Morphology and phylogeny of Alternaria species in Korea

摘要

Two hundred and seventy isolates of Alternaria collected in Korea were classified by morphological analyses. They were seperated into three groups according to the catenulation pattern and conidial morphology. Group Longicatenatae, Brevicatenatae and Noncatenatae contained 10, 10 and 21 species of Alternaira, respectively. However, morphological characters often vary among isolates of the same species, and show significant overlap among species. To elucidate relationships among Alternaria species, 28S ribosomal DNA (28S rDNA), internal transcribed spacer (ITS) and histone H3 gene sequences from 41 Alternaria, five Stemphylium and one Ulocladium species were determined and compared. Phylogenetic analys of Alternaria species by 28S and and ITS rDNA sequences revealed that A. helianthi, A. longissima and A. padwickii were phyogenetically distinct from the other Alternaria spp., as well as the Stemphylium spp. The three species of Alternaria should belong to the different genera because they had genetically and morphologically unique charateristices. The ITS and mtSSU rDNA sequence variability within the small- spored (Longicatenatae) Alternaria spp. was relatively limited. A number of small-spored taxa such as A. alternata, A. arborescens, A. citri, A. gaisen, A. longipes, A. mali and A. tenuissima could not reliably be distinguished from each other using this method. However, cluster analysis of universal rice primer (URP)-PCR fragment patterns was useful for establishing relationships among the species of small-spored Alternaria. Based on phylogenetic analysis of histone H3 gene sequence, the large- spored (Noncatenatae) Alternaria spp. were clustered into several distinct specesis-clades, most of which correlated with species previously established based upon morphological characteristics. URP-PCR analysis was also useful for establishing systematic relationships among the large-spored Alternaria spp.