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Thousands of plant diseases have been recorded throughout the world, many of these causing heavy crop loses. Early detection and accurate diagnosis is essential for the effective management of plant disease. Thus the first step in studying any disease is its timely detection of the diseased plant. Quick initial detection is largely based on the signs and symptoms of disease.〔http://www.plantpath.iastate.edu/〕 Signs are the visible physical presence of either the pathogen itself or the structures formed by the pathogen. Common examples of easily detected signs are those such as the fungal mycelia and spore masses of downy mildews observed on infected leaves and the bacterial ooze of ''Xanthomonas'' leaf streak disease on rice.〔http://plantpath.psu.edu/〕 Symptoms are the visible changes that occur in the host plant in response to infection by pathogens. For any disease in a given plant, there is the characteristic expression of symptoms, usually occurring in a sequential series during the course of the disease. This series of symptoms depicting the disease picture is referred to as the disease syndrome.〔http://www.plantpath.wisc.edu/〕 Morphological symptoms may be exhibited by the entire plant or by any organ of the plant. These have been categorized into different groups for easy of study. Primarily, morphological symptoms of plant diseases can be categorized into 6 different types.〔http://plantpathology.ucdavis.edu/〕 * Necroses * Growth abnormalities * Metaplastic symptoms * Proleptic symptoms * Color changes * Wilts ==Necroses== Necroses are caused due to necrosis or death of plant cells. The affected plant tissue usually turns brown to black in color. Necrotic symptoms could appear in any part of the plant such as in storage organs, in green tissues, or in woody tissues.〔http://homeguides.sfgate.com/necrosis-plant-diseases-39504.html〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Morphological symptoms of plant diseases」の詳細全文を読む スポンサード リンク
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