Location: Crops Pathology and Genetics Research
2020 Annual Report
Objectives
Objective 1: Characterize the spread of trunk pathogens and other wood-infecting
fungi of grape, at the plant, field, and landscape scales. Subobjective 1.A. Evaluate alternative hosts as inoculum reservoirs.
Subobjective 1.B. Define the stages of wood colonization, in terms of the infection process and the plant response to infection.
Objective 2: Identify the physiological and genetic bases of grapevine resistance to abiotic and biotic stresses using a combination of advanced-imaging methods, nucleic acid-based analyses, light and confocal microscopy, and hydraulic physiological measurements.
Subobjective 2.A. Determine how drought stress alters the hydraulic permeability of grapevine root systems and the capacity for hydraulic redistribution among grapevine rootstocks.
Subobjective 2.B. Determine the roles that xylem network connectivity, cavitation, and embolism repair play in drought resistance of grapevine rootstocks.
Objective 3: Characterize the relationship between vineyard floor management practices (including, but not limited to, sustainable weed management) and biogeochemical cycles.
Subobjective 3.A. Quantify greenhouse gas emissions resulting from current vineyard floor management practices, to refine existing biogeochemical models.
Subobjective 3.B. Examine soil microbial communities associated with vineyard floor management, and edaphic and environmental gradients.
Subobjective 3.C. Examine weed communities associated with vineyard floor management, and edaphic and environmental gradients to develop ecologically-based weed control strategies.
Approach
Objective 1, Subojective 1.A. - Compare population genetic diversity, host specificity, and spore dispersal of E. lata among three hosts (grape, apricot, willow), in CA landscape that include vineyards, stonefruit orchards, and riparian areas.
Subobjective 1.B. - Identify unique plant-molecular responses in leaves, which coincide with the early stage of canker development, and to then develop a PCR-based assay for these plant molecular responses for use as an early detection tool.
Objective 2, Subobjective 2.A. - Combine hydraulic physiological measurements with anatomical assessments to determine how stress and rootstock genotype affect the hydraulic permeability of roots.
Subobjective 2.B. - Use HRCT to evaluate the structure and function of grapevine xylem.
Objective 3, Subobjective 3.A. - Assess the effects of pulse events (fertigation or irrigation of equal volumes in the ‘in-row’ region, 70% regulated deficit irrigation; tillage or no tillage in alleys) on CO2 and N2O emissions.
Subobjective 3.B. - Soil samples will be extracted, quantified and pooled to link landscape patterns of soil microbial communities and specific populations (e.g., nitrifiers, denitrifiers) with functions that facilitate winegrape production, specifically transformations that control nutrient availability to plants and GHG emissions.
Subobjective 3.C. - Survey weed communities in the Napa AVA up to 90 existing field sites for which grower interviews and soil data exist.
Progress Report
This is the final report for project 2032-21220-007-00D Sustainable Vineyard Production Systems, which has been replaced by new project 2032-21220-008-00D Resilient, Sustainable Production Strategies for Low-Input Environments. For additional information, see new project report.
In support of Objective 1, during the prior project period, we conducted a set of experiments with the goals of improving disease management and detection, after first developing the methods to address our research questions in the greenhouse and field.
In support of Objective 2, new learning tools and data extraction techniques were developed to analyze hydraulic functioning and vascular disease in plant xylem, water uptake by roots, transport processes in leaves, and fruit developmental dysfunction. Building on their original work that showed clear evidence for xylem embolism repair in grapevines, ARS researchers in Davis, California, discovered that Vitis species differ in their ability to repair embolism once formed, and that the mechanism was localized to the cells surrounding the xylem vessels. More recently they confirmed that embolism repair can occur in the absence of root pressure in excised stems, is not conferred to a common scion, and can occur via water absorbed radially through woody roots.
