First report of enhanced contents of nine macro- and micronutrients in gymnosperms via arbuscular mycorrhizal fungi

Traditionally, it is thought that arbuscular mycorrhizae establish a mutualist symbiosis only with the roots of angiosperm plants. In this mutualism, fungi receive carbon from the plants, and angiosperms receive nutrients through the external mycelium of the arbuscular mycorrhizal fungi (AMF). However, the enhanced contents of macro- and micronutrients in gymnosperm plants, and therefore the mutualistic relationship, with AMF has not been reported so far. The present work evaluated whether arbuscular mycorrhizae were able to establish and enhance 9 nutrient contents in the neotropical Pinaceae species Pinus greggii. The tree seedlings were inoculated with three consortia of AMF isolated from an agricultural site, a forest of Cupressus lusitanica and a forest of Pinus hartwegii. The effect of AMF inoculation on plant growth and nutrient enhancement, in addition to colonization, was evaluated. There was evidence of enhancement of plant growth and 9 macro- and micronutrients in plants inoculated with the three evaluated consortia. After 7 months, the translocation was greater for Mg, Mn and Zn in plants inoculated with the consortium of AMF from pine forest. The presence of hyphae, vesicles and arbuscules was detected in the roots of the Pinus greggii plants inoculated with the AMF consortia. In addition to these positive effects, colonization of 10 to 15% and 20 to 38% was observed depending on the AMF consortia after 2 and 7 months, respectively. The presence of arbuscules which is the translocation structure among involved symbionts was also recorded; and photographed for the first time. In the present work, we report for the first time that arbuscular mycorrhiza affects the mobilization of N, P, K, Ca, Mg, Fe, Mn, Zn, Cu and B in gymnosperms, indicating that this mycorrhizal symbiosis is more complex than previously believed.