Variation in seed protein content within and among soybean lines

Soybean (Glycine max (L.) Merr.) is unique as a producer of high quality vegetable protein. In breeding programs for increase soybean protein special attention must be given to sampling procedures if seed protein is to be determined. There is evidence that seed protein differ at different seed positions within a plant, but little research has been conducted. To determine if there are differences in seed protein percentage at different nodes within soybean plants and within the pod, an experiment was conducted during two years with normal and high protein, and determinate and indeterminate soybean lines. Seeds at different nodes and pod positions were analyzed in a LECO nitrogen analyzer to determine protein percent. Highly significant differences in seed protein percent were found at different nodes within the plant in the normal and high protein lines, and in the determinate and indeterminate soybean types. Seeds located in pods at the top of the plant have higher protein values than seeds in the middle and at the bottom of the plant. No significant differences were found in seed protein at different positions within the pod in any of the soybean types studied. In another experiment, plants of normal and high protein content were crossed reciprocally to determine the effect of crossed vs selfed seed on protein content, highly significant differences were found between seed from reciprocal crosses between normal and high protein lines. In each cross, the crossed seed produced on each parent was similar in protein percentage to selfed seed produced on the female parent