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BUNCH GRAPE FIELD D
July 15, 1987
Research and Education Cent
IFAS, University of Fl
Leesburg CFREC Research Report (LBG 87-2)
The Institute of Food and Agricultural Sciences is an Equal Employment Opportunity Affirmative Action Employer authorized to provide research,
educational information and other services only to individuals and institutions that function without regard to race, color, sex, or national origin.
BUNCH GRAPE FIELD DAY
Central Florida Research and Education Center-Leesburg
IFAS, University of Florida
July 15, 1987
Dr. Mary C. Halbrooks, Fruit Crops Department Moderator
9:30 Registration (no charge), lunch ticket sales first-come,
first-serve. $5.00 each.
9:45 Taste Test Panel.
10:30 Questions and answers, announcements.
10:45 Vineyard Tour. Tour will include new plantings for
cultural practices research, experimental selections,
screenhouse with parental lines, and vineyard sprayer
11:30 Travel to Oxford Estates community building for those
attending afternoon program.
Noon Catered Lunch by Sonny's barbeque includes chicken, BBQ
beans, cole slaw, potato salad, rolls/butter and ice tea.
LUNCH TICKET REQUIRED AS SEATING IS LIMITED
(lunch tickets may only be purchased at registration!)
12:50 Opening Remarks, C. A. Conover, Center Director.
1:00 J. A. Mortensen, Geneticist, CFREC-Leesburg
Bunch Grape Breeding Program.
1:15 D. J. Gray, Developmental Biologist, CFREC-Leesburg
Synthetic Seeds of Grape.
1:30 M. C. Halbrooks, Extension Viticulturist, Fruit Crops
Cultural Practices Research for Commercial Grape
1:45 D. L. Hopkins, Plant Pathologist, CFREC-Leesburg
Plant Disease Research on Grape.
2:00 C. A. Sims, Enologist, Food Science & Human Nutrition
Grape Utilization Research at the University of Florida.
2:15 R. P. Bates, Food Technologist, Food Science & Human Nutr.
Florida Grape Juice Considerations.
2:30 Close of Program.
BUNCH GRAPE BREEDING PROGRAM
J. A. Nortensen
Since 1945 the breeding of bunch grapes has been under way
here at Leesburg without interruption. Objectives have been to
combine the longevity, vigor, and disease resistance of wild
Florida bunch grapes with the high fruit quality and productivity
of highly favored bunch grape cultivars from Europe, California,
and New York State. Seedlessness has been a high priority for
table grapes, since these sell best to the public.
Table Grape Types
With the release of 'Orlando Seedless' in 1986 we now have
for the first time a long-lived seedless bunch grape that is
resistant to Pierce's disease (PD). While we are glad for
'Orlando Seedless', it is still a slipskin type grape. We had a
breakthrough from the slipskin type to adherent skin when we
released 'Daytona' in 1983. 'Daytona' is fully resistant to PD
and long-lived, with attractive clusters of seeded fruit. It
would be desirable to have the good berry size and adherent skin
of 'Daytona' combined with the seedlessness of 'Orlando
Seedless'. This we can accomplish through controlled cross-
pollinations, saving the seed, and growing out the progeny to
fruiting stage. The steps involved in this procedure are
illustrated with colored slides. Crosses of seedless x seedless
are being obtained, and through embryo rescue and tissue culture
are being grown and fruited out. This gives greater chances of
getting seedless cultivars. Cold storage tests show us which are
best for keeping. One of the top-rated cultivars in our fresh
fruit taste panels has been 'Conquistador'. This is a slipskin,
seeded grape of Concord-like flavor. It was developed through
breeding and released in 1983. Its greatest use is for
pick-your-own and fresh market. This year we are seeing among
our fruiting seedlings some table type grapes that may surpass
'Conquistador', 'Daytona', and 'Orlando Seedless' in one or more
ways. In our plan of crossing we are using purple or red colored
parents to increase the possibility of getting red or purple
seedless types for industry use. We are also using parents
resistant to fruit rot to incorporate this trait into future
Juice Type Grapes
At present 'Conquistador' is probably our best juice grape,
but other promising selections are appearing in the program that
may surpass 'Conquistador' for juice purposes.
