|St Martin, S|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/20/2002
Publication Date: N/A
Citation: N/A Interpretive Summary: In high yield environments (> 50 bushels per acre), traditional indeterminate varieties often get too tall and lodge (fall over) which interferes with efficient light utilization, reducing seed yield. Determinate semidwarf varieties were developed to help overcome this lodging barrier to higher soybean yields. The first semidwarf variety, Elf, was released in 1977. Semidwarf varieties have specific adaptation to high yield environments because of their shorter plant height and greater lodging resistance. They are being grown primarily on highly productive soils, such as river bottom land and soils with excellent water holding capacity, as well as under irrigation. Stalwart was released because of its superior yield potential and resistance to a serious disease of soybeans, Phytophthora root rot. It is anticipated the Stalwart will replace susceptible semidwarf varieties where this disease is a serious problem.
Technical Abstract: Stalwart is a determinate semidwarf soybean variety released in September, 2001 because of its superior yield potential and carries the Rps1k gene for multiple race resistance to Phytophthora sojae, the causal agent of Phytophthora root rot. In an irrigated, maximum yield environment, Stalwart has averaged 5723 kg/ha (85.8 bu/a). Like all semidwarf varieties, Stalwart is recommended only for soils with a history of high yields (>3300 kg/ha) and should be solid-seeded in 17 to 20 cm row spacing at a seeding rate of 675,000 viable seeds/ha. Stalwart was developed by backcrossing the Phytophthora resistant gene, Rps1k, from the semidwarf breeding line, HC94-634REBC, into the semidwarf breeding line, HC85-606. HC94-634REBC was developed by backcrossing the Rps1k gene from Williams 82 into the semidwarf breeding line, HC94-634, from the cross, Williams x Ransom. HC85-606 is from the cross, Sprite x Asgrow 3127. The homozygous resistant BC3F2-derived lines the HC85-606 x HC94-634REBC backcross program were yield tested in 1-row plots in 1994. The line HC94-96 was identified for further testing in bordered row plots at multiple locations in Ohio in 1995-96 and entered in the Uniform Tests, Northern States, 1997-2000 under the designation, HC94-96PR. Breeder's seed of Stalwart was distributed to the Ohio Foundation Seeds, Inc. for Foundation seed production in 2001. Breeder's seed of Stalwart will be maintained by OARDC/OSU with the cooperation of Ohio Foundation Seeds, Inc. A small sample of seed for research purposes can be obtained from the corresponding author.