Phylogenetic Analysis of Iranian Powdery Mildew Fungi using Nucleotide Sequences of ۲۸S Ribosomal DNA

The nucleotide sequences of ۲۸S nuclear rDNA were determined for ۳۴ powdery mil-dew taxa mostly collected from Iran in order to infer the phylogenetic relationships of these fungi. Total DNA was isolated from cleistothecia or mycelia using the chelex method. About a ۶۵۰ nucleotide length of the ۵´end of the ۲۸S rDNA was amplified twice by the PCR using a nested primer set, PM۳, TW۱۴ and NLP۲. Direct sequencing of the PCR product was done in an Applied Biosystems ۳۷۳A sequencer. The results showed that powdery mildew taxa are divided into five groups, which were distinguished by their morphology. Members of Erysiphe section Erysiphe, Microsphaera and Uncinula clustered together. E. sect. Galeopsidis and E. sect. Golovinomyces were seperated from E. sect. Ery-siphe and formed the Euoidium without fibrosin bodies group. Leveillula and Phyllactinia showed a close evolutionary relationship and clustered together. The genera Cystotheca, Podosphaera, Sawadaea, and Sphaerotheca formed a monophyletic group (fibrosin body lineage) with ۹۸% bootstrap support. These fungi are well characterized by the presence of fibrosin bodies in their conidia. Blumeria graminis, which is characterized by some unique morphological characters, clustered with fibrosin body lineage with a low boot-strap value. This result shows that B. graminis is not closely related to the Erysiphe spe-cies. The nucleotide divergence between the genera analyzed in this study ranged from ۰.۵۰ to ۱۴.۱۰%. The lowest nucleotide divergence was found between Microsphaera and E. sect. Erysiphe (۰.۵۰–۴.۵۰%). Podosphaera and Sphaerotheca showed a low level of diver-gence, too (۲.۳۰-۲.۶۰%), which suggests a close relationship between these two genera.

Keywords:

IRAN , Erysiphaceae , Phylogeny , powdery mildew , rDNA