This study was conducted to investigate the various factors affecting the rough-bark disorder on the stem of the dwarf apple tree in 1986 and 1987. The disorder has recently become a significant problem to Korean apple growers. The symptom of the disorder develops on the stem bark around the graft union, both of rootstock and scion cultivars. The damaged trees show severe inhibition of active vegetative growth, bear small fruit and result in death.
The obtained results were summarized as follows:
1. No differences in anatomical characteristics (cell size and structure) were observed among the 3 cultivars, `Fuji´, `Golden Delicious´ and `Tsugaru´.
2. Anatomical observation of the rough-bark disorder indicated that the rough-bark detachment associated with the disorder started from the band of phloem fibers. The cracks in the bark of severe rough-bark `Fuji´, susceptible cultivar, were clearer and wider than `Tsugaru´, relatively resistant cultivar.
3. Shoot and root growth of the disordered tree was poorer than those of a normal tree. Particularly, the growth of the primary root was significantly reduced by rough-bark.
4. The physical characters of soil in which the disordered trees were planted showed higher soil hardness, lower air in 3-phase and higher clay content in soil texture as compared with normal tree planted soil.
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