Imed E. Dami

Morphological, Physiological, and Biochemical Changes in Vitis Genotypes in Response to Photoperiod Regimes

The purpose of this study was to identify morphological, physiological, and biochemical changes in Vitis genotypes in response to photoperiod regimes. Experiments were conducted under greenhouse conditions using cold-sensitive Cabernet franc (Vitis vinifera) and cold-tolerant Couderc 3309 (3309C, V. riparia × V. rupestris) and Concord (V. labruscana). Potted vines were exposed to short day (SD) (8 hr) or long day (LD) (16 hr) for 4, 6, and 8 weeks. Shoot growth, periderm formation, dormancy, freezing tolerance (lethal temperature that kills 50% of primary buds: LT50), and soluble sugar concentrations in leaf and bud tissues were examined. Shoot growth slowed in all cultivars under SD accompanied with increased periderm formation and dormancy depth. Concord initiated these changes first, followed by 3309C, then Cabernet franc. The three cultivars did not show differences in freezing tolerance under LD, with LT50 ranging between −6.1 and −8.1°C. However, freezing tolerance increased by 0.7, 2.0, and 2.7°C after 4, 6, and 8 weeks under SD, respectively. Freezing tolerance of Concord increased after 4 weeks of SD treatment, whereas that of 3309C and Cabernet franc did not increase until after 6 weeks of SD treatment. Among all sugars, raffinose had distinctive responses associated with photoperiod, remaining low and similar (0.5 to 2.3 mg/g dry weight) under LD. Under SD, raffinose concentration was generally higher, ranging from 2.2 to 5.7 mg/g dry weight in leaves and 1.6 to 3.7 mg/g dry weight in buds, with cold-tolerant 3309C and Concord accumulating higher concentrations compared to cold-sensitive Cabernet franc. These results suggest that raffinose accumulation might be an early step in response to photoperiod coinciding with slowed shoot growth, the induction of endodormancy, and the initial acquisition of freezing tolerance.

Foliar Application of Abscisic Acid Increases Freezing Tolerance of Field-Grown Vitis vinifera Cabernet franc Grapevines

The purpose of this study was to develop a method to increase freezing tolerance of field-grown grapevines using foliar application of abscisic acid (ABA). The specific objectives were to evaluate the morphological and physiological changes of field-grown Vitis vinifera Cabernet franc grapevines in response to exogenous ABA application and to determine an optimum timing for foliar application of ABA that results in enhanced freezing tolerance. Cabernet franc grapevines grown at two locations were treated with 400 and 600 mg/L ABA at different stages of development corresponding to veraison and 20, 30, 40, and 55 days postveraison. ABA did not affect yield components or basic fruit chemical composition. However, it enhanced anthocyanin concentration, advanced dormancy, decreased bud water content, and ultimately increased freezing tolerance under simulated freezing events. The increased freezing tolerance by ABA was confirmed by assessing bud injury following natural freezing events of −19°C and −23°C in two locations. The effectiveness of ABA may have been enhanced by application timing, which was optimum at veraison and 20 to 30 days postveraison. Results suggest that ABA application has the capacity to enhance dormancy and increase freezing tolerance and can be used as a prophylactic tool to protect against winter injury of grape cultivars grown in cold regions.

Utilizing GIS Technologies in Selection of Suitable Vineyard Sites

Abstract Geographic information system (GIS) technologies and a weighted linear indexing model were used for suitability analysis of potential vineyard sites in Illinois. The model included a macroscale climate variables layer (40 points), a mesoscale climate variables layer (40 points), a soil properties layer (10 points) and a current land use variables layer (10 points) for a possible 100 points. Macroscale climate variables, growing degree day summation for a 33-year period (1969-2002) and occurrence of -26°C were interpolated using thin plate smoothing splines over the Illinois terrain using 100 m2 resolution digital elevation models (DEM). Using the same DEMs, absolute elevation, slope, and aspect were reclassified using surface analysis of the terrain to model the effects of mesoscale climate variables in Jackson and Union Counties in Illinois (study area). Locations in the study area above 259 m in absolute elevation (above sea level), with gently rolling slopes (5 to 10%), and facing North, East, or Northeast received the most points within the mesoscale climate layer. Soils that drained well or moderately well with moderate organic matter content (2 to 3%) received the most points in the soil properties layer. Lands that promoted ease of conversion to vineyards were assigned the most points in the current land use layer. The resulting four layers were arithmetically summed and suitability maps with 760 m2 resolution were developed. In the study area, over 18,155 hectares of land highly suitable or suitable for viticulture were identified. A portion of the existing orchard and vineyard acreage (223 ha) in the study area were surveyed with a global positioning system. Of the surveyed vineyard acreage, over 81% lies within the suitable or better ranking according to the model. Of the surveyed orchard acreage, over 50% lies within the suitable or better ranking.

