Submitted to: Southern Nursery Association Research Conference
Publication Type: Proceedings
Publication Acceptance Date: 8/15/2004
Publication Date: 2/16/2005
Citation: Cheatham, C.L., Copes, W.E. 2005. Inoculation Efficacy of the Medium Used for Suspension of Puccinia hemerocallidis Urediniospores. Southern Nursery Association Research Conference. 49:243-246.
Interpretive Summary: We present a reliable technique to point-inoculate daylily leaves with the daylily rust pathogen. The greatest number of pustules resulted from urediniospores suspended in mineral oil and applied as dispersed drops to the lower leaf surface, in experiments one, two, and five. In experiment three, the greatest number of pustules resulted from application of urediniospores in mineral oil applied to the lower leaf surface, regardless of drop dispersal. In experiment four, pustules developed from urediniospores in mineral oil, but the number of pustules was greatest with spore suspended in Nu-Film® 17.This technique should be particularly useful to plant pathologists studying daylily rust and to hybridizers and plant breeders developing resistant cultivars.
Technical Abstract: A susceptible daylily (Hemerocallis spp.) ‘Pardon Me’ was inoculated with Puccinia hemerocallidis. Urediniospores were suspended in liquid media (deionized water, mineral oil, 0.1% agar, 0.1% agar plus 0.125% Tween 20, 0.1% agar plus Nu-Film® 17, 0.1% agar plus Bio-90™, and 0.1% agar made with buffered solutions at pH 4, 6, 8, and 10) that were applied as five non-dispersed or dispersed drops or as a spray to the adaxial and/or abaxial leaf surfaces. Controls consisted of the media applied without urediniospores. No infection or leaf damage resulted from the media without spores. A higher number of pustules was achieved when leaves were inoculated with urediniospores in mineral oil than the other media in experiments one, two, three, and five (16.7, 106.3, 72.0, and 137.7 pustules per leaf, respectively), and 0.1% agar plus Nu-Film® 17 (200.3 pustules per leaf) in experiment four. Also, pustule number was highest when the suspension was placed on the abaxial surface, but the influence of the dispersion method varied. The medium in which urediniospores were suspended, the leaf surface to which the inoculum was applied, and how the inoculum was dispersed affected success of the infection process.