Coulure

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Young grapes are most susceptible to coulure right after flowering when they need vital carbohydrate resources in order to develop fully. Young grapes.jpg
Young grapes are most susceptible to coulure right after flowering when they need vital carbohydrate resources in order to develop fully.

Coulure (pronounced coo-LYUR) is a viticultural hazard that is the result of metabolic reactions to weather conditions that causes a failure of grapes to develop after flowering. In English the word shatter is sometimes used. Coulure is triggered by periods of cold, cloudy, rainy weather or very high out-of-season temperatures. The condition is most often manifested in the spring. It also occurs in vines that have little sugar content in their tissue. Flowers stay closed and are not fertilized. Thus the vines are not pollinated as the grape fails to develop and falls off. Coulure can also cause irregular bunches of grapes which are less compact than normal. These bunches are more sensitive to developing various grape diseases. The yield of a vine with coulure will decrease substantially. Grape varieties with high proclivity to coulure are Grenache, Malbec, Merlot, and Muscat Ottonel. Other causes of coulure may be vineyard conditions and practices, pruning too early or too severely, excessively fertile soils or overuse of fertilizers, and improper selection of rootstocks or clones. [1]

Grape spherical berry from vines of Vitis spp.

A grape is a fruit, botanically a berry, of the deciduous woody vines of the flowering plant genus Vitis.

Spring (season) one of the Earths four temperate seasons, occurring between winter and summer

Spring is one of the four temperate seasons, following winter and preceding summer. There are various technical definitions of spring, but local usage of the term varies according to local climate, cultures and customs. When it is spring in the Northern Hemisphere, it is autumn in the Southern Hemisphere and vice versa. At the spring equinox, days and nights are approximately twelve hours long, with day length increasing and night length decreasing as the season progresses.

Vascular tissue complex conducting tissue

Vascular tissue is a complex conducting tissue, formed of more than one cell type, found in vascular plants. The primary components of vascular tissue are the xylem and phloem. These two tissues transport fluid and nutrients internally. There are also two meristems associated with vascular tissue: the vascular cambium and the cork cambium. All the vascular tissues within a particular plant together constitute the vascular tissue system of that plant.

Contents

During the flowering part of the growing season (May-June in the Northern Hemisphere, November-December in the Southern Hemisphere), grapevines often need dry conditions with sufficient sunlight and ambient air temperature around 15 °C (59 °F) for pollination to go smoothly. Less ideal conditions, particularly wet, rainy weather, increases the odds that a higher than normal numbers of flowers go unpollinated and coulure to occur. [2]

Coulure is a distinct phenomena unrelated to another viticultural hazard, millerandage, where the flowers are pollinated but the resulting berries develop with seeds and remain small. Like coulure, millerandage is often caused by inclement weather during the flowering and fruit set period and cause reduced yields. [2]

Millerandage

Millerandage is a potential viticultural hazard problem in which grape bunches contain berries that differ greatly in size and, most importantly, maturity. Its most common cause is cold, rainy or otherwise bad weather during the flowering stage of the vines though other factors, such as boron deficiency or fanleaf degeneration, may also play a role.

Cause and effect

Grapevines need a balance of sufficient leaf cover in order to produce photosynthesis but not shade the grapes too much from sunlight. Grapes03.jpg
Grapevines need a balance of sufficient leaf cover in order to produce photosynthesis but not shade the grapes too much from sunlight.

Coulure is caused by a carbohydrate deficiency in the plant tissues that causes the vine to conserve resources that would otherwise be funneled into the developing grape berries. As carbohydrate levels drop, soon after flowering the stems connected to the berries shrivel as the small grapes (0.2 inches/5 millimeters in diameter) eventually fall off.

Carbohydrate organic compound that consists only of carbon, hydrogen, and oxygen

A carbohydrate is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula Cm(H2O)n (where m may be different from n). This formula holds true for monosaccharides. Some exceptions exist; for example, deoxyribose, a sugar component of DNA, has the empirical formula C5H10O4. The carbohydrates are technically hydrates of carbon; structurally it is more accurate to view them as aldoses and ketoses.

Most likely a clear example of coulure. Coulure 2014 P7053002 bew.jpg
Most likely a clear example of coulure.