In support of Objective 3, the effect of soil type and vineyard management on greenhouse gas emissions was measured across the Lodi wine grape production region. Three dominant soil types across nine vineyards were selected, and greenhouse gas emissions and the related soil nitrogen and carbon dynamics were measured biweekly to monthly for nearly two years. These measurements were taken to reflect the heterogeneity in the vineyard floor: the vine row (drip zone and no-drip zone), with bare exposed soil, and alley, where cover crops or resident vegetation resides. Specific management practices included tillage, fertilization and irrigation, and responses to weather events like precipitation and the dry season. This work demonstrated that annual sources of greenhouse gas emissions from vineyards are episodic and spatially distinct, responding to precipitation and tillage in the alleys and irrigation and fertigation in the vine rows. These accurate measurements of greenhouse-gas emissions help in the process of estimating the impacts on global climate change specific to viticulture (also known as a ‘Tier 3’ method, as proposed by the Intergovernmental Panel on Climate Change), rather than substituting default levels of emissions from other crops.
Accomplishments
1. A new method for tracking crop water use, using a wavelet analysis on semi-high frequency canopy temperature measurements. Low cost and reliable ground-based sensor systems are needed to complement remote sensing efforts to quantify crop water use. ARS researchers in Davis, California, in collaboration with researchers at University of California, Davis, utilized Infrared Radiometers (standard equipment that measures canopy temperatures) at semi-high frequency, to measure water use at the single plant. Such durable and affordable sensors can simultaneously measure water use and drought stress, and further serve to ‘ground truth’ our remote-sensing data. Canopy temperatures exhibited ramp-like features, which represent the energy exchanged between the air and the canopy. A wavelet analysis was used to quantify the ramps and found a strong correlation between water use measured with this new method and those of nearby flux towers.
2. Novel methodology to prioritize ‘healthy soils’ practices for productive crops. Soil-health management practices that sustain crop productivity include cover cropping, compost, crop rotations, and reduced tillage. ARS researchers in Davis, California, developed a novel methodology to identify where in the Central and Coastal Valleys of California such practices may have their greatest impact. Covering 5.6 million hectares, this region supports high-value specialty crops, including wine grapes, almonds, citrus, and vegetables. The USDA-NRCS Soil Survey Geographic (SSURGO) database was refined into regions of ‘soil-health identity’, which better reflect crop performance and responses to soil-health management practices. Outcomes of this research are the new framework to define ‘soil health identity’ and a map of soil-health regions, based on a complex range of soil properties. Such a map could help growers decide which practices to adopt to improve soil health, given limited labor and revenue.
3. Evidence of trunk-pathogen spores in young vineyards highlights the need for preventative practices. The timing of preventative practices for grapevine trunk diseases (December to March) is based in part on high spore counts of the causal fungi ('trunk pathogens'), which are reported in published studies from mature, symptomatic vineyards. The relevance of such data to young, asymptomatic vineyards, however, is not clear. ARS researchers in Davis, California, compared detections of spores for four years, in two wine-grape crush districts (Napa and San Joaquin) in six young (less than 5-years-old, asymptomatic) versus six mature (13 to 18-years-old, symptomatic) vineyards. From 769 spore-trap samples, a combination of culture- and DNA-based methods qualitatively detected 19 species of fungal pathogens that cause dieback-type trunk diseases. Sporadic detections in Years 1 and 2, restricted statistical analyses to Years 3 and 4, when total detections of species cultured were lower in young sites than mature sites, especially in Napa. Nonetheless, the presence of virulent pathogens Neofusicoccum parvum and Eutypa lata at similar levels in both young and mature sites makes it clear that growers should adopt preventative practices in young vineyards.
Review Publications
Yu, O.T., Greenhut, R.F., O'Geen, A.T., Mackey, B.E., Horwath, W.R., Steenwerth, K.L. 2019. Precipitation events, soil type and vineyard management practices influence soil C dynamics in a Mediterranean climate (Lodi, California). Soil Science Society of America Journal. 83(3):772-779. https://doi.org/10.2136/sssaj2018.09.0345.
Maier, P.A., Vandergast, A., Ostoja, S.M., Aguilar, A., Bohonak, A. 2019. Pleistocene glacial cycles drove lineage diversification and fusion in the Yosemite toad (Anaxyrus canorus). Ecology and Evolution. 73(12):2476-2496. https://doi.org/10.1111/evo.13868.
Brown, A.A., Lawrence, D.P., Baumgartner, K. 2019. Role of Basidiomycete fungi in the grapevine trunk disease Esca. Plant Pathology. 69(2):205-220. https://doi.org/10.1111/ppa.13116.
