VIEW ARTICLE

Resistance

Relationship of Wound Periderm Formation to Resistance to Ceratocystis fimbriata in Almond Bark. R. M. Bostock, Assistant professor, Department of Plant Pathology, University of California, Davis 95616; G. E. Middleton, Graduate research assistant, Department of Plant Pathology, University of California, Davis 95616. Phytopathology 77:1174-1180. Accepted for publication 20 March 1987. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/Phyto-77-1174.

Bark wounds in branches on almond trees of the cultivar Nonpareil became resistant to infection by Ceratocystis fimbriata within 10–14 days after injury in summer. Frequency and size of cankers declined significantly as the time interval between wounding and inoculation increased on Nonpareil and also on the cultivar Carmel. The development of complete resistance in wounds on Nonpareil that had aged for 14 days was related by histochemical analyses to extensive deposition of lignin and suberin in a well-developed wound periderm. The difference in canker size at bark injury sites inoculated after 6, 10, and 14 days was not significant and was related to browning and death of cells at the wound surface followed by deposition of lignin and suberin near a wound meristem. On potted trees, wounds that were reinjured after 14 days of aging became susceptible to infection, similar to fresh bark wounds. These results suggest that treatments applied to fresh bark wounds should protect for 14 days after wounding to be effective and should not impair the development of natural resistance in the host tissue.