Physiological and Biochemical Seasonal Changes in Vitis Genotypes with Contrasting Freezing Tolerance

In this study, we characterized the influence of genotype and bud position on seasonal changes in freezing tolerance (FT, LT50) and soluble sugars, especially raffinose, and the affect of artificial deacclimation in buds of three field-grown cultivars over two years. Generally, basal buds were more freeze tolerant, and the cold-hardy cultivars Couderc 3309 (3309C; Vitis riparia x V. rupestris) and Concord (CD; V. labruscana) had the lowest LT50 compared to the cold-sensitive Cabernet franc (CF; V. vinifera). Among all sugars, fructose, glucose, sucrose, raffinose, and stachyose had strong correlation with LT50, but distinctive responses associated with bud position and cultivar were related to raffinose. Basal buds accumulated the most raffinose, and raffinose concentrations were two- to three-fold higher in the cold-hardy CD and 3309C than those in the cold-sensitive CF. Furthermore, CD and 3309C started accumulating raffinose with decreasing photoperiod prior to exposure to cold temperature, resulting in an early increase of FT. These results suggest that raffinose accumulation might be an early step in the process of cold acclimation that coincides with early development of FT. We concluded that bud raffinose concentration might be a useful detection tool and a metabolic marker during the early stages of cold acclimation to distinguish various Vitis genotypes with contrasting FT.

Quantification of Carbohydrates in Grape Tissues Using Capillary Zone Electrophoresis

Soluble sugars play an important role in freezing tolerance in both herbaceous and woody plants, functioning in both the reduction of freezing-induced dehydration and the cryoprotection of cellular constituents. The quantification of soluble sugars in plant tissues is, therefore, essential in understanding freezing tolerance. While a number of analytical techniques and methods have been used to quantify sugars, most of these are expensive and time-consuming due to complex sample preparation procedures which require the derivatization of the carbohydrates being analyzed. Analysis of soluble sugars using capillary zone electrophoresis (CZE) under alkaline conditions with direct UV detection has previously been used to quantify simple sugars in fruit juices. However, it was unclear whether CZE-based methods could be successfully used to quantify the broader range of sugars present in complex plant extracts. Here, we present the development of an optimized CZE method capable of separating and quantifying mono-, di-, and tri-saccharides isolated from plant tissues. This optimized CZE method employs a column electrolyte buffer containing 130 mM NaOH, pH 13.0, creating a current of 185 μA when a separation voltage of 10 kV is employed. The optimized CZE method provides limits-of-detection (an average of 1.5 ng/μL) for individual carbohydrates comparable or superior to those obtained using gas chromatography–mass spectrometry, and allows resolution of non-structural sugars and cell wall components (structural sugars). The optimized CZE method was successfully used to quantify sugars from grape leaves and buds, and is a robust tool for the quantification of plant sugars found in vegetative and woody tissues. The increased analytical efficiency of this CZE method makes it ideal for use in high-throughput metabolomics studies designed to quantify plant sugars.

Evaluation of Primary Bud Freezing Tolerance of Twenty-three Winegrape Cultivars New to the Eastern United States

Plantings of Vitis vinifera L. cultivars have increased significantly in the eastern United States due to market demand for their wines. However, V. vinifera is a cold-sensitive species and planting new cultivars of unknown cold susceptibility in cold areas has resulted in frequent winter damage and crop loss. It is the purpose of this study to determine the freezing tolerance of 23 winegrape cultivars predominantly grown in Europe and South Africa and to compare three statistical methods [mode-date, piecewise regression, and annual mean LT50 (AFT)] for determining the minimum low temperature that will kill 50% of primary buds (LT50). Primary bud freezing tolerance (FT), expressed as LT50 in °C, was determined biweekly over three dormant seasons under field conditions in Ohio. Minimum LT50 was most accurately determined using the AFT method. AFT provided a lower error estimate than mode-date or piecewise regression and best corresponded with the percentage of vines that survived exposure to the polar vortex freeze events of 2014. The two-year average AFT ranged from −19°C for Gamay noir to −15°C for Barbera and distinguished a 1°C difference among cultivars in primary bud FT. We proposed to express cultivar AFT relative to a standard cultivar grown in the same location (Merlot in this study), termed RAFT. The results from this study can be used to assist selection of V. vinifera cultivars suitable for vineyard sites where freezing temperatures limit winegrape production.

