Viticultural Information

RS-3

RS-3 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-3 is the first medium 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 less than half the population level normally associated with ring nematode, Mesocriconema xenoplax. 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-3 and multiple mechanisms can provide more durable nematode resistance. For example, a hypersensitive response is triggered as root-knot nematodes 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 beyond third generation offspring. The result is that any visible root galling and adult females are limited to the youngest roots.

RS-3 is relatively tolerant of Grapevine Fan Leaf Virus and in a five-year trial displayed greater tolerance than Boerner rootstock. We have evidence that roots, leaves, and stems of RS-3 are resistant to the invasive vine mealybug. Resistance mechanisms in RS-3 against ring nematode appear heat stable and therefore useful in warmer climates.

Freedom is still the favored rootstock for sandy soils unless virulent root-knot nematode populations are prevalent in the vineyard. In the presence of these virulent populations RS-3 is currently the only option but closer vine spacing should be considered. In sandy loam soils RS-3 provides a better option for those concerned with excess vigor from Freedom or Harmony rootstocks. Fumigation is needed prior to replanting vineyards on RS rootstocks. RS-3 should not be over-irrigated.

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.