Within‐plot and within‐plant variation for seed content of soya bean protease inhibitors

Abstract

AbstractExperiments were designed to determine the seed content of protease inhibitors in different plants of a plot or at different nodes along the main stem. The inhibitory activity of the samples was measured in vitro using sodium benzoyl‐DL‐arginine‐p‐nitroanilide as chromogenic substrate and bovine trypsin as target enzyme. Six soya bean (Glycine max Merr) strains were used, three capable of synthesizing the Kunitz trypsin inhibitor (L62‐364, Williams 82, and 594‐1) and three lacking this particular function (L81‐4590, L81‐4871, and L83‐4387). In all genotypes on trial, remarkable plant‐to‐plant variation was found, so that most 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. Gradients interior to the plant varied according to the tested strain but those of Williams 82 and of its near isogenic line L81‐4590 were very similar, indicating that the amount and type of variation depended on genotype and that changes in the inhibitory activity were attributable to variation in the synthesis of inhibitors other than Kunitz.