Effects of Mycorrhizal Inoculation on Root Morphology and Nursery Production of Three Grapevine Rootstocks

Grapevines form mutualistic symbioses with arbuscular mycorrhizal (AM) fungi that have been shown to enhance plant growth and nutrition. In the field, AM fungal populations may be low or nonexistent (in fumigated soils), suggesting the need for AM inoculation of grapevine plants at the nursery. Addition of AM fungal inoculum to rooting substrate could be an effective strategy for the nursery production of mycorrhizal plants. The effects of inoculation of three grapevine rootstocks on root morphology and growth were tested. Results indicated that inoculation with the AM fungus Glomus aggregatum in rooting beds of grapevine cuttings changed root morphology, increasing branching of first-order lateral roots. When rooted cuttings were transplanted to pots, with soil sufficient in P and including indigenous AM fungi, and grown for nine months, a significant growth enhancement was found in two of the inoculated rootstocks. Glomus aggregatum, alone or in synergy with the indigenous AM fungi, seemed to have a higher affinity for 161-49 Couderc, the roots of which were more extensively colonized and exhibited a greater positive growth response.