Eight-Year Nematode Study from Uniformly Designed Rootstock Trials in Fifteen Table Grape Vineyards

Abstract

Ten grape rootstocks were evaluated in 15 fumigated replant settings for their resistance to nematode build-up. Ramsey, Harmony, Freedom, VR O39-16, Teleki 5C, 5BB, 101-14 Mgt, 1103P, 3309C, and own-rooted vines were planted into various soil textures in a completely randomized block design with five replications for each rootstock. Each site was planted to a single scion variety and farmed commercially. Own-rooted control vines at all sites were sampled during spring 1992, 1993, and 1994 to determine nematode infestation. All rootstocks were then sampled from eight infected sites until 1998. Nematode counts differed among rootstocks, but Xiphinema index populations performed similarly at seven sites as they increased, peaked, and then declined within several years. Based on nematode densities, Harmony, Freedom, and VR O39-16 were rated resistant to X. index. In two vineyards Xiphinema americanum multiplied equally well on all rootstocks and exhibited minimal population decline thereafter. No single rootstock performed optimally with any consistency. Annual fruit yields (marketable + cull fruit) over a six-year interval (1993 to 1998) were accumulated to obtain average yield. Among the best rootstocks was 1103P, but it also supported highest population levels of X. index. Harmony and 101-14 Mgt were generally the lowest yielding, but other rootstocks performed poorly within specific scion and field settings. This study provides information on two dagger nematode species, their population dynamics after soil fumigation, and their interactions with selected grape rootstocks. It also raises questions about field trial designs for rootstock studies.