Rootstock Tolerance to Soil Salinity: Impact of Salinity on Popular Grape Rootstocks Grown in Contrasting Soil Types

The major goal of this study is to define the tolerance of particular winegrape rootstocks for saline irrigation conditions. This project addresses a problem of major importance for irrigated vineyards in California. The rootstocks and soil types in this study have been specifically selected for their relevance to the California winegrape industry. The soil types in the study area are extensive in the central and southern Coast Ranges, an area of rapid vineyard expansion. During the first year, we accomplished two major goals:

  1. Vineyard site selection, soil sampling and soil characterization.
    The two selected vineyard sites are underlain by contrasting soils. Site 1 contains soil profiles in the Arbuckle series, classified as fine-loamy, mixed thermic Typic Haploxeralfs. These soils contain a thick argillic (clay) horizon and have moderately slow to slow permeability. Site 2 contains soils of the Hanford series, with parent material rich in coarse sand and gravel. These soils are classified as coarse-loamy, mixed, non-acid, thermic Typic Xerorthents. They are coarse textured, welldrained soils with little to low runoff and moderately rapid permeability. These two distinct soil types should provide good contrast for the irrigation studies proposed in this project. Soil chemical analysis is currently underway and will lead to a soil map of the area.
  2. Grafting and planting of 10 rootstocks and own-rooted controls at each of the two vineyard sites.
    During the first year of this project, ten different rootstocks were grafted with Cabernet Sauvignon scion and planted at the two designated vineyard sites. A total of 352 vines were planted at each site. Eighty-eight vines (8 replicates of each rootstock plus ownrooted controls) were planted in each of four rows; the four rows will each be subjected to different saline irrigation conditions beginning in Year 2. The rootstocks were selected based upon their popularity and known hardiness in salt-affected soils; for comparison, a few rootstocks with expected intermediate and low salt tolerance were also included. The final list of rootstocks included 101-14 Mgt, 110R (Richter), 1103 P (Paulsen), 140R (Ruggeri), 1616C (Couderc), Harmony, Freedom, Ramsey (Salt Creek), Schwartzmann, and St. George. Ownrooted Cabernet Sauvignon vines (clone 7) were used as a control. The plants are currently being monitored for growth characteristics but were too small for tissue sampling and analysis to be carried out during Year 1.

Having accomplished these two important goals during Year 1, we hope to proceed during Year 2 to begin the irrigation studies, along with detailed soil water sampling and plant tissue sampling. This project benefits from excellent cooperation with an industry collaborator, who also supplies field labor and some technical support.

Aquaporin-regulated response of grapevine roots to salinity

Soil salinization is an emerging problem in California vineyards. Research is needed to more fully understand the physiological response of grapevine roots to salt stress in order to develop cultural strategies that improve in-field management and to facilitate breeding of tolerance. Upon exposure to salinity, roots often exhibit a rapid decrease of water uptake capacity caused by inhibition of water-channel proteins called aquaporins. Aquaporins are found throughout fine root cellular membranes and can control the efficiency of water extraction from the soil. Prevention and/or alleviation of salinity-induced aquaporin inhibition have been demonstrated for some plants using calcium supplements in experimental conditions. Such a mechanism may contribute to the success of gypsum (i.e. calcium sulfate) applications used to lessen the detrimental effects of vineyard salinity. In the original grant, we proposed to address the following short-intermediate term goals:

  1. To quantify aquaporin response to salinity and the ameliorative effects of calcium in a suite of grapevine rootstocks using both hydraulic physiology and molecular probes under hydroponic and soil growth conditions;
  2. To investigate the role that aquaporins play in grapevine rootstock physiological responses to other abiotic factors (i.e. drought, anoxia, nutrient status) and their contribution to vine vigor. We are on target to achieve these goals over a two year funding period. The awarded monies only became available in October 2008 through a Research Support Agreement (RSA) between USDA-ARS and UCDavis. This delayed the initiation of hydroponic studies and molecular analyses to address the first goal listed above. In the mean time, we initiated studies to address the second goal listed above. The current RSA expires 31 September 2009, and an additional year of funding would be used for a 2nd RSA (01 Oct 2009-31 Sept 2010) that would allow completion of all short-intermediate term objectives.

