First Report of Root Rot of Cocoyam Caused by Pythium myriotylum in Sri Lanka

Plant Disease
M TojoJ A S Jayakody

Abstract

Root rot of cocoyam (Xanthosoma sagittifolium L. Schott) caused by Pythium myriotylum Drechsler is a major disease of this crop in Africa (1,2) but is unreported from other regions of the world. During September 1999, commercially grown cocoyam (cv. Ratu-kiri-ala) in Gampaha (7°05'N, 80°00'E), Sri Lanka suffered from severe root rot. Initial symptoms were water-soaked lesions at the root tips that gradually enlarged to rot the entire root system and tuber. Wilting and yellowing of leaves were observed in advanced stages of disease. A Pythium sp. was regularly isolated from the affected roots and an isolate, SC5, was identified as P. myriotylum on the basis of morphology and the internal transcribed spacer (ITS) rDNA sequence. Characteristics of isolate SC5, grown on a grass-leaf water culture (3) were main hyphae up to 8.5 μm wide, oogonia terminal or intercalary (22.5 to 33.8 μm in diameter), antheridia diclinous occasionally monoclinous, one to eight per oogonium, stalks branched, often more or less loosely enveloping the oogonium, antheridium clavate or crook-necked, making apical contact with the oogonium, breadth of antheridium 2.5 to 7.0 μm, oospores aplerotic (17.0 to 22.5 μm in diameter), oospore wall 0.8 to 2.0 μm in t...Continue Reading

Citations

Jan 24, 2017·Parasite Immunology·N H ManamperiN D Karunaweera

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