ABSTRACT
Gummosis can be seen in many diseased plants and is abundant in several groups, including the order Leguminosae and the families Anacardiaceae, Meliaceae, Rosaceae, and Rutaceae. The first sign of brown rot gummosis caused by Phytophthora citrophthora in Citrus trees, is often the secretion of gum. The fungus usually attacks healthy and well-developed trees and can cause rapid death. The main threat is the death of large areas of the bark and girdling of the tree. Early stages of gum duct formation were described by different authors as being either lysigenous or schizogenous. Gum ducts formed lysigenously are the result of the dissolution of cell walls at the cambial zone where xylem mother cells form, as in cherry shoots. Although gumming probably represents a general response to injury and infection, the proven effectiveness of the response as a protective barrier has yet to be documented.
