Studies on Citrus Melanose and Citrus Stem-End Rot by Diaporthe citri (Faw.) Wolf. Part 12

Identification of a Wound Hormone-like Substance in Melanose Spot

Abstract

The self-defense reaction of Citrus unshiu Marc. was initiated by a response to the hyphal penetration of Diaporthe citri (Faw.) Wolf, and the melanose spot consisted of brown cells and a cork layer was formed as a result of the reaction. A series of experiments was conducted to clarify the mechanism of cork layer formation by the abnormal division of cells which occur at just under the brown cells. It was found that citrus produced cell-division inducer (CD inducer) by the self-defense reaction with infection of D. citri, and a wound hormone-like substance, CD-4 was isolated from melanose spots on fruit of C. unshiu. This substance was not detected in the healthy fruit and leaves of citrus. The wound hormone-like substance was identified as γ-amino n-butyric acid (GABA), on both physical properties and biological activity.