الفهرس 
Helminthosporium spp. and favorable conditionsOnly 14 pages are availabe for public view
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Abstract
Sorghum leaf blight disease caused by Helminthosporium turcicum is considered one of the most serious diseases which threat the green substances of sorghum cultivars consequently cause severe loss. Controlling that disease and increasing the grass yield is the main goal of this study. So, this work includes pathological, electrophoretical, varietal resistance, biological, inducers and agricultural practical studies. The obtained results could be summarized in the following points: A. Pathological studies: 1. The diseased samples of sorhgum collected from Delta Egypt reveal that presence of H. turcicum, H. carbonum and H. rostratum. 2. H. turcium isolates were the most frequent one and showed the highest mean of disease severity (24.00%), while H. rostratum and HG. carbonum scored 2.66 and 2.22%, respectively. 3. Pathogenicity of six isolates of H turcicum gave evidence that isolate of Kafr El-Sheikh (No. 6) showed the highest disease severity (55.00%), followed by Damietta isolate (50.00%), then both of Dakahlia and El-Gharbia isolates, 45.00% for each. Isolates of Qalubia and El-Giza were the least, 35.00% for each. B. Varietal resistance: Nine sorghum varieties were evaluated against artificial inoculation of H. turcicum. Under wire green-house. The obtained results were: 1. Four cultivars were highly resistant i.e. local hybrid-102, Kena Sudan grass, IS-22315 and Giza-3. 2. Two cultivars were resistant i.e. Giza-1 and Sids. 3. The cultivars 106-009-2000 B showed moderate resistant response, while, 106-400-2000 C cultivar was susceptible. C. Chemical changes in constituents of some sorghum cultivars: Changes of phenols (free, conjugated and total), and sugar contents (reducing and non-reducing) were determined in two sorghum cultivars i.e. local hybrid 102 (resistant) and imported hybrid 106-1004-2000 C as affected by artificial inoculation with H. turcicum. 1. Free, conjugated and total phenols in healthy plants of both resistant and susceptible hybrids were higher than that of in the infected plants.