Selecting Wine Grape Clones to
Improve Yield and Quality
Matthew Fidelibus
Department of Viticulture and Enology
University of California, Davis
Species, cultivars, and clones
• California’s wine industry based on a single species of grape, Vitis vinifera L.
• Most wines made from traditional (old) cultivated varieties of V. vinifera
• Old cultivars have accumulated many ‘clones’ due to mistaken identity, mutation, or both
• Variation among clones may be exploited to improve grapevine yield and quality
What is a grapevine clone?
• A population of vines propagated
asexually (e.g., by cuttings) from a single
mother vine.
• Virtually all propagated grapevines are
technically ‘clones’
• Of particular interest are clones or
‘selections’ having distinctive, beneficial,
characteristics
How to make a mammalian clone
How to make a grapevine clone
How can clonal selection
research benefit growers?• Nurseries offer many different clones of a
given cultivar
• These may differ dramatically with respect to
yield, yield components, fruit composition,
and susceptibility to pests and diseases
• The performance of a given clone can
depend on the climatic region where it is
grown
Materials and methods
• Chardonnay, Merlot, and Zinfandel/Primitivo vines planted in 1997
• Bilateral cordons, two-wire trellis, spur pruned
• Vine x row spacing = 7.5’ x 10’
• Ten single-vine replicates
• Randomized complete block design
• Within a year, all clones harvested on the same day
Chardonnay characteristics
• Most widely cultivated wine grape in CA
• > 70 different registered clones in CA
• Clone 4, industry standard
• High yields, good fruit composition
• 4 has large, heavy clusters—susceptible
to sour rot
Chardonnay clones
Clone Source
4 Martini 5V21, Olmo #66
6 Martini 3V4, Olmo #68
15 Prosser, WA, LR2V6
18 Rauscedo 8, Italy
20 Cornegliano 7, Italy
37 France, 95
Chardonnay yield components
Clone Clusters / vine Cluster wt.
(kg.)
Yield / vine
4 78 d 0.29 a 21.9 a
6 107 a 0.22 c 22.0 a
15 107 a 0.20 d 19.9 b
18 93 c 0.26 b 22.6 a
20 98 bc 0.25 b 22.1 a
37 105 ab 0.24 bc 23.2 a
Chardonnay berries
Clone Berries / cluster Berry wt
(g)
4 192 a 1.5 b
6 147 cd 1.5 b
15 138 d 1.4 c
18 172 b 1.5 b
20 153 c 1.6 a
37 158 c 1.5 b
Chardonnay fruit composition
Clone Brix pH TA
(g/100 ml)
4 23.7 a 3.60 c 0.584 a
6 22.9 b 3.70 a 0.555 b
15 22.8 b 3.69 ab 0.581 a
18 22.7 bc 3.67 b 0.534 c
20 22.4 c 3.68 ab 0.555 b
37 23.0 b 3.68 ab 0.534 c
Chardonnay, sour rot incidence
Clone Sour rot incidence
(%)
4 16 a
6 10 b
15 4 c
18 14 ab
20 13 ab
37 15 a
Chardonnay clones summary
• Clone 4 had good yields, large clusters,
and good fruit composition but was very
susceptible to sour rot
• Clone 15 had 10% lower yields than 4, but
had much less sour rot than 4
Merlot characteristics
• Merlot among the most important red wine
grapes in Calif.
• 20%, by area, and 45%, by yield, grown in
Central Valley
• Clone 3 is standard; consistent set, yield,
fruit composition
• Relative performance compared to other
clones in the valley has not been tested
Merlot clones
Clone Source
1 Inglenook, Calif.
3 Inglenook, Calif.
9 Rauscedo, Italy #3
10 Cornegliano, Italy ISV-V-F2
11 Cornegliano, Italy ISV-V-F5
14 Chamber d’Agriculture de al
Gironde, France
Merlot yield components
Clone Clusters / vine
(no.)
Cluster wt.
(kg)
Yield / vine
(kg)
1 90 b 0.24 19.83 c
3 91 b 0.25 20.75 bc
9 90 b 0.25 21.50 ab
10 103 a 0.24 22.21 a
11 92 b 0.26 21.08 abc
14 85 b 0.23 18.11 d
Merlot berries
Clone Berries / cluster
(no.)
Berry wt
(g)
1 150 1.57 c
3 148 1.66 b
9 149 1.65 b
10 145 1.57 c
11 145 1.73 a
14 146 1.54 c
Merlot fruit composition
Clone Brix pH TA
(g/100 ml)
1 23.6 c 3.91 b 0.377 cd
3 23.4 c 3.90 bc 0.374 d
9 23.7 c 3.90 bc 0.373 d
10 23.65 bc 3.87 c 0.398 a
11 24.0 b 3.94 a 0.391 ab
14 24.4 a 3.94 a 0.385 bc
Merlot clones summary
• Selection 10 performed best; consistently
higher yields of fruit with low pH and high
TA
• Selection 11 was undesirable; the largest
berries, was the most susceptible to rot,
and had high pH
• Selection 3 performed similar to selections
1 and 9 and was not superior to 10
‘Crljenak kastelanski’
• “The red grape of Kastela”
• Zinfandel and Primitivo are probably
selections of the “Red grape”
• Origin of Zinfandel is obscure, 1850s?
• Primitivo means “early” in Italian
• Primitivo has been grown in Italy for about
200 years
Zinfandel characteristics
• Big berries, large clusters, high
fruitfulness, high yields
• Very susceptible to “sour rot” in warm
climates
• Uneven ripening
• Yield declines as the season progresses
• Color can be poor, especially in warm
climates
Zinfandel & Primitivo Clones
Clone Source
Zinfandel 1A Lodi, CA, Handel
Zinfandel 2 Lodi, CA, Handel
Zinfandel 3 Livermore, CA, Ruetz
Primitivo 3 Bari, Italy
Primitivo 5 Calo, Italy
Primitivo 6 Calo, Italy
Zinfandel, cluster characteristicsClone Clusters / vine
(no.)
Cluster wt.
(kg)
Yield / vine
(kg)
1A 73 b 0.30 20.4 c
2 75 b 0.31 21.3 bc
3 75 b 0.35 23.4 b
P3 91 a 0.32 26.0 a
P5 79 b 0.30 22.2 bc
P6 80 b 0.31 22.1 bc
Zinfandel, berry characteristics
Clone Berries /
cluster
Berry wt
(g)
1A 104 2.77 a
2 107 2.75 a
3 126 2.76 a
P3 116 2.64 b
P5 117 2.57 b
P6 110 2.78 a
Zinfandel, fruit composition
Clone Brix pH TA
(g/100 ml)
1A 20.05 c 3.47 b 0.60
2 20.16 c 3.45 b 0.60
3 19.56 d 3.45 b 0.59
P3 21.10 b 3.46 b 0.61
P5 20.82 b 3.48 b 0.62
P6 22.00 a 3.52 a 0.60
Zinfandel, sour rot susceptibility
Clone Sour rot incidence
(%)
1A 50 ab
2 55 a
3 52 ab
P3 40 cd
P5 44 bc
P6 34 d
Zinfandel clones summary
• Few differences between the Zinfandel
selections tested
• Primitivo selections generally were better
• Earlier maturing
• Similar or higher yield
• Similar or less sour rot
Acknowledgements
• Thanks to L. Peter Christensen, Kimberley
Cathline, Jorge Aguilar Osorio, Don
Katayama, & Karin Kawagoe
• Viticulture Consortium & American
Vineyard Foundation
