The reaction of grape rootstocks to the ring nematode Mesocriconema xenoplax was studied in glasshouse experiments and in a vineyard trial. Growth of one Oregon population of M. xenoplax differed among 20 rootstock and self-rooted cultivars grown in the glasshouse for eight months. The reproductive factor, Rf (final nematode density divided by initial nematode density), was ≤0.5 for 420A Mgt rootstock and ≤2.4 for 101-14 Mgt and 110R rootstocks; Rf values ≤1 indicate high nematode resistance. Other rootstocks had Rf values between 6.9 and 52.5. Root dry weights of all varieties except 420A Mgt were reduced by M. xenoplax. In another glasshouse experiment, 420A Mgt and 101-14 Mgt were found to be resistant to one Washington State and four Oregon populations of M. xenoplax, although both were moderately susceptible to a California population. A root-stock trial was planted in 1997 in a vineyard infested with M. xenoplax. After six and seven years, population densities of M. xenoplax were lowest in vines on 420A Mgt (≤0.08 g−1 soil) and 101-14 Mgt (≤0.24 g−1 soil) rootstocks. Population densities on other rootstocks ranged from 1.25 to 4.57 g−1 soil. 420A Mgt produced good vine vigor and yield and showed the highest degree of M. xenoplax resistance. Rootstock 101-14 Mgt, which is widely used in Oregon, was also resistant but produced only average vigor and yield. Other common Oregon rootstocks, Riparia Gloire, 3309C, and self-rooted Pinot noir, were highly susceptible to M. xenoplax and were among the least vigorous vines.
The ring nematode Mesocriconema xenoplax has a cosmopolitan distribution throughout the world’s grape production regions. Mesocriconema xenoplax was found in 75% of Germany’s vineyards (Weischer 1960) and 98% of Switzerland’s vineyards, where it was the most abundant nematode (Güntzel et al. 1987), and it has been reported in vineyards in Australia (Walker 1995), Italy (Ambrogioni et al. 1980), Spain (Pinochet and Cisneros 1986), and France (Scotto La Massese et al. 1973). In Europe, M. xenoplax has been associated with depression of vine vigor (Ambrogioni et al. 1980, Klingler 1975, Klingler and Gerber 1972). McKenry (1992) estimated that M. xenoplax populations >500 kg−1 soil reduce grape yields in California by 10 to 25%.
In Oregon, M. xenoplax was found in 85% of the vineyards surveyed and 20% had populations >500 kg−1 soil (Pinkerton et al. 1999). Population densities were not associated with reduced yield in mature vineyards, although density did affect vineyard establishment (Pinkerton et al. 2004). Thus, it was hypothesized that mature vines compensate for nematode parasitism (Pinkerton et al. 1999). Stress on vines in Oregon is often low because of the mild climate and light crop loads (~4,500 kg ha−1). Therefore, the impact of M. xenoplax will be most evident in replanted vineyards. As soil fumigation is limited in Oregon vineyards, because of difficulties with site preparation and its expense, an attractive management option would be to plant rootstocks resistant or tolerant to the nematode.
Although grape has been reported to be a very good host for M. xenoplax (Lownsbery 1961, Nigh 1965, Santo and Bolander 1977), the impact of this nematode on growth and productivity of grapevines is poorly understood. Raski and Radewald (1958) and Nigh (1965) reported that M. xenoplax neither reduced root weight nor caused noticeable symptoms on the roots of Thompson seedless grapes in glasshouse experiments. Conversely, Santo and Bolander (1977) observed stunting of tops and darkened, small root systems of potted Concord grapes infested with M. xenoplax. McKenry et al. (2001) reported that 14 cultivars tested in microplots were susceptible to M. xenoplax, but seven of these cultivars appeared tolerant (based on vine weights) after 21 months. Ramsdell et al. (1996) reported that M. xenoplax reduced fruit yield of only one of 10 grapevine cultivars in a six-year microplot study. Pinkerton et al. (2004) observed that M. xenoplax reduced growth of 3- to 4-year-old Pinot noir and Chardonnay vines planted in microplots. These studies suggest that the impact of M. xenoplax on grapevines varies with cultivar, plant age, and other stresses on the plant.
