First record of the rust Puccinia lagenophorae Cooke on Emilia spp. in the UK

Emilia coccinea (tasselflower) and E. sonchifolia (Cupid's shaving brush) are widely available ornamentals, that are grown in the UK for their attractive display of small red flowers during the summer. In July 2004, plants showing symptoms of rust were found at Wisley gardens in Surrey (Fig. 1).

Aeciospores were orange, round to obovate, 16-18 x 16-20 µm in diameter. Aecia appeared on both sides of the leaves and stems. Production of teliospores was noted during August. Telia appeared as black raised blisters on the stems, sometimes several centimetres long (Fig. 2). Teliospores were stalked, two-celled (Fig. 3), rarely three-celled (Fig. 4), constricted between the cells and their colour ranged from light to dark-brown, 38-56 µm long and 16-21 µm across. The terminal cell was rounded sometimes with a pointed apex. One-celled mesospores were not observed. The diameter of the stalk measured at the point of attachment of the spore body was 7.4 µm (average made from 30 spores). Based on morphological characters described above, this rust pathogen was identified as Puccinia lagenophorae (Weber et al., 1998).

The 5'end of the large ribosomal subunit (LSU) and the ITS region were amplified using the primers NL1/NL4 and ITS4/ITS5 respectively and the amplification procedures described by Maier et al. (2003) and Weber et al. (2003). The ITS and LSU amplicons were sequenced and their sequences deposited in GenBank (accession numbers AY808060 and AY808061 respectively). The ITS sequence was identical to that of Puccinia lagenophorae (AF468041). However, as this was the first sequence of LSU submitted for this fungus no comparison was possible.

Puccinia lagenophorae was first discovered in Britain in 1961 on Senecio spp. The rust originated from Australia and is now causing epidemics on Senecio spp. in Europe. Other hosts affected in the UK are Calendula officinalis, Pericallis hybrida and Bellis perennis (Henderson, 2000), although natural infection of this fungus on the latter host has been questioned (Weber et al., 1998). This rust has never been recorded on Emilia spp. in the UK or in other parts of the world. The only rust recorded so far on Emilia spp. in the UK is Coleosporium tussilaginis (Henderson, 2000).