Author
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FLOYD, D - OSU, CORVALLIS, OR |
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Barker, Reed |
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Submitted to: Grassland International Congress
Publication Type: Proceedings Publication Acceptance Date: 11/6/1996 Publication Date: N/A Citation: N/A Interpretive Summary: Seedling root fluorescence trait in ryegrass has been used to separate Italian from perennial ryegrass. The separation is critical because there is a large differential in seed price. Generally, roots of Italian ryegrass, growing on white filter paper, secrete a compound that fluoresces under ultraviolet light. Similarly cultured seedlings of perennial ryegrass generally do not. Rules of the Federal Seed Act specify that fluorescence over a defined perennial ryegrass cultivar level is automatically classified as Italian ryegrass. However, fluorescent perennial ryegrass lines exist and there are nonfluorescent Italian ryegrass lines. Our objective was to determine if genetic change for the expression of fluorescence during generations of seed multiplication was present. Four ryegrass populations, differing in fluorescence levels were constructed and increased 3 generations at each of 3 OR locations. Fluorescence levels were measured for each generation cycle at each location. Variation was present for fluorescence among locations within populations and for seed production generation within locations. One population,initially at 10% fluorescence increased to 36% over 3 generations of seed multiplication at 1 location but decreased to 8 and 2% at the other 2 locations. This large genetic shift for fluorescence expression, related to location of increase and generation, must be examined and carefully considered when describing fluorescence levels of cultivars for seed certification. Rules of the Federal Seed Act ultimately will have to be modified to account for genetic shift of populations during seed increase. Technical Abstract: Seedling root fluorescence has generally been used to discriminate perennial ryegrass (Lolium perenne L.) from Italian ryegrass (L. multiflorum Lam.). The trait, however, has introgressed between the two species and breeders determine fluorescence levels for new ryegrass cultivars. Our objective was to ascertain genetic change for fluorescence expression during generations of seed multiplication. Four ryegrass populations, differing in fluorescence levels were increased three generations at each of three Oregon locations. Fluorescence levels were measured for each generation cycle at each location. Variation was present for fluorescence among locations within populations and for seed production generation within locations. One population, for example, initially at 10% fluorescence increased to 36% for three generations of seed multiplication at one location but decreased to 8 and 2% at the other two locations. This large effect of location of increase and seed generation on fluorescence expression must be examined and carefully considered when describing fluorescence levels of cultivars for seed certification. |