Mesocriconema xenoplax is a fastidious ectoparasite that may feed for up to eight days from a single cortical cell (Hussey et al. 1992). The nematode stylet invaginates the plasma membrane of a cortical “food cell” without penetrating it, and plasmodesmata are modified such that nutrient flow probably increases into this cell. Such elaborate modifications may explain why grape roots show little noticeable damage from M. xenoplax (Raski and Radewald 1958, Nigh 1965, Schreiner 2004, personal communication). Pinkerton et al. (2004) hypothesized that the effects of M. xenoplax parasitism on grapevine growth and yield were mediated through competition for carbohydrates in grapevines. Anwar and Van Gundy (1989) reported a shift in root:shoot dry weight ratios biomass ratio in grapes parasitized by nematodes, with shoot growth less affected than root growth for tolerant compared to susceptible vines. They hypothesized that the shift in root:shoot was due to changes in the partitioning of carbohydrates in the plant. Melakeberhan and colleagues reported the total energy demand of Meloidogyne incognita was greater on a highly susceptible cultivar than on a moderately resistant grape cultivar (Melakeberhan and Ferris 1988, Melakeberhan et al. 1990). Therefore, similar levels of nematode parasitism may affect physiology of grape cultivars differentially.
Planting nematode-resistant rootstocks has proven to be the most cost-effective means to maintain vine productivity in infested soils (Winkler et al. 1974). However, the degree of resistance among rootstocks may vary with nematode populations (Cain et al. 1984) or with site conditions (Nicol et al. 1999). The objective of the present research was to identify rootstocks with resistance and/or tolerance to populations of M. xenoplax found in the Pacific Northwest.
Materials and Methods
Grape cultivars (Table 1⇓) were evaluated for resistance to M. xenoplax in two glasshouse trials. Greenwood cuttings were collected on 15 Aug 1997 (trial 1) and dormant wood cuttings on 5 Feb 2001 (trial 2) from foundation blocks of rootstocks and cultivars maintained by the Oregon State University (OSU) Department of Horticulture. The cuttings were rooted under intermittent mist with bottom heat. Once rooted, the plants were transplanted into 30:70 (v/v) peat:perilite mix in Deepot Cone-tainers (Stuewe and Sons, Corvallis, OR). Plants were grown in the glasshouse until they were needed for the experiments. Before transplanting, rooted cuttings of each cultivar were sorted and plants the same caliber and root mass were paired. One plant of each pair was infested with nematodes and the other served as a noninfested control in each replicate. At the start of each experiment, plants were transplanted into 4.0-L plastic pots filled with steam-pasteurized Willamette Valley alluvial loam mixed 2:1 (v/v) with washed sand. Plants were fertilized twice a week with Long Ashton nutrient solution (Hewitt 1966) and grown in a glasshouse maintained at 20 to 25°C with 14 hr of supplementary light (400 μmol m2 s−1) per day. The experimental design was a split block with 10 replicates in trial 1 and eight replicates in trial 2. In trial 1, rooted cuttings were transplanted on 31 Oct 1997, soil was infested with M. xenoplax on 20 Dec 1997, and plants were harvested on 2 Aug 1998. In trial 2, rooting cuttings were transplanted on 18 Apr, soil was infested on 17 June, and plants were harvested on 28 Jan 2002.
A population of M. xenoplax was collected for the study in a nonirrigated, block of self-rooted Pinot noir at the OSU Woodhall Research Vineyard in Alpine, OR. Based on high nematode population densities (8 to 12 nematodes g−1 soil), stressed vines, and low fruit yields (1600 kg ha−1) in the vineyard, the population appeared to be pathogenic. Nematodes were extracted from field soil, and handpicked M. xenoplax were placed on Prunus root-stock (GI 148/2) in glasshouse pot cultures. Nematodes used in the experiments were collected from the pot cultures using a wet-sieving sucrose flotation method and centrifugation to extract the nematodes (Jenkins 1964). Nematodes were adjusted to a concentration of 100 nematodes mL−1 of water. Grapevines were infested by pipetting 5.0 mL of nematode suspension into each of eight holes made in the soil around the crown of each vine, for a total of 4000 nematodes per pot or ~1.0 nematode g−1 soil.