To some extent coulure and the dropping of fruit is a natural and healthy reaction of a vine that is self-regulating its resource and the amount of fruit that it produces. But when the situation is exacerbated by certain weather conditions and disruption to photosynthesis, coulure can have a more severe impact on yields that may negatively affect a region's grape supply and thus influence pricing. [1]

Photosynthesis Biological process to convert light into chemical energy

Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organisms' activities. This chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water – hence the name photosynthesis, from the Greek φῶς, phōs, "light", and σύνθεσις, synthesis, "putting together". In most cases, oxygen is also released as a waste product. Most plants, most algae, and cyanobacteria perform photosynthesis; such organisms are called photoautotrophs. Photosynthesis is largely responsible for producing and maintaining the oxygen content of the Earth's atmosphere, and supplies all of the organic compounds and most of the energy necessary for life on Earth.

When the weather is the primary instigator of coulure, the French term this phenomenon coulure climatique. This describes the cloudy and wet conditions that limit the amount of photosynthetic activity that takes place during the flowering cycle of a grapevine. Limited sunshine means lower sugar levels that can be converted into resources to develop grape berries. Warm temperatures can also exacerbate coulure in some grape varieties by promoting cellular respiration and excessive shoot growth that further competes with the berries for the resources derived from carbohydrates. Other contributing factors include excessively fertile vineyard soils, either naturally or enhanced by the use of nitrogen-rich fertilizers, overly vigorous rootstock and severe pruning that too drastically limits the amount of leaf surface needed to sustain photosynthesis. [1]

Cellular respiration Cellular enzymatic release of energy from compounds

Cellular respiration is a set of metabolic reactions and processes that take place in the cells of organisms to convert biochemical energy from nutrients into adenosine triphosphate (ATP), and then release waste products. The reactions involved in respiration are catabolic reactions, which break large molecules into smaller ones, releasing energy in the process, as weak so-called "high-energy" bonds are replaced by stronger bonds in the products. Respiration is one of the key ways a cell releases chemical energy to fuel cellular activity. Cellular respiration is considered an exothermic redox reaction which releases heat. The overall reaction occurs in a series of biochemical steps, most of which are redox reactions themselves. Although cellular respiration is technically a combustion reaction, it clearly does not resemble one when it occurs in a living cell because of the slow release of energy from the series of reactions.

Shoot new plant growth

In botany, shoots consist of stems including their appendages, the leaves and lateral buds, flowering stems and flower buds. The new growth from seed germination that grows upward is a shoot where leaves will develop. In the spring, perennial plant shoots are the new growth that grows from the ground in herbaceous plants or the new stem or flower growth that grows on woody plants.

Nitrogen Chemical element with atomic number 7

Nitrogen is the chemical element with the symbol N and atomic number 7. It was first discovered and isolated by Scottish physician Daniel Rutherford in 1772. Although Carl Wilhelm Scheele and Henry Cavendish had independently done so at about the same time, Rutherford is generally accorded the credit because his work was published first. The name nitrogène was suggested by French chemist Jean-Antoine-Claude Chaptal in 1790, when it was found that nitrogen was present in nitric acid and nitrates. Antoine Lavoisier suggested instead the name azote, from the Greek ἀζωτικός "no life", as it is an asphyxiant gas; this name is instead used in many languages, such as French, Russian, Romanian and Turkish, and appears in the English names of some nitrogen compounds such as hydrazine, azides and azo compounds.

Prevention

Malbec can be highly susceptible to coulure but newer clones are being produced with less sensitivity. Malbec grapes.jpg
Malbec can be highly susceptible to coulure but newer clones are being produced with less sensitivity.

Coulure is not 100% preventable but a vineyard manager can take several precautions to lessen the severity and impact of coulure. Some grape varieties are more prone to develop coulure than others, such as Grenache, Malbec, Merlot and Muscat Ottonel. A grower can choose to grow clones of those varieties, now commonly available for Merlot and Malbec, that have less susceptibility to developing coulure. In the vineyard, care can be taken to not prune so severely and insure that there is adequate leaf coverage for photosynthesis. Trimming the tips of developing shoots near the end of the flowering period can lessen the competition for sugar resources between berries and new shoot development. For non-organic viticulture, chemical growth inhibitors can be applied to the vine to limit shoot growth as well. [1]

Related Research Articles

Merlot dark blue-colored variety of wine-making grape

Merlot is a dark blue-colored wine grape variety, that is used as both a blending grape and for varietal wines. The name Merlot is thought to be a diminutive of merle, the French name for the blackbird, probably a reference to the color of the grape. Its softness and "fleshiness", combined with its earlier ripening, makes Merlot a popular grape for blending with the sterner, later-ripening Cabernet Sauvignon, which tends to be higher in tannin.

