A settling tower for quantitative deposition of urediniospores of Uromyces viciae-fabae

Abstract

An inoculation technique resulting in uniform spore deposition for obtaining reproducible and accurate data on host responses is required for quantitative studies of resistance expression. The feasibility of obtaining uniform spore deposition on Lens culinaris, a plant with compound leaves, was investigated using a settling tower. Uniformity of spore deposition on adhesive coated glass slides was assessed by dispersing 1,2,4 and 8 mg spores of Uromyces viciae-fabae, the causal agent of lentil rust, into the tower. When an 8 mg spore quantity was discharged the number of spores deposited per square centimetre did not vary significantly (P > 0.05) between the different locations of the glass slides on the target area. A linear, relation was found between mass of spores discharged into the tower and spores deposited. Counts for 1, 2, 4 and 8 mg were, respectively, 82, 244, 384 and 972 spores per square centimetre. Uniformity of spore deposition increased as the amount discharged increased, and the coefficient of variation was inversely related to the spore quantity dispersed. When plants of lentil cultivar EL-142 were exposed to spores in the settling tower, differences in numbers of lesions per square centimetre leaf area were non-significant (P > 0.05) within and between inoculation runs. Following dispersal of 8 mg urediniospores for a 3 min settling period, a mean of 140 uredinia (standard deviation = 7) occurred per square centimetre leaf area.