Resistance to Cronartium ribicola in Pinus monticola: an analysis of needle-spot types and frequencies

Publisher Website
Google Scholar
Abstract
Two kinds of needle spots, red and yellow, were found 9 months after artificial inoculation of 2-and 3-year-old, nursery-grown western white pine seedlings with field-run Cronartium ribicola inoculum. The causal agent was verified by histological examination of samples of the two spot types, by exclusion of inoculum from a portion of the seedlings, and by comparison of stem symptoms originating from the two spot types. When seedlings from three populations and two inoculation years were classed according to spot type, the class proportion varied from 68.4 to 9.0% yellow-type plants, 5.7 to 63.9% red-type plants, and 25.8 to 41.7% double-type plants. However, the mean spot frequency of each class for all three populations exhibited little variation. One population yielded frequencies of 12.11, 9.55, and 20.12 spots per metre of needle length on yellow-type, red-type, and double-type seedlings respectively. The second population yielded 7.66, 9.85, and 17.14; and the third, 7.00, 9.14, and 18.49. The existence of distinct seedling classes combined with evidence that the sum of the means of the two single-type classes (12.11 + 9.55 = 21.66) was nearly equal to the mean of the double-type class (20.12) led the authors to conclude that field-run inoculum was composed of at least two races and that the pine seedlings exhibited differential resistance to those races.

This publication has 0 references indexed in Scilit: