MYCORRHIZAL INOCULATION ENHANCES GROWTH AND DEVELOPMENT OF MICROPROPAGATED PLANTS OF AVOCADO

Micropropagated plantlets of avocado (Persea americana Mill.) exhibit a very slow rate of growth during the acclimatization phase, possibly because mycorrhizae are absent. Inoculation of plantlets with the vesicular-arbuscular mycorrhizal fungus Glomus fasciculatum (Thaxter sensu Gerd) Gerd and Trappe improved formation of a well-developed root system that was converted into a mycorrhizal system. Introduction of the mycorrhizal fungus at the time plantlets were transferred from axenic conditions to ex vitro conditions improved shoot and root growth; enhanced the shoot : root ratio; increased the concentration and/or content of N, P, and K in plant tissues; and helped plants to tolerate environmental stress at transplanting. Inclusion of soil as a component of the potting medium appeared to favor mycorrhiza formation and effectiveness. Thus, mycorrhiza formation seems to be the key factor for subsequent growth and development of micropropagated plants of avocado.