U.S. Department of Agriculture: Agricultural Research Service, Lincoln, Nebraska
Date of this Version
2006
Citation
CROP SCIENCE, VOL. 46, JANUARY–FEBRUARY 2006; doi:10.2135/cropsci2005.04-0026
Abstract
‘Choptank’ (Reg. no. CV-976, PI 639724) is a soft red winter wheat (Triticum aestivum L.) that was jointly developed and released by the Maryland Agricultural Experiment Station, Department of Natural Resource Sciences and Landscape Architecture, and the Virginia Agricultural Experiment Station in 2004. Choptank is named after Maryland’s longest scenic river, which flows 70 miles from the western part of Delaware through Maryland and into the Chesapeake Bay, on Maryland’s Eastern Shore. Choptank has performed well in Maryland, Virginia, and Delaware and provides growers with a high-yielding cultivar with short stature, excellent powdery mildew [caused by Blumeria graminis (DC.) E.O. Speer f. sp. tritici Em. Marchal] resistance and early heading date.
Choptank was derived from the cross ‘Coker 9803’ (PI 548845)/‘Freedom’ (PI 562382) that was made in 1990 at Virginia Polytechnic Institute and State University. The population was advanced from the F2 to F5 generation using a modified bulk breeding method. Wheat spikes were selected in Virginia from the population in each generation (F2–F5) based on the absence of obvious disease, early maturity, short straw, and desirable head shape and size. Selected spikes were threshed in bulk and the seed was planted the following fall of each selection year. Spikes selected from the F5:6 bulk block were threshed individually and planted in separate headrows in the fall of 1996 at Beltsville, MD. Choptank was derived as a bulk of one of these F6:7 headrows selected in 1997 and assigned the breeding line designation MD11–52. In addition to high grain yield, Choptank was selected on the basis of earliness of head emergence, short plant height, and resistance to powdery mildew. Choptank was evaluated in the Maryland Wheat Variety Test for 5 yr (from 2000–2004), in the Virginia and Delaware State Wheat Variety Tests for 3 yr, and in the USDA-ARS Uniform Eastern and Uniform Southern Soft Red Winter Wheat Nurseries in 2004.
Coleoptiles of Choptank are white. Juvenile plants exhibit a semierect growth habit. Plant color at boot stage (Feekes growth stage 9–10) is blue green and a waxy bloom is present on the stem and flag leaf sheath. Anther color is yellow. Spikes are tapering, middense, and awnletted. Glumes are long and wide, with oblique shoulders and obtuse beaks. Kernels of Choptank are red, soft, and ovate with a crease of medium width and depth, rounded cheeks, and a long noncollared brush. Choptank carries the 1BL.1RS wheat–rye chromosomal translocation.
Head emergence of Choptank in Maryland is similar to that of ‘Sisson’ and 2 d earlier than Pioneer brand ‘25R37’. In Maryland, average plant height of Choptank (77.5 cm) is 5 cm shorter than that of Sisson and 2 cm shorter than that of USG ‘3209’. Average straw strength (0.0 lodging score) of Choptank in Maryland is similar to that of Sisson (0.3).