Effects of inoculating arbuscular mycorrhizal fungi on growth and phosphorus uptake of soybean under low phosphorus conditions

Objective  To illuminate the response of different P-efficient soybean genotypes to arbuscular mycorrhizal fungi inoculation at different growth stages and the relationship with P efficiency, and provide a theoretical basis for research of arbuscular mycorrhizal fungi inoculation improving crop P efficiency.

Method  The experiments were conducted using three soybean genotypes of ‘Weilianmusi 82’ ‘Yuechun 04-5’ and ‘Baxi 10’ under mycorrhizal and non-mycorrhizal inoculation treatments at flowering and podding stages. The effects of arbuscular mycorrhizal fungi inoculation on soybean plant dry weight, arbuscular mycorrhizal colonization rate, P nutrition status, root traits, and expression of arbuscular mycorrhizal inducible phosphate transporter genes were analyzed.

Result  The mycorrhizal responses of different soybean genotypes to arbuscular mycorrhizal fungi inoculation were significantly different at different growth stages. Compared with non-mycorrhizal inoculation treatment, the inoculation treatment significantly improved the expression levels of three arbuscular mycorrhizal inducible P transporter genes of GmPT8, GmPT9 and GmPT10 in the roots of three soybean genotypes at flowering stage, which resulted in the significant increase of P concentrations in roots of these three soybean genotypes, and the inoculation treatment significantly improved the root dry weight of these three soybean genotypes, as well as shoot dry weight, P concentration and total P uptake amount of ‘Baxi 10’ at podding stage. At flowering stage, non-mycorrhizal ‘Weilianmusi 82’ and ‘Yuechun 04-5’ plants had significantly higher shoot dry weight, total P uptake, total root length and root surface area than ‘Baxi 10’, while mycorrhizal growth response and mycorrhizal P response of arbuscular mycorrhizal fungi inoculated ‘Baxi 10’ were significantly higher than those of ‘Weilianmusi 82’ and ‘Yuechun 04-5’.

Conclusion  ‘Weilianmusi 82’ and ‘Yuechun 04-5’ have higher P efficiency, while ‘Baxi 10’ has higher mycorrhizal dependence. The prolonged growth period from flowering stage to podding stage promotes the transformation of acquired P by mycorrhizal plants into biomass, which further stimulates the beneficial symbiosis between soybean and arbuscular mycorrhizal fungi.