CSIRO PUBLISHING www.publish.csiro.au/journals/apdn Australasian Plant Disease Notes, 2009, 4,21–22
S-type powdery mildew on lilac in Australia
J. H. Cunnington A,B and R. W. Brett A
ABiosciences Research Division, Department of Primary Industries, Knoxfield, Private Bag 15, Ferntree Gully Delivery Centre, Victoria 3156, Australia. BCorresponding author. Email: [email protected]
Abstract. In 2004, powdery mildew on lilac (Syringa vulgaris) was collected in a home garden in an inner suburb of Melbourne. At that time it could not be identified, but appeared to be the only verifiable record of powdery mildew on lilac in Australia. A recombinant DNA internal transcribed spacer sequence from a 2008 sample, collected from the same garden, revealed that the fungus is the S-type lilac powdery mildew that lacks a clear name.
Powdery mildew occurs on lilac (Syringa spp.) in many parts of the world. Braun (1987) recognised two species of powdery mildew fungi; Erysiphe syringae Schwein. ( Microsphaera syringae (Schwein.) H. Magn.) and E. syringae-japonicae U. Braun & S. Takam. ( Microsphaera syringae-japonicae U. Braun). The former occurs in Europe and North America. The latter occurs in Asia. The main morphological difference between the two species is that E. syringae forms four or fives ascospores per ascus, while E. syringae-japonica forms 6–8 spores per ascus. However, Bolay (2005) could not find this difference in ascospore numbers and concluded that they were both the same species. A molecular phylogenetic study was undertaken by Seko et al. (2008) to clarify the status of the two species. Seko et al. (2008) demonstrated that two species were present, but could not assign names to them, instead calling them K-type and S-type. Interestingly, the S-type appeared to have been present for a long time in Europe and North America, while the K-type originated in Asia. The K-type then spread to Europe in the early 1990s and out-competed the S-type to become the dominant species. In December 2004, powdery mildew on lilac (Syringa vulgaris) was collected in a home garden in an inner Melbourne suburb. The shrub was very heavily infected (Fig. 1). Microscopic examination of the fungus revealed that it was a typical Pseudoidium-type anamorphic powdery mildew. Basic morphological characters agreed with those of both E. syringae and E. syringae-japonica (Braun 1987). Conidia were formed singly, ovoid-to-ellipsoid, ~25–30 Â 10–15 mm, without fibrosin bodies. Appressoria were multilobed. At that time no further identification was possible. Material was collected from the same garden in April 2008. Fig. 1. Powdery mildew on lilac (VPRI 41368). On this occasion it was decided to obtain a ribosomal DNA internal transcribed spacer (rDNA ITS) sequence to compare with the sequences of the S-type and K-type lilac powdery Total DNA was extracted from leaf material of specimen mildews published by Seko et al. (2008). Both specimens VPRI 41368 using a DNeasy Plant Mini Kit (Qiagen, have been deposited in the Department of Primary Industries Melbourne, Australia). The rDNA ITS region was amplified Victoria Plant Pathology Herbarium (VPRI 32130 and 41368). using primers PMITS1 and PMITS2 (Cunnington et al. 2003).