WITHIN-PLOT AND WITHIN-PLANT VARIATION FOR SEED CONTENT OF SOYA BEAN PROTEASE INHIBITORS

Experiments were designed to determine the seed content of protease in hibitors in different plants of a plot or at different nodes along the main stem. The inhibitory activity of the samples was measured in vit ro using sodium benzoyl-DL-arginine-p-nitroanilide as chromogenic subs trate and bovine trypsin as target enzyme. Six soya bean (Glycine max Merr) strains were used, three capable of synthesizing the Kunitz tryp sin inhibitor (L62-364, Williams 82, and 594-1) and three lacking this particular function (L81-4590, L81-4871, and L83-4387). In all genoty pes on trial, remarkable plant-to-plant variation was found, so that m ost strains had at least one part of the data distribution in common. Significant differences were also noted for antitryptic activities of seed samples collected at different positions on the main stem. Gradie nts interior to the plant varied according to the tested strain but th ose of Williams 82 and of its near isogenic line L81-4590 were very si milar, indicating that the amount and type of variation depended on ge notype and that changes in the inhibitory activity were attributable t o variation in the synthesis of inhibitors other than Kunitz.