Our results from summer 2008 indicate that aquaporins play an integral role in water uptake across numerous Vitis rootstocks and respond rapidly to nutrient supplements. Aquaporin activity measured with chemical inhibitors was consistently high among several rootstocks, and responded rapidly to calcium nitrate for 110R. We documented significantly higher inherent aquaporin expression in high vigor and drought resistant rootstocks (1103P and 110R) compared to those with low vigor and drought intolerance ratings (420A and 101-14). These inherent differences may explain the known variation in vigor among these rootstocks, likely play a role in divergent patterns of drought tolerance, and represent potential target genes for breeding similar traits.

Since the start of the RSA in October 2008, we optimized methods to quantify aquaporin gene expression for a range of rootstocks subjected to salt stress in an ebb and flow system. Expression analysis in four rootstocks that vary in salt tolerance (Ramsey, Riparia, French Colombard, Thompson seedless) revealed that aquaporins are highly and variably responsive to salt stress among the rootstocks. Preliminary results are reported here. Fine roots for ten additional rootstocks (3309C, 5BB, 420A, 101-14, 110R, 039-16, 1103P, SO4, 140R, Schwarzman) under salt stress have been sampled, and these samples are currently being analyzed.

Influence of Soil Type and Changes in Soil Solution Chemistry During the

The overall goal of this project is to understand differences in soil properties that contribute to significant differences in vine vigor, fruit yield and properties, and ultimately wine quality. Our collaborators at J. Lohr identified a unique opportunity to study a single vineyard consisting of four separate plots, each planted with Cabernet Sauvignon grapes on their own roots. The plots are managed in an identical manner. Wines made from these four plots had different sensory characteristics in an informal tasting, and preliminary field studies revealed four distinct soil types in the different vineyard plots.

During the past year, we have made excellent progress in accomplishing the objectives of this grant. Briefly, these objectives were: (1) to study variation in soil physical and chemical properties between the four sites; (2) to study differences in plant growth and yield between the four sites, and relate these differences to soil variability; and (3) to study differences in berry juice and wine quality between the four sites, and if possible relate these to soil variability. Thanks to outstanding collaboration from J. Lohr Vineyards, we opened eight sampling pits (two per site), and obtained multiple replicate samples from each site for chemical and physical analysis. Soil moisture probes and suction devices for obtaining soil solution samples were implanted in each site. Canopy temperature sensors were also set up, and the locations of sampling sites were georeferenced for mapping purposes. We obtained vine leaf and petiole samples throughout the growing season (bloom, veraison and harvest) from each site and are currently analyzing these tissues. We also measured vine diameters, pruning weights, cluster weights at harvest and cluster numbers. Small lot wines have been made from grapes at each site and will undergo thorough chemical and sensory analysis.

Soil solution chemistry, plant chemistry and wine chemistry analyses are underway. Our results to date indicate clear differences in soil properties between sites. The soils at the four sites fall into three distinct categories: two different types of Alfisols, a Mollisol and a Vertisol.

Soil Salinity Survey of Central Coast Vineyards

The objective of this project was to evaluate the current soil salinity status of established vineyards in the area east of Paso Robles in San Luis Obispo County. Surface soil samples from within the vine row were taken at 100 locations. The results indicate that the soil electrical conductivity, the principle component of interest, is on average 2.2 dS/m, approaching the threshold value of 2.5 above which appreciable growth and yield reductions may occur. Twenty-nine percent of the sites had electrical conductivity values between 2.5 and 4.1, and six percent above 4.1, over which severe effects on growth and yield can be expected. That these values were measured after two relatively wet winters suggests that during drier cycles, many soils may have, or will have, significantly higher soil EC levels. Re-sampling of the same locations is planned to take place every three years to evaluate any long term trends in soil salinity.

