Effects of Mycorrhizal Fungi on Grapevine Health

The first objective of our research was to identify indigenous arbuscular-mycorrhizal (AM) fungi in California vineyards. We collected grapevine roots from North Coast and Central Valley vineyards and cultured the AM fungi from their roots onto the roots of potted Sudan grass in the greenhouse. From the Sudan grass pot cultures, we identified nine putative Glomus species. Further characterization of the nine putative species will be done in February 2003 to determine if they represent distinct Glomus species. The second objective of our research was to examine dormant roots and new roots initiated from dormant benchgrafts and potted dormant benchgrafts for AM fungi. We quantified AM fungal colonization of dormant roots and new roots initiated from dormant benchgrafts and potted dormant benchgrafts of Cabernet Sauvignon (clone 8) on three rootstocks, 101-14, 110R, and St. George. Mean percent root colonization of dormant roots from dormant benchgrafts was significantly higher than that of potted dormant benchgrafts. After seven months of growth in our greenhouse, new roots initiated from dormant benchgrafts had higher mean percent root colonization than new roots from potted dormant benchgrafts. These results show that both dormant benchgrafts and potted dormant benchgrafts can serve as a source of AM fungi in new vineyards. Dormant benchgrafts, with their higher percent root colonization by AM fungi, may be better suited for fumigated and/or low phosphorus soils.