Controlled inoculation provides insight into western redcedar resistance to multiple root- and butt-rot pathogens

Area of Science:

• Forestry and Plant Pathology
• Mycology
• Plant Breeding

Background:

• Western redcedar (Thuja plicata) is economically vital but susceptible to root and butt rot diseases.
• Despite natural resistance, genetic disease resistance is underutilized in breeding programs.
• Understanding host-pathogen interactions is crucial for managing forest health.

Purpose of the Study:

• To evaluate western redcedar resistance to eight wood decay fungi.
• To develop and validate artificial inoculation methods for disease screening.
• To investigate latent infections and their impact on seedling growth.

Main Methods:

• Artificial inoculation of three-year-old seedlings using wood block-stick and dowel-plug methods.
• Assessment of disease symptoms and infection processes over 18 months.
• Molecular diagnosis using internal transcribed spacer region (ITS) next-generation sequencing (NGS) for latent infection detection.

Main Results:

• Five pathogens (Armillaria ostoyae, Coniferiporia weirii, Heterobasidion occidentale, Poriella subacida, Postia balsamea) caused varying disease incidence (10-60%).
• Coniferiporia weirii and Poriella subacida induced both discoloration and decay.
• Latent infections detected by ITS-NGS in asymptomatic seedlings impaired growth, indicating molecular infection severity (MIS) as a key trait.

Conclusions:

• Latent infection is a significant factor in western redcedar disease resistance, measurable by MIS.
• Developed inoculation and molecular diagnostic tools are valuable for breeding programs.
• Insights aid in predicting disease outbreaks and improving forest health management.