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Title: FIRST REPORT OF THE RUST MELAMPSORA EUPHORBIAE ON EUPHORBIA HETEROPHYLLA IN OMAN

Author
item DEADMAN, M - OMAN
item AL SADI, A - OMAN
item AL MAQBALI, Y - OMAN
item AL JAHDHAMI, S - OMAN
item PATZELT, A - OMAN
item Aime, Mary

Submitted to: Journal of Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/28/2006
Publication Date: 5/19/2006
Citation: Deadman, M.L., Al Sadi, A.M., Al Maqbali, Y.M., Al Jahdhami, S., Patzelt, A., Aime, M.C. 2006. First report of the rust Melampsora euphorbiae on Euphorbia heterophylla in Oman. Journal of Plant Pathology. 88(2):121.

Interpretive Summary: Rust fungi are a very large and diverse group of parasites that attack plants and can be used as biological control agents for noxious weeds. Accurate knowledge about the distribution of rust fungi is important for discovering and identifying potential rust biological control agents. Mexican fireplant or painted spurge is a weed poisonous to animals that is common in tropical regions but has spread and become invasive in warm temperate areas. In this research a rust fungus was discovered for the first time in the country of Oman causing disease on painted spurge. This rust will be screened to determine its potential as a biological control agent of its host. This research will be used by plant pathologists who are searching for biological agents to control this invasive weedy plant.

Technical Abstract: Euphorbia heterophylla L. or painted spurge or is a serious weed in many parts of the world and considerable efforts have been made to limit its invasiveness and impact on crop productivity. This has included evaluation of fungi as biocontrol agents. In Oman, E. heterophylla is a rare, introduced weed of irrigated fields. In April 2005, leaf samples of E. heterophylla, showing rust symptoms were collected from Mudhaibi, 100 km south of Muscat. Orange pustules covered both sides of the leaves and yielded urediniospores typical of Melampsora euphorbiae. Urediniospores were variable but mostly subglobose, measuring 16-20 x 14-16 µm, and echinulate, intermixed with hyaline, capitate paraphyses, similar to recent reports for the same pathogen on related hosts. Pathogen identity was confirmed by nuclear ribosomal large subunit DNA analysis (voucher sequence deposited in GenBank, voucher specimen deposited in the U.S. National Fungus Collections). M. euphorbiae has previously been reported from the Middle East, but not from Oman. The pathogen has been suggested as a biocontrol agent against weeds including E. esula L. and E. cyparissias L.. Current research is examining the ability of M. euphorbiae to limit growth and reproduction of E. heterophylla under local conditions.