Wine Type Grapes
'Conquistador' and 'Black Spanish' seem to be best among the
dark wine sorts, but both lack long-lasting pigment stability
during and after fermentation. Well-pigmented cultivars
'Cascade' and 'Ruby Cabernet' used as parents should help us
obtain stable-pigment cultivars in the future. 'Suwannee',
released in 1983, and 'Blanc Du Bois', released in 1987 are very
good white wine cultivars. Both perform well without grafting
and are fully resistant to PD. These two, along with 'Stover'
and 'Lake Emerald' (released in 1968 and 1954, respectively) form
the backbone of the Florida wine industry. Newer selections are
being tested for their value in making red or white wines.
Rootstock Type Grapes
A screening program of 18 rootstock clones for resistance to
grape root borer revealed 2 of the 18 with some resistance.
These 2 were crossed with each other this spring, and the progeny
will be grown and tested, looking for a rootstock type fully
resistant to grape root borer. Other traits already present in
our recommended rootstocks ('Tampa', 'Dog Ridge', and 'Lake
Emerald') are nematode resistance, drought resistance, and
resistance to PD.
SYNTHETIC SEEDS OF GRAPE
D. J. Gray
One long-term goal of the grape tissue culture research
program is to develop high efficiency propagation systems. Grape
vineyards are now established from vegetative cuttings. This is
because sexually produced embryos contained in seeds do not
produce uniform plants. Genetic incompatibility and loss of
vigor from inbred plants prohibit the development of uniform
grape seed. Although establishment of vineyards from cuttings is
labor intensive, it is necessary for grafted varieties. However,
for propagation and planting of nongrafted varieties, other
possibilities exist. One alternative to cuttings is to use plant
tissue culture technology to develop propagules that have the
handling efficiency of seeds but produce genetically uniform
plants. This use of plant tissue culture has come to be known as
synthetic seed technology.
With tissue culture, it is possible to produce embryos that
arise from cells of only one donor plant without sexual
reproduction. The plants that grow from such embryos are
identical to the donor plant. This method of vegetative
propagation is a type of cloning known as somatic embryogenesis
and forms the basis for synthetic seed technology. However,
somatic embryos tend to be fragile and develop in a rapid,
nonuniform manner. Our research on synthetic seeds seeks to
produce somatic embryos that are durable, uniform and in a state
of rest. Such embryos would have the handling efficiency of seed
but would produce uniform plants upon germination.
To date, we have initiated numerous long-lived cultures that
continuously produce somatic embryos. By careful culture and
medium manipulation, we have obtained uniform, well-developed
embryos. These embryos tend to mature rapidly but normally never
attain a resting stage as seed embryos do. To induce a resting
stage, the embryos are dehydrated to controlled moisture
contents. The embryos cease growth, become discolored and
decrease in size during dehydration but rapidly assume a normal
appearance when water is added. We are able to store resting
dehydrated somatic embryos for up to three weeks at room
temperature and obtain a 30 percent germination rate after
rehydration. These responses are not yet adequate for synthetic
seed to be commercially useful. However, they are the longest
storage and highest germination responses thus far obtained for
somatic embryos of any plant species. Therefore, grape appears
to be a good model system for advances in synthetic seed
technology. Our continuing research will emphasize increasing
CULTURAL PRACTICES RESEARCH FOR COMMERCIAL GRAPE PRODUCTION
M. C. Halbrooks
Improved Methods of Bench Grafting for High Volume Production of
Bench grafting is a series of grafting procedures done
indoors rather than in the field. This allows the grower to
plant out only those cuttings which lived, thus eliminating the
need to regraft under field conditions. For nursery operators,
bench grafting techniques can be utilized to produce large
quantities of grafted vines efficiently and economically.
Traditional field grafting requires 2-2 1/2 years from the time
the rootstock is rooted until the scion is grafted on to the
rootstock in the vineyard. Furthermore it is labor intensive.
With bench grafting techniques, a grafted vine can be
transplanted to the field within 4-6 months.
Nurseries utilizing bench graft methods can produce large
volumes of grafted vines ready for field planting within 1 year.
Losses due to graft failure, however, are substantial and current
methods involve 3 separate handling steps (callusing, greenhouse
forcing, and lining out in the nursery or potting up for
on-growing). Highest rates of loss occur during the 2nd and 3rd
steps, with overall losses nearing 50%. Inadequate acclimation
of callused grafts to greenhouse conditions, and asynchronous
development of shoots and roots during greenhouse forcing, are
the primary reasons for graft failure. A method of bench
grafting which improves labor efficiency and reduces graft
failure rates is currently under evaluation. This "one-step
greenhouse method" involves a unique pretreatment of the
rootstock which is practical and economical. High quality vines
ready to be transplanted to the field can be produced in 4-5
months. Potential savings to the nursery industry would be
substantial as losses may be significantly reduced. Current
industry practices have not been researched or updated in over 10
years. Objectives of this research project are to (1) evaluate
this method on several Florida cultivars and experimental
rootstock selections and (2) determine the optimum methods for
best possible efficiency and profitability for nursery operators
serving the needs of Florida's rapidly expanding grape industry.
Influence of Gibberellic Acid and Various Management Practices on
Berry, Seed and Cluster Development in 'Orlando Seedless' Grape
'Orlando Seedless' is the first Pierce's disease resistant
seedless variety to be released from the UF-IFAS grape breeding
program. Limitations in market acceptability of 'Orlando
Seedless' due to its small berry size and presence of occasional
gritty seed traces, need to be overcome if Florida is to have a
table grape industry. Small berry size is a common
characteristic of seedless cultivars and is generally overcome by
a combination of gibberellic acid (GA ) treatments and other
cultural practices such as girdling, tipping, or cluster removal.
(GA3 is a plant growth regulator which occurs naturally in seeds
of grapes.) Elimination of gritty seed traces may be
accomplished by use of GA also. The effect of GA applications
made early in flower development is to inhibit seed development.
Timing,.however, is of critical importance and response varies
among cultivars. In Japan, seedless grapes of 'Delaware',
normally a seeded type, are produced by applying GA3 prebloom.
In a 3-year study, methods to improve the quality and market
acceptability of 'Orlando Seedless' grapes have been evaluated.
Applications of GA3 made within 1-2 weeks after bloom have been
effective in increasing berry size by as much as 32% over
untreated fruit. Formation of occasional gritty seed traces was
inhibited by GA applied within 1 week after bloom. GA3 was not
effective in reducing fruit set. Girdling of canes (removal of a
complete strip of bark 3/16" wide around cane circumference) and
cluster tipping (removal of lower 2/3 of cluster) were associated
with small increases in berry size. Long-term objectives of this
project are to develop the information necessary to establish a
table grape industry in Florida. Knowledge gained on the
cultural requirements for 'Orlando Seedless' can be applied to
other cultivars in a systematic way. Future seedless selections
can be evaluated for adaptability to a table grape management
program prior to release. This will insure the future of an
expanding table grape industry in Florida.
PLANT DISEASE RESEARCH ON GRAPE
D. L. Hopkins
Anthracnose Control, 1987 Test
Grape Variety: 'Stover'
Application Dates: April 2, 21, May 5, 19, June 3, 17, and
Results to date:
TreatmentI Anthracnose rating
4/24 5/8 6/16
(C) Rally + Dithane M-45 + Triton B-1956 1.6 a 1.0 a 1.0 a
(0.125 lb. ai + 3.0 lbs. + 2 oz.)
(E) Rally + Triton B-1956 1.6 a 1.3 ab 1.0 a
(0.25 lb. ai + 2 oz.)
(A) Rally + Triton B-1956 1.8 a 1.1 a 1.0 a
(0.125 lb. ai + 2 oz.)
(D) Benlate + Captan + Triton B-1956 2.7 ab 1.2 ab 1.0 a
(1.5 lbs. + 3.0 lbs. + 2 oz.)
(B) Dithane M-45 + Triton B-1956 2.9 ab 1.9 bc 1.0 a
(3.0 lbs. + 2 oz.)
(F) Unsprayed 3.7 b 2.6 c 2.3 b
Rate of formulation per acre is given unless labeled ai
active ingredient. Anthracnose rated on 0-10 scale.
Natural Hosts of the Xylem-limited Bacteria That Cause Pierce's
Disease of Grapevine
Pierce's Disease (PD) of grapevine is endemic and limits
grape production in Florida to resistant cultivars. The
xylem-limited bacterium that causes PD has a very wide host range
that includes members of at least 28 different families of
plants. Many of the host plants are symptomless. The PD
bacterium has been shown to also cause almond leaf scorch,
alfalfa dwarf, and possibly citrus blight.
Bacteria that are similar to the PD bacterium cause large
losses in many economically important crops and in urban trees.
These diseases are serious problems primarily in areas with
tropical or subtropical climates and include phony disease of
peach, plum leaf scald, periwinkle wilt, oak leaf scorch, elm
leaf scorch, mulberry leaf scorch, and sycamore leaf scorch. We
conducted a study to identify natural hosts of the PD bacterium
in Florida that may be important in the epidemiology of PD of
grapevine and to identify natural hosts of other xylem-limited
bacteria in Florida.
