VARIATION IN SEED PROTEIN AMONG NODES OF DETERMINATE AND INDETERMINATE SOYBEAN NEAR-ISOLINES

Soybean, Glycine max (L.) Merr., seed protein differs considerably amo ng seeds from different nodes of indeterminate plants. Determinate soy bean plants grown in the northern USA have fewer nodes, shorter flower ing periods, but similar reproductive periods compared to indeterminat e plants. The objective of this study was to determine nodal variabili ty in seed protein of determinate vs. indeterminate soybean near-isoli nes. Ten pairs of near-isolines from four soybean crosses were include d in a 2-yr study at West Lafayette, IN. Protein content was evaluated for seeds from individual fruiting nodes on three plants from the ten determinate and indeterminate near isolines each year. Seed protein i ncreased linearly from 397 at Node 5 to 442 g kg(-1) seed weight at No de 11 on determinate plants. On indeterminate plants, seed protein inc reased from 398 at Node 6 to 441 g kg(-1) at Node 14. Protein contents of seeds from Nodes 12 through 16 of indeterminate plants were all hi gh but values did not differ significantly among these upper nodes. Th e greatest range in protein among all nodes from three plants of an in dividual line was from 349 to 510 g kg(-1) for indeterminate and from 34 to 487 g kg(-1) for determinate plants. The data demonstrate that a ccurate protein determinations for determinate, as well as indetermina te soybean plants, requires adequate sampling to represent the nodal v ariability occurring in both plant types.