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Title: WHAT IS OOSPORA ORYZETORUM SACC.?

Author
item GAMS, WALTER - NETHERLANDS
item Rossman, Amy

Submitted to: Mycotaxon
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/11/2005
Publication Date: 8/1/2005
Citation: Gams, W., Rossman, A.Y. 2005. What is Oospora oryzetorum Sacc.? Mycotaxon 92:339-340.

Interpretive Summary: Invasive fungi cause tens of billions of dollars damage to crop plants in the U.S. each year; thus it is essential that harmful fungi not be allowed entry into the country. Plant quarantine policy makers must make decisions about whether or not agricultural commodities can safely be brought into the country and thus they must know about fungi that pose a threat to agriculture. A fungal species of obscure identity has been considered as a potential threat to rice growing in the U.S.; however, this fungus was known only from the Philippines. After examining specimens of the fungus, we determined that it is not a fungus at all. Instead it is a natural part of the rice plant that had been mistakenly identified as a fungus. This research clears up the mistake and eliminates this as a potential threat to rice production in the U.S. The results are of immediate use to plant quarantine inspectors and policy makers.

Technical Abstract: Oospora oryzetorum Sacc. was described by Saccardo (1916) as consisting of a white powder covering dying glumes of young rice grains (Oryza sativa L.) in Los Baños in the Philippines. The disease has apparently not been observed since. For many years Saccardo had included several acremonium-like fungi with catenate conidia in Oospora and therefore most of these species were revised by Gams (1971). Of Oospora oryzetorum Gams (l.c.) examined the material distributed as C.F. Baker, Fungi Malayana No. 264, lodged in the herbaria in S, B, K and PAD. In none of them could he find fungal material that matched the meager description and therefore he concluded that the identity of the fungus could not be assessed. Because of an interest by plant quarantine authorities, the second author started a reexamination of two further specimens of the same collection lodged in BPI. In one of these (BPI 408511), originating from the herbarium of O. Reinking, some glumes showed a rather conspicuous white covering that seemed to match the diagnosis of this species. Upon closer examination, we could only see irregular masses of refringent, more or less angular, hyaline bodies with a central dot, which obviously represent starch grains and are not fungal. It thus seems plausible that Saccardo (1916) may have mistaken these structures for fungal conidia. One must conclude that the description of Oospora oryzetorum as a fungus is a mistake. All specimens represented by this name were examined and none of them contain material that agrees with the type description is fungal in nature. The scientific name Oospora oryzetorum should be ignored and, most certainly, does not constitute a threat to rice cultivation.