The Effect of Herbicides and Cultural Practices on Weed Communities in Vineyards: An Ohio Survey

Thirty-one Ohio vineyards were surveyed in 2004 to document weeds that persisted following weed control practices. Weeds were identified and density was determined during visits to each vineyard. Herbicide-use history, grape varieties, and grape age were recorded during interviews with the growers. Data were analyzed by SAS 9.1 with the use of the generalized linear model (GLM), and means were compared according to Student–Newman–Keuls (SNK) at the 0.05 level. Crabgrass, dandelion, pigweed, foxtail, fall panicum, clover, chickweed, common ragweed, smartweed, and oxalis were the most prevalent 10 weeds in Ohio vineyards based on relative abundance values. The frequency and density of crabgrass, dandelion, fall panicum, oxalis, and common purslane were significantly higher in vineyards in which glyphosate was the only herbicide used than in vineyards where other herbicides were applied. The number of species and density were higher in vinifera vineyards that had been hilled for winter protection than in vineyards that had not been hilled. Nomenclature: Glyphosate, chickweed, Stellaria media (L.) Vill. or Cerastium fontanum ssp. vulgare (Hartman) Greuter & Burdet, clover, Trifolium repens L. or Trifolium pratense L., common purslane (Portulaca oleracea), common ragweed, Ambrosia artemisiifolia L., crabgrass, Digitaria sanguinalis (L.) Scop., dandelion, Taraxacum officinale G.H. Weber ex Wiggers, fall panicum, Panicum dichotomiflorum Michx., foxtail, Setaria faberi Herrm. or Setaria pumila (Poir.) Roemer & J.A. Schultes or Setaria viridis (L.) Beauv., oxalis, Oxalis corniculata L., pigweed, Amaranthus hybridus L. or Amaranthus retroflexus L., smartweed, Polygonum pensylvanicum L., vinifera grape, Vitis vinifera L

Cane Morphology and Anatomy Influence Freezing Tolerance in Vitis vinifera Cabernet franc

ABSTRACT In 2014 and 2015, Ohio vineyards were exposed to multiple freeze events of –20 °C or lower, resulting in vine dieback, i.e., complete damage of above ground parts in Vitis vinifera. Grapevines that sustained dieback were rehabilitated for trunk replacement by training 1-year-old shoots with two distinct morphologies, based on internode diameter of large (L) and normal (N). This study evaluated the impact of cane morphology (L and N) in V. vinifera Cabernet franc on freezing tolerance (FT) of bud, phloem, and xylem tissues in relation to their respective anatomical structures and carbohydrate concentrations. Compared to N canes (7–9-mm diameter), L canes (10–15 mm) in Cabernet franc were considered vigorous and had the following morphological characteristics: long and heavy, with long and wide internode, and presence of numerous laterals. Furthermore, cane anatomy was also different with L canes having a significantly higher number of vascular transport units, xylem vessels, and phloem fibers than those in N canes. Freezing tolerance of buds and phloem was also different between the two cane types, with L canes being more cold sensitive than N canes, especially during fall acclimation and late-winter deacclimation. Sugar concentrations, however, were not different between L and N canes. These results suggest that cane morphology and anatomy play a significant role in affecting FT and the large and abundant anatomical structures of phloem and xylem contributed to the reduced FT of these tissues. In all practicality, this study suggests the best cultural practice for trunk replacement, and vine recovery should include the removal of the undesirable vigorous and cold sensitive canes during pruning.

Effects of Mulching on Soil Temperature, Scion Rooting, and Soil Moisture of Mounded Grapevines

ABSTRACT Soil-hilling around grapevines is required in the eastern United States for winter protection of grafted and cold sensitive grape cultivars (Vitis vinifera). The effects of simazine-treated mulches (STM) on soil temperature, scion rooting, and soil water conservation were measured. Neither simazine nor interactions between simazine and mulches affected any variables measured in this study. Wood and straw mulches increased the minimum temperature of media around the graft union as effectively as hilled soil, reduced scion rooting by a factor of 2 to 75 compared with soil-hilling, and increased soil moisture content 45 to 75% at Wooster and 8 to 23% at Kingsville. These results indicate that mulches have positive attributes and should be considered as an alternative to traditional soil-hilling in vineyards for temperature mitigation around graft union.