REDUCTION OF THE JUVENILE PERIOD OF NEW OLIVE PLANTATIONS THROUGH THE EARLY APPLICATION OF MYCORRHIZAL FUNGI.

This study reports the responses of olive plantlets (cv. Cornicabra) to arbuscular mycorrhizal (AM) colonization by Glomus intraradices, Glomus mosseae, and Glomus claroideum, in terms of changes in the number and length of shoots and trunk diameter. In colonized plants, the number of shoots increased by 29% 3 months after transplanting, reaching as high as 121% at 12 months after transplanting. G. mosseae was the most influential species in this respect. Six months after transplanting, the colonized plants showed a greater number of shoots than did the control plants at 12 months after transplanting. Arbuscular mycorrhizal colonization may therefore provide a mechanism by which the juvenile growth period of these olive trees can be reduced. G. claroideum-colonized plants showed 118% more shoots than did control plants at 6 months after transplanting; at 12 months, they showed 100% more shoots. This fungus was the most effective at increasing trunk diameter and plant biomass at 12 and 24 months after transplant. Three months after transplanting, the trunk diameter in G. claroideum-colonized plants was similar to that observed 12 months after transplanting in noncontrol plants-a 10-month growth advantage. To maximize root and shoot growth and to reduce juvenile growth, Cornicabra olive plantlets apparently need to enter into a symbiotic relationship with Glomus species. The present results show the effectiveness of Glomus colonization in reducing the juvenile period of these trees; inoculation with Glomus species is therefore recommended as an olivicultural practice.