1. U.S. Department of Agriculture–Agricultural Research Service (USDA-ARS), Dale Bumpers National Rice Research Center, 2890 Hwy 130 E., Stuttgart, AR 72160, U.S.A. Mention of a trademark or proprietary product in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the USDA. USDA is an equal opportunity provider and employer.
2. USDA-ARS, Southern Plains Area, College Station, TX 77840, U.S.A.
3. Corresponding author. Phone: (870) 672-9300, ext. 223. Fax: (870) 673-7581. E-mail: bob.fjellstrom@ars.usda.gov