Vineyard Plantation of grape-bearing vines

A vineyard is a plantation of grape-bearing vines, grown mainly for winemaking, but also raisins, table grapes and non-alcoholic grape juice. The science, practice and study of vineyard production is known as viticulture.

Pinot noir Wine-making grape

Pinot noir is a red wine grape variety of the species Vitis vinifera. The name may also refer to wines created predominantly from pinot noir grapes. The name is derived from the French words for pine and black. The word pine alludes to the grape variety having tightly clustered, pine cone-shaped bunches of fruit.

Malbec wine varietal

Malbec is a purple grape variety used in making red wine. The grapes tend to have an inky dark color and robust tannins, and are known as one of the six grapes allowed in the blend of red Bordeaux wine. The French plantations of Malbec are now found primarily in Cahors in South West France. It is increasingly celebrated as an Argentine varietal wine and is being grown around the world.

Viticulture science, production and study of grapes

Viticulture or winegrowing is the cultivation and harvesting of grapes. It is a branch of the science of horticulture. While the native territory of Vitis vinifera, the common grape vine, ranges from Western Europe to the Persian shores of the Caspian Sea, the vine has demonstrated high levels of adaptability to new environments. Thus, viticulture can be found on every continent except Antarctica.

Carménère varietal

The Carménère grape is a wine grape variety originally planted in the Médoc region of Bordeaux, France, where it was used to produce deep red wines and occasionally used for blending purposes in the same manner as Petit Verdot.

Grenache red wine grape

Grenache or Garnacha is one of the most widely planted red wine grape varieties in the world. It ripens late, so it needs hot, dry conditions such as those found in Spain, where the grape most likely originated. It is also grown in the Italian isle of Sardinia, the south of France, Australia, and California's Monterey AVA and San Joaquin Valley.

Chlorosis

In botany, chlorosis is a condition in which leaves produce insufficient chlorophyll. As chlorophyll is responsible for the green color of leaves, chlorotic leaves are pale, yellow, or yellow-white. The affected plant has little or no ability to manufacture carbohydrates through photosynthesis and may die unless the cause of its chlorophyll insufficiency is treated, although some chlorotic plants, such as the albino Arabidopsis thaliana mutant ppi2, are viable if supplied with exogenous sucrose.

<i>Vitis labrusca</i> species of plant

Vitis labrusca, the fox grape, is a species of grapevines belonging to the Vitis genus in the flowering plant family Vitaceae. The vines are native to eastern North America and are the source of many grape cultivars, including Catawba, Concord, Delaware, Isabella, Niagara, and many hybrid grape varieties such as Agawam, Alexander and Onaka. Among the characteristics of this vine species in contrast to the European wine grape Vitis vinifera are its "slip-skin" that allows the skin of the grape berries to easily slip off when squeezed, instead of crushing the pulp, and the presence of tendrils on every node of the cane. Another contrast with European vinifera is the characteristic "foxy" musk of V. labrusca, best known to most people through the Concord grape. This musk is not related to the mammalian fox, but rather to the strong, earthy aromas characteristic of the grapes that were known by early European-American settlers in the New World. The term "foxy" became a sort of catchall for the wine tasting descriptors used for these American wines that were distinct from the familiar flavors of the European viniferous wines.

Cahors wine appellation dorigine contrôlée

Cahors is a red wine from grapes grown in or around the town of Cahors, France. Cahors is an Appellation d'origine contrôlée (AOC) which forms part of the South West France wine region. The dominant grape variety in AOC Cahors wines is Malbec, which must make up a minimum of 70% of the wine, and which is known locally as "Côt", "Côt Noir" or "Auxerrois". It is supplemented by up to 30% Merlot and Tannat.

Washington wine

Washington wine is wine produced from grape varieties grown in the U.S. state of Washington. Washington ranks second in the United States in the production of wine. By 2017, the state had over 55,000 acres (220 km2) of vineyards, a harvest of 229,000 short tons (208,000 t) of grapes, and exports going to over 40 countries around the world from the 940+ wineries located in the state. While there are some viticultural activities in the cooler, wetter western half of the state, the majority (99.9%) of wine grape production takes place in the shrub-steppe eastern half. The rain shadow of the Cascade Range leaves the Columbia River Basin with around 8 inches (200 mm) of annual rain fall, making irrigation and water rights of paramount interest to the Washington wine industry. Viticulture in the state is also influenced by long sunlight hours and consistent temperatures.

