No abstract

The seeds of the federally-listed noxious weed and parasitic plant small broomrape (Orobanche minor Smith) are extremely small, averaging 200 to 300 μm in size. Because of its miniscule seed size, contamination of fields and seed lots by small broomrape seeds is difficult to detect and confirm via conventional methods. Complementary polymerase chain reaction (PCR) primers based upon unique sequences in the internal transcribed spacer (ITS) regions of the nuclear ribosomal DNA (nrDNA) of small broomrape were developed. The PCR amplified small broomrape DNA and did not amplify DNA from other Orobanche species with similar host ranges found in Oregon. The primers also did not amplify the DNA of red and white clover (Trifolium pratense L. and T. repens L., respectively), two agricultural hosts for this parasite. The PCR-based assay was sensitive enough to detect a single small broomrape seed. Accepted for publication 14 October 2002. Published 18 October 2002.

The federally regulated noxious weed small broomrape (Orobanche minor Smith) is a parasite of several plant species including alfalfa (Medicago sativa L.) and red and white clover (Trifolium pratense L. and T. repens L., respectively) (4). Because of its seed size (200 to 300 mm), it is difficult to detect in harvested clover seed and in soil (3). Recently, we reported a polymerase chain reaction (PCR) assay that can detect small broomrape seed in clover seed (2). This paper reports the testing of this assay for its ability to detect small broomrape in soil. Accepted for publication 10 June 2003. Published 1 July 2003.