alismatis comb. nov. a new placement for the Alismataceae pathogen Rhynchosporium alismatis.

The phytopathogen Rhynchosporium alismatis, occurring on Alisma, Sagittaria and other genera in the Alismataceae, is under investigation as a mycoherbicide for alismataceous weeds in Australian rice crops. The type species of Rhynchosporium, R. secalis, belongs in the Helotiales while the phylogenetic relationships of R. alismatis were unknown. To identify fungi related to R. alismatis, the internal transcribed spacer (ITS) region of the ribosomal DNA (ITS1, 5.8S rRNA gene, ITS2) of 56 isolates was sequenced and compared to those available in databases. Analysis of ITS sequences revealed close relationships between R. alismatis and the teleomorph genus Plectosphaerella, as well as several anamorphic fungi which were primarily species of Verticillium. Rhynchosporium alismatis and Plectosphaerella cucumerina clustered together with 98 % bootstrap support. Morphological comparisons supported this relationship indicating that R. alismatis and the anamorphic genus Plectosporium are congeneric. Rhynchosporium alismatis is transferred to Plectosporium, a name proposed for conservation.

Infection process of Plectosporium alismatis on host and non-host species in the Alismataceae.

In Australia, the endemic fungus Plectosporium alismatis (syn. Rhynchosporium alismatis) has potential use as a mycoherbicide for several species in the Alismataceae, a family of aquatic and semi-aquatic marsh herbs, which are considered to be important weeds in rice crops. Of five species identified in south-eastern Australia where rice is grown, two species, Sagittaria graminea and Sagittaria montevidensis are resistant (non-hosts), and no records of P. alismatis on these species have been reported. To better understand the interactions that lead to resistance in these pathosystems, the infection process of the fungus was studied on these species and also on the host Alisma plantago-aquatica, using light, fluorescent and scanning electron microscopy. On all three species both conidial germination and appressorium formation commenced within 6 h of inoculation with greater than 50 % of conidia elongating to form germ tube structures and associated appressoria 12-18 h post inoculation. Germ tube elongation and appressorium formation occurred randomly over the leaf surface. Direct host penetration was facilitated by the production of penetration hyphae that emerged from beneath appressoria. Penetration sites were clearly identified by the presence of spherical holes 0.25-0.5 microm in diam, and were frequently accompanied by resistance reactions in non-host species. Visible symptoms of disease occurred 4-6 d after inoculation of susceptible (host) species.