At harvest, plants were removed from the pots and the soil was carefully shaken and brushed from roots. A 250-g sample of soil was processed for nematode analysis by a wet-sieving and centrifugation-floatation process (Jenkins 1964). The population density of M. xenoplax in each sample was counted under 40x magnification. Total number of nematodes in each pot was estimated from average weight of soil in the pots and nematode density in the 250-g sample. For analysis, data were expressed as a reproductive factor (Rf), defined as the final population/initial population. High resistance to nematode infestation was defined by Rf values ≤1.0.
Washed root systems harvested from the pots were dried at 50°C for 48 hr and weighed. Plant tolerance was estimated by comparing the root dry weight of each pair of infested and noninfested plants in each replicate. Shoot biomass was not recorded because vines were pruned throughout the study.
Nematode population trial.
The reactions of resistant and susceptible cultivars to six populations of M. xenoplax were evaluated. Four populations were collected in Aug 2004 from vineyards in the following regions: Rogue Valley American Vineyard Area (AVA) near Cave Junction, Oregon (OR-RV), North Willamette Valley AVA near Dundee (OR-NWV-D), and Eola Hills near Salem (OR-NWV-E), and Yakima Valley AVA near Grandview, Washington (WA-YV-G). One population was collected in the Central Valley near Fresno, California (CA-CV) and was reported to reproduce on Mgt 420A (McKenry 2004, personal communication). The remaining population originated from a southern Willamette Valley AVA population located at the OSU Woodhall Research Vineyard (OR-SWV) and was collected from a glasshouse grape culture. Nematode reproduction was evaluated on three rootstock cultivars and self-rooted Pinot noir clone 2A. Pinot noir vines were propagated from dormant wood cuttings at the USDA-ARS Horticultural Crops Research Laboratory. Green-grafted Pinot noir 667 vines on 420A Mgt, 101-14 Mgt, and 3309C rootstocks were supplied by Duarte Nursery, Hughson, CA. Vines were planted in 4.0-L pots using the same soil and maintained as in the previous trial.
One hundred M. xenoplax individuals of mixed stages were handpicked and suspended in 20 mL of water. The suspension was pipetted into four holes made in the soil around the crowns of the vines to yield a nematode density of ~0.025 g−1 soil. Vines were arranged in a randomized block design (nematode populations as main blocks) with five replicates. After 20 weeks, soil was gently shaken from the root system. Roots and a 250-g sample of soil from each pot were soaked for >4 hr in 2.0 L of water before extracting nematodes by a wet-sieving and centrifugation-floatation process (Jenkins 1964). Nematodes in the samples were counted and total population density in each pot was estimated from average weight of soil in the pots and nematode density in the 250-g sample. Since the condition and activity of nematodes collected from different vineyards varied, nematode reproduction on the rootstock cultivars was standardized by calculating a comparative resistance value; nematode Rf value on rootstocks were divided by Rf values on self-root Pinot noir, a highly susceptible cultivar.
A rootstock trial was established at the OSU Woodhall Research Vineyard. The vineyard is located on a south-facing slope with vine rows orientated on a north-south axis. Soil on the upper slope is Bellpine series (Haplohumult) silty-clay loam derived from marine sedimentary parent material; soil on the lower slope is Jory series (Palehumult) silty-clay loam derived from igneous material. A self-rooted Merlot vineyard on the site was removed in 1995 and the soil was tilled and rotovated. Winter cover crops were planted in fall 1995 (cereal rye, common vetch) and 1996 (cereal rye, common vetch, oilseed radish). Cover crops were mowed and incorporated into the soil each spring. In June 1997, the rootstock vineyard was planted on a 1.2 x 2.1 m spacing using a randomized complete block design with five blocks. Certified vines used in the plots were supplied by a commercial nursery (Vinifera, Inc., Woodburn, OR). Rootstocks (Table 1⇑) were grafted with Pinot noir clone FPS 2A scion. Self-rooted Pinot noir 2A vines served as a control in the experiment. Each block contained five vines per plot for each rootstock treatment.
