Inoculating arbuscular mycorrhizal fungi promotes the growth and phosphorus uptake of phosphorus-efficient soybean genotype
[Objectives]We investigated the effects of phosphorus(P)supply level and inoculation of arbuscular mycorrhizal fungus(AMF)strains on the growth,phosphorus(P)uptake,and the expression of mycorrhiza-induced phosphate transporter and sucrose transporter genes in soybean genotypes with different P efficiency,as well as the relationship of AMF and P efficiency.[Methods]A pot experiment was conducted using P-efficient soybean genotype Baxi 10(BX10)and P-inefficient genotype Bendi No.2(BD2)as experimental materials.The treatment was composed of two P supply levels(low P,and high P),and exogenous inoculation of two AMF strains,Rhizophagus irregularis(Ri)or Rhizophagus custos(Rc),taking no AMF(NM)inoculation as the controls.After 6 weeks of treatment,the plant dry weight,P uptake,root-to-shoot ratio,mycorrhizal infection rate,root traits,and the expression of mycorrhiza-induced phosphate transporter genes and sucrose transporter gene were analyzed.[Results]Compared with low P,high P significantly increased the shoot and root dry weights as well as P uptake in soybean,reduced the mycorrhizal growth response(MGR)and mycorrhizal P response(MPR)of both genotypes of soybean.Under low P condition,both Ri and Rc significantly increased the shoot and root dry weights and P uptake of both the soybean genotypes,increased the total root length,root surface area,and root volume of the P-efficient genotype BX10.The expression of the phosphate transporter gene GmPT9,which is primarily responsible for P uptake via the mycorrhizal pathway,was significantly upregulated by AMF inoculation in both soybean genotypes as well.The expression of mycorrhiza-induced GmPT8 was also significantly upregulated in P-inefficient genotype BD2.However,there was no significant difference in the expression of GmPT4,which is primarily responsible for P uptake via root pathway,between the treatments with and without AMF inoculation.The root dry weight and root-to-shoot ratio of BX10 were significantly higher than those of BD2 under both low P and high P conditions without AMF inoculation,and the average root diameter of BX10 was significantly higher than BD2 under high P conditions without AMF inoculation.Under low P conditions with AMF inoculation,the total root length,root surface area,and root volume of BX10 were significantly higher than BD2.Under high P conditions with AMF inoculation,the root surface area and root volume of BX10 were also significantly higher than BD2.Therefore,the shoot and root dry weights and P uptake of BX10 inoculated with Ri were significantly higher than BD2.However,the expression levels of GmPT8,GmPT9,and GmSWEET6 in BD2 roots were significantly higher than those in BX10 under low P conditions with Ri inoculation.[Conclusion]High P supply significantly promoted plant growth and improved plant P uptake in two soybean genotypes,whereas the MGR and MPR of the two genotypes were all higher in low P than in high P.Inoculation with AMF further increased the shoot and root dry weights as well as P uptake in BX10 at high P,but did not have that effect in BD2.Under low P condition,AMF inoculation could simultaneously activate both root and mycorrhizal pathways to uptake P,and thereby significantly increased the shoot and root dry weights as well as P uptake in both soybean genotypes.The promotion of root growth by AMF inoculation in BX10 was greater than in BD2.The relative expression levels of mycorrhiza-induced phosphate and sugar transporter genes could not directly reflect the amount of P and sugar allocation in the mycorrhizal symbiotic system.
万方数据
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