Marselan varietal

Marselan is a red French wine grape variety that is a cross between Cabernet Sauvignon and Grenache. It was first bred in 1961 by Paul Truel near the French town of Marseillan. The vine is grown mostly in the Languedoc wine region with some plantings in the Northern Coast of California. It has also become very popular in China. The grape usually produces a medium body red wine.

Annual growth cycle of grapevines

The annual growth cycle of grapevines is the process that takes place in the vineyard each year, beginning with bud break in the spring and culminating in leaf fall in autumn followed by winter dormancy. From a winemaking perspective, each step in the process plays a vital role in the development of grapes with ideal characteristics for making wine. Viticulturalists and vineyard managers monitor the effect of climate, vine disease and pests in facilitating or impeding the vines progression from bud break, flowering, fruit set, veraison, harvesting, leaf fall and dormancy-reacting if need be with the use of viticultural practices like canopy management, irrigation, vine training and the use of agrochemicals. The stages of the annual growth cycle usually become observable within the first year of a vine's life. The amount of time spent at each stage of the growth cycle depends on a number of factors-most notably the type of climate and the characteristics of the grape variety.

Canopy (grape)

In viticulture, the canopy of a grapevine includes the parts of the vine visible aboveground - the trunk, cordon, stems, leaves, flowers, and fruit. The canopy plays a key role in light energy capture via photosynthesis, water use as regulated by transpiration, and microclimate of ripening grapes. Canopy management is an important aspect of viticulture due to its effect on grape yields, quality, vigor, and the prevention of grape diseases. Various viticulture problems, such as uneven grape ripening, sunburn, and frost damage, can be addressed by skillful canopy management. In addition to pruning and leaf trim, the canopy is often trained on trellis systems to guide its growth and assist in access for ongoing management and harvest.

This glossary of viticultural terms list some of terms and definitions involved in growing grapes for use in winemaking.

Irrigation in viticulture

Irrigation in viticulture is the process of applying extra water in the cultivation of grapevines. It is considered both controversial and essential to wine production. In the physiology of the grapevine, the amount of available water affects photosynthesis and hence growth, as well as the development of grape berries. While climate and humidity play important roles, a typical grape vine needs 25-35 inches of water a year, occurring during the spring and summer months of the growing season, to avoid stress. A vine that does not receive the necessary amount of water will have its growth altered in a number of ways; some effects of water stress are considered desirable by wine grape growers.

Vine training

The use of vine training systems in viticulture is aimed primarily to assist in canopy management with finding the balance in enough foliage to facilitate photosynthesis without excessive shading that could impede grape ripening or promote grape diseases. Additional benefits of utilizing particular training systems could be to control potential yields and to facilitate mechanization of certain vineyard tasks such as pruning, irrigation, applying pesticide or fertilizing sprays as well as harvesting the grapes.

Bianca (grape) varietal

Bianca is a white Hungarian wine grape variety that was developed in 1963 in the Eger wine region of northeast Hungary. The grape is a hybrid crossing of Bouvier and Eger 2. The grape was officially register for use in wine production in 1982 and today is used to make a wide assortment of wines from dry varietals to sweet dessert wines. Bianca is growing in popularity among organic vineyards due to its natural high resistance to many fungal diseases that affect grapevines.

Propagation of grapevines

The propagation of grapevines is an important consideration in commercial viticulture and winemaking. Grapevines, most of which belong to the Vitis vinifera family, produce one crop of fruit each growing season with a limited life span for individual vines. While some centenarian old vine examples of grape varieties exist, most grapevines are between the ages of 10 and 30 years. As vineyard owners seek to replant their vines, a number of techniques are available which may include planting a new cutting that has been selected by either clonal or mass (massal) selection. Vines can also be propagated by grafting a new plant vine upon existing rootstock or by layering one of the canes of an existing vine into the ground next to the vine and severing the connection when the new vine develops its own root system.

References

  1. 1 2 3 4 J. Robinson (ed) "The Oxford Companion to Wine" Third Edition pg 207-208 Oxford University Press 2006 ISBN   0-19-860990-6
  2. 1 2 Wine & Spirits Education Trust "Wine and Spirits: Understanding Wine Quality" pg 25, Second Revised Edition (2012), London, ISBN   9781905819157