Fluorescence microscopy, enzyme-linked immunosorbent assay
(ELISA), and culturing on synthetic media were used to detect the
PD bacterium and other xylem-limited bacteria in various weeds
and wild plants. The PD bacterium was identified in elderberry,
Virginia creeper, American beautyberry, blackberry, peppervine,
citrus, and wild grapevine. Bacteria similar to the PD bacterium
were identified from eastern baccharis, sumac, goldenrod,
southern red oak, laurel oak, water oak, peach, and sycamore.
This points out the large number of natural hosts of
xylem-limited bacteria that occur in Florida. The role of these
natural hosts as sources of PD bacteria to infest a vineyard
needs to be studied further.
Toxin Production by the Pierce's Disease Bacterium
Bacteria-free fractions from liquid cultures of the PD
bacterium were found to have toxin activity in a grape leaf
bioassay. The symptoms in the grape leaf are typical of those
produced in grapevines infected with PD, and even include the red
or yellow margin to the necrotic tissue. This typical symptom in
the toxin bioassay usually occurred 3-7 days after the crude
culture filtrate was applied to the grape leaves. However,
filtrates sometimes produced a rapid (<6 hrs) wilt and necrosis.
Apparently, the PD bacterium can produce 2 toxic materials, one
that produces rapid wilting in the leaf and another that produces
symptoms more typical of the disease.
When chromatographed on a column of Sephadex G-50, the toxin
activity separated into 2 fractions, a high molecular weight
fraction and a lower molecular weight fraction. The larger
fraction produced wilting and necrosis within 24 hrs; whereas,
the smaller fraction produced symptoms later.
Although some avirulent strains of the PD bacterium do not
produce a toxin, the addition of toxin from virulent strains to
avirulent strains did not increase the multiplication of
avirulent strains in grapevine. It appears that toxin production
is not the sole determinant of Pierce's disease development in
grape. We hope to be able to use the toxin preparations to
screen breeding lines and cultivars for resistance to PD, using
either the leaf bioassay or tissue culture.
GRAPE UTILIZATION RESEARCH AT THE UNIVERSITY OF FLORIDA
C. A. Sims
There are many problems and handicaps that are currently
hindering the expansion of commercial grape processing and
utilization in Florida. Several studies were initiated during the
summer of 1986 to address some of these problems.
Evaluation of Wines From Florida Breeding Lines and Cultivars
In an attempt to identify breeding lines and cultivars that
produce the highest quality wines in Florida, experimental wines
were produced from 16 bunch grape and 10 muscadine breeding lines
and cultivars grown at CFREC-Leesburg. The wines were evaluated by
sensory panel (color, aroma, taste, overall acceptability) using a
hedonic scale. The pH, color, color stability and acidity of the
wines were also determined.
Quality Comparison of 'Orlando Seedless' With 'Thompson Seedless'
As a result of the commercial interest in 'Orlando Seedless',
a study was conducted to compare the sensory quality of 'Orlando
Seedless' to that of 'Thompson Seedless', a standard white seedless
grape in retail markets.
Effects of Maturity, Skin Contact and Press Fraction on the Quality
of 'Stover' wine
Since 'Stover' is currently the leading bunch grape cultivar
in Florida in terms of acreage and amount of wine produced, a study
was conducted to determine the effects of maturity ("optimum" vs.
late season), skin contact prior to fermentation (non vs. 24 hr.)
and press fraction (free run vs. full press) on the quality of
Effects of Maturity, Skin Contact, and Carbonation on Quality of
Sterile-filtered Muscadine Grape Juice
Due to increasing interest in the commercial production of
muscadine grape juice in Florida and throughout the South, the
effects of grape maturity (early, middle, late season), skin
contact (minimal vs. 24 hr.), and carbonation (carbonated vs. non-
carbonated) on the quality and stability of unheated, sterile-
filtered 'Dixie' muscadine juice were investigated.
Postharvest Characteristics of Bunch and Muscadine Grapes for Wine
Production in Florida
Since commercial vineyards in Florida are often located large
distances from the wineries, extensive postharvest handling is
often required. A factorial study was established to examine the
effects of harvest method (hand vs. machine), sulfur dioxide
additions (none vs. 100 ppm immediately after harvest) and
postharvest holding time (0, 24, 48 hrs.) on the raw product
quality and subsequent wine quality of 'Stover' and 'Noble' grapes.
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