Characterization of Microbial Communities in Vineyard Soils

Microbial communities are responsible for numerous processes in soil important to agriculture. The development of new methods now makes it possible to rapidly characterize the complex microbial communities inhabiting soils. Such information ultimately will be useful in solving agronomic problems and improving management systems. The objective of this project was to measure microbial biomass, diversity and community composition by analyzing membrane lipids extracted from whole communities in vineyard soils. We sampled ten Pinot Noir vineyards in Carneros, Anderson, and Russian River Valleys in June 1998, 2000, and 2001. Vineyards sampled included Buena Vista, Cuvaison, Gloria Ferrer, Handley, Roederer, Scharffenberger, Sterling, Steve Kistler, Swan, and Vino Farms, primarily under 3309 rootstock. Microbial properties of vineyard and immediately adjacent soils under different land uses, as well as communities under different grapevine rootstocks on the same soil type, were also compared.
There were no distinctive regional patterns (e.g. by wine growing region) in microbial biomass or diversity. Across all vineyards, samples from 1998 had higher biomass and lipid diversity than 2000 or 2001 samples, most likely due to heavier than normal rainfall in 1997-1998. Microbial biomass over the 3 years varied four-fold over all vineyards, with the Scharffenberger soils consistently highest. Biomass in adjacent pasture/woodland soil was approximately two times higher than mean values in vineyard soils. Differences in “diversity” (measured by number of lipids detected) were small across vineyards as well as between vineyards and adjacent pasture soils. There were no consistent patterns in microbial biomass associated with particular rootstocks.

There were no distinct differences in microbial community composition among wine-growing regions. Despite biomass differences, annual variations in community composition were small and usually less than differences between vineyards. Microbial communities in rootstock 3309 in Roederer, Scharffenberger, Gloria Ferrer, Vino Farms, Sterling, Cuvaison, and Swan vineyards were suprisingly similar, with Kistler vineyards somewhat distinct but still not very different from the other vineyards. Several but not all samples collected in 2001 from Buena Vista and Handley were substantially different from other vineyard samples. At Cuvaison, communities associated with rootstock 110R and UCDS SO4 were distinctly different from the 3309 rootstock, yet such strong differences were not evident at Gloria Ferrer. Microbial community composition in pasture/woodland soils were very similar to the compositions of adjacent 3309 vineyard soils at Gloria Ferrer, Cuvaison, and Buena Vista, but not at Sterling Vineyards where differences were greater. Fungi were a minor component of all communities sampled, most abundant in the Kistler vineyard, and more abundant in pasture/woodland than vineyard soils. High relative proportions of bacteria, particularly gram positive bacteria (e.g., actinomycetes), were present in all soils. Future work should explore the agronomic significance of differences observed among microbial communities on different rootstocks and whether the relatively small differences between community composition of vineyards and adjacent pasture/woodlands will increase with time under cultivation. It is worth exploring whether more sensitive methods (e.g., DNA fingerprinting) will reveal larger differences among Pinot Noir soil communities than were detected using lipid analysis.

PDF: Characterization of Microbial Communities in Vineyard Soils

Characterization of Microbial Communities in Vineyard Soils

The purpose of this study was to continue the characterization of soil microbial communities in Pinot Noir vineyard soils by comparing the variability in microbial community composition over time in a specific vineyard relative to the variability in composition across many vineyards. The study also aimed to show the effect that vineyard management has on the diversity of soil microbial communities, by comparing a vineyard microbial community to an adjacent microbial community under a different land use on the same soil type.

