Sooty Mould on Hibiscus rosa-sinensis Caused by Leptoxyphium kurandae is Associated with Extrafloral Nectaries

Abstract

In August 2013, sooty mould was observed on Chinese hibiscus (Hibiscus rosa-sinensis) in a propagation nursery in Seoul, Korea. The sooty mould initially developed at the junction between the leaf blade and leaf petiole and then dispersed along the vein on the abaxial surface. The fungal growth pattern on the plants was quite different from general sooty moulds growing on honeydew secreted by insects on the plants. On the basis of the morphological characteristics and phylogenetic analysis using the internal transcribed spacer rDNA, this fungus was identified as Leptoxyphium kurandae. A pathogenicity test was carried out to fulfil Koch's postulates. Through field observation and a pathogenicity test, we found an association between the sooty mould and extrafloral nectaries. To our knowledge, this is the first report of sooty mould caused by L.kurandae on the extrafloral nectaries of H.rosa-sinensis.