Waxy Mannagrass is Established in Two Oregon Counties

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B. Shaun Bushman, 695 N 1100 E, USDA-ARS, Logan, UT 84322; Richard R. Halse, 2082 Cordley Hall, Department of Botany and Plant Pathology, Oregon State University, Corvallis 97331; and Mohamed Sedegui, 635 Capitol St. NE, Oregon Department of Agriculture, Salem 97301

During official regulatory testing of grass seed shipments bound for Australia in 2006, seeds of a Glyceria species were detected in eleven seed lots of annual ryegrass (Lolium multiflorum Lam.) from four growers’ fields in Linn and Benton counties, Oregon, the major grass seed-growing counties in the state. Seven of the 18 Glyceria species known to occur in North America are found in Oregon (1,3). The majority of these species are considered noxious weeds by Biosecurity Australia, their national agency responsible for plant protection. Biosecurity Australia presently allows only waxy mannagrass (G. declinata Brebiss.) as a contaminant in grass seed shipments (2). G. declinata is not native to the United States. Previously, this introduced plant species was recorded only in Louisiana, New York, and California (3,4); only recently was it detected in Benton County, Oregon (4).

In an effort to identify the unknown Glyceria to species and confirm the establishment of G. declinata in Oregon, four to five seeds were planted in a greenhouse in a sterile commercial potting medium and then grown at 65°C and relative humidity 75% for 6 to 7 months until flowering. In addition, official inspectors collected suspected Glyceria plants that were in flower from ditch banks near grass seed fields in Linn Co. (Fig. 1). Flowering plants from seed and from the field were sent to the Oregon State University Herbarium. The material was identified as G. declinata based on morphological characteristics. The plants examined exhibited the morphological characteristics of G. declinata. This species is distinguishable from G. occidentalis (Piper) J.C. Nels., G. leptostachya Buckl., and G. fluitans (L.) R. Br. by the morphology of the palea and of the tip of the lemmas (1). The tip of the lemmas of G. declinata has three distinct teeth, the center tooth being well developed with a single smaller tooth on either side of it. The lemma apices of the other taxa are blunt or acute, with any teeth if present being equal in size. The apex of the palea of G. declinata is distinctly bifid with a deep notch between the two teeth. In the other taxa the palea apices are shallowly cleft or entire.

Fig. 1. Waxy mannagrass (Glyceria declinata) growing in a grass seed field in Linn Co., Oregon (May, 2007) with the flowers noted (arrows).

Leaf tissue samples from eight field-collected plants were also sent to the USDA-Agricultural Research Service Forage and Range Research Laboratory in Logan, Utah for identification using trnk-rps16 chloroplast (4) and nuclear ribosomal internal transcribed spacer (ITS) DNA sequences. DNA was extracted from the plant tissue using the DNeasy Plant Kit (Qiagen, Valencia, CA) according to the manufacturer’s instructions. PCR amplification and sequencing was performed as previously described (4). The DNA sequences of the eight samples were compared to known sequences published in the NCBI GenBank database; three were identified as Glyceria species. All three had chloroplast and ITS sequences identical to previously published G. declinata voucher sequences (GenBank Accession Nos. DQ665569 and EF674557) and were clearly distinguishable from G. notata Chevall., G. occidentalis, G. leptostachya, and G. fluitans voucher sequences (GenBank Accession No. EF674584) (4).

In 2007, G. declinata has been detected in seed lots from an additional four growers’ fields in Linn County. It has also been detected in one grower’s field for the second year in a row. These results confirm that the non-native species G. declinata is established in Oregon. This finding may have implications for the international trade of grass seed with Australia.

Literature Cited

1. Barkworth, M. E., Capels, K. M., Long, S., Anderton, L. K., and Piep, M., eds. 2007. Flora of North America North of Mexico, Vol. 24. Oxford Univ. Press, New York.

2. Purdue Research Foundation. 2007. Australia: Seed that must meet general requirements "D-G". Online. EXCERPT: Export Certification Project, Center for Environ. and Regulatory Info. Systems (CERIS), West Lafayette, IN.

3. USDA, Natural Resources Conservation Service. 2007. The PLANTS Database. Online. National Plant Data Center, Baton Rouge, LA.

4. Whipple, I. G., Barkworth, M. E., and Bushman, B. S. 2007. Molecular insights into the taxonomy of Glyceria (Poaceae: Meliceae) in North America. Amer. J. Bot. 94:551-557.