Use of chrysanthemum plantlets grown in vitro to test cultivar susceptibility to white rust, Puccinia horiana P. Hennings

An efficient incubation and inoculation system for white rust was establish ed using plantlets of chrysanthemum growing in vitro. The internal conditio ns of a culture vessel (plant box) were maintained at a humidity of 90-100% and an optimum temperature of 20-25 degreesC, which are suitable condition s to germinate teliospores and basidiospores of the pathogen. Telia were ma intained continuously on plants in the plant bos and were used as an inocul um for infection experiments throughout the gear, allowing differences in s usceptibility to white rust among chrysanthemum cultivars to be detected. S usceptibility to white rust in the plant-box evaluation showed a good corre lation with the rating of sporulation on plants grown in a greenhouse. The method described here is a simple, space-saving inoculation system to evalu ate the susceptibility of chrysanthemums to white rust.