Abstract

Twelve date palm cultivars were evaluated for resistance to Graphiola leaf spot caused by Graphiola phaenicis (Moug) poit. The disease incidence and number of sori were compared on both surface of leaf, pinnae position on leaves and plant age. Cultivars Gizaz, Tha'al and Khodari showed negligable infection and fewer number of sori on the leaf surface and rachis. Symptom of disease was absent on leaves and rachis in cultivar Sagaee. These cultivars differed significantly from susceptible cultivars Shahree, Soqotree and Khalas (P = 0.01). Abundant distribution of sori caused a drastic reduction of the leaf area covered by the fungus. Adaxial leaf surface trapped more number of sporidia and significant differences were detected among test cultivars (P = 0.05). The temperature ranging between 32°C-38°C in summer and humidity accompanied by heavy dew in the night and early morning favored the development of infection. Correlation of age on cultivar "Shahree" and disease incidence revealed that older trees are more susceptible to disease.

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