GRAPE BIOLOGYRebecca Harbut

Dept of Horticulture, UW-Madison

VITACEAE• Mostly woody, tree-climbing vines• Tendrils and inflorescences opposite

the leaves• 12 genera within the family

– Vitis– Ampelocissus– Clematicissus– Parthenocissus (Virginia Creeper)– Ampelopsis– Cissus (Kangaroo vine)

GENUS VITIS

• 60 species of grape– 30 species native to North America

• Two subgenera:– Euvitis (38 chromosomes)

• Grapes adhere to cluster – Muscadinia (40 chromosomes)

• Grapes fall off cluster as they mature

GENUS VITIS• Euvitis

– Vitis vinifera European wine grapes

» Over 5000 cultivars» 90% of world grape production

– Vitis labrusca American species, fox grape

– Vitis riparia American species, ‘cold-climate grapes

• French-American hybrids– ‘Marechal Foch', ‘Vidal Blanc', ‘Chambourcin', and

‘Seyval'.

• Muscadinia– Vitis rotundifolia Muscadine grapes (grown

in SE USA, lack cold hardiness

EUROPEAN VS. AMERICAN

Vitis Vinifera

• Cold tender• More upright growth• Phloxera susceptible

Vitis Labrusca &Vitis Riparia

• More cold hardy• More trailing

growth• More vigorous

growth

GRAPE USE IN U.S.

Wine - 50-55%   Raisins - 25-30%Table - 10-15%            Juice, jelly, etc. - 6-9%Canned - < 1%

GRAPE ANATOMY

ROOTS• Grapes have tap root system

– Main tap root with lateral roots

• Most absorption (nutrients and water) carried out by root tips and root hairs– Soil conditions are critical (proper soil

test and site prep)

• Vesicular arbuscular mycorrhizae (VAM)– Most associated with plants in low P

soils– Most grapes have VAM infecting roots

ROOTSTOCKS• Primary reason - Phylloxera

resistance

• 3 species used: 1) Vitis rupestris: A native of the eastern United States which provides vigor2) Vitis berlandieri: A native of the dry southwestern United States which provides drought tolerance.3) Vitis riperia: A native of the northeastern United States which provides cool weather tolerance. Photo: OSU

OWN ROOTED VS. ROOTSTOCKS

• Grafted vines can be more expensive– Increased time in nursery– More labor

• Own rooted can be better in areas prone to winter damage as new growth can come from established roots

• Rootstocks can be used to compensate for less than ideal sites

ROOT GROWTH AND IRRIGATION

• Root growth is critical for vine establishment

• Irrigation during can allow for improved root establishment

• Deep watering encourages roots to move down into the soil profile

TRUNK

• Primary support structure• Important in carbohydrate storage• May be single or split

CANES, CORDONS AND SHOOTS…OH MY!

• Cordon-permanent stem– Trained horizontally– Not all systems have cordons

• Cane– One year old shoot– SPUR- Canes pruned to 2-3 buds

• Shoot– Current seasons growth– Bear fruit clusters

One year old cane

Shoot

Cluster

Tendril

BUDS INITIATION

• Primordia- undefined tissue with potential to develop into a defined structure

• Primordia can become: tendril, shoot, inflorescence– Temperature, vine vigor, light affect cluster size

and number

• Primordia initiate when only few inches from growing shoot tip

BUDS DIFFERENTIATION

• Differentiation- process in which primordia become committed to develop into a specialized tissue– Tendril, inflorescence, shoot

• Secondary buds differentiate later– Important if primary bud is killed

Primary Bud

Tertiary Bud

Secondary B

ud

TENDRILS

• Specialized lateral branches– Derived from same undifferentiated primordia

as flowers• Grow away from the light• Become lignified• Allow plant to invest less in structural

trunk• If tendril does not latch onto anything it

will wither and die• Tendrils have determinate growth

FLOWERS• Small 1/8 inch, indiscrete• 5 sepals, petals, stamens• Superior ovary

– 2 locules/2 ovules per locule• Cultivated grapes have perfect

flowers– Some wild have male and female flowers– Evidence that cross pollination increases

size

Fused petals = calyptra

INFLORESCENCE/CLUSTER

• Panicle inflorescence– Inflorescence

usually on 3rd or higher node

– # of inflorescence (clusters)/shoot varies by:• Management,

cultivar, environment

• 0 to 5 (or more)

HARDINESS

• Vinifera 0 to -10°F bud injury <-10°F trunk injury

• French hybrids -10°F bud and trunk injury -20°F kill buds and trunks

• American types -20°F would cause crop reduction

FLOWERING

• Grapes flower long after bud-break• Shoot must develop enough leaves

to support fruit development• Flowers open when shoots have 15-

17 nodes• Length of flowering period dependent

on environment

POLLINATION

• Wind pollinated– Weather dependent

• Fertilization dependant on weather– Pollen tube must grow down through

style (highly temperature dependent) – Cool weather during fertilization

decreases fruit set

FRUIT SET

• Fruit Set- percent of flower buds that develop fruit

• Auxins (hormone) are released from pollen tube which stimulates growth of ovarian tissue

• Factors affecting fruit set:– Temperature– Light (photosynthesis)– Stored carbohydrates– Water– Nutrients ~ primarily Zn and B

FRUIT• Grapes are true berries

– primary tissue from ovarian tissues• Berry size influenced presence or absence of

seeds and then seed mass– V. vinifera- 1-2 seeds– V. lubrusca >2 seeds

• Seedless grapes– Most not really seedless (stenospermocarpic)– Seeds form, but abort – Still enough hormone production to stimulate large

berry growth– Truly seedless (parthenocarpic) have smaller berries

BERRY COMPOSITION

• 75-85% water• 15-25% sugar• 0.5-1.0% organic acids (malic,

tartaric, citric)• 0.25% pectin• Secondary metabolites

BERRY COMPOSITION:SECONDARY METABOLITES

• Components that make grapes distinctive

• Not essential for survival of the plant• Thousands have been identified,

likely many more– Phenolics, anthocyanins, flavenoids

• Synthesis is genetically controlled• Influenced by:

– Environment, plant age

Phase I Phase II Phase III

BERRY DEVELOPMENT:PHASE I (0-40 DAF)

• Phase I- cell division and expansion– 17 cells to 200,000 (600,000 cells at

veraison)– No carbohydrate accumulation– Accumulation of tartaric and malic acid– Duration is similar for most cultivars– Berries are green due to cholorophyll

BERRY DEVELOPMENT:PHASE II (40-60 DAF)

• Phase II-lag phase– Slowest phase of development– Berries are firm– Berries begin to loose chlorophyll– Organic acids accumulation peaks

BERRY DEVELOPMENT:PHASE III (60-120 DAF)

• Phase III- Fruit softening (véraison)– Rapid berry growth (cell enlargement)– Initiation of ripening– Chlorophyll breaks down– Anthocyanins accumulate in skin (red

grapes)– Sugars accumulate– Organic acids decline– Secondary metabolites accumulate

Cabernet Sauvignon

Flame

Sauvignon blanc

PROPAGATION

• Cuttings root easily• Cut canes with three nodes (bud)• Can also tip layer• Be careful about propagating your

own material– Royalties, quality, identity

SUMMARY

• Spend the time to understand the critical growth periods of the grape

• Grapes are one of the most complex crops to grow

• Before you grow it, be sure you know it!