Utilization of Nitrogen to Sulfur Ratio for Evaluating Sulfur-Containing Amino Acid Concentrations in Seed of Glycine max and G. soja1
- R. L. Radford,
- C. Chavengsaksongkram and
- T. Hymowitz2
A screening procedure using the ratio of total N to total S (N/S) was developed for indexing methionine and cystine concentrations in seed of soybeans—Glycine max (L.) Merrill—and its putative ancestor G. soja Sieb. and Zucc. Percent N was determined by the standard micro-Kjeldahl procedure. Total S was analyzed by reducing SO4-S (from nitric acid-perchloric acid digestion) to H2S and then percent S was determined by titration with HgCl2 using dithizone as an indicator.
The N/S values found in the soybean genetic type collection ranged from 24.5 to 15.4 with the mean being 18.3. The N/S values found in plant introductions of G. max that were formerly known as G. gracilis Skvortz. ranged from 20.1 to 16.3 with the mean being 18.4. The N/S values found in plant introductions of G. soja ranged from 21.5 to 12.5 with the mean being 17.5.
Results from a 2-year investigation on the effect of growing seasons on the N/S ratios in seed revealed that the N/S ratios were quite stable from year to year in G. max and somewhat less stable in G. gracilis and G. soja. Attempts to identify the source of variation indicated that the variation in N/S values in seed of G. gracilis and G. soja largely were due to N content.
The reasonably high correlation coefficients between mg of methionine and cystine with percent S (r = 0.846) and g methionine and cystine/16 g N with N/S ratios (r = 0.787) suggest that rapid screening for N and S Glycine germplasm would be helpful in directing investigators to lines that warranted further study.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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