Vines were trained using a double-Guyot system with the training wire set at 0.8 m aboveground. Vines were pruned to two buds per vine in 1997 and 1998, four buds in 1999, nine buds in 2000, and 14 buds in 2001. In 2002 and 2003, vines were balance pruned to 30 buds per kg of pruning wood, which averaged 12 buds per vine. Canes were topped at 2.2 m aboveground in mid-July each year. Vines were hand irrigated in 1997. Irrigation was applied through a drip system once every two weeks during July, Aug, and Sept in 1998 through 2001. Because of differential growth of vines between blocks, vines located at the bottom of the slope with lowest vigor received 13.7 L of water per plant in 1999 and 2000, while those located on the upper slope with higher vigor received 7.6 L per plant. Vines were not irrigated in 2002 and 2003, which is common for established vineyards in the Willamette Valley. Fertilizer (20-10-20 with micronutrients) was delivered at a rate of 3.6 g per plant with each irrigation through 2001. Urea (46-0-0) was broadcast at 35 kg N ha−1 in 2002 and no fertilizer was applied in 2003. Ground cover between rows was a mixture of grass, clover, and weeds. The upper 15 cm of soil was mobilized with a tractor-powered spader in alternate rows each year. A 0.6-m herbicide strip was maintained in each vine row with glyphosate applied at the labeled rate (Roundup, Monsanto, St. Louis, MO). Vines were sprayed with wettable sulfur and demethylation-inhibiting fungicides from the three-leaf stage until veraison for powdery mildew control as needed. Fruit was harvested and weighed on 3, 15, and 5 Oct in 2000, 2001, and 2002, respectively, and on 27 Sept 2003. The harvest dates were determined by the Brix and pH of juice of grapes sampled in the vineyard. Pruning weights were recorded in Feb 2001 through 2004.
A composite soil sample consisting of 50 soil cores collected in a “W” pattern in the rootstock trial site was taken for plant-parasitic nematode analysis in June 1995 before the Merlot vineyard was removed. Soil samples were also collected on 26 Mar 2003 and 23 Mar 2004 from each treatment plot. A composite sample of 10 soil cores (0.02 x 0.45 m) was collected in the vine row 0.30 to 0.40 m from each vine in each plot. Nematodes were extracted (Jenkins 1964) from a 250-g subsample of soil from each plot and counted.
Randomized block and split-plot experimental designs were used for the vineyard and glasshouse trials, respectively. Nematode and plant data were analyzed by multifactor ANOVA using glm procedures and means were separated using Fisher’s protected LSD procedure (StatGraphics Plus, version 5; Manugistics Inc., Rockville, MD). Linear regression analysis was used to investigate relationships between nematode population densities in the vineyard plots and vine yields or pruning weights.
The degree of resistance to M. xenoplax varied greatly among rootstocks and self-rooted cultivars, although rankings of resistance were consistent between cultivars that were included in both trials (Table 2⇓). For example, 420A Mgt was highly resistant (low Rf values) in trial 1 with 7.0 nematodes g−1 root and in trial 2 when plants grew poorly with 552 nematodes g−1 root. Two other rootstocks, 110R and 101-14 Mgt, also appeared resistant. All other rootstocks were susceptible and supported nematode reproduction with Rf values >6.9. One rootstock widely used in Oregon, 3309C, ranked among the most susceptible rootstocks. Self-rooted Pinot noir was the most susceptible cultivar tested in trial 1 and was infested with the greatest number of nematode g−1 root tissue in trial 2. Self-rooted Chardonnay, Riesling, and Pi-not gris were also highly susceptible.
Root dry weight was significantly reduced by M. xenoplax in most rootstocks tested in trial 1, which indicates these cultivars were intolerant of the nematode (Table 3⇓). Root weight was not affected by nematode infestation in 101-14 Mgt and St. George, and root weight was actually increased by infestation in 420A Mgt. Riesling and Chardonnay were the least tolerant cultivars tested, with root weights reduced by more than 50%. Unfortunately, there were not enough plants to include non-infested controls for Pinot noir and Pinot gris in trial 1 because of their low rooting success. Vines were much less vigorous in trial 2. Consequently, only rootstocks with large root systems, such as 101-14 Mgt, 99R, and Schwarzmann, produced significant differences in root dry weights between infested and control treatments (Table 3⇓).
Nematode population trial.
