Effect of mycorrhizal fungal inoculation on the growth and phosphorus uptake by soybean genotypes with different phosphorus use efficiency

Inoculation of arbuscular mycorrhizal fungi (AMF) can significantly promote soybean growth and phosphorus (P) uptake. However, information about the growth response of soybean genotypes with different P use efficiency to AMF inoculation is limited. In order to explore the effects of AMF inoculation on the growth and phosphate transporter gene expression in different soybean genotypes, a pot experiment was conducted to analyze plant dry weight, mycorrhizal infection characteristics, nitrogen and P contents, root traits, and mycorrhizal inducible phosphate transporter gene expression using P-efficient soybean BX10 and P-inefficient soybean BD2 under mycorrhizal (AM) and non-mycorrhizal (NM) inoculation treatments. The results showed that AMF inoculation significantly increased P uptake in the two soybean genotypes, and there were significant genotypic differences in mycorrhizal effects. Mycorrhizal inoculation significantly increased the shoot dry weight, P content, and total P uptake in BD2, but only significantly increased shoot P content and total P uptake in BX10. BD2 showed higher shoot P content than BX10 irrespective of the inoculation treatments, indicating that a high content of P was translocated from the roots to shoots in P-inefficient BD2. There was no significant difference in root traits between the two soybean genotypes under the NM treatment. However, BX10 showed higher root volume and average diameter than BD2 in the AM treatments. BD2 presented higher mycorrhizal dependence, mycorrhizal growth response, and mycorrhizal P response than BX10. Additionally, the expression of phosphate transporter genes GmPT8, GmPT9, and GmPT10, which indicate mycorrhizal P uptake pathway, was significantly higher in the mycorrhizal roots of BD2 than those of BX10, and consequently, total P uptake of BD2 was higher than that of BX10. The results indicate that mycorrhizal inoculation has greater effects on the growth and P uptake of BD2 than BX10, which can be attributed to the higher P uptake via the mycorrhizal pathway and higher P translocation efficiency of BD2 plants. The results provide a theoretical basis for studying the contribution of mycorrhizal inoculation to P uptake.