Factors affecting arbuscular mycorrhizal dependency of wheat genotypes with different phosphorus efficiencies

Three wheat (Triticum aestivum L.) genotypes with high, intermediate and lo w phosphorus (P) efficiency were grown in a pot experiment with low P suppl y and adequate P supply either inoculated with the arbuscular mycorrhizal f ungus Glomus versiforme or uninoculated. The mycorrhizal dependency of the genotype with relatively high P efficiency was lower than that of the genot ypes with lower P efficiencies. Linear correlation analysis revealed that m ycorrhizal dependency was primarily controlled by P uptake efficiency. More carbohydrate was translocated to the roots of genotypes with low P efficie ncy than of those with high P efficiency. In a second pot experiment the sa me three genotypes were grown in low P soils. Higher hyphal length density arising from carbohydrate translocation led to more P uptake, and this may account for higher mycorrhizal dependency.