Didymium azorellae, a new myxomycete from cushion plants of cold arid areas of South America.

A new species of Didymium (Myxomycetes), D. azorellae, isolated from plant debris in a moist chamber, collected during studies of cold arid areas of Argentina and Peru, is described. It can be distinguished by its small size, the tightly packed layer of lime crystals on the peridium, the very scant, or absent, capillitium, and the unique spore ornamentation, especially by scanning electron microscopy. The species developed on dead leaves of cushion plants growing in the extremely harsh environments of the central Andean puna at almost 5000 m elevation and the Andino-Patagonian steppe. Morphology was examined with scanning electron microscopy and light microscopy, and micrographs of relevant details are included here. In order to confirm the identity of the new species described in this paper, a molecular study was conducted based on partial sequences of both the 18S rRNA and the elongation factor 1-alpha gene. Phylogenetic analysis including two specimens from different countries of the newly described species, Didymium azorellae, strongly supports the grouping of these specimens as a separate clade from the rest of the analyzed species.

Mitochondrial inheritance patterns in Didymium iridis are not influenced by stage of mating competency.

To test whether the timing of transition to mating competency affected mitochondrial transmission patterns in D. iridis. Reciprocal crosses were made by combining mating compatible strains that differed in their competency to mate. The results were compared to crosses where both mating strains were competent at the time of combining and crosses where somatic fusion of plasmodia was allowed. The results show that the mating competency of the parental strains at the time of confronting a compatible mate does not affect mitochondrial transmission patterns, mating efficiency or the likelihood of biparental inheritance. However the timing of plasmodial formation is delayed when precompetent and competent strains are mated compared to when both strains are competent at the time of mixing. We also observed that somatic fusion of plasmodia did not appreciably increase the incidence of biparental inheritance compared to crosses where individual plasmodia were isolated. These results provide additional evidence of the variable nature of mitochondrial inheritance in D. iridis within crosses and between mating trials.