• Corpus ID: 34257055

THE ISOLATION OF THE FUNGUS THAT CAUSES CITRUS

@inproceedings{Wolf2010THEIO,
  title={THE ISOLATION OF THE FUNGUS THAT CAUSES CITRUS},
  author={Frederick Adolph Wolf},
  year={2010}
}

• F. A. Wolf
• Published 2010

Citrus melanose* is characterized by the presence of small, pustular lesions that look like drops of caramelized sugar on leaves, twigs, and fruits. These lesions are initiated while the parts are still young, and at maturity they may occur as isolated dots or may be arranged in streaks, rings, or extensive irregular patches. The fungus that causes melanose possesses two stages, a pycnidial one, Phomopsis citri {2)y^ described in 1912, and an ascigerous one, Diaporthe citri {10)j described in 1926. Melanose was first described in 1896 by Swingle and Webber (8), who first observed it in November, 1892, at Citra, Fla. They were unable to estabhsh the cause definitely, but assumed it to be a fungus. Furthermore, until now, no one has succeeded, even after repeated attempts, in isolating the causal organism from melanose lesions. The pathogène has been isolated repeatedly, however, from dead twigs and from fruits affected with stem-end rot, two manifestations of the disease that can not properly be designated melanose, but that result from infection by the same organism. The relationship between stem-end rot and dying back of twigs has been determined by the investigations of Fawcett {2) and the relationship of melanose to the other two manifestations by Stevens (7) and by Floyd and Stevens (4). ; Fawcett {2) isolated Phomopsis citri from the interior oí iruits affected with stem-end decay and from the interior of dead twigs. He showed by the cultural similarity of isolations from theise two sources and by inoculations that these two forms of the disease are caused by the same fungus. Floyd and Stevens (4), who did not suspect at first that melanose and stem-end rot were related, later found that the two forms, were undoubtedly caused by the same fungus. They occasionally found particles of fungous hyphae in melanose lesions, but were not able to demonstrate whether these were parts of the causal organism or of some secondary invader. They concluded from their microscopic examination of lesions of different ages that no bacterial or fungous organism that could be considered a cause of the disease could be found connected with the affected tissues or the adjoining cells. They tried to isolate the causal organism by planting on various media bits of