Plant parasitic nematodes are recognized today as important pests of grapevines. The root-knot nematodes (Meloidogyne spp.) are the most prevalent of the many types of nematodes existing in California vineyards. Root-knot infestations are widespread in the San Joaquin Valley. They are probably the most important single grape-growing problem of those vineyards on the light sandy soils of this area. Nematode-resistant grape rootstock varieties have been used for many years as grafting stock in

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... vineyards of California where nematodes are troublesome. On the other hand, only a few rootstock varieties have been available for the growers' consideration. This paper reports on an extensive series of field trials of experimental grape rootstocks. These stocks were chosen from a wide array of rootstock varieties on the basis of their nematode resistance, vigor, compatibility, and nursery performance. The trials were conducted as cooperative tests in commercial vineyards at locations chosen to represent a wide range of environmental conditions throughout the grape-growing areas of the interior valleys of California. Data gathered for twenty-two years from the scions in these trials, including vine vigor, fruit quality, and fruit yields, show that very vigorous rootstocks are available and that these show a high degree of nematode resistance. These stocks are capable of producing heavy-yielding scions in the sandy, low-fertility, nematode-infested vineyard soils.