Fewer nematodes were collected from pots infested with OR-NWV-D, OR-SWV, and WA-YV than from those infested with the other populations (Table 4⇓). However, the five M. xenoplax populations collected in Pacific Northwest vineyards reacted similarly on all cultivars. 420A Mgt was highly resistant with estimated population densities ≤0.025 nematodes g−1 soil and comparative resistance values <0.002. These populations also reproduced poorly on 101-14 Mgt (Table 4⇓). In contrast, the California population (CA-CV) reproduced moderately well on 420A Mgt and 101-14 Mgt, that is >0.62 nematodes g−1 soil and comparative resistance values >0.04. All populations reproduced well on 3309C and reached the greatest densities on self-rooted Pinot noir vines.
Population densities of plant-parasitic nematodes in the Merlot vineyard measured prior to establishing the rootstock block were M. xenoplax at 0.83 g−1 soil, Xiphinema americanum at 0.11 g−1 soil, Pratylenchus crenatus at 0.03 g−1 soil, and Paratylenchus spp. at 0.03 g−1 soil. Population densities of M. xenoplax at six and seven years after planting the rootstock trial are presented in Table 5⇓. In general, population densities of M. xenoplax were not affected by year (p = 0.29). In both years studied, nematode density was <0.25 g−1 in plots of vines planted on 420A Mgt and 101-14 Mgt rootstock and was <2 g−1 soil on 110R, 99R, and Schwarzmann rootstock. Self-rooted Pinot noir, 1103P, 3309C, Gravesac, and Riparia Gloire supported the highest nematode densities at 2.8 to 4.5 g−1 soil. Mean population densities of other nematode species were <0.1 g−1 soil in both years and were not significantly different (p > 0.05) among rootstocks.
Ranking of pruning weights and fruit yields among rootstocks were also similar among the four years. Data are presented only for the last two years when nematode data were collected (Table 5⇑). The reaction of roostocks did not differ (p > 0.05) between these years. Riparia Gloire, 3309C, 44-53 Malègue, self-rooted Pinot noir, and Schwarzmann had the lowest pruning weights in 2002 and 2003 (Table 5⇑) as well as from 2000 to 2002 (data not shown), while 1103P, 140Ru, 5C, 99R, 420A Mgt, and 5BB Kober had the highest pruning weights. Similarly, Riparia Gloire, self-rooted Pinot noir, 3309C, 44-53 Malègue, 110R, and 101-14 Mgt had the lowest fruit yield, while 1103P, 140Ru, 5C, 99R, 5BB Kober, and 420A Mgt had the greatest yields (Table 5⇑).
Negative correlations between M. xenoplax population densities and fruit yield and pruning weight were significant when all rootstocks were combined (Table 6⇓). Among rootstocks, significant negative correlations occurred between yield and M. xenoplax populations on 44-53 Malègue, Gravesac, 140Ru, 1103P, and 5BB Kober rootstock, with 1.0 M. xenoplax g−1 soil corresponding to a reduction of 0.11 to 0.52 kg1 fruit per vine (Table 6⇓). Significant negative correlations also occurred between pruning weight and M. xenoplax populations on 44-53 Malègue, Gravesac, and 1103P (Table 6⇓). Regression model slopes were highest (−0.097 to 1.149 kg−1 vine yield) for resistant rootstocks (420A Mgt, 101-14 Mgt, 110R, and 99R) and for highly-susceptible rootstocks (Pinot noir, Riparia Gloire, and 3309C) (Table 6⇓).
Ranking resistance of cultivars.
Based on vineyard and glasshouse trials, self-rooted Pinot noir was highly susceptible to M. xenoplax. Self-rooted Chardonnay, Riesling, and Pinot gris were rated as susceptible or highly susceptible based on glasshouse trials only. The comparative resistance levels of rootstock cultivars in relationship to Pinot noir are presented in Table 7⇓. The only rootstock cultivars not rated susceptible or highly susceptible were 420A Mgt, 101-14 Mgt, and 110R.
Three grape rootstocks, 420A Mgt, 101-14 Mgt, and 110R, showed good resistance to ring nematode under glasshouse conditions. All other rootstocks were susceptible, with population densities increasing 7- to 35-fold in eight months. The self-rooted varieties were among the most susceptible cultivars evaluated.
