Abstract
Molybdenum (Mo) is essential for nitrogen fixation in legume nodules. In the early developmental stages, soybean (Glycine max L. Merr.) relies on Mo present in seed for growth and nodulation. Supernodulating soybeans may require a larger amount of Mo than normally nodulating soybeans. However, previous field studies on supernodulating soybeans have not focused on seed Mo content. Therefore, in the present study, we examined the effect of seed Mo enrichment on the growth and yield of supernodulating soybean. Seed Mo content of the normally nodulating variety ‘Enrei’ and its supernodulating lines ‘En6500’, ‘En-b0-1’, and ‘Kanto 100’ was increased by foliar application of Mo at the R5 (beginning of seed filling) stage of the preceding generation. Nodulation, nitrogen fixation, growth, and yield of plants grown from Mo-enriched seeds were compared with those of plants grown from control seed. In the supernodulating lines, nodule mass of plants grown from Mo-enriched seeds was smaller than that from control seeds. However, nodule Mo content and stem ureide content of the former were higher than those of the latter. The yield of plants grown from Mo-enriched seeds was 1.2-2 times that of plants grown from control seeds. In the normally nodulating variety ‘Enrei’, no significant difference was observed in nodule mass; however, the yield of plants grown from Mo-enriched seed was 10% higher than that of plants grown from control seeds. These results indicate that Mo enrichment of seed of supernodulating soybean partially suppresses supernodulation and improves nitrogen fixation, plant growth, and yield.
