A NEW YELLOWS-DISEASE OF DAMES-VIOLET (HESPERIS-MATRONALIS) IN ALBERTA, CANADA, CAUSED BY AN UNIDENTIFIED PHYTOPLASMA

Using transmission electron and fluorescent microscopy, phytoplasma bo dies were found in phloem cells of stems and leaves of the flowering o rnamental dame's violet (Hesperis matronalis). The diameter of these b odies ranged from 0.26-0.56 x 0.25-0.50 mu m and averaged 0.38 x 0.43 mu m Most of the phytoplasma bodies were spherical, although pleomorph ic types occurred in the sieve tube cells. Low percentages of vacuole- like spaces and inner bodies were observed in che phytoplasmas. Shrunk en and degenerated phytoplasmas were also found in phloem cells of inf ected plants. Symptoms induced by phytoplasma infection included chlor osis, stunting, bladder-like siliques, and phyllody of inflorescences. The mode of transmission of the pathogen under natural conditions is discussed. This is the first report of a phytoplasma being associated with disease in H. matronalis.