APS Abstract of Presentation

Identification of powdery mildews anamorphs (Order Erysiphales) from Puerto Rico
D. Torres (1), L. I. RIVERA-VARGAS (1)
(1) University of Puerto Rico
Phytopathology 98:S157

Worldwide, powdery mildew (Ascomycetes; Order Erysiphales) causes economic losses on a large variety of plants. In Puerto Rico, taxonomic studies related to this order of fungi have been very limited. A major constrain is that their teleomorph is frequently absent, which is an important criteria for their identification. To precisely identify their species, the broad based anamorph identification of powdery mildew as Oidium sp. needs to be resolved, especially those of economic importance. Thus, the basis of this research was to identify powdery mildews using different techniques such as Scanning Electron Microscopy (SEM) of infected tissues and sequencing of the nuclear internal transcribed spacer (ITS) of ribosomal DNA (rDNA) gene. On the basis of SEM examination, the following powdery mildews have been identified: Erysiphe australiana in Lagerstroemia indica (crabmyrtle); Erysiphe poligoni in the weeds, Desmodium podocarpus and Euphorbia heterophyla; Golovinomyces cichoracearum in two weed legumes; and Leveillula taurica in onions. Nested PCR of the ITS region of the rDNA produced fragments of 750 to 766 bp. DNA sequencing of these products are in progress. Identification of the powdery mildews will enable us to establish protocols to handle symptomatic introduced plant material and to apply appropriate controls in case of an outbreak. Finally, the data collected will allow for the revision of prior reports of Erysiphales in order to identify the arrival of new species into the island. This effort will be fundamental in establishing guidelines for quarantine or to implement management strategies for invasive species.