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Title: EARLY-MATURING SOYBEAN CROPPING SYSTEM: III. PROTEIN AND OIL CONTENTS AND OIL COMPOSITION

Author
item KANE, MARK - UNIVERSITY OF KENTUCKY
item STEELE, COLLEEN - UNIVERSITY OF KENTUCKY
item GRABAU, LARRY - UNIVERSITY OF KENTUCKY
item MACKOWN, CHARLES
item HILDEBRAND, DAVID - UNIVERSITY OF KENTUCKY

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: The soybean industry is now looking at new breeding lines with altered fatty acid profiles. We may eventually see soybean farmers growing licensed varieties on a contract basis with processors to provide consumers with oils that are more healthy. Environmental conditions, particularly temperature, during soybean seed-filling can affect protein levels and the oil content and composition. Southeastern USA experiences warmer temperatures than the north and has a wider range of available planting dates, which means that temperature ranges during seed fill are greater than in the north. With expanding use of earlier-maturity soybean varieties in the southeast, the effects of planting and maturity date on soybean grain quality needs to be determined. Soybean varieties from maturity group 00 to IV were planted in late April to late June. In general, environmental effects on protein and oil contents and fatty acid profiles were relatively small. However, delayed planting increased protein content, reduced oil content, and altered oil composition of most varieties. Levels of saturated fatty acids were less affected than those of unsaturated fatty acids. Delayed planting increased linolenate, an undesirable fatty acid that contributes to off-flavored oil, but had little effect on palmitic acid, an undesirable saturated fat. Early planting resulted in periods of higher temperature during seed-fill and higher seed oil content and oleic acid levels but reduced levels of linolenic acid. Warmer seed-fill conditions of the southeastern USA may amplify the effects of new cultivars selected for low linolenate. These results will be useful to agronomist, soybean geneticists, and producers seeking to improve grain quality of soybeans.

Technical Abstract: Expanding production of early-maturing soybean [Glycine max (L.) Merrill] cultivars in the southeastern USA has exposed such cultivars to a wide range of environmental conditions during seed-fill. Temperatures during this growth stage influence levels of specific fatty acids, particularly of the unsaturated fatty acids. Our objective was to evaluate the grain quality responses of early-maturing cultivars to the wide range of planting dates in the southeastern USA. Protein and oil contents, along with fatty acid profiles were assessed for cultivars from Maturity Group (MG) 00 through IV using late April, mid-May, early June, and late June planting dates on a well-drained Maury silt loam (fine, mixed, mesic Typic Paleudalf) in 1990 through 1993. Across years and cultivars, delayed planting increased protein content and linolenic acid levels and reduced oil content and oleic acid levels. The higher seed-fill temperatures associated with early planting were strongly correlated with increased oil content and oleic acid levels and reduced linolenic acid levels. Increasing seed-fill temperatures were closely associated with reduced linolenic acid levels for all six cultivars. However, the oleic acid response to seed-fill temperatures strongly depended on cultivar maturity. Oleic acid levels of early-maturing cultivars were much more sensitive to seed-fill temperatures than were those of later maturing cultivars. While overall effects of environment on grain quality characteristics may be relatively small, perhaps the quality of new linolenic acid cultivars could be amplified through culture under the warmer conditions of southeastern USA.