Post-anthesis N and P dynamics and its impact on grain yield and quality in mycorrhizal barley plants.

An essential goal for modern agriculture is the simultaneous improvement of productivity efficiency and nutrient use efficiency. One way to achieve this goal in crops is to enhance nitrogen (N) and phosphorus (P) acquisition through the mycorrhizal association. This study examined the effect of mycorrhization on post-anthesis N and P dynamics and its impact on grain yield and quality in barley. In addition, the efficiency of both N and P utilization and remobilization was evaluated. With those purposes, barley plants inoculated or not with Rhizophagus intraradices were grown in a soil poor in N and P under greenhouse conditions. Inoculation with R. intraradices in barley enhanced both N and P content in grain and vegetative tissue and reduced phloem amino acid export rate. On the other hand, both N and P vegetative tissue content and phloem amino acid and P export rates decreased during grain filling, whereas N and P grain content increased in both treatments according to the senescence process. However, whereas N grain concentration decreased during grain filling, P grain concentration did not vary, thus suggesting a differential regulation on grain filling. Inoculation with R. intraradices improved the yield and grain quality, thus demonstrating that inoculation with R. intraradices in barley is beneficial, but mycorrhization caused a diminution in nutrient utilization efficiency. As the phloem remobilization rate of amino acids and P did not decrease during grain filling in R. intraradices-inoculated plants compared to non-inoculated ones, these results suggest that nutrient utilization efficiency is most probably regulated by sink strength rather by a mycorrhizal effect.