Invasive Species Compendium

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Abstract Full Text

First report of Alternaria alternata on Verbesina encelioides in Saudi Arabia.


In the winter of 2009, severe foliar infections were observed on Verbesina encelioides in the greenhouse of the King Saud University at Riyadh (Saudi Arabia). Symptoms appeared as greyish brown patches around the tips and margins of young leaves that later extended towards the midrib, causing curling and shedding of the leaves. Leaf pieces with lesions plated on potato dextrose agar yielded fungal colonies with brown septate hyphae bearing straight, 1- to 3-septate conidiophores, 50 × 3-6 µm in size. Conidia were obclavate to ellipsoidal, with a short cylindrical pale-brown to light-brown beak with muriform septation, usually solitary, occasionally in short chains. Based on these morphological characters, the fungus was identified as Alternaria alternata. This is thought to be the first report of a pathogenic A. alternata affecting V. encelioides.