|St Martin, S|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/26/2002
Publication Date: N/A
Citation: Interpretive Summary: Apex is a new semidwarf soybean variety jointly released by the USDA, Agricultural Research Service and the Ohio Agricultural Research and Development Center (OARDC) in September, 2002. Semidwarf varieties are developed for their specific adaptation to high yield environments where traditional indeterminate varieties tend to get too tall and lodge, reducing their yield potential. Semidwarf varieties are primarily grown in uniformly high yielding environments (river bottom soils and soils with excellent water holding capacity). In fields that have different soil types, highly variable in yield potential, semidwarf varieties have had limited acceptance because they are too short for efficient harvest and good yields on the poorer, usually drought prone soils. However with the adoption of the site specific farming concept, planting the semidwarf varieties in the higher yielding areas within a field and taller, more drought tolerant varieties in the lower yielding areas, it is anticipated the overall field yield can be significantly increased. This could lead to more widespread use of semidwarf varieties in the Midwest. In research plots, Apex has shown the potential to produce non-irrigated yields of 80 bu/acre and irrigated yields in excess of 100 bu/acre. This new semidwarf has the potential for significantly increasing grower soybean yields and profits on fields with uniformly high yielding soils and on the higher yielding areas within a field in site-specific-farming.
Technical Abstract: Apex is a mid-to late Group III determinate semidwarf (dt1e1) soybean cultivar, developed from the cross between two semidwarf breeding lines, HC85-607 x HC74-676BC and jointly released by the USDA/ARS and the Ohio Agricultural Research and Development Center in 2002. Apex was released because of its demonstrated high yield potential and resistance to Phytophthora root rot (Rps1k). Averaged over 3 years in Ohio maximum yield tests, Apex has yielded 5976 kg/ha. In the five highest yielding locations in the 2002 Uniform Regional trials, Apex significantly out yielded all other entries in the test with and average yield of 5300 kg/ha. Apex has purple flowers, tawny pubescence, brown pods and shiny yellow seed with black hilum. Like all semidwarf varieties, Apex is recommended primarily 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 750,000 seeds/ha. Semidwarf varieties are recommended for uniformly high yielding soils and for site specific farming, planting of the semidwarf varieties in the higher yielding areas within a field and taller, drought tolerant varieties in the lower yielding areas.