Facteurs antitryspiques de la graine de soja: Évaluation de la variabilité génotypique dans une collection de référence; effet du semis précoce et de la réduction de l'irrigation

Abstract

Soybean seed is a highly edible source of proteins and polyinsaturated fatty acids. However, it contains many antinutritional components (FAN) that pose restriction to the consumption of raw soybean. Among them, trypsin inhibitors (FAT) strongly reduce the growth of monogastric animals by the reduction of protein digestibility and the induction of pancreatic disorders. Two kinds of FAT are found in soybean seed: Kunitz inhibitors (KTI) and Bowman-Birk inhibitors (BBI). The trypsin inhibition activity (AAT) can be reduced by the use of a KTI null allele in breeding programs but the activity due to the BBI peptides remains too high to allow the use of raw soybean in animal feeding. Environmental growth conditions can also influence the seed AAT. The aim of this work was the evaluation of genotypic variability in a core collection and the study of the effect of a modification of the agronomic practices on the AAT of the seed by the use of a faster and cheaper microanalysis. The relative error was 7%. The AAT of the sampled accessions of the core collection was between 23 and 60 TIU.mg-1. The correlation between AAT and protein content was not significant. Some accessions with a high protein content are probably homozygous for the KTI null allele. Very early sowing induces a slight but significant decrease of the AAT. Thus, such a change in agronomic practices can both preserve the high protein content and the seed nutritional quality.