Viticultural Information

RS-9

RS-9 rootstock is the result of an interspecific cross of the grape rootstocks Ramsey (Vitis champinii) and Schwarzmann (Vitis riparia X Vitis rupestris). Ramsey parentage supplied high vigor plus resistance mechanisms useful against endoparasitic nematodes. Schwarzmann parentage supplied reduced vigor, resistance mechanisms useful against ectoparasitic nematodes, and a mechanism for resistance to Meloidogyne javanica.

RS-9 is the first low vigor rootstock with resistance to all species of root-knot nematode, Meloidogyne spp, including virulent populations of M. incognita, M. arenaria and M. chitwoodi. It is also resistant to root-lesion nematode, Pratylenchus vulnus, pin nematode, Paratylenchus hamatus, and dagger nematode, Xiphinema index. It is slightly susceptible to citrus nematode, Tylenchulus semipenetrans and supports lower population levels of ring nematode, Mesocriconema xenoplax, than those normally associated with Vitis vinifera.

To date it does not support populations of any nematode species in great numbers, thus we refer to it as having broad nematode resistance. There are at least three different mechanisms of resistance in RS-9 and these multiple mechanisms should also provide more durable nematode resistance. For example, a hypersensitive response triggers resistance as root-knot nematode juveniles enter near the root tip. A few juveniles survive this mechanism and circumvent it to develop into egg-laying females. However, these females are only partially successful at enlarging enough plant cells to provide adequate feeding area. As the original female dies within 30 to 60 days after entry her poorly developed feeding site is inadequate for feeding beyond third generation offspring. The result is that visible root galling and associated adult females are limited to the youngest vine roots and are absent on roots older than 60-80 days.

RS-9 has nematode resistance characteristics similar to RS-3 except it is more susceptible to ring nematode but more resistant to Xiphinema index. This low vigor selection has not received evaluation against Grapevine Fan Leaf Virus. RS-9 does not resist the rejection component of the replant problem that can occur in some locations when replanting after removal of own-rooted V. vinifera vineyards. We have evidence that roots, leaves, and stems of RS-9 are resistant to the newly invasive, vine mealybug.

Foundation Plant Services at UC Davis is the source of Foundation grapevine material for the nursery industry, and the staff can provide information about possible sources for obtaining this stock.

The National Grape Registry (NGR) contains information about varieties of wine, juice, and table grapes, raisins, and grape rootstocks available in the United States. Growers, nurseries, winemakers and researchers can find background information and source contacts for those grape varieties in this single convenient location.

Anwar, S. A. and M. V. McKenry. 2002. Developmental response of a resistance breaking population of Meloidogyne arenaria on Vitis spp. Journal of Nematology 34 (1): 28-33.