Double-stranded RNA viruses infecting Epichloe festucae

Some isolates of Epichloë festucae are asymptomatically infected by Epichloë festucae virus 1 (EfV1), a member of the family Totiviridae. This virus has a genome composed by a 5109 bp molecule of double stranded RNA (dsRNA). In addition, a 3 kbp dsRNA molecule which could be the genome of another virus (EfV2) was frequently found in isolates of the fungal endophyte. In a survey of two populations of E. festucae it was found that 73% of the isolates were infected by one or both viruses. Although both viruses are very efficiently transmitted to conidia, a barrier to virus transmission occurs during ascospore formation. Keywords: Epichloë festucae, virus, dsRNA, Totivirus

Candida floccosa sp. nov., a novel methanol-assimilating yeast species

Two methanol-assimilating yeast strains were isolated from a flux of a sessile oak (Quercus petrea) in Hungary and one genetically and phenotypically very similar strain from a flux of a red oak (Quercus rubra) in Canada. The strains exhibited ascomycetous affinity but ascospore formation was not observed. On the basis of the sequence of their D1/D2 domain of the large subunit rDNA, as well as of their physiological characteristics, they represent a novel yeast species of the genus Candida. Therefore Candida floccosa sp. nov. is proposed, with NCAIM Y.01581T (=CBS 10307T=NRRL Y-27951T) as the type strain.

Comparison among tomato juice agar with other three media for differentiation of Candida dubliniensis from Candida albicans

The purpose of the present study is to compare the tomato juice agar, a well known medium employed to observe ascospore formation, with niger seed agar, casein agar and sunflower seed agar, applied to a differentiation between C. dubliniensis and C. albicans. After 48 hours of incubation at 30 ºC all 26 (100%) C. dubliniensis isolates tested produced chlamydospores on tomato juice agar as well as in the other three media evaluated. However, when we inoculated all media with C. albicans, the absence of chlamydospores became resulting in the following percents: tomato juice agar (92.47%), niger seed agar (96.7%), casein agar (91.39%), and sunflower seed agar (96.7%). These results indicate that tomato juice agar is another medium which can also be used in the first phenotypic differentiation between C. dubliniensis and C. albicans.

Full-season and post-harvest applications of sterol-inhibiting fungicides to reduce ascospore formation in Venturia inaequalis

Several sterol-inhibiting (SI) fungicides were tested in post-harvest and full-season spray programs for the inhibition of ascospore formation by Venturia inaequalis, the causal fungus of apple scab. Post-harvest treatments with flusilazole and diniconazole were comparable to or better than those with benomyl and suppressed ascospore production by 55 to 90 %, although bitertanol stimulated ascospore production by up to 52 %. When applied nine times in full-season programs, bitertanol, flusilazole, and triflumizole reduced ascospore formation to a degree similar to or greater than that achieved with dodine. Full-season programs with SI fungicides in combination with mancozeb were highly effective for reducing ascospore production.

Cytogenetics of Colletotrichum lindemuthianum (Glomerella cingulata f. sp. phaseoli)

Cytogenetic and morphological studies were conducted with Colletotrichum lindemuthianum (Glomerella cingulata f. sp. phaseoli), the pathogen responsible for anthracnose of common bean (Phaseolus vulgaris). In this species, there is some evidence of genomic variation but it is unknown whether the process occurs in a manner similar to other fungal genetic models. Six isolates from bean plants were used and sexual reproduction was observed in vitro. Meiosis and ascospore formation were investigated by cytogenetical approaches and light microscopy. To study the nucleus and chromosome numbers, a mixture of carmine and orcein propionic dyes was used. Nucleus divisions as well as ascospore maturation were asynchronous. Meiosis was observed in three isolates. In the asexual form, chromosomal polymorphism in conidia was also observed microscopically and the mitosis process was described.

eEF1A Controls Ascospore Differentiation Through Elevated Accuracy, but Controls Longevity and Fruiting Body Formation Through Another Mechanism in Podospora anserina

Antisuppressor mutations in the eEF1A gene of Podospora anserina were previously shown to impair ascospore formation, to drastically increase life span, and to permit the development of the Crippled Growth degenerative process. Here, we show that eEF1A controls ascospore formation through accuracy level maintenance. Examination of antisuppressor mutant perithecia reveals two main cytological defects, mislocalization of spindle and nuclei and nuclear death. Antisuppression levels are shown to be highly dependent upon both the mutation site and the suppressor used, precluding any correlation between antisuppression efficiency and severity of the sporulation impairment. Nevertheless, severity of ascospore differentiation defect is correlated with resistance to paromomycin. We also show that eEF1A controls fruiting body formation and longevity through a mechanism(s) different from accuracy control. In vivo, GFP tagging of the protein in a way that partly retains its function confirmed earlier cytological observation; i.e., this factor is mainly diffuse within the cytosol, but may transiently accumulate within nuclei or in defined regions of the cytoplasm. These data emphasize the fact that the translation apparatus exerts a global regulatory control over cell physiology and that eEF1A is one of the key factors involved in this monitoring.