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Variation of Cottonseed Quality With Stratified Harvests¹

Selected constituents of mature cottonseed harvested at weekly intervals (up to 6 weeks) from opened bolls of seven entries were measured during 2 crop years (1976, 1979). The seed were analyzed for weight, oil, protein, gossypol, and selected fatty acids and amino acids. Major weather differences between years during the periods of flowering and seed maturity caused variations in seed composition. Part of these variations was probably due to weather conditions that affected cottonseed development and differentiation, and energy demands within the cotton plants as the growing seasons progressed. Seed weights decreased, oil and free gossypol percentages declined and proteins increased with progressively later harvest dates during the 2 crop years. In oil, palmitic acid percentages decreased with later harvest dates during both crop years, and oleic and linoleic acid values were variable between seasons and over harvest dates, but these fatty acids followed a consistent reciprocal relationship. The percentages of amino acids in proteins including lysine, threonine, isoleucine, methionine, and half-cystine increased during later harvest dates in 1976. Positive correlations for all amino acids and harvest dates were noted, but these values were significant only for total amino acids (similar to total protein), lysine, and methionine. The amount of oil and protein in seed decreased with harvest date, but the greatest change was in the amount of oil. These data provide information on the variation of the composition within and between crop years, and they indicate the need for additional research on factors contributing to variation in cottonseed composition.

Key Words: Gossypium hirsutum L. • Seed oil • Fatty acids • Proteins • Amino acids • Gossypol • Intra- and interseasonal variation

² Research geneticist, Cotton Genetics Research Laboratory, College Station, TX 77841, associate director, Eastern Regional Research Center, Philadelphia, PA 19118, respectively, both of USDA-ARS.

Received for publication February 25, 1983.