Population densities were much greater in the glasshouse soil than those observed in previous microplot studies (Pinkerton et al. 2004) or in our current vineyard trial. Population differences were most likely due to much higher densities of roots and better growing conditions in pots. However, despite differences between growing environments, the ranking of population densities of M. xenoplax collected from rootstocks growing in vineyard plots corresponded to those in the glasshouse experiments. Mean densities in the vineyard ranged from 0.05 to 4.57 g−1 soil and were not different for each rootstock between years. These data suggest that M. xenoplax densities were near the carrying capacity of each rootstock six and seven years after planting the vineyard. We found that the carrying capacity of Pinot noir and Chardonnay vines was reached within four years in microplots at the same location (Pinkerton et al. 2004). Overall, the most resistant rootstocks grown in the glasshouse experiments (420A Mgt, 101-14 Mgt, and 110R) had the lowest M. xenoplax densities in vineyard plots, while some of the most susceptible rootstocks (Riparia Gloire, 3309C, 1103P, and Gravesac) had the highest. Population densities were greatest in Pinot noir plots, with mean density >4 g−1 root, which was similar to those observed in the 4-year-old Pi-not noir vines in microplots (5 to 8 g−1 soil) (Pinkerton et al. 2004), but greater than those found in many commercial vineyards in Oregon (Pinkerton et al. 1999).
Nematode tolerance is the ability of a plant to withstand nematode parasitism without loss of plant growth or productivity (Roberts 2002). Plant tolerance is more difficult to quantify than plant resistance because it is unlikely to be a monogenetic trait (Starr and Bendezu 2002). Tolerance can be affected by environmental conditions, plant age, and other stresses on the plant. Pot studies confine roots, resulting in root-bound conditions that can affect plant response (Goheen and Smith 1956), and luxurious quantities of water and nutrients may mitigate the effect of nematode parasitism. In this study, root dry weights were reduced ~25% in infested treatments compared to noninfested treatments. That is in contrast to glasshouse studies where M. xenoplax did not affect growth of Thompson seedless grapes (Nigh 1965, Raski and Radewald 1958). In our first glasshouse trial, only root dry weight of 420A Mgt and St. George was not reduced by M. xenoplax. In the second trial, root dry weight of all rootstocks and scion varieties was less in infested pots than in controls, except for 420A Mgt, although growth was generally much lower than in the previous trial. Poor vine growth in the second trial may have been due to plant material source (vines in trial 1 were propagated from greenwood cuttings; vines in trial 2 were propagated from dormant hardwood cuttings) and/or time of year when trials were conducted.
The relationship between M. xenoplax populations and grapevine vigor and fruit yield is complex. Across root-stocks in the vineyard, blocks 1, 2, and 3, had lower population densities of M. xenoplax and greater plant growth and yield than blocks 4 and 5. Schreiner (2003) reported significant differences in root densities between blocks in this vineyard corresponding to the difference we observed in plant vigor. It is not possible to determine from our data whether nematode parasitism caused the reduction in root density, as observed in microplots infested with M. xenoplax (Pinkerton et al. 2004), or whether soil factors or a combination of edaphic factors interacting with nematodes limited plant growth (Ferris and McKenry 1975). Regression analysis suggests that vine growth and yield were depressed by M. xenoplax. However, this relationship is confounded because the nematode density values of the highly susceptible and resistant rootstocks cluster at the extreme limits of the range of values for the whole vineyard. In addition, vigor and yield of a specific variety-rootstock combination may be dependent on site, soil, climatic, and management characteristics. Given these constraints, some conclusions can be drawn regarding the resistance and tolerance of rootstocks from our vineyard data.
Under Oregon’s moist climatic conditions, vigorous rootstocks produce an excess of vegetative growth, which can delay fruit ripening and decrease fruit quality. Therefore, the most widely used rootstocks in Oregon are those that suppress vine vigor: 3309C, 101-14 Mgt, and Riparia Gloire, representing 37%, 33% and 12%, respectively, of rootstock planted. The level of resistance to M. xenoplax (Table 7⇑) did not always correspond to the plant parameters because of the inherent vigor imparted by the root-stock. For example, Pinot noir on highly resistant 420A Mgt was a moderately vigorous and fruitful rootstock in 2002 and 2003, and over four years. However, resistant 101-14 Mgt, which is popular in Oregon vineyards, and 110R (both apparently resistant in this study) ranked in the lowest half of rootstocks for fruit yields and pruning weights. Highly-susceptible 1103P was intolerant to increasing nematode densities, although its high vigor led to the highest yields. However, excessive vigor is associated with delayed ripening and poor wine quality, which makes this rootstock poorly suited for use in Oregon vineyards (Shaffer et al. 2004). Moderately-susceptible 140Ru, 5C, 5BB Kober, and 99R exhibited some tolerance, with yield and pruning weights among the top third of all rootstocks. 3309C and Riparia Gloire proved to be both intolerant and susceptible. Self-rooted Pinot noir, the most highly-susceptible variety, also was the most intolerant. In fact, self-rooted vines were difficult to establish in several blocks, and some vines had to be replanted.
