Pathological anatomy of nectria canker on Fraxinus mandshurica var. japonica

Abstract

The anatomical characteristics of Nectria canker on Fraxinus mandshurica var. japonica were analyzed. Typical cankers were conspicuous, round to oval, with uniform concentric rings of affected xylem in a target-like structure. Each concentric annual growth ring was wider than the corresponding annual rings lateral to the cankers. The xylem elements were extremely disoriented. The cambial zone became discontinuous and disappeared. An inoculation test with the causal fungus, Nectria galligena, produced similar anatomical abnormalities and revealed the process of canker formation. Fewer and narrower vessels were formed, and water conduction took place only in the large vessels of the current year in the cankers.