Location: Crops Pathology and Genetics Research2010 Annual Report
1a. Objectives (from AD-416)
1. Develop sustainable disease control practices for grapevines. 2. Develop sustainable vineyard floor management practices. 3. Develop sustainable water management practices for vineyards. 4. Investigate the impacts of vineyard practices on soil microbial ecology. 5. Identify & characterize viral & graft-transmissable agents of grapevine.
1b. Approach (from AD-416)
1. Characterize the infection process of grapevine roots by the fungal pathogen Armillaria mellea, the causal agent of Armillaria root disease; Characterize the significance of riparian areas in the spread of Pierce's disease; and Identify and characterize viral and graft transmissible agents. 2. Identify differences in regional populations of Conyza canadensis, cover crops that effectively compete with c. canadensis, and effects of soil resource availability on competition between cover crops and C. canadensis; and Identify cover crops that effectively compete with problematic weeds. 3. Evaluate the interactive effects of irrigation practices and vineyard floor management practices on grapevine yield, growth, physiology, and nutrition. 4. Examine the effect of cover crop functional type on soil microbial communities and microbially-mediated soil processes; Characterize rhizosphere communities associated with Vitis rootstocks; and Examine the impacts of vineyard floor practices on mycorrhizae. REPLACING 5306-21220-003-00D (01/07)
3. Progress Report
FY2010-we initiated experiments to identify host genes linked to resistance to Armillaria root disease of grapevine. As control of this disease relies almost exclusively on methyl-bromide (MB) fumigation, development of high-risk sites with Armillaria-resistant rootstocks, as an alternative to MB, would reduce greenhouse gas emissions, lessen human health risks, & reduce production costs. This work, conducted in cooperation with specialists in grape genomics & grape breeding (USDA-ARS,Geneva,NY; Univ of NV,Reno; Univ of CA,Davis). The pathogen attacks not only grape, but also other specialty crops (peach, almond, & walnut). Our focus on grape is due to availability of genomic study tools for grape: a public genome sequence & oligonucleotide arrays. Our approach was to inoculate tolerant (Freedom) & susceptible (3309C)rootstocks with Armillaria mellea, extract RNA at various stages of infection, & use GeneChip oligonucleotide arrays of the grape genome to identify differentially-expressed genes. This will reveal genes expressed early in the infection process in the tolerant rootstock. Such genes will be investigated in terms of the metabolic pathways with which they are involved & the possible roles of such pathways in the grape defense response. Future objectives are physical mapping & characterization of such genes for use as markers to aid in selection of resistant progeny from crosses between Armillaria-resistant & susceptible cultivars. A classical breeding approach can make very rapid progress with such DNA marker-assisted selection. Disease incidence of grapevine necrotic union in Pinot Noir clones on 110R in Sonoma Co. climbed from 2% in 2004 to over 20% in 2009. Grapevines inoculated by side grafts in Yr 08 using canes obtained from diseased grapevines with grapevine necrotic union are being monitored. New bench grafts were made this spring to test different sources of Chardonnay 04 & Pinot Noir 02A on 110R to determine the stocks free from the agent associated with grapevine necrotic union. Collaborative efforts with UCD are in progress to determine viruses associated with the necrotic union disorder on rootstock 110R using deep sequencing technology. Preliminary results point towards 2 viruses, Grapevine redglobe virus & Grapevine leafroll-associated virus-7, as the pathogens involved in necrotic union. This year we applied treatments in a field trial established to investigate the role of surfactants, used for herbicides application, in the development of syrah vine decline. In FY2010-we conducted the 3rd year of a field trial to identify vineyard floor management practices that control weeds. Findings show weed encroachment under the vine is greater in no-till treatments, & planting cover crops suppresses weed establishment regardless of whether tillage is implemented or not. Although lower soil water content was detected in the no-till treatment, little effect of floor management practices is evident in grapevine nutrition, annual yields, & grape juice properties (titratable acidity, soluble solids, and pH). This study is expected to continue greater than 5yr to assess long-term effects of practices on perennial grape production.
1. Resistance to Eutypa dieback identified in grapevines. Eutypa dieback, caused by the fungus Eutypa lata, impacts all vineyard production systems (wine, table, raisin, juice) and affects all US grape-growing regions, with net income losses of $260 M annually – an estimate that is for the winegrapes, alone. Given that preventative sprays must be used each year throughout a lengthy period of susceptibility, coupled with the fact that infections are chronic once established, our goal is to identify disease-resistant grape varieties, as an effective, long-term, and environmentally-sensitive solution to fungicides. ARS scientists in the Crops Pathology and Genetics Research Unit, in Davis, CA identified Eutypa-resistant grape hybrids (V. rupestris x V. cinerea ‘Ill547-1’, Muscadinia rotundifolia x V vinifera ‘NC6-15’, and V. riparia ‘37’), by screening plant material from the USDA-ARS National Clonal Germplasm Repositories in Davis, CA and Geneva, NY. This preliminary result is based on a greenhouse experiment carried out by inoculations of a virulent strain of the fungus to non-grafted vines, including seven commercial varieties of Vitis vinifera and seven experimental varieties of Vitis species or interspecific hybrids, the latter of which are components of breeding programs in California, New York, and Australia. As these Eutypa-resistant hybrids are also resistant to the destructive and widespread fruit and foliar pathogens powdery and downy mildews, establishing vineyards with such varieties, or using them to breed other varieties, is likely to reduce pesticide use and, thus, lessen the impacts of grape production on human health.
