Related Experiment Video
Updated: Jan 30, 2026

Bioassays for Monitoring Insecticide Resistance
Published on: December 30, 2010
Use of Mycelium and Detached Leaves in Bioassays for Assessing Resistance to Boxwood Blight
Yonghong Guo1, Richard T Olsen1, Matthew Kramer2
1U.S. Department of Agriculture/Agricultural Research Service, U.S. National Arboretum - Floral and Nursery Plants Research Unit, Beltsville, MD 20705.
Abstract:
Boxwood blight caused by Calonectria pseudonaviculata is a newly emergent disease of boxwood (Buxus spp. L.) in the United States that causes leaf drop, stem lesions, and plant death. A rapid and reliable laboratory assay that enables screening hundreds of boxwood genotypes for resistance to boxwood blight is needed to enable breeding and selection of resistant cultivars. Using eight boxwood cultivars with differing susceptibilities, we examined parameters for a screening assay comparing whole plant inoculation with detached leaf inoculation, use of mycelium versus spores as the inoculum, comparison of times of the year for inoculation, and comparison of two leaf inoculation methods. Inoculation of detached leaves gave comparable results to inoculation of whole plants when compared across genotypes, although the detached leaf assay resulted in greater percentages of symptom expression. The time of year of plant inoculation (spring, summer, or winter) did not affect the relative expression of symptoms among the most resistant and susceptible genotypes. Inoculating plants with mycelium was as effective as spore inoculation for causing disease symptoms and allowed us to distinguish the more resistant genotypes, yet mycelium inoculation was much easier to prepare in large quantities for multiple assays.
Related Concept Videos
Leaving Groups
In general, in a nucleophilic substitution reaction, a nucleophile displaces a functional group, called the leaving group, from the substrate to give a substituted product. A leaving group departs the substrate molecule through heterolytic cleavage, taking the pair of electrons with it to become a relatively stable weak base in the form of an anion or a neutral molecule.
In a...
Resistivity
Resistance
Basic Plant Anatomy: Roots, Stems, and Leaves
Equivalent Resistance
Resistance and Conductance
Various factors impact the resistance of a conductor. Spiraling in stranded conductors increases their...

