NITROGEN TRANSPORT BY HYPHAE OF ARBUSCULAR MYCORRHIZAL FUNGI BETWEEN GRAPEVINE AND COVER CROP (VULPIA MYUROS)

To study nutrient transport between grapevine and a cover crop grown in humic andosol via arbuscular mycorrhizal (AM) fungi links, we grew a new dwarfing grape rootstock, a tetraploid of Kober 5BB [5BB (4x), Vitis riparia × V. berlandieri], and rat-tail fescue (Vulpia myuros) in specially designed containers that restricted their respective root systems to compartments separated by 20 micrometer Nylon mesh, but allowed AM fungi to colonize both root systems. Microcuttings of 5BB (4×) rootstock propagated in vitro were transplanted and seeds of V. myuros were sown in a small pot containing autoclaved andosol. Half of the plants of both species were inoculated with spores of AM fungi (Gigaspora margarita). After 1-month growth, a pair of two plant species was transplanted into the specially designed container with autoclaved andosol. Four combinations between plant species and AM fungi inoculation were adopted; inoculated 5BB (4×) rootstock and inoculated V. myuros (+/+), inoculated 5BB (4×) rootstock and non-inoculated V. myuros (+/-), non-inoculated 5BB (4×) rootstock and inoculated V. myuros (-/+), and non-inoculated 5BB (4×) rootstock and non-inoculated V. myuros (-/-). After one month, leaves of either 5BB (4×) rootstock or V. myuros were labeled with 10.2 atom% ¹⁵N solution for 6 days and plants were analyzed for ¹⁵N content 7 days after labeling. Results showed that AM fungi mediated ¹⁵N transfer between 5BB (4×) rootstock root to V. myuros. Delta ¹⁵N value of the non-labeled plant was significantly higher in the treatment with spore inoculation to both plants (+/+) than that in the treatment with inoculation to one of the pair plants (+/- and -/+).