2. New Phomopsis species identified from grapevine. Phomopsis cane and leaf spot, caused by the fungus Phomopsis viticola, is a destructive foliar disease in eastern North American vineyards, and its control requires a minimum of four preventative sprays per growing season. Infections can become so numerous on leaves and stems that the vine drops many of its leaves or the rachis is girdled (and the fruit subsequently shrivels). In evaluating a vine’s pruning wounds as a potential point of Phomopsis attack, ARS scientists in the Crops Pathology and Genetics Research Unit in Davis, CA and the Systematic Mycology and Microbiology Lab in Beltsville, MD, in cooperation with scientists from University of California-Riverside, CA and Cornell University, Geneva, NY, identified two new species not previously found on grapevines: P. fukushii and Diaporthe eres. We are currently evaluating the virulence of these new species, in comparison to P. viticola, on potted plants in the greenhouse. If these new species infect grapevines via pruning wounds, then standard controls aimed at preventing infections of leaves and stems may not be effective against pruning wound infection.
3. Grapevine necrotic union disorder in grapevines. Two viruses, Grapevine redglobe virus (previously reported only in Italy) and GLRaV-7 are two strong suspects as causal agents of grapevine necrotic union disorder in grapevines on 110R rootstock. The two graft union disorders, grapevine necrotic union and necrotic distortion, on 110R and 3309C, are recognized only by bench grafts in biological assays. Researchers in the Crops Pathology/Genetics Research Unit in Davis, CA have established a field trial to confirm usefulness of two rootstocks, 110R and 3309C. These rootstocks will serve as indicators to recognize infected scion material that cause necrotic union and necrotic distortion diseases.
4. Reducing Vineyard Weed Biomass. In the vineyard, pairing cultivation with glyphosate was as effective at reducing vineyard weed biomass as two glyphosate applications in 2 of 3 years, suggesting that substituting a glyphosate application with cultivation may be an effective method of reducing herbicide use in vineyards. Different combinations of glyphosate and soil cultivation were applied for weed control in a California vineyard. ARS scientists in the Crops Pathology and Genetics Research Unit, in Davis, CA studied the effects on both weed seedbank composition to determine potential long-term problems from using these practices. After three years, specific weed species were associated with seedbanks of certain treatments. These were Carolina geranium, annual bluegrass, brome grasses, California burclover, and scarlet pimpernel. These do not pose problems with regard to the harvest of grapes, as such species are low-growing, suggesting that in the immediate future strong interference from these practices with production is unlikely.
5. Through implementation of no-till practices, vineyards may be a potential source of carbon sequestration. Due to the low level of soil disturbance in vineyards as compared to annual cropping systems like vegetables, vineyards represent a potential source for enhancing soil carbon pools in agriculture. Three management practices were employed (no-till + cover crop, tillage + cover crop, and tillage plus resident vegetation) and CO2 emissions, soil water content and temperature were measured for 2 years. Effects of management practice interacted with climate and soil conditions before disturbance (i.e., management and rainfall) and influenced CO2 emissions. Analyses of CO2 emissions on GWC and soil temperature indicated that CO2 emissions increased until water content (gravimetric water content) reached 14 to 15% in tilled treatments and 20% in the mown treatment, subsequently declining, indicating thresholds of water content at which soil temperature more strongly influences CO2 emissions. Findings suggest that no-till practices in vineyards may lead to greater soil carbon stabilization.
6. Grapevine water-use measured with a novel sap flow sensor technique compares favorably with known crop water utilization patterns. With impending limits on irrigation water in California and other arid grape growing regions of the US, growers need to more accurately measure water use by grapevines, in order to irrigate more efficiently. ARS scientists in the Crops Pathology and Genetics Research Unit, in Davis, CA used their newly-developed heat pulse technique to track water use in several grape varieties across growing regions. Sap flow sensors accurately tracked seasonal water use at all sites and changes in water use imposed by irrigation and atmospheric conditions. Accurate on site measurements of sap flow will help growers conserve irrigation water by applying exact, site-specific amounts as needed.
7. Grapevines are far less vulnerable to water-stress induced formation of vapor bubbles than previously reported. Vulnerability to drought-induced formation of vapor bubbles was evaluated in grapevines using Nuclear Magnetic Resonance in in situ imaging of live grapevines to track movement of, and subsequent vessel blockage by vapor bubbles. ARS scientists in the Crops Pathology and Genetics Research Unit, in Davis, CA revealed grapevines are not susceptible to significant drought-induced vessel blockage within normal operating water potentials. ARS Scientists also used High Resolution Computed Tomography (HRCT; a type of CAT scan) to model the xylem network of grapevines. Using unprecedented resolution of the HRCT, we are able to describe the mechanism of air bubble blockage repair in grapevines; researchers worldwide had suspected this mechanism for decades but until now were unable to visualize this process in living plants.Steenwerth, K.L., Pierce, D.L., Carlisle, E.A., Spencer, R.G., Smart, D.R. 2010. A Vineyard Agroecosystem: Disturbance and Precipitation Affect Soil Respiration under Mediterranean Conditions. Soil Science Society of America Journal. 74:231-239.