Analysis of cultivar variability in arbuscular mycorrhizal responsiveness in soybean varieties

ABSTRACT

In modern agricultural systems, high crop yields depend on the high input of orthophosphate-based fertilizers. Owing to the looming scarcity of rock phosphate in the near future, utilization of arbuscular mycorrhizal (AM) symbiosis for the efficient uptake of phosphorus is a necessary approach to maintain crop yield. Plant responsiveness to AM fungi is assessed based on the difference in biomass between plants with and without AM fungal inoculation. Soybean is a plant which establishes both mycorrhizal and rhizobial symbiosis. Therefore, it is difficult to eliminate the symbiotic effects of rhizobial nitrogen fixation during long-term cultivation until soybean harvest. In this study, Bradyrhizobium diazoefficiens USDA110 was inoculated at the same time as soybean seeds were sown, and soybean was grown under Rhizophagus irregularis inoculated and non-inoculated conditions to verify whether the mycorrhizal inoculation effect was observed at the yield level. In 2013, two soybean cultivars Tachinagaha and Williams 82, were grown at five levels of phosphate availability (0, 5, 10, 20, and 40 kg P 10a⁻¹) in an open greenhouse in Tsukuba, Japan. Among the several growth indices analyzed, seed weight per plant was selected as a reliable indicator of plant response. Mycorrhizal inoculation showed a positive effect on soybean under 20 kg P 10a⁻¹ phosphorus fertilization for Williams 82, while Tachinagaha showed almost no effect. This trend was replicated in 2014 and 2016, indicating that Tachinagaha has a lower AM responsiveness than Williams 82.

KEY WORDS:

• Arbuscular mycorrhizal symbiosis
• soybean
• phosphorus
• plant responsiveness
• rhizophagus irregularis

Acknowledgments

I thank Masao Ishimoto for providing seeds of the three soybean cultivars. I also thank Emiko Kobayashi, Yumiko Nakane, and Tamie Shimamura for technical assistance.

Disclosure statement

No potential conflict of interest was reported by the author.

The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.

Authors contribution

Wrote the paper, Methodology, Formal analysis and investigation and Funding acquisition: [Haruko Imaizumi-Anraku].

Additional information

Funding

This work was supported by a grant from the Ministry of Agriculture, Forestry, and Fisheries of Japan (SFC2006) to H. Imaizumi-Anraku.