A technique for screening seedlings of the saskatoon for resistance to the rust Gymnosporangium nelsonii

Abstract

A method was developed to rapidly screen saskatoon seedlings for resistance to rust caused by Gymnosporangium nelsonii. Telial galls collected from wild Juniperus horizontalis were used to produce basidiospores in the laboratory. The basidiospores were sprayed on the leaves in a 1 or 2% solution of molasses which served to adhere the spores to the leaf surface. The inoculated plants were placed in a 100% RH atmosphere at 16 °C in the dark for 24 h and then moved to a greenhouse. Pycnial lesions were apparent after 12 d. Because lesion density decreased with leafage, the mean density of pycnial lesions on the youngest three leaves was used to assess disease severity.Key words: Amelanchier alnifolia, rust resistance, screening