A set of soil samples was collected from nine Pinot Noir vineyards in Anderson Valley, Russian River Valley and Los Carneros in June of 2000. These samples were analyzed for microbial community biomass and composition using phospholipid fatty acid (PLFA) analysis. In June of 1998, the microbial biomass in the soils ranged from 14 to 107 nanomoles per gram soil, as compared with a range of 11 to 85 in June of 2000. There was a substantial drop in microbial biomass in all vineyard soils between 1998 and 2000. The total number of fatty acids detected ranged from 38 to 58 for both years. Despite differences in biomass, the differences in community composition between the two years were small and usually less than differences between vineyards. Although some samples from within a particular region were similar to one another, overall there was still not a strong relationship between wine region and a particular kind of microbial community. A set of paired vineyard and adjacent land use sites are currently being identified with the help of growers.

PDF: Characterization of Microbial Communities in Vineyard Soils

Characterization of Microbial Communities in Vineyard Soils

The purpose of this study was to continue the characterization of soil microbial communities in Pinot Noir vineyard soils by comparing the variability in microbial community composition over time in a specific vineyard relative to the variability in composition across many vineyards. The study also aimed to show the effect that vineyard management has on the diversity of soil microbial communities, by comparing a vineyard microbial community to an adjacent microbial community under a different land use on the same soil type. A set of soil samples was collected from nine Pinot Noir vineyards in Anderson Valley, Russian River Valley and Los Carneros in June of 2000. These samples were analyzed for microbial community biomass and composition using phospholipid fatty acid (PLFA) analysis. In June of 1998, the microbial biomass in the soils ranged from 14 to 107 nanomoles per gram soil, as compared with a range of 11 to 85 in June of 2000. There was a substantial drop in microbial biomass in all vineyard soils between 1998 and 2000. The total number of fatty acids detected ranged from 38 to 58 for both years. Despite differences in biomass, the differences in community composition between the two years were small and usually less than differences between vineyards. Although some samples from within a particular region were similar to one another, overall there was still not a strong relationship between wine region and a particular kind of microbial community. A set of paired vineyard and adjacent land use sites are currently being identified with the help of growers.

Characterization of Microbial Communities in Vineyard Soils

The purpose of this study was to characterize soil microbial communities in vineyard soils and to determine if particular kinds of microbial communities are associated with specific wine regions or soil properties. Representative soil samples were collected from twelve Pinot Noir vineyards in Anderson Valley, Russian River Valley, Los Carneros, Chalone, and Santa Maria Valley at the time of first bloom. These samples were analyzed for microbial community biomass and composition using phospholipid fatty acid (PLFA) analysis. A subset of samples were also analyzed at times of veraison and harvest. PLFA analysis provides a measure of living microbial biomass, a “fingerprint” of the soil community; and biomarkers for specific groups of microorganisms. Physical and chemical properties of the soils were also measured, including pH, electrical conductivity, cation exchange capacity, total nitrogen, total carbon, carbonate carbon, sulfate, particle size distribution, total phosphorus, potassium, nitrate nitrogen, and ammonium nitrogen. Microbial biomasses ranged from 72.2 to 234 nanomoles per gram soil and the total number of fatty acids detected ranged from 39 to 56. Although some samples from within a particular region were similar to one another, overall there was not a strong relationship between wine region and a particular kind of microbial community. At the subset of sites sampled at different times over the growing season, seasonal changes in microbial communities were detectable, but smaller than the differences between sites. There appeared to be small seasonal changes in the community that were common to all soils. The texture of the soils reflected considerable variation with clay contents ranging from 7% to 38% and sand contents from 23% to 68%. Soil pH also varied substantially from 4.8 (in pastureland adjacent to a vineyard) to 7.4. Total organic carbon ranged five-fold from 0.82% to 4.85%. Ammonium levels were for the most part lower than 13 ppm and nitrate less than 18 ppm. As we continue to catalog differences in microbial communities across a larger set of vineyard soils and at additional times, we will have better information to answer questions such as whether there are unique traits common to all vineyard communities, or whether region has a stronger influence than crop on microbial communities. Also this information will help us begin to understand how vineyard management practices and seasonal fluctuations affect microbial community composition.

