Seed weight affects shoot and root growth among and within soybean genotypes beyond the seedling stage: implications for low P tolerance screening

Aims Soybean is a relatively large-seeded species and variation in seed size can affect plant establishment especially under phosphorus-deficient conditions. We evaluated to what extent differences in seed weight and seed phosphorus (P) content among genotypes and within genotypes affect plant growth at low and high P supply. Methods Seedling growth of 42 soybean genotypes was evaluated in a pot trial. In addition, plant growth of selected genotypes was evaluated at different growth stages in two pot trials using various seed lots differing in seed weight per genotype. Results Correlations between seed weight and plant biomass, shoot P content and root length among 42 genotypes were stronger at low than at high P supply. Within-genotype variation in seed weight affected shoot and root growth at different plant growth stages. At low P supply, plant growth was correlated with seed weight up to the flowering stage. Conclusions It is concluded that seed weight largely affects growth especially at low P supply. Confounding effects due to variation in seed weight must be taken into account when screening soybean genotypes for low P tolerance.