Molecular systematics of the dimorphic ascomycete genus Taphrina

Abstract

The ascomycete genus Taphrina Fries comprises nearly 100 species recognized by their mycelial states when parasitic on different vascular plants. Whereas the filamentous state is strictly phytoparasitic, the yeast state is saprobic and can be cultured on artificial media. Taphrina species are differentiated mainly on the basis of host range and geographical distribution, type and site of infection and morphology of the sexual stage in infected tissue. However, there has been little progress in the systematics of the genus in recent years, mainly because of the scarcity of molecular studies and available cultures. The main aim of the present study was the reappraisal of species boundaries in Taphrina based on the genetic characterization of cultures (yeast states) that represent about one-third of the currently recognized species. The molecular methods used were (i) PCR fingerprinting using single primers for microsatellite regions and (ii) determination of nucleotide sequences of two approx. 600 bp nuclear rDNA regions, the 59 end of the 26S rRNA gene (D1/D2 domains) and the internal transcribed spacer region (which includes the 5.8S rRNA gene). Sequencing results confirmed the monophyly of the genus (with the probable exclusion of Taphrina vestergrenii) and the combined analysis of the two methods corroborated, in most cases, separation of species defined on the basis of conventional criteria. However, genetic heterogeneity was found within some species and conspecificity was suggested for strains that have been deemed to represent distinct species. Sequences from the ITS region displayed a higher degree of divergence than those of the D1/D2 region between closely related species, but were relatively conserved within species (>99 % identity) and were thus more useful for the effective differentiation of Taphrina species. The results further allowed other topics to be addressed such as the correlation between the molecular phylogenetic clustering of certain species and the respective host plant family and the significance of molecular methods in the accurate diagnosis of the different diseases caused by Taphrina species.

Fungal Morphogenesis

“…In Taphrina deformans, the causal agent of leaf curl in peach and almond, yeast cells land on leaves and undergo a mitotic nuclear division to establish a binucleate condition. The resulting dikaryotic cells subsequently switch to parasitic filamentous growth in planta (Rodrigues and Fonseca 2003). Similarly, in the biotrophic maize pathogen Ustilago maydis, haploid yeast cells of compatible mating types fuse to form a dikaryon, which subsequently generates the infectious dikaryotic hyphae to continue growth and development in vivo (Banuett 1991).…”

Candida khmerensis sp. nov., a novel cation-tolerant yeast isolated from dry salted shrimp and sewage in Cambodia

“…nov., P. burtonii, and C. fennica, MSP-PCR fingerprinting with micro-satellite oligonucleotide primers (GTG) 5 and (GAC) 5 , which have been demonstrated to be appropriate for inter-and intra-species differentiation for ascomycetous yeasts (Baleiras Couto et al, 1996;Capece et al, 2003;Rodrigues and Fonseca, 2003), was carried out. The PCR fingerprints are depicted in Fig.…”

New records for powdery mildews and Taphrina species in Idaho and Washington

“…Callan (1998) reported Taphrina populina Fries on P. tremuloides in British Columbia, but the dimensions she provided for asci, precisely congruent with Mix (1949), are shorter than those of our specimen, and the symptoms were deformations of leaves (as opposed to deformation of catkins). Rodrigues and Fonseca (2003) also noted this difference in symptoms, although T. johansonii and T. populina clustered closely together in their phylogenetic analysis. Occurring each spring during the past three years in Moscow, the disease has varied in severity among female trees.…”

“…The relation between T. amentorum and T. occidentalis appears not substantially investigated since the publications of Mix (1940) and Ray (1939). Rodrigues and Fonseca (2003) conducted molecular-genetic analyses of some other species on Alnus, including T. robinsoniana Giesenhagen, a name applied to the causal agent of catkin disease of A. incana and A. rugosa in eastern North America (Mix 1940). The dimensions of asci of our specimen were more in accord with those of T. occidentalis than those of T. amentorum according to Mix (1949), and exhibited basal cells, whereas those of T. amentorum do not (Ray 1939).…”