| Table 1. Companies with hybrids included in 1998 trials | | | | | |
| Brand | Company | Address | City | State | Zip |
| Agripro | Agripro Seeds Inc. | 824 2nd St. S., Box 250 | Brookings | SD | 57006-0250 |
| Asgrow | Asgrow Seed Company | P.O Box 7570 | Des Moines | IA | 50322-7570 |
| Brown | Brown Seed Farms | P.O. Box 186 | Prescott | WI | 54021 |
| Brunner | Brunner Seed Farm | W3850 US Hwy 10 | Durand | WI | 54736 |
| Cargill | Cargill Hybrid Seeds | P.O. Box 5645 | Minneapolis | MN | 55440-5645 |
| Carharts Blue Top | Carharts Blue Top Seed, Inc. | N14743 County Rd. M | Galesville | WI | 54630-8323 |
| Cornelius | Cornelius Seed Corn Co. | 31578 150th St. | Bellevue | IA | 52031 |
| Crows | Crows Hybrid Corn Company | P.O. Box 306 | Milford | IL | 60953 |
| Dahlco | Dahlco Seeds, Inc. | 14730 15th St. SW | Cokato | MN | 55321 |
| Dairyland Seed | Dairyland Seed Company, Inc. | P.O. Box 958 | West Bend | WI | 53095 |
| Dekalb | DeKalb Genetics Corp. | 3100 Sycamore Road | DeKalb | IL | 60115 |
| Garst | Garst Seed Company | P.O. Box 500 | Slater | IA | 50244 |
| Golden Harvest | Golden Seed Company, Inc. | 27420 137th Avenue N. | Cordova | IL | 61242 |
| Great Lakes | Great Lakes Hybrids | P.O. Box 637 | Ovid | MI | 48866 |
| Growmark | Growmark, Inc. | 1701 Towanda Avenue | Bloomington | IL | 61701 |
| Gutwein | Gutwein Seeds | Rt 1, Box 40 | Francesville | IN | 47946 |
| Hughes | Hughes Hybrids, Inc. | 206 N. Hughes Rd | Woodstock | IL | 60098 |
| Hytest | Agribiotech, Inc. | 120 Corporate Park, Dr | Henderson | NV | 89014 |
| Jung | Jung Seed Genetics, Inc. | 335 S. High St. | Randolph | WI | 53957 |
| Kaltenberg | Kaltenberg Seed Farms, Inc. | 5506 Hwy 19, Box 278 | Waunakee | WI | 53597 |
| Kussmaul | Kussmaul Seed Company | 9020 Hwy 18 | Mt. Hope | WI | 53816 |
| Lemke | Lemke Seed Farms, Inc. | 10220 North Granville Road | Mequon | WI | 53097 |
| LG Seeds | L.G. Seeds | 925 Dexter St. Box 216 | Prescott | WI | 54021-0216 |
| Linco | Linco Seeds | P.O. Box B | Dassel | MN | 55325 |
| M/W Genetics | Midwest Seed Genetics | P.O. Box 518 | Carroll | IA | 51401 |
| Mallard | Mallard Seed Company | P.O. Box 637 | Plainview | MN | 55964 |
| Midstate Genetics | Midstate Genetics | 1395 Roberts Road | Hutchinson | MN | 55350 |
| Mycogen | Mycogen Seeds | P.O. Box 21428 | St. Paul | MN | 55121-1428 |
| NC+ | NC+ Hybrids | 3820 N. 56 St, P.O. Box 4408 | Lincoln | NE | 68504-0408 |
| NK Brand | Novartis Seeds, Inc. | 2622 Blaney Road | Madison | WI | 53711 |
| Payco | Garst Seed Company | P.O. Box 500 | Slater | IA | 50244 |
| Pfister | Pfister Hybrid Corn Co. | P.O. Box 187 | El Paso | IL | 61738 |
| Pioneer | Pioneer Hi-Bred International, Inc. | 414 D'Onofrio Dr. Suite 200 | Madison | WI | 53719 |
| Renk | Renk Seed Company | 6800 Wilburn Road | Sun Prairie | WI | 53590 |
| Spangler | Spangler Bros., Inc. | 803 West Racine St. | Jefferson | WI | 53549 |
| Terra | Terra Industries Inc. | P.O. Box 6000 | Sioux City | IA | 51102-6000 |
| Top Farm | Top Farm Hybrids, Inc. | P.O. Box 850 | Cokato | MN | 55321 |
| Trelay | Trelay Seed Co. | 11623 Hwy 80 N | Livingston | WI | 53554 |
| Wensman | Wensman Seed Company | P.O, Box 190 | Wadena | MN | 56482 |
| Wolf River Valley | Wolf River Valley Seeds | N2976 Cty M | White Lake | WI | 54491 |
| Wyffels | Wyffels Hybrids, Inc. | P.O. Box 246 | Atkinson | IL | 61235 |