In a compilation of published data on nematode resistance in grape rootstocks, 13 rootstocks that we evaluated were listed as susceptible to M. xenoplax, including 420A Mgt, 101-14 Mgt, and 110R (Nicol et al. 1999). In most cases, however, our findings are consistent with other published research. Walker (1995) reported nematode densities collected in the Loxton foundation planting in South Australia, which included 14 rootstocks that we evaluated in vineyard and/or glasshouse experiments. Based on their findings, 101-14 Mgt, 110R, 420A Mgt, and SO4 supported the lowest M. xenoplax population densities, while Riparia Gloire, 3309C, 1103P, and 8B Teleki supported the highest densities. McKenry et al. (2001) reported that 15 rootstocks tested in microplots were susceptible to M. xenoplax, including 5C, 99R, 3309C, and Schwarzmann, which also were susceptible in our trials. They noted that M. xenoplax stimulated the top growth of Schwarzmann vines, while we observed that it reduced root weight in our glasshouse experiment. Pieterse and Meyer (1987) reported that M. xenoplax reduced the root weight of 110R in pot experiments, but population densities in the soil increased minimally from the initial density. Similarly, 110R displayed resistance and intolerance to M. xenoplax in our glasshouse and vineyard trials. In contrast to our results, Ramsdell et al. (1996) concluded that 8 out of 10 grapevine cultivars were either resistant or tolerant to M. xenoplax, including 3309C and 5C. Only 5BB Kober and Seyval vines were susceptible in that six-year microplot experiment. The difference between experiments may be the result of different edaphic and management factors, different strains of a nematode species (Anwar et al. 2000, Cain et al. 1984), or differences in criteria for evaluating resistance.
McKenry (2004, personal communication) observed differences in population dynamics of five California populations of M. xenoplax on identical grape rootstock cultivars, with the Central Valley population appearing somewhat aggressive on 420A Mgt. Analysis of molecular and morphological markers further revealed two prevalent internal transcribed spacer region variants in M. xenoplax populations collected from different geographical regions in California (De Ley et al. 2004). The population from the Central Valley (CA-CV) included in our study also differed from Pacific Northwest populations of M. xenoplax in its reproduction on 420A Mgt and 101-14 Mgt. These data suggest that strains of M. xenoplax occur on grape root-stock cultivars, as was previously reported for Meloidogyne spp. (Anwar et al. 2000, Cain et al. 1984).
Glasshouse and vineyard trials demonstrated differences in resistance and tolerance to an Oregon population of Mesocriconema xenoplax in 20 rootstocks and/or cultivars. The self-rooted Vitis vinifera cultivars evaluated (Pi-not noir, Chardonnay, Riesling, and Pinot gris) supported high nematode reproduction (susceptible) and reduced plant growth (intolerant). Of the most widely planted rootstocks in Oregon, Riparia Gloire and 3309C were highly susceptible and intolerant to M. xenoplax, while 101-14 Mgt was resistant. 420A Mgt and 110R were also resistant and 420A Mgt appeared tolerant. Based on the reproduction of six M. xenoplax populations on 420 Mgt and 101-14 Mgt, the strain of M. xenoplax found in Pacific Northwest vineyards differs from a strain in the Central Valley of California.
Acknowledgments: Research was funded partially by the Oregon Wine Advisory Board. The authors thank Kelly Ivors, Timothy Lair, Charles Hand, and Megan Kitner for assistance and technical support. The authors thank M.V. McKenry for supplying the nematode population from the Central Valley of California.
- Received March 2005.
- Revision received August 2005.
- Copyright © 2005 by the American Society for Enology and Viticulture