Methyl Bromide Alternatives and Improvements

This report culminates a 5-year multi-commodity study to find the best field-testable methods for using methyl bromide with reduced volatilization and/or identifying alternatives to its use as a pre-plant soil treatment. No systemic herbicides or treatment methods could be found that would kill old roots prior to vine removal. The best treatment was Garlon painted to cut trunks which only provided kill to 18 inch soil depth. Root kill in the surface 4 to 6 ft of soil is common following 350 lb/acre methyl bromide. Root kill in the surface 4 to 5 ft of soil is common following 350 lb/acre Telone when applied to dried soil. A drench of Vapam at 325 lb MITC in 6 acre inches water (100 gal/acre) can kill roots to 2XA to 3 ft depth. Doubling the Vapam rate provides kill to 4 ft depth but plants do not grow well after such doses unless there is a one year waiting after the drenching. Non-tarped methyl iodide at 325 lb/acre performs as well as methyl bromide but with Prunus spp. we have observed phytotoxicity so a range of grape rootstocks would have to be screened after various treatment rates to determine its feasibility. Enzone at 300 gal/acre drenched in 6 acre inches water will not kill remnant roots. Clorox solutions, urea, extracts of marigolds or safflower or walnut hulls drenched in 6 acre inches water will not kill old roots nor the nematodes within. Eighteen months of cover cropping involving Sudan grass, vetch or barley will not kill old roots or the nematodes within although they can reduce nematode populations within soil. Forty days of flooding during winter time will not kill old roots. The delivery of Vapam via an existing drip line at 250 ppm MITC in enough water to uniformly spread product 4 ft deep and 4 ft wide will kill old roots within that zone but provide no more than one year of nematode protection. This treatment in combination with rootstocks having broad resistance to soil pests is a tactic in need of field testing. Telone shanked at 35 gal/acre followed in one to two days with a drenching of 250 ppm MITC will produce vine growth and nematode control comparable to methyl bromide while reducing Telone volatilization. Chloropicrin is a mediocre nematicide at 350 lb/acre but promotes plant growth when present at 125 lb/acre or more. There needs to be field testing of Telone C-35 at 50 gal/acre. The use of composts, manures and soil amendments can improve vine growth but do not solve the replant problem nor nematode problems. Portions of the replant problem can be solved by killing old roots and waiting 18 mo. before replanting.

Alternatives and Improvements to Soil Fumigation with Methyl Bromide

Methyl bromide is the last preplant soil fumigant which, when properly applied, kills roots and soil microbes throughout the surface 5 feet of soil. The current estimate is that 20%to 70%of the applied product is volatilized from the soil surface. Polyethylene tarps slow the volatilization rate but not the overall amount. In 1987 I published an article indicating there would be a 25%reduction in efficiency of tree and vine production if the soil fumigants are lost. Nematode resistant rootstocks are not a replacement for pre-plant treatments but are more accurately a replacement for post-plant nematicides. The current alternative to soil fumigation is 4 years of fallowing, a very expensive option. At this time we have initiated studies on glyphosate, Vapam, and lower rates of methyl bromide for their efficacy against Lovell, Nemaguard, Marianna, and Myrobalan roots. We are field evaluating a portable soil drenching device for delivery of water transported biocides. For growers who use Nemaguard with resistance to all root knot nematodes, we will initiate studies on the use of Sudan grass which increases root knot populations but is detrimental for all other nematodes of trees and vine crops. Application procedures in the study include: a) Use of a dual application of MB totaling 200-250 lb. MB applied at 30-inch depth. b) Use of a portable soil drenching device for delivery of Vapam, Telone, Furfural, Urea, and other biocides. c) Soil pasteurization with steam or super critical water (4,000 psi and 750°F). d) Roundup treatments to foliage prior to removal of orchards and vineyards. e) Flooding. f) Trunk injections prior to tree removal. g) Antagonistic rotation crops especially in concert with treatments listed above.