Y. J. Choi

New smut-specific primers for the ITS barcoding of Ustilaginomycotina

The smut fungi (Ustilaginomycotina) are a highly diverse group, containing about 115 genera and 1700 species, most of which are biotrophic plant pathogens. As for other fungal groups, the ITS rDNA region is widely used to determine smut fungi at species level due to its high discriminatory power and for phylogenetic reconstructions within genera. So far, two primer sets, ITS1/ITS4 and M-ITS1/ITS4, were generally used to amplify smut fungi, but these often co-amplify host plants or contaminant fungi and do not yield satisfactory amplification for a variety of smut fungi. In the present study, based on a selection of genera that include more than 90% of the species of smut fungi (more than half of the genera of smut fungi), three new primers, smITS-F, smITS-R1 and smITS-R2, situated in the SSU or LSU region, were designed to avoid the amplification of host plants and to extend the coverage of PCR amplification for as many smut genera as possible.

Revision of Plasmopara (Oomycota, Peronosporales) parasitic to Impatiens

The oomycete Plasmopara obducens was first described on wild Impatiens noli-tangere in Germany in 1877. About 125 years later the first occurrence of P. obducens on cultivated I. walleriana in the United Kingdom was reported, and a worldwide epidemic followed. Although this pathogen is a major threat for ornamental busy lizzy, the identity of the pathogen remained unconfirmed and the high host specificity observed for the genus Plasmopara cast doubts regarding its determination as P. obducens. In this study, using multigene phylogenies and morphological investigation, it is revealed that P. obducens on I. noli-tangere is not the conspecific with the pathogen affecting I. walleriana and another ornamental balsam, I. balsamina. As a consequence, the new names P. destructor and P. velutina are introduced for the pathogens of I. walleriana and I. balsamina, respectively.

The only known white blister rust on a basal angiosperm is a member of the genus Albugo

Rare pathogens on unusual hosts are often providing valuable insight into the evolution of the pathogen group concerned, but it is often challenging to obtain sequence data for these, as because only very few, often decades-old specimens are available. One such example is Albugo tropica, the white blister pathogen of a basal angiosperm in the genus Peperomia (Piperaceae). For this species, only two, more than 70 and over 120-year-old collections available. Here, sequence data for A. tropica are reported and phylogenetic reconstructions reveal it as the sister group to all other white blister rusts of the genus Albugo. Its isolated position is also reflected by several morphological differences to the other species of the genus, such as very thin-walled sporangia and almost smooth oospores. The isolated phylogenetic position of the pathogen and its host might indicate that it is a relict species trapped on its host. The sister-group relationship to all members of the genus Albugo s.str., which have been investigated using molecular phylogenetics, hints at the possibility, that Albugo might have originated in South America or Gondwana and has later radiated in the holarctic on members of the Brassicales.

First Report of Downy Mildew Caused by Sclerophthora sp. on Zoysiagrass (Zoysia japonica) in Korea

Korean lawngrass (Zoysia japonica Steud.) produces a highly dense, drought-tolerant, and wear-resistant turf that makes it desirable for golf courses, home lawns, parks and sports fields. Because of its cold tolerance, it was adopted in many countries with temperate climates, from East Asia (China, Japan, and Korea) to as far north as Maryland of the United States. In Korea, the demand for zoysiagrass has recently increased roughly threefold between 2003 and 2012 (Kang et al. 2016). During May 2015, zoysiagrass showing typical downy mildew symptoms was first observed in a golf course in Gyeonggi province, Korea, and since then it has rapidly spread into other regions in Korea. Symptoms begin as yellowing of leaves, and develop a raised, tufted appearance, resulting from the shorten internodes of rhizome and an increased number of tillers. A sample of infected zoysiagrass was deposited in the Kunsan National University Herbarium (Acc. no. KNUH 45). Sporangia were hyaline, lemon